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  • Articles  (103)
  • rice  (56)
  • Nitrification  (47)
  • 1985-1989  (103)
  • 1965-1969
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (103)
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  • Articles  (103)
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  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (103)
  • Geosciences  (21)
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  • Energy, Environment Protection, Nuclear Power Engineering
  • Biology  (43)
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  • 1
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    Biology and fertility of soils 8 (1989), S. 335-338 
    ISSN: 1432-0789
    Keywords: Autotrophy ; Lime ; Lolium perenne ; Nitrate reductase ; Nitrification ; Stagnohumic gley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three different nitrification assays (short-term nitrifier activity, assimilatory nitrate reductase activity of Lolium perenne, and nitrate accumulation in the absence of plants) were performed either on soil from a naturally acidic stagnohumic-gley or on leaves from L. perenne grown in this soil. Before the investigation the soil was limed and fertilised in a manner consistent with established agricultural pasture improvement strategies. Short-term nitrifier activity was only detected in soils above pH 5.6. However, nitrate reductase activity and nitrate accumulation both showed a near linear increase between soil pH 3.8 and 6.8. These findings are attributed to the nature of the assays, each of which considers a different component of the soil nitrifier population.
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  • 2
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    Biology and fertility of soils 8 (1989), S. 247-254 
    ISSN: 1432-0789
    Keywords: Nitrification ; Abiotic factors ; Ammonium concentration ; Vmax of nitrification ; Michaelis-Menten constant for ammonium oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of temperature, water potential and ammonium concentrations were studied in field and laboratory experiments on arable soil. The two field experiments used different sampling intervals, one at daily (short-term) and the other at monthly (long-term) intervals. In the short-term field experiment, the numbers and activities of nitrifiers were assessed before and after natural rain or irrigation. The nitrifiers were apparently outcompeted by heterotrophs during the first days after wetting the soil. Potential nitrification was affected only slightly by changes in water potential, whereas the numbers of ammonium and nitrite oxidizers appeared more sensitive to these changes. The numbers of ammonium and nitrite oxidizers correlated strongly during the daily samplings. The potential nitrite-oxidation rates correlated with water potentials whereas the potential ammonium oxidation rates did not. Extractable ammonium decreased in proportion to increasing nitrate concentrations in both the rain-fed and the irrigated plots. In the long-term field experiments, the numbers of ammonium oxidizers correlated with water potentials but not with in situ temperature or with ammonium concentrations. The potential ammonium-oxidation rates correlated with water potentials and with ammonium-oxidizer numbers. The potential nitrite-oxidation rates correlated strongly with the potential ammonium-oxidation rates. The field experiments implied that nitrite oxidizers obtained substrate from ammonium oxidizers but also from nitrate reduction. In laboratory experiments nitrate accumulated at a Q 10 of about 2 and the V max for nitrification was observed at a water potential of −0.11 MPa (65% of water-holding capacity). The K m for ammonium oxidation at pH 8.2 was 1.72 mg l−1 soil water.
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  • 3
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    Biology and fertility of soils 5 (1987), S. 195-202 
    ISSN: 1432-0789
    Keywords: Nitrogen mineralization ; Nitrification ; Organic quality ; New Mexico
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest floor and mineral soil from ponderosa-pine, Douglas-fir, aspen and spruce-fir ecosystems located along a rising gradient in New Mexico were tested with laboratory assays for factors controlling N mineralization and nitrification. We concluded that low pH in combination with factors associated with organic quality controlled N mineralization and almost completely limited nitrification in spruce-fir soils, while N mineralization in the forest floor of ponderosa-pine was limited by low nutrient availability (other than N). Organic quality of the substrate and temporal changes in organic quality appeared to control N-mineralization and nitrification processes in forest-floor and mineral soils from all other sites.
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  • 4
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    Biology and fertility of soils 2 (1986), S. 65-70 
    ISSN: 1432-0789
    Keywords: Fertilized soil ; Nitrification ; Denitrification ; N2O production ; C2H2 blockage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A sandy soil amended with different forms and amounts of fertilizer nitrogen (urea, ammonium sulphate and potassium nitrate) was investigated in model experiments for N2O emission, which may be evolved during both oxidation of ammonia to nitrate and anaerobic respiration of nitrate. Since C2H2 inhibits both nitrification and the reduction of N2O to N2 during denitrification, the amount of N2O evolved in the presence and absence of C2H2 represents the nitrogen released through nitrification and denitrification. Results show that amounts of N2O-N lost from soils incubated anaerobically with 0.1% C2H2 and treated with potassium nitrate (23.1 µg N-NO 3 − /g dry soil) exceeded those from soils incubated in the presence of 20% oxygen and treated with even larger amounts of nitrogen as urea and ammonium sulphate. This indicates that nitrogen losses by denitrification may potentially be higher than those occurring through nitrification.
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  • 5
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    Biology and fertility of soils 2 (1986), S. 77-82 
    ISSN: 1432-0789
    Keywords: Ecosystem production ; Mineralization ; Nitrification ; Ion exchange resin bag method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Estimates of ammonium and nitrate availability in conifer and hardwood forests using an ion exchange resin (IER) bag method and with on-site incubations of soil cores in buried bags were compared. Correlations between the two methods were generally high. Correlation coefficients (r) between IER nitrate and buried-bag mineralized nitrate ranged from 0.87 to 0.92. Both methods also correlated well with aboveground net primary production, litter fall N content, and fine root biomass. The major differences between the methods related to the relative importances of ammonium and nitrate forms of available N. The IER method indicated that both ammonium and nitrate were important on all sites, with nitrate predominating in most soils. The buried-bag results indicated that available N was primarily in the form of nitrate (all ammonium was oxidized), but that nitrate was insignificant on infertile sites.
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  • 6
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    Biology and fertility of soils 2 (1986), S. 97-104 
    ISSN: 1432-0789
    Keywords: Nitrogen mineralization ; Nitrification ; Water-soluble inhibitors ; Allelochemic control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Bioassay experiments were performed to test for inhibition of the processes of nitrogen mineralization and nitrification by organics in the forest floor of a ponderosa pine ecosystem. Water-extractable organics in the forest floor were tested by applying filtered extracts to the assay soil. The extract decreased nitrate production by 17.0% and decreased net mineralization by 4.1%. Inhibition by volatile organics was tested by placing vials containing forest floor or selected terpenoids of ponderosa pine in sealed jars containing the assay soil. Nitrate production was inhibited by 87.4% and 100%, and net nitrogen mineralization was inhibited by 73.3% and 67.7% in the jars with forest floor and terpenoids, respectively. Organics which are partially water-soluble and are volatile (such as terpenoids) would be very effective inhibitors of nitrogen cycling processes.
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  • 7
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    Biology and fertility of soils 2 (1986), S. 87-95 
    ISSN: 1432-0789
    Keywords: Fire effects on mineralization ; Ammonification ; Nitrification ; Ponderosa pine soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of a prescribed fire in a ponderosa pine ecosystem on the rates of decomposition and nitrogen mineralization (including ammonification and nitrification) in the forest floor and mineral soil horizons were evaluated. The prescribed fire immediately increased the rates of nitrogen mineralization and nitrification in the forest floor of all burned plots and in the mineral soil of one plot. The rates of decomposition, as measured by CO2 evolution, in both the forest floor and mineral soil were not significantly different immediately after the burn when expressed on an organic matter basis. The rates of nitrogen mineralization in the forest floor and mineral soil were higher 6 and 10 months after the burn. The rate of decomposition (as measured by respiration) was lower in the forest floor but not in the mineral soil 6 and 10 months after the burn. Volatile organics that may inhibit rates of nitrogen mineralization may have been consumed by prescribed fire.
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  • 8
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    Biology and fertility of soils 6 (1988), S. 33-38 
    ISSN: 1432-0789
    Keywords: Microbial activity ; Nitrification ; Taiga ; Tillage system ; Crop residue management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary C and N mineralization potentials were determined, in a 12-week laboratory incubation study, on soil samples obtained from recently cleared land which had been cropped to barley for 4 years (field soils) and from nearby undisturbed taiga (forest soils). Treatments for the cropped soils were conventional and no-tillage with and without crop residues removed. An average of about 3% of the total C was evolved as CO2 from the field soils compared with 〉 10% and 4% for the upper (Oie) and lower (Oa) forest-floor horizons, respectively. Significantly more C was mineralized from the Ap of the no-till treatment with residue left on the surface than from the other field Ap horizons. Both forest-floor horizons showed rather long lag periods for net mineralization compared with the field soils, but at the end of the incubation, more mineral N was recovered from the forest Oie despite a rather wide C:N ratio, than from the field soils. After 12 weeks about 115, 200 and 20 μg mineral N/g soil were recovered from the field Ap, the forest Oie and the forest Oa horizons, respectively. Very little C or N was mineralized from the B horizon of the forest or the field soils. Nitrification was rapid and virtually complete for the field soils but was negligible for both forest-floor O horizons.
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  • 9
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    Biology and fertility of soils 2 (1986), S. 201-204 
    ISSN: 1432-0789
    Keywords: Fertilizer ; Nitrification ; Denitrification ; N2O emission ; Anhydrous ammonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field studies to determine the effect of different rates of fertilization on emission of nitrous oxide (N2O) from soil fertilized with anhydrous ammonia showed that the fertilizer-induced emission of N2O-N in 116 days increased from 1.22 to 4.09 kg ha−1 as the rate of anhydrous ammonia N application was increased from 75 to 450 kg ha−1. When expressed as a percentage of the N applied, the fertilizer-induced emission of N2O-N in 116 days decreased from 1.6% to 0.9% as the rate of fertilizer N application was increased from 75 to 450 kg N ha−1. The data obtained showed that a 100% increase in the rate of application of anhydrous ammonia led to about a 60% increase in the fertilizer-induced emission of N2O. Field studies to determine the effect of depth of fertilizer injection on emission of N2O from soil fertilized with anhydrous ammonia showed that the emission of N2O-N in 156 days induced by injection of 112 kg anhydrous ammonia N ha−1 at a depth of 30 cm was 107% and 21 % greater than those induced by injection of the same amount of N at depths of 10 cm and 20 cm, respectively. The effect of depth of application of anhydrous ammonia on emission of N2O was less when this fertilizer was applied at a rate of 225 kg N ha−1.
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  • 10
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    Biology and fertility of soils 2 (1986), S. 195-199 
    ISSN: 1432-0789
    Keywords: Fertilizer N ; Nitrification ; Denitrification ; N2O emission ; Anhydrous ammonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field studies of the effects of different N fertilizers on emission of nitrous oxide (N20) from three Iowa soils showed that the N2O emissions induced by application of 180 kg ha−1 fertilizer N as anhydrous ammonia greatly exceeded those induced by application of the same amount of fertilizer N as aqueous ammonia or urea. On average, the emission of N2O-N induced by anhydrous ammonia was more than 13 times that induced by aqueous ammonia or urea and represented 1.2% of the anhydrous ammonia N applied. Experiments with one soil showed that the N2O emission induced by anhydrous ammonia was more than 17 times that induced by the same amount of N as calcium nitrate. These findings confirm indications from previous work that anhydrous ammonia has a much greater effect on emission of N2O from soils than do other commonly used N fertilizers and merits special attention in research relating to the potential adverse climatic effect of N fertilization of soils. Laboratory studies of the effect of different amounts of NH4OH on emission of N2O from Webster soil showed that the emission of N2O-N induced by addition of 100 μg NH4OH-N g−1 soil represented only 0.18% of the N applied, whereas the emissions induced by additions of 500 and 1 000 μg NH4OH-N g−1 soil represented 1.15% and 1.19%, respectively, of the N applied. This suggests that the exceptionally large emissions of N2O induced by anhydrous ammonia fertilization are due, at least in part, to the fact that the customary method of applying this fertilizer by injection into soil produces highly alkaline soil zones of high ammonium-N concentration that do not occur when urea or aqueous ammonia fertilizers are broadcast and incorporated into soil.
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  • 11
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    Biology and fertility of soils 5 (1988), S. 344-349 
    ISSN: 1432-0789
    Keywords: Nitrification ; Deamination ; Grassland ; N fertilisers ; pH ; Denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil nitrification was compared in soils from 89-year-old grassland experimental plots with diverse chemical characteristics. Measurements of NaClO3-inhibited short-term nitrifier activity (SNA) and deamination of 1,2-diamino-4-nitrobenzene were used to study nitrification and deamination activities, respectively, in soil from each of 12 plots. Using multiple regression analysis, an expression for the relationship between SNA, soil pH and fertiliser N additions was derived which indicated that both the frequency and the quantity of farmyard manure additions were important in determining the rate of nitrification. SNA was greatest where there were large and frequent additions of farmyard manure. In soil with pH below 5.2 SNA was very low or insignificant. The effect of (NH4)2SO4 additions could not be assessed because they acidified the soil. We suggest that additions of farmyard manure increase the potential for NO3 − leaching or for denitrification. Deaminase assays indicated that soils with a higher pH showed greater N mineralisation than soils with a lower pH, except at the low extreme. There was no obvious relationship between SNA and deaminase activity at higher levels of pH.
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  • 12
    ISSN: 1432-0789
    Keywords: Ammonium ; Nitrate ; N-mineralization ; Nitrification ; Fertilization ; Irrigation ; Forest ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest-floor and 0–10 cm depth mineral soil horizons in two stands of Douglas fir were sampled for available NH4 +-N and NO3 −-N, N-mineralization potentials, and nitrification potentials for 2 years. The plots in each stand were sampled for 1 year, treated with either ammonium sulfate, carbohydrate (sawdust-sucrose), irrigation, carbohydrate plus irrigation, or no treatment (control), and then sampled for 1 year following treatment. In general, the direction of change following the treatments was the same for both the forest-floor and the mineral soils. Fertilization increased the NH4 +-N and NO3 −-N pools, nitrification potential, and N-mineralization potential, while treatment with carbohydrate decreased all of these characteristics. Irrigation generally increased NH4 +-N pools, nitrification potential, and N-mineralization potential, but decreased these characteristics in the soil at one site. Irrigation plus carbohydrate gave similar results to those of carbohydrate alone. Treatments altered pool sizes and/or potentials, but did not reduce within-year variance in any of these characteristics. Distinct seasonal patterns occurred in all measurements, suggesting that control of short-term variation in N-transformation processes is by factors which are dynamic in nature.
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  • 13
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    Biology and fertility of soils 6 (1988), S. 106-111 
    ISSN: 1432-0789
    Keywords: Nitrification ; Denitrification ; Soil water content ; N2O production ; Acetylene ; Ammonium fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of soil water content [60%–100% water-holding capacity (WHC)] on N2O production during autotrophic nitrification and denitrification in a loam soil was studied in a laboratory experiment by selectively inhibiting nitrification with a low C2H2 concentration (2.1 Pa). Nitrifiers usually produced more N2O than denitrifiers. During an initial experimental period of 0–6 days the nitrifiers produced more N2O than the denitrifiers by a factor ranging from 1.4 to 16.5, depending on the water content and length of incubation. The highest N2O production rate by nitrifiers was observed at 90% WHC, when the soil had become partly anaerobic, as indicated by the high denitrification rate. At 100% WHC there were large gaseous losses from denitrification, while nitrification losses were smaller except for the first period of measurement, when there was still some O2 remaining in the soil. The use of 10 kPa C2H2 to inhibit reduction of N2O to N2 stimulated the denitrification process during prolonged incubation over several days; thus the method is unsuitable for long-term studies.
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  • 14
    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrification ; Selective inhibitors ; Nitrapyrin ; Acetylene ; Nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrapyrin and C2H2 were evaluated as nitrification inhibitors in soil to determine the relative contributions of denitrification and nitrification to total N2O production. In laboratory experiments nitrapyrin, or its solvent xylene, stimulated denitrification directly or indirectly and was therefore considered unsuitable. Low partial pressures of C2H2 (2.5–5.0 Pa) inhibited nitrification and had only a small effect on denitrification, which made it possible to estimate the contribution of denitrification. The contribution of nitrification was estimated by subtracting the denitrification value from total N2O production (samples without C2H2). The critical C2H2 concentrations needed to achieve inhibition of nitrification, without affecting the N2O reductase in denitrifiers, must be individually determined for each set of experimental conditions.
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  • 15
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    Biology and fertility of soils 7 (1988), S. 79-87 
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Mineralization ; Nitrification ; Subarctic ; Volcanic ash
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary C and N pool sizes and rates of mineralization were studied in volcanic-ash deposits found in different subarctic habitats in southwestern Alaska. Surface ash samples were taken from white-spruce, alder, and moist- and dry-tundra habitats and were analysed for total and microbial C and N. C and N dynamics were studied using a 28-day aerobic laboratory incubation, with weekly measurement of evolved CO2 and determination of inorganic-N pools initially and after 10 and 28 days. Total and microbial C and N and cumulative respired CO2 all followed a similar pattern among the different habitats, with the moist-tundra habitat having the highest values and the spruce site the lowest. The size of the microbial biomass C and N pool in the spruce habitat was among the lowest reported for any ecosystem. Little net N mineralization occurred in the spruce-forest and dry-tundra ash over 28 days. Ash from the moist-tundra habitat immobilized a significant amount of N during the first 10 days of incubation, yet showed a large net release of N after 28 days. In contrast, the ash from the alder site exhibited net mineralization after both periods, with N production after 28 days being about 3.5 times that after 10 days. In addition, the alder-habitat ash was the only soil that showed net nitrification. Rates of total C and N accretion in the tundra and alder habitats were rapid relative to rates found for primary successions. The results of this study show that habitat has a profound effect on C and N cycling in subarctic environments.
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  • 16
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    Biology and fertility of soils 7 (1989), S. 254-258 
    ISSN: 1432-0789
    Keywords: N-mineralisation ; Nitrification ; Arginine ammonification ; Inorganic pollutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Long-term effects of 12 inorganic pollutants on N transformations were studied in a sandy cambisol. As, Be, Br, Cd, Cr, F, Pb, Hg, Se, Sn, and V were added to the soil as inorganic salts in 1975 and 1976. Soil samples were taken in 1984 to determine total N mineralisation and nitrification. All pollutants except Se and Sn inhibited N mineralisation. The most toxic elements under investigation were Be and Hg. Nitrification was reduced to a lower degree than total N mineralisation. As, Be, Cd, Cr, F, Pb, Se, and Sn failed to inhibit this process at all. It is assumed that nitrifying bacteria became adapted to these pollutants in the course of time. The arginine-ammonification method was less sensitive in detecting the effects of pollutants on N transformation than the N mineralisation test.
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  • 17
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    Biology and fertility of soils 8 (1989), S. 204-211 
    ISSN: 1432-0789
    Keywords: Nitrification ; Heterocyclic N compounds ; Pyrazoles ; Triazoles ; Pyridines ; Thiadiazoles ; 2-Ethynylpyridine ; Nitrapyrin ; Etridiazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relationship between the structures of diverse heterocyclic nitrogen (N) compounds and the effectiveness of these compounds for the inhibition of nitrification in soil was studied by determining the effects of different amounts of 12 unsubstituted and 33 substituted heterocyclic N compounds on the production of (NO 2 − +NO 3 − )-N in soils incubated at 25 °C for 21 days after treatment with ammonium sulfate. The results showed that unsubstituted heterocyclic N compounds containing two adjacent ring N atoms inhibit nitrification in soil and that two of these compounds, pyrazole and 1,2,4-triazole, are potent inhibitors. They also showed that several substituted pyrazoles and thiadiazoles are good inhibitors of nitrification in soil (e.g., 3-methylpyrazole and 3,4-dichloro-1,2,5-thiadiazole).
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  • 18
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    Biology and fertility of soils 4 (1987), S. 205-212 
    ISSN: 1432-0789
    Keywords: Nitrate production ; Nitrification ; Humisol ; Methane oxidation ; Methanotrophs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The coexistence of chemoautotrophic nitrifiers and methanotrophs in a cultivated humisol was investigated. Under laboratory conditions which supported the growth and activity of methanotrophs, the nitrifiers were partially or completely inhibited. The inhibition was related to a competition for available oxygen and a high assimilatory requirement for inorganic nitrogen by the Methanotrophs. Dissolved methane concentrations as high as 250 μM had no direct effect on the oxidation of ammonium. Simultaneous nitrification and methane oxidation was observed only if relatively high levels of ammonium and oxygen were maintained. Coupled nitrification-assimilatory/dissimilatory nitrate reduction resulted from the high oxygen demand of the actively growing methanotrophs. This study suggests that the potential competitive effects of methanotrophs may influence nitrification by chemoautotrophic nitrifiers in certain environmental systems.
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  • 19
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    Biology and fertility of soils 6 (1988), S. 341-346 
    ISSN: 1432-0789
    Keywords: Nitrification ; Phosphatase ; Dehydrogenase ; Aerosol ; Soil thickness ; Soil enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil was exposed to red phosphorous/butyl rubber (RP/BR) aerosols at various relative humidities in a recirculating environmental wind tunnel. Soil microbial and enzymatic activities were measured immediately after exposure and periodically thereafter for 56 days. The nitrification potential was significantly reduced in soil amended with ammonium sulfate and exposed to RP/BR smoke, and could be related to a decline in soil pH. The rate of nitrate formation in unamended soil with time was also reduced, but by 57 days postexposure, concentrations were similat to those of unexposed controls in all but the thinnest soil lense. Soil dehydrogenase and phosphatase enzyme activities were sensitive to RP/BR smoke and in some treatments no activity was detected. The measured activities did not recover within the 56-day postexposure period and in some cases declined. Soil lense thickness was the greatest factor controlling the degree of RP/BR effects, indicating that injury to soil microbial and enzymatic activities may be surficial. Deposition of smoke particles increased with increasing relative humidity, which had a significant impact on the activities measured.
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  • 20
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    Nutrient cycling in agroecosystems 16 (1988), S. 257-272 
    ISSN: 1573-0867
    Keywords: NH3-volatilization ; nitrogen-transformations ; denitrification ; nitrogen leaching ; nitrogen-application time ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ammonia volatilization losses and other N transformations were studied in drill sown rice bays fertilized with urea at various times between permanent flooding (PF) and panicle initiation (PI). Ammonia loss was measured directly with flow chambers and indirectly through application of Freney et al.'s (1985) model. Both techniques indicated that ammonia volatilization was negligible from fields fertilized immediately before PF. Applying 100 kg urea-N ha−1 to floodwater one day after flooding significantly increased floodwater ammoniacal-N and urea-N content, however the concentrations fell rapidly over the following five days. Fertilizer-N dissolved in the floodwater was in the urea rather than the ammoniacal-N form, indicating slow hydrolysis until it moved into the soil. Floodwater on plots receiving urea one day after PF frequently had more than double the NO3-N concentration of plots fertilized before flooding. Applying up to 140 kg urea-N ha−1 at PI increased floodwater ammoniacal-N concentrations from almost zero to over 27 g m−3, but three days after fertilization there was less than 3 g m−3 present. Fertilization also increased NH4-N concentration in the top 40 mm of soil. Higher ammoniacal-N concentration at PI suggests higher urease activity. Floodwater pH at PI was low, with a mean daily maximum of 7.8 and this reduced ammonia loss to less than 1% of the applied N. The results indicate that volatilization from fields fertilized prior to PF is minimal because of the low floodwater pH and ammoniacal-N concentration, while low floodwater pH restricts volatilization from fields topdressed at PI.
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  • 21
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    Nutrient cycling in agroecosystems 17 (1988), S. 47-59 
    ISSN: 1573-0867
    Keywords: Azolla pinnata (Bangkok) ; blue-green algae (BGA) ; N accumulation ; nitrogen fertilizer ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Application of higher levels (60 and 90 kg N ha−1) of nitrogen fertilizer (Urea) inhibited the growth ofAzolla pinnata (Bangkok) and blue-green algae (BGA) though the reduction was more in BGA thanAzolla. Inoculation of 500 kg ha−1 of freshAzolla 10 days after transplanting (DAT) in the rice fields receiving 30, 60 and 90 kg N ha−1 as urea produced an average of 16.5, 15.0 and 13.0 t ha−1 fresh biomass ofAzolla at 30 DAT, which contained 31, 31 and 27 kg N ha−1, respectively. The dry mixture of BGA (60%Aulosira, 35%Gloeotrichia and 5% other BGA on fresh weight basis) inoculated in rice field 3 DAT at a rate of 10 kg ha−1 showed a mat formation at 80 DAT with an average fresh biomass of 8.0, 5.8 and 4.2 t ha−1 containing 22, 17 and 12 kg N ha−1, respectively with those N fertilizer doses. Application ofAzolla showed positive responses to rice crop by increasing the panicle number and weight, grain and straw yields and nitrogen uptake in rice significantly at all the levels of chemical nitrogen. But, the BGA inoculation had a significant effect on the grain and straw yields only during the dry season in the treatment where 30 kg N was applied. During the wet season and in the other treatments performed during the dry season no significant increase in yields, yield components and N uptake were observed with BGA. The intercropping ofAzolla and rice in combination with 30, 60 and 90 kg N ha−1 as urea showed the yields, yield attributes and nitrogen uptake in rice at par with those obtained by applying 60, 90 and 120 kg N ha−1 as urea, respectively but, the BGA did not. The analysis of soil from rice field after harvest showed thatAzolla and BGA intercropping with rice in combination with chemical fertilizer significantly increased the organic carbon, available phosphorus and total nitrogen of soil.
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  • 22
    ISSN: 1573-0867
    Keywords: farmyard manure ; maize ; nitrogen ; phosphorus ; rice ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field experiments with rice-wheat rotation were conducted during five consecutive years on a coarse-textured low organic matter soil. By amending the soil with 12t FYM ha−1, the yield of wetland rice in the absence of fertilizers was increased by 32 per cent. Application of 80 kg N ha−1 as urea could increase the grain yield of rice equivalent to 120 kg N ha−1 on the unamended soil. Although the soil under test was low in Olsen's P, rice did not respond to the application of phosphorus on both amended and unamended soils. For producing equivalent grain yield, fertilizer requirement of maize grown on soils amended with 6 and 12 t FYM ha−1 could be reduced, respectively to 50 and 25 per cent of the dose recommended for unamended soil (120 kg N + 26.2 kg P + 25 kg K ha−1). Grain yield of wheat grown after rice on soils amended with FYM was significantly higher than that obtained on unamended soil. In contrast, grain yield of wheat which followed maize did not differ significantly on amended or unamended soils.
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  • 23
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    Nutrient cycling in agroecosystems 20 (1989), S. 27-32 
    ISSN: 1573-0867
    Keywords: Cropping system ; phosphorus ; rice ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A long term field experiment was conducted on a sandy loam soil from 1983 to 1987 to determine how to best apply phosphorus fertilizer in a rice-wheat cropping system. The treatments included 9 combinations of phosphorus application either to both rice and wheat or to rice or wheat alone. Direct application of phosphorus at 13 kg/ha to both the crops resulted in significantly higher total productivity of the rice-wheat cropping system as compared with 26 kg P/ha applied either to rice or wheat alone. Phosphorus at 13 kg/ha for rice and 26 kg/ha for wheat was as efficient as 13 kg P/ha for rice and 13 kg P/ha for wheat. The higher rate of P (26 kg/ha) applied to both rice and wheat resulted a decline in the total productivity. The residual effects of phosphorus applied to either rice or wheat were significant to the succeeding crop but was inferior to its direct application. Phosphorus increased the leaf area index, chlorophyll content of leaves, and interception of more photosynthetically active radiation (PAR) which resulted in increased grain yield of rice and wheat. Phosphorus status of the surface soil declined markedly, in the absence of P application from 15.4 to 6.4 kg P/ha. Phosphorus applied at 26 kg P/ha to both the crops resulted a build up of the available P status of soil. Phosphorus application at 13 kg/ha to both rice and wheat maintained the phosphorus status of the soil at original level.
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  • 24
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    Nutrient cycling in agroecosystems 21 (1989), S. 113-123 
    ISSN: 1573-0867
    Keywords: Nitrogen use ; farmer risk aversion ; rice ; Asia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Year to year variability in nitrogen response is widely believed to be responsible for low levels of fertilizer application by risk averse farmers. Certain authors have claimed that production risk is not responsible for sub-optimal applications of fertilizer. Since these studies estimated fertilizer response in irrigated areas or in simulated rainfed areas in experiment stations they may have underestimated the degree of risk faced by the majority of farmers. This study seeks to address this issue of risk under farmers' conditions by using data from rainfed farmers fields in a risky rice growing area of the Philippines. Long term distributions of factors responsible for temporal variability in N-response, such as moisture stress and typhoons, are derived by using a rainfall simulator and a water balance model. These distributions are combined with a hetereoscedastic nitrogen response function to simulate long term yield distributions at different N-rates. The application of risk averse and risk neutral decision making models shows that risk aversion reduces fertilizer application by only 7–9%. These results occur because as N-rates increase, the benefits from increased average profits outweigh the disadvantages of increased variability in profits. These findings provide additional evidence to support the emerging consensus that the impact of risk aversion on fertilizer use is much smaller than previously believed.
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  • 25
    ISSN: 1573-0867
    Keywords: Nitrification ; nitrate movement ; urea ; ammonium sulphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two successive applications of urea and ammonium sulphate (AS) at varying intervals were given in two soils, one of which was salt affected. The nitrification and nitrate leaching after both the applications of fertilizers was studied. The nitrification of first application of AS was faster than urea on both soils. However, the nitrification rate of both fertilizers was slow in salt effected soil. The same trend of results was observed with second application of fertilizers. However, the nitrification of second application given within 6 weeks of the first application proceeded at a much faster rate than that of the first application. The amount of NO 3 - that moved down with periodic water application was related with nitrification rate and the amount of fertilizer nitrified at the time of water application.
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  • 26
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    Nutrient cycling in agroecosystems 9 (1986), S. 149-160 
    ISSN: 1573-0867
    Keywords: Nitrogen fertilizers ; rice ; fertilizer efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The efficiency of nitrogen (N) fertilizer products and practices currently used on rice is low, and improving this efficiency would be very beneficial to rice-growing countries. The development of new N fertilizers is best achieved by following a logical sequence of testing and evaluation procedures in a variety of settings from the laboratory to the farmer's field. Novel N fertilizers currently at various stages of testing include urea supergranules for deep placement, urea coated with various materials to control the N release rate, mixtures of a urease inhibitor with urea to reduce losses, and organic N sources other than urea.
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  • 27
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    Nutrient cycling in agroecosystems 10 (1986), S. 119-133 
    ISSN: 1573-0867
    Keywords: ammonium sulphate ; fertilizer-N recovery ; NH3 volatilization ; rice ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a pot experiment it was established that NH4 volatilization losses were larger with urea than with ammonium sulphate used as a basal fertilizer for lowland rice. The difference arose from the pH-increasing effect of urea in the floodwater. This rise in pH promoted the growth of algae which in turn were responsible for large diurnal fluctuations in the pH of the floodwater thus enhancing the loss of NH3 during daytime. Ammonium sulphate lowered the pH of the water which suppressed the growth of algae. Once the rice canopy had closed, the algal population declined and the diurnal pH fluctuations largely disappeared. Urea as a topdressing was found to be less liable to give rise to NH3 volatilization than when added as basal dressing. The highest N recovery was obtained with ammonium sulphate used as basal dressing and urea as topdressing. Working a basal dressing into the soil improves the fertilizer-N recovery of urea-N, but not of ammonium sulphate-N, the latter being already high without soil incorporation.
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  • 28
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    Nutrient cycling in agroecosystems 16 (1988), S. 37-45 
    ISSN: 1573-0867
    Keywords: Leaching losses ; N movement ; deep placement ; rice ; soil texture ; urea supergranule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a glasshouse experiment, the periodic movement, loss and uptake of N by lowland rice fertilized with point-placed urea supergranule (USG) was studied in two soils differing in texture. Movement of urea-N, NH 4 + -N and NO 3 - -N was significantly faster in Patharchatta sandy loam (Typic Hapludoll) than in Beni silty clay loam (Aquic Hapludoll) and was mostly downward with peak concentration near the placement site. Nitrogen in leachate was higher in Patharchatta sandy loam than in Beni silty clay loam. About 60–70% of leaching of urea-N took place within 2 days of USG placement. The leaching of NH 4 + -N and NO 3 - -N increased till 14 and 21 days of USG placement in Patharchatta sandy loam and Beni silty clay loam, respectively. Nitrogen leached through urea, NH 4 + and NO 3 - forms was, respectively, 64, 25 and 25% higher from sandy loam. During 49 days, 49 and 32% of the applied N was recovered by rice plants from silty clay loam and sandy loam, respectively.
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  • 29
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    Nutrient cycling in agroecosystems 17 (1988), S. 177-188 
    ISSN: 1573-0867
    Keywords: Ammonium concentration ; Incubation experiments ; Kinetic model ; Lysimeter experiments ; Nitrification ; Maize (Zea mays)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Lysimeter experiments with maize and incubation experiments showed that increased ammonium concentrations in soil reduced nitrification rates. A modified Lees and Quastel kinetic model was proposed for predicting the relation between initial ammonium concentration in soil and nitrification rate. A term Mi strongly dependent on initial ammonium concentration ([NH40]) was introduced into the model which took the form: dy/dt = R(A − y)(Mi + y), where R is a rate constant, y represents the concentration of formed nitrate and A is an asymptotic value of initial ammonium concentration. Mi was obtained by a curve fitting procedure applied to experimental data. An exponential decay of Mi with [NH4]0 was formulated. The modified model thus obtained provides an effective tool for predicting nitrification rates related to a wide range of ammonium concentrations.
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  • 30
    ISSN: 1573-0867
    Keywords: calcium ammonium nitrate ; calcium cyanamide ; humid tropics ; maize ; nitrate leaching ; rice ; ultisol ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Leaching loss of N applied as calcium cyanamide (CaCN2 — 19% N), urea and calcium ammonium nitrate (CAN — 26% N) to a coarse textured, kaolinitic ultisol profile was studied in the laboratory using undisturbed soil columns. The soil columns were leached with an amount of water equivalent to the annual rainfall of the sampling site (2420mm) using a rainfall simulator over a period of 42 days. The ‘leachability’ of the three N fertilizers differed greatly and followed the order of CAN 〉 urea 〉 CaCN2. Most of the N lost through leaching was in NO3 form. Calcium cyanamide lost only 3% of applied N. Breakdown of CaCN2 to NH4 was incomplete (64%) and nitrification in the soil was inhibited resulting in negligible leaching loss. Nitrogen retained in the soil columns after the leaching cycle was mainly in ammoniacal form irrespective of source of N used. Effectiveness of CaCN2 as a N source was also studied in a greenhouse experiment with maize (Zea mays) and upland rice (Oryza sativa) as testing crops. Calcium cyanamide applied one week before sowing of crops was as effective as CAN and urea under conditions of no N leaching. When applied at the time of planting and two or more weeks before planting gave lower dry matter yields and N uptake than CAN and urea.
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  • 31
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    Biology and fertility of soils 1 (1985), S. 3-7 
    ISSN: 1432-0789
    Keywords: Nitrification ; Denitrification ; Soil profile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrous oxide (N2O) fluxes at the soil surface and concentrations at 0.1, 0.2, and 0.3 m were determined in a 40-year-old planted tallgrass (XXX) prairie, a 40-year-old white pine (Pinus strobus) plantation, and field plots treated annually for 18 years either with 33 metric tons of manure ha−1 (330 kg N ha−1) and NH4NO3 (80 kg N ha−1) or with only NH4NO3 (control). Nitrous oxide fluxes from the prairie, forest, manure-amended, and control sites from 13 May to 10 November 1980 ranged from 0.2 to 1.3, 3.5 to 19.5, 3.7 to 79.0, and 1.7 to 24.8 ng N2O-N m−2s−1, respectively. We observed periods when there was no apparent relationship between the N2O flux from the surface and N2O concentrations in the soil profile. This was generally the case in the prairie and in the field sites following the application of N fertilizer. The N2O concentrations in the soil profile increased markedly and coincided with increased soil water content following periods of heavy rainfall for all sites except the prairie. Nitrous oxide concentration gradients indicate that following heavy rainfalls the site of N2O production was moved from the surface deeper into the soil profile. We suggest that the source of N2O production near the surface is nitrification and that N2O is produced by denitrification of NO3 leached into the soil following heavy rainfall.
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  • 32
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    Biology and fertility of soils 1 (1985), S. 131-140 
    ISSN: 1432-0789
    Keywords: Nitrification ; MPN of ammonium oxidizers ; Chlorate inhibition ; Arable soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The number of ammonium-oxidizing bacteria was measured with the most probable number (MPN) method while potential ammonium oxidation rates were determined with a chlorate inhibition technique in two arable soils. A new method for measuring actual in situ ammonium oxidation in soil cores is presented. One soil was cropped for 4 years with one of four crop-fertilizer combinations: Unfertilized lucerne ley, unfertilized barley, nitrate-fertilized grass ley, or nitrate-fertilized barley. The highest ammonium oxidizer numbers and potential rates were found in the grass ley. The unfertilized barley had one-third the number and activity of the grass ley. Actual rates were in general 5–25 times lower than potential rates. The other soil was that undergoing a 27-year-old field trial with a fallow and four different cropping treatments: No addition, nitrate, nitrate + straw, or manure. Ammonium oxidizer numbers were highest in the manure and straw treatments. MPN numbers and potential rates were lowest in the fallow treatment. Typical specific potential rates were 30 ng N oxidized cell−1 h−1. Actual rates were in general 40 times lower than potential rates. Actual ammonium oxidation measurements seem to correspond to actual in situ activity at the moment of sampling, whereas the MPN technique and the potential measurements reflect events that occurred weeks to months before the sampling.
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  • 33
    ISSN: 1573-5036
    Keywords: fertilization ; nitrate reductase activity ; paddy soil ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract When following the pattern of the disappearance of NH 4 + −N from ammonium sulfate applied to the flooded soil-rice plant system (field and greenhouse experiments) during a growing season, it was observed that the lowest NH 4 + −N level coincided with the highest value of NR activity in the leaves. Nitrate was detected in both the root and shoot systems of the rice plants and autotrophic nitrifiers (Nitrosomonas and Nitrobacter) were particularly abundant. Since it was also demonstrated in this work that the NR activity of rice plants grown with nitrate fertilization (growth chamber culture experiments) was inducible by its substrate, it can be assumed that NH 4 + −N oxidation takes place in the water-logged soil studied. Therefore, the occurrence of the nitrification process following NH 4 + −N fertilizer application can be predicted by thein vitro orin situ evaluation of the NR activity of the rice leaf as an indicator.
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  • 34
    ISSN: 1573-5036
    Keywords: antibiosis ; bacterization ; biological control ; rice ; sheath-blight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Strains of fluorescent and nonfluorescent bacteria that were isolated from rice rhizospheres of Southern India and showed antagonism towardsRhizoctonia solani were evaluated for biological control of rice sheath-blight (ShB). Efficient strains of bacteria inhibited mycelial growth ofR. solani, affected sclerotial viabilityin vitro and protected IR 20 and TKM 9 rice seedlings from infection byR. solani in greenhouse tests. Pretreatment of sclerotia in bacterial suspensions resulted in reductions in ShB lesion sizes up to 31 to 44% in IR20 and 58 to 74% in TKM 9 rice. In field plots, IR 50 and TKM 9 rice plants raised from bacterized seeds had 65 to 72% less ShB than those plants from untreated seeds.
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  • 35
    ISSN: 1573-5036
    Keywords: Azolla pinnata ; biomass ; critical P level ; flooded soil ; N2-fixation ; P fertilizer ; P transfer ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment was conducted at the Bangladesh Rice Research Institute, Joydebpur, Dhaka during the late wet season. Basal application of P at both 5 and 10 kg ha−1 significantly increased total biomass production and nitrogen fixation byAzolla pinnata R. Brown (local strain). Addition of both 5 and 10 kg P ha−1 in equal splits at inoculation and at six day intervals thereafter during growth periods of 12, 24 and 36 days increased biomass production and nitrogen fixation by Azolla over that attained with the basal application. Biomass and nitrogen fixation using a split application of 5 kg P ha−1 exceeded that attained with basal application of 10 kg P ha−1 and split application of 10 kg P ha−1 resulted in 0.58, 11.2, and 18.3 t ha−1 more biomass, and 0.47, 18.9, and 18.3 more kg fixed N ha−1 at 12, 24 and 36 days, respectively, than the same amount applied as a basal application. Analyses indicated that the critical level of dry weight P in Azolla for sustained growth was in the range of 0.15–0.17%. Compared with the control, where no P was added, and additional 30 and 36 kg N ha−1 were fixed after 24 and 36 days, respectively, when P was provided at 10 kg ha−1 using a split application. A separate field study showed that flooded rice plants received P from incorporated Azolla with about 28% of the P present in the supplied Azolla being incorporated into the rice plants.
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  • 36
    ISSN: 1573-5036
    Keywords: black gram ; boron deficiency ; borax rates ; green gram ; hollow heart ; hot-water-soluble boron ; kernel boron ; leaf boron ; peanut ; rice ; soybean ; sunflower ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of boron (B) on peanut and soybean was examined in two omission and one B fertilizer rate trial on a Typic Tropaqualf in Northern Thailand. The B rate trial was combined with a comparison of the response of sunflower, green gram, black gram, wheat, and rice in addition to peanut and soybean grown in irrigated rice-based cropping sequences over two years. Omitting B induced the hollow heart symptom in 10% of peanut kernels with the incidence of hollow hearts closely related to B concentration in the kernels. Omission of B had no effect on the appearance of soybean seed or on the grain yield of either soybean or peanut. In the B rate experiment, omitting B depressed grain yield by 50% in sunflower and by 40% to 80% in black gram, induced B deficiency symptoms in green gram and the hollow heart symptom in peanut kernels, but had not significant effect on the grain yield of soybean, peanuts, rice, or wheat. B deficiency apparently depressed grain yield in black and green gram by delaying or inhibiting reproductive development thus reducing pod set.
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  • 37
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    Plant and soil 104 (1987), S. 175-181 
    ISSN: 1573-5036
    Keywords: rice ; soils ; submergence ; transformation ; zinc fractions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Distribution of different forms of Zn in 16 acid alluvial rice growing soils of West Bengal (India) and their transformation on submergence were studied. The results showed that more than 84% of total Zn occurred in the relatively inactive clay lattice-bound form while a smaller fractionviz. 1.1, 1.6, 11.1 and 2.0 per cent of the total occurred as water-soluble plus exchangeable, organic complexed, amorphous sesquioxide-bound and crystalline sesquioxide bound forms, respectively. All these four Zn forms showed significant negative correlations with soil pH (r=−0.48**, −0.39*, −0.61** and −0.67**, respectively), while the latter two Zn forms showed significant positive correlations with Fe2O3 (0.68** and 0.88***) and Al2O3 (0.89*** and 0.75***) content of the soils. The different Zn forms were found to have positive and significant correlations amongst each other, suggesting the existence of a dynamic equilibrium of these forms in soil. Submergence caused an increase in the amorphous sesquioxide-bound form of Zn and a decrease in each of the other three forms. The magnitude of such decreases in water-soluble plus exchangeable and crystalline sesquioxide-bound forms was found to be correlated negatively with initial pH values of the soils and positively with the increase in the amorphous sesquioxide-bound form, indicating their adsorption on the surface of the freshly formed hydrated oxides of Fe, which view was supported by the existence of significant positive correlation between the increase in the amorphous sesquioxide-bound form of Zn and that in AlCl3-extractable iron. The existence of a positive correlation between the decrease in crystalline sesquioxide-bound Zn and that in Fe2O3 content in soil suggested that on waterlogging the soil Zn occluded in the cry talline sesquioxide was released as a result of reduction of Fe2O3.
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  • 38
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    Plant and soil 92 (1986), S. 341-362 
    ISSN: 1573-5036
    Keywords: Eucalypt forests ; Fire Immobilizxtion ; Nitrogen mineralization ; Nitrogen turnover ; Nitrification ; Nitrogen conservation ; Resilience
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen mineralization was measured in the laboratory andin situ in eight eucalypt forests covering a wide range of climates and soil types. Aerobic and anaerobic incubations as well as chemical indices showed consistently higher rates of mineralization and nitrification and higher mineralization potentials in the wetter, high productivity forests. Nitrification was not confined to these forests and appears best related to soil C/N ratios and the rate of N turnover. Immobilization is recognized as a major process in eucalypt forest soils; in two forests which were burnt by bushfire during this study immobilization prevented over-accumulation of inorganic-N and possible leaching of NO 3 − −N. Calculated fromin situ incubations, annual uptake of inorganic-N ranged from 27 to 160 kg N ha−1; in two of four forests nitrate uptake was not apparent, in a third forest nitrate accounted for 10% of total uptake and in the remaining forest nitrate comprised about one-third of inorganic-N taken up. Ammonium is thus the dominant inorganic form taken up in eucalypt forests of this region. There was general agreement between laboratory andin situ incubations as to the occurrence of nitrification and the difference in mineralization rates between forests. In conjunction with previous studies, the turnover and maintenance of N-pools in eucalypt forests is discussed; forests with low N-capital appear to be resistant to possible N-loss after perturbation, forests with higher N-capital are more susceptible to loss but recover quickly. Immobilization of inorganic-N is central to the recovery process. These results agree with recent hypotheses proposed by Vitousek and Boerner.
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  • 39
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    Plant and soil 93 (1986), S. 133-135 
    ISSN: 1573-5036
    Keywords: Azadiractin ; Heterotrophic flora ; Neemcake ; Nimbidin ; Nitrification ; Nitrifying bacteria ; Zymogenous flora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Application of neem products like neem leaf and neem cake to wetland soil did not have any adverse effect on the population of heterotrophic microflora; nitrifying bacteria, on the other hand, decreased significantly due to addition of neem cake and fresh and dried neem leaf with urea. It is suggested that neem leaf could be used as an inhibitor of nitrification for enhancing nitrogen use efficiency of fertilizers where neem leaf is available in plentiful supply.
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  • 40
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    Plant and soil 94 (1986), S. 109-123 
    ISSN: 1573-5036
    Keywords: Denitrification ; Isobutylidene diurea ; N balance ; Nitrification ; 15N Oxamide ; Rice ; Slow-release N ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two15N-labelled slow-release nitrogen (N) sources, oxamide and isobutylidene diurea (IBDU), each at two particle sizes, and15N-labelled urea were compared at two rates as sources of N for rice (Oryza sativa) under two watering regimes which simulated a transplant (continuous flood, CF) and a direct-seeded (A/F) system of paddy rice culture. Highest grain yields were obtained from −8+10-mesh oxamide particles applied at the rate of 2,000 mg of N/5 kg of soil, CF series; this yield was slightly higher than that obtained from −3+4-mesh oxamide, A/F series. Incubating the N fertilizers in moist (22% water) soil for 21 days immediately before flooding and transplanting rice greatly reduced N supply because of nitrification during the preflood period, followed by denitrification after flooding. This resulted in less plant uptake of N and less grain yield from urea, fine oxamide and IBDU, A/F series. For coarse oxamide, N release during the preflood period resulted in higher N uptake and grain yield in the A/F rather than in the corresponding CF series. The pattern of fertilizer N uptake by rice plants was affected by kind of fertilizer, particle size of oxamide and IBDU, and watering regime. Uptake of fertilizer N generally paralleled uptake of soil N throughout the growth period. Plant tops continued to accumulate some N during the period of grain filling, but much of the N in plant tops was translocated to the grain after heading. There was a large decrease in dry weight, N content, and15N content of tops after heading. Root weight and N content increased rapidly at first, and then at a diminishing rate until maturity. Unexplained N deficits occurred in the CF series (14–23% of the N applied, depending on N rate and source), and in the A/F series for IBDU (37–43% of the N applied).
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  • 41
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; O. perennis ; F1 weakness ; geographical distribution of gene ; Indica-Japonica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Distribution of two complementary genes Hwc-1 and Hwc-2 causing F1 weakness was examined using 159 native rice cultivars and 30 strains of wild relatives collected from various sites of tropical Asia including the Himalayan foothills. Hwc-1 is carried by a Peruvian cultivar, Jamaica, a tester cultivar of this experiment. It was not found in the tested cultivars and strains. Hwc-2 was widely distributed in the Japonica types tested. No wild strains had either Hwc-1 or Hwc-2. Hwc-2 was infrequent in the Japonica types collected from Southern Asian countries. Hwc-2 was estimated to be indigenous to the Japonica types, may be linked with certain gene(s) related to adaptation.
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  • 42
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; Oryza glaberrima ; African rice ; interspecific hybrids ; hybrid sterility ; male sterility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Several hybrids between Oryza sativa and O. glaberrima and their backcrosses with O. sativa were studied. Their seed sterility was very different; large differences were also observed in the level of pollen sterility and in the earliness of microspore failure. The proportion of aborted embryo sacs was much lower than the rate of sterile male gametophytes. The backcross populations were much more sterile than the corresponding F1 hybrids. On the base of our observations and according to the literature, we may conclude that genic unbalance is the main cause of sterility of these hybrids, but that physiological factors may also be involved. Thus a restoration of fertility is generally possible by selection. On the other hand, male-sterile lines could be bred from some of these hybrids.
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  • 43
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; floating habit ; genetics ; linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Deep water rice varieties in general have certain peculiar characters which are associated with floating habit. These characters are (i) early nodal differentiation, (ii) nodal rooting, (iii) spreading habit, (iv) awned grains, (v) brown hull colour, (vi) red pericarp (red rice), and (vii) seed dormancy. Inheritance of these characters and linkage relationship of genes governing these characters were studied in a cross between Pankaj (non floating) and Nageribao (floating) rice varieties. Nageribao, a cultivar from Assam possesses these characters. Early nodal differentiation was observed to be controlled by a single dominant gene, designated as ‘Nd’. Nodal rooting was controlled by two dominant complementary genes, designated as ‘Nr 1’ and ‘Nr 2’. We found an inhibitory factor for spreading habit and one for brown hull colour in Pankaj; the operation of two dominant duplicate genes ‘An 1’ and ‘An 2’ for controlling awning characters, a single dominant gene ‘Rd’ for red pericarp colour and a single dominant gene ‘Gd’ for grain dormancy. Joint segregations between these characters resulted in the assignment of genes in the X linkage group of indica rices with estimated map distances based on the cross-over values. The genes ‘An’ (awning), ‘Es’ (spreading habit), ‘Nr’ (nodal rooting) and ‘Nd’ (nodal differentiation) were observed to be associated with each other. The gene for red pericarp (Rd) was observed to be linked with the grain dormaney gene ‘Gd’.
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  • 44
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    Euphytica 34 (1985), S. 587-592 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; Oryza glaberrima ; African rice ; cytoplasmic male sterility ; anther dehiscence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary To study differential nucleus-cytoplasm interactions between the two cultivated rice species, Oryza sativa and O. glaberrima, cytoplasmic substitution lines were made by using a glaberrima strain (G) and an Indica strain of sativa (S). The G cytoplasm had no adverse effect on pollen development when combined with the nucleus of S. On the other hand, when the S cytoplasm was combined with the G nucleus, the substitution line showed no seed set because of male sterility although the pollen grains were normally stained with I2-KI solution. A dominant gene derived from S strain seemed to cause anther indehiscence in the substitution line. Further, a restorer gene (Rf j)from Akebono of Japonica type was effective on pollen restoration in the male sterile line, suggesting that the S cytoplasm is the same as those of Japonica type in terms of a fertility-restoring system.
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  • 45
    ISSN: 1573-5036
    Keywords: antibiotic resistance ; Azospirillum inoculation ; establishment ofAzospirillum ; establishment ofHerbaspirillum ; Herbaspirillum inoculation ; rice ; sorghum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two field experiments were carried out at the UAPNPBS experimental station, Seropédica, with two sorghum and one rice cultivars. The establishment, and inoculation effects, ofAzospirillum spp. andHerbaspirillum strains marked with antibiotic resistance were investigated. One grain sorghum (BR 300) and one sugar sorghum (Br 505) cultivar were used.Azospirillum lipoferum strain S82 (isolated from surface sterilized roots of sorghum) established in both cultivars and comprised 40 to 80% of theAzospirillum spp. population in roots and stems 60 days after plant emergence (DAE).Azospirillum amazonense strain AmS91 (isolated from surface-sterilized roots of sorghum) reached only 50%. At 90 DAE, S82 almost disappeared (less than 30% of establishment) while the establishment of AmS91 remained constant in roots and stems. No establishment ofH. seropedicae strain H25 (isolated from surface-sterilized roots of sorghum) orA. lipoferum strain S65 (isolated from the root surface of sorghum) could be observed on inoculated roots. Inoculation with S82, AmS91 or S65 but not withH. seropedicae H25, increased plant dry weight of both cultivars and total N in grain of the grain sorghum. In rice,A. lipoferum Al 121 andA. brasilense Sp 245 (isolated from surface sterilized rice and wheat roots respectively) established in the roots but there was no increase inAzospirillum spp. numbers due to inoculation. None of the strains affected plant growth or rice grain yield.Azospirillum amazonense, A82 andH. seropedicae Z95, which did not establish in roots, significantly enhanced seed germination.
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  • 46
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    Plant and soil 106 (1988), S. 135-141 
    ISSN: 1573-5036
    Keywords: flooding ; organic matter ; rice ; sodic soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of organic matter, added in the form ofCasuarina equisetifolia andAcacia nilotica leaves, on the chemical and electrochemical kinetics of a flooded sodic soil and rice growth, was studied in a pot experiment. With the addition of organic matter, not only the peaks of CO2 production and maximum concentrations of extractable Fe and Mn and other cations occurred earlier, but their concentrations were also significantly higher as compared to the control (no organic matter). The high concentrations of CO2 and reduced redox potential (Eh) appeared to influence the soil pH, exchangeable sodium percentage (ESP) and the accumulation of cations and to be chiefly responsible for better rice growth. Acacia proved more effective than Casuarina in improving rice yield and the sodic soil.
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  • 47
    ISSN: 1573-5036
    Keywords: organic matter ; rice ; submergence ; transformation ; zinc fraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory and greenhouse experiments were conducted with two soilsviz., laterite and alluvial to study the transformation of applied Zn in soil fractions under submerged condition in the presence and absence of added organic matter and its relationship with Zn nutrition of rice plants. The results showed that application of organic matter caused a decrease in the concentration of Zn in shoot and root of rice plants and helped in translocating the element from root to shoot. The per cent utilization of applied Zn by plants was also found to increase by the application of organic matter. The transformation of applied Zn in different fractions in soils showed that a major portion (53.6–72.6%) of it found its way to mineral fractions leaving only 1.0–3.3, 6.6–18.9, 11.0–21.6 and 2.3–8.8% of the applied amounts in water soluble plus exchangeable, organic complexed, amorphous sesquioxides and crystalline sesquioxides bound fractions respectively. Application of organic matter favoured such transformation of applied Zn into these fractions except the mineral and crystalline sesquioxides bound ones. Simple correlation and multiple regression analyses between applied Zn in different soil fractions and fertilizer Zn content in plants showed that organic matter application increased the predictability of fertilizer Zn content in plants which has been attributed to the higher per cent recovery of applied Zn in plant available fractions in soils in presence of added organic matter.
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  • 48
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    Plant and soil 102 (1987), S. 49-54 
    ISSN: 1573-5036
    Keywords: Azolla pinnata ; Azolla dual cropping ; N ; P uptake ; rice ; soil fertility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Azolla and urea application in a rice field transplanted with square (20 cm×20 cm) and rectangular (10 cm×40 cm) spacings for three consecutive seasons were found to increase significantly uptake of N and P by the rice plants, irrespective of seasons. Azolla treatments increased the organic C content of the soil during both wet and dry seasons, while its N and P contents were more only during the wet seasons. Urea did not affect N, P and organic C contents of the soil. Spacing had no significant effect on N and P uptake by the rice plant or N, P and C contents of the soil. Maximum N and P uptake in rice were obtained by growing two crops of Azolla after transplanting in addition to its incorporation before transplanting. This treatment showed significantly more N uptake than the urea at 60 kg N ha−1 during wet and dry seasons of 1982. Among Azolla treatments, twice Azolla dual cropping although showed comparatively lower uptake of N and P, it was comparable to that of 60 kg N ha−1 urea.
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  • 49
    ISSN: 1573-5036
    Keywords: corn ; cropping pattern ; inoculum potential ; mungbean ; rice ; VAM fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The numbers of infectious propagules of indigenous vesicular-arbuscular mycorrhizal (VAM) fungi were determined at different stages of the rice-based cropping systems in two irrigated rice fields of varying strata and in a rainfed field. The most-probable-number method was used to estimate the infective VAM fungal population. On the irrigated farms the mycorrhizal inoculum was consistently less in the poorly drained low-lying field with a rice-rice cropping pattern than in the field in the better-drained upper stratum with a rice-corn-mung-bean pattern. The population of infective VAM fungi was generally low after the wet season rice crop when the field was inundated for a long period, increased during fallow in the presence of weeds, and was highest upon the maturity of the dry-season corn or rice crop. In the rainfed area the highest endophytic population was found at maturity of the mungbean crop and the lowest after land preparation prior to rice seeding.
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  • 50
    ISSN: 1573-5036
    Keywords: leaf elongation rate ; leaf water potential ; maize ; nitrogen ; nutrient uptake ; phosphorus ; potassium ; rice ; soybean ; transpiration rate ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted in the greenhouse to determine and compare the responses of rice (Oryza sativa L. var, IR 36), maize (Zea mays L. var. DMR-2), and soybean (Glycine max [L.] Merr. var. Clark 63) to soil water stress. Leaf elongation, dawn leaf water potential, transpiration rate, and nutrient uptake in stressed rice declined earlier than in maize and soybean. Maize and soybean, compared with rice, maintained high dawn leaf water potential for a longer period of water stress before leaf water potential. Nutrient uptake under water stress conditions was influenced more by the capacity of the roots to absorb nutrients than by transpiration. Transport of nutrients to the shoots may occur even at reduced transpiration rate It is concluded that the ability of maize and soybean to grow better than rice under water stress conditions may be due to their ability to maintain turgor as a result of the slow decline in leaf water potential brought about by low, transpiration rate and continued uptake of nutrient, especially K, which must have allowed osmotic adjustment to occur.
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  • 51
    ISSN: 1573-5036
    Keywords: calcium deficiency ; Na/Ca ratio ; Na/K ratio ; rice ; saline culture solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two experiments were conducted in saline culture solution to find out the causes of rolling and bleaching of young leaves of rice, observed previously in experiments on coastal saline-sodic soil. Symptoms similar to those methioned above were observed on young leaves of cv. KS282 in saline culture solution with Na/Ca ratios of 100 or greater. These symptoms were due to Ca deficiency but not of Cu, since Cu concentration was higher in saline shoots than in the control. The decreasing Na/K or Na/Ca ratio in the saline solution decreased Na and Cl concentration in the shoot. In addition to salinity, Na/Ca and Na/K ratios of the growth medium significantly influenced the shoot and root growth of rice.
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  • 52
    ISSN: 1573-5036
    Keywords: floodwater ; nitrogen ; phosphorus ; potassium ; oxygen ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Concentrations of N, P and K were measured in floodwater and in floating rice cultivars growing at up to 2m water depths in the central flood plain of Thailand. Concentrations of N, P and K in floodwater were often higher than those reported for oligotrophic lakes, nevertheless the floodwater contained 4–45 times less K and 15–90 times less N than concentrations reported in most soil solutions. P concentrations were similar in the floodwater and in most soil solutions. Concentrations of nutrients in leaves indicated there may be deficiencies of P at two sites and a deficiency of N at one of two sites. Data are discussed in terms of reduced nutrient uptake in rice fields at low O2 concentrations which have recently been measured in these areas.
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  • 53
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    Plant and soil 92 (1986), S. 153-157 
    ISSN: 1573-5036
    Keywords: Liming ; Nitrate leaching ; Nitrification ; N-mineralization ; Rain forest ; Soil acidity ; Tropics ; Ultisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We studied the effect of liming on the rates of mineralization and nitrification in a coarse-textured kaolinitic Ultisol. Soil samples were taken from field plots which received lime rates from 0 to 4mt/ha three years prior to the study. The pH of the soil samples varied from 4.2 to 6.1. Ammonification of soil organic N and added urea source proceeded readily and was not affected by lime rate. Nitrification occurred in both limed and unlimed soils but the rate of nitrification depended upon the rate of lime application. Soil pH, exchangeable Ca and exchangeable A1 were significantly correlated with the amount of NO3-N accumulated at the end of the 65 days incubation period. Nitrification of NH4-N from ammonium sulfate was absent in soils receiving lower rates of lime which gave pH values ranging from 4.2 to 4.8. Added ammonium source was nitrified readily after a 3-week delay period in the soil (pH 6.1) which received a higher rate of lime (4 mt/ha).
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  • 54
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    Plant and soil 94 (1986), S. 313-320 
    ISSN: 1573-5036
    Keywords: Alkali soil ; Ammonia volatilization ; Nitrification ; Phenylphosphorodiamidate ; Rice ; Urea ; Urease inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In order to improve nitrogen recovery by rice, the effect of a urease inhibitor phenylphosphorodiamidate (PPD) on the efficiency of fertilizer urea was studied in laboratory and greenhouse. Addition of PPD to urea (5% w/w) delayed urea hydrolysis by 3 to 4 days and reduced ammonia volatilization from 45% (without PPD) to 8.5% (with PPD). Ammonia volatilization obeyed first order kinetics. Urea hydrolysis was sufficiently strongly inhibited to match the nitrification potential of the soil. N application to rice by three different modes showed that a delayed mode (4 splits) was superior to two conventional modes (3 splits) in nitrogen recovery and fertilizer efficiency since it met nitrogen requirement of plants at reproductive stage. In 2 out of 3 modes of application, there was a 14% increase (relative) in grain yields and dry matter, and 6.8% increase in N uptake efficiency on application of PPD along with urea. The results indicate that urease inhibitors like PPD can be effectively used to block urea hydrolysis, reduce ammonia volatilization losses and improve N use efficiency by rice.
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  • 55
    ISSN: 1573-5060
    Keywords: Orvza sativa L. ; rice ; drought tolerance ; genetics ; leaf water potential ; root pulling resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Avoidance of drought stress is commonly associated with root system characteristics and root development. The inheritance of root pulling resistance in rice (Oryza sativa L.) was investigated and its relationship with visual field scores for drought tolerance was studied. Transgressive segregation for high root pulling resistance was observed in 3 crosses (high x high, low x high, and intermediate x intermediate). Both dominant and additive genes control the variation. F1 superiority for high root pulling resistance was observed and could be exploited in an F1 hybrid breeding program. F2 distribution curves indicated that plants highly resistant to root pulling can be obtained not only from low x high and high x high crosses, but also from intermediate x intermediate crosses. Root pulling resistance in rice has a low heritability (39 to 47%). Thus, breeding for a high root pulling resistance may best be accomplished by selection based on line means rather than individual plant selection. Field screening showed significant differences in leaf water potential among random F3 lines. F3 lines with higher leaf water potential had better visual scores for drought tolerance. Visual drought tolerance scores were correlated with root pulling resistance. Plants with high root pulling resistance had the ability to maintain higher leaf water potentials under severe drought stress. The usefulness of the root pulling technique in selecting drought tolerant genotypes was confirmed.
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  • 56
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    Euphytica 38 (1988), S. 261-269 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; amylose content ; single grain analysis ; cooking characteristics ; dosage effects ; dull endosperm ; translucent endosperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The inheritance of low and very low amylose contents in six rice crosses and their reciprocals was studied by single grain analysis of parents F1, F2, B1 and B2 seeds. To minimize the environmental effects, the seeds of all generations of all crosses were produced in a single season. The results indicated different dosage effects in different crosses. One major gene was found to govern a difference of 6–12% in amylose content in low and intermediate amylose parents. Very low amylose content was similarly found to be governed by one major gene in crosses between very low- and low-amylose content parents. Minor genes and modifiers also seem to play some role. In the cross between two low amylose parents differing by about 2.5% in amylose content, the differences appeared to be controlled by some minor genes and modifiers. The selection program in different crosses has been suggested.
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  • 57
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    Euphytica 40 (1989), S. 97-102 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; ratooning ability ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Genetic analysis of generation means of F1, F2, F3, F4, and the parental populations of the cross IR10154-23-3-3A/IR15795-232-3-3-2 for ratooning ability was conducted. Good ratooning ability is a recessive trait. The parents differed by at least two pairs of major genes for ratooning ability. A large proportion of transgressive segregants in F2 suggested that the expression of ratooning ability is influenced not only by major genes but also by modifiers. Broad-sense heritability estimates computed by different methods ranged from 0.66 to 0.88. Narrow-sense heritability by the F4–F3 regression method was 0.39. The heritability estimates were 0.42 and 0.33 by the variance component method. The prevalence of additive x additive type of gene effects along with prominent additive effects imply some scope for selection in the segregating generations. However, non-additive type of gene action also affects the expression of ratooning ability.
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  • 58
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    Euphytica 42 (1989), S. 35-40 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; epistasis ; additive ; dominance ; genetic system ; homozygote x heterozygote ; heterozygore x heterozygote
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The triple test cross analysis in rice brought out that significant epistasis is present for most of the characters in the three crosses except for 100 grain weight in two crosses (Co 39 × Co 41) and (Co 39 × Co 40) and plant height in one cross (Co 39 × IR 20). Epistasis of ‘i’ (homozygote × heterozygote) and ‘l’ (heterozygote × heterozygote) interactions are also detected in all the three crosses. The D component was significant for all the traits in the three crosses and H was significant in cross Co 39 × Co 41 for all characters. For tiller number in cross Co 39 × IR 20 and for tiller number and 100 grain weight in cross Co 39 × Co 40, the H component was not significant. In all the crosses D component was higher than H.
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  • 59
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    Euphytica 42 (1989), S. 265-268 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; photosynthesis ; grain yield ; genotype ; isozyme ; esterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Four Indica and one Japonica (Tainung 67) of rice (Oryza sativa L.) varieties had an esterase band (tentatively designated as E1), and also had higher photosynthetic ability than other five Japonica varieties without E1 band. The F1 plants of Tainung 67 × Mineyutaka (low photosynthetic ability, no E1 band) showed E1 band and a low photosynthetic ability. Of 34 F2 plants, 28 had E1 band, but 6 had no E1 band of which 5 plants showed a low photosynthetic ability. These results suggest that an esterase gene and one of the photosynthesis gene are linked, and the gene for low photosynthetic ability is dominant. Among 42 new Japonica strains and 2 control varieties bred in Taiwan, most genotypes with E1 band showed higher grain yield potential (grain field/growth days) in local test. Esterase band may be used as a marker for high photosynthesis and grain yield ability in breeding.
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  • 60
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    Euphytica 43 (1989), S. 47-51 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; protein content ; protein quality ; amino acid concentration ; nutritive value ; animal growth test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three breeding lines (F8) of rice, derived from cross between Brimful X Koshihikari were tested for protein, amino acid, growth test with rats and yield parameters in field trials. The breeding lines had higher protein and amino acid concentrations than the leading Japanese cultivar Koshihikari, which was grown as a control. Grain yield in the breeding lines was lower than that of Koshihikari (4.5 t/ha). The grain-protein yield of the breeding lines was higher (500 kg/ha) than that of Koshihikari (440 kg/ha). The average gain in weight of rats fed brown and milled rices of the breeding line was 19 and 21 g, respectively: in control rats fed Koshihikari average gain was −1 and 8 g. These results showed that the breeding lines of rice can be developed which possess higher food value than the available varieties.
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  • 61
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    Plant and soil 114 (1989), S. 147-157 
    ISSN: 1573-5036
    Keywords: copper ; DTPA ; flooded ; iron ; manganese ; redox ; rice ; soil catena ; waterlogged ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil samples from surface and sub-surface horizons in the well-drained and poorly-drained members of three soil catenas were incubated under submergence or at field capacity to study the effects of these incubation conditions and prior natural drainage on the solubility of four plant micro-nutrients. Iron, Mn, Zn and Cu were extracted by water using a 1∶1 water:soil ratio. The four micronutrient metals were also extracted by DTPA solutions buffered at either pH 5.3 or pH 7.3 to compare the effectiveness of these two extractants under these incubation conditions with acid soils. Generally the extractability of the nutrients was much affected by the horizon (A, E or B) with A horizons having the greatest amounts of all nutrients and undergoing greater changes in water- and DTPA-extractability during incubation. Soil drainage class (wellvs. poorly drained) had few effects. Incubation moisture regime had major effects on water extractable Fe and Mn with lesser effects on Zn and Cu. Submerged soils generally had the greatest levels of water extractable nutrients, though rice uptake did not reflect this. DTPA at pH 5.3 extracted 2 to 3 times as much Fe, Mn, Zn and Cu as did DTPA at pH 7.3 and about 50 to 100 times as much as did water. Correlations between DTPA extractable nutrients and rice uptake were significant only for Fe and Cu and declined during incubation. The changes in all variables during incubation were complex, being related to soil properties such as organic matter content, pH and mineralogy as well as to incubation conditions.
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  • 62
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    Plant and soil 114 (1989), S. 173-185 
    ISSN: 1573-5036
    Keywords: acidity ; aluminium ; mineral nutrition ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A study of the effect of increasing aluminium concentration in a dilute nutrient solution on various aspects of the mineral nutrient uptake by the rice plant has shown that aluminium exerts a stimulation on dry matter production and nutrient uptake until a concentration threshold was reached. The value of this threshold was influenced by nutrient solution composition and cultivar. Its location could be calculated by adjusting to the experimental points a rate law from enzyme kinetics on substrate inhibition curve. On the other hand, total uptake of aluminium and its concentration in the tops was a monotonic function of aluminium concentration in the nutrient solution, the effect of which was greatly enhanced by increased phosphate concentration. A sensitive cultivar accumulated more aluminium than a resistant one. The effect of phosphate on the alleviation of aluminium toxicity was slight in the range of concentration studied. Nitrogen uptake either as ammonium or nitrate nitrogen was clearly influenced by aluminium concentration when its instantaneous value was measured by the technique of the continuously flowing culture solution. The ammonium uptake rate of two cultivars different in sensitivity to aluminium was such that the sensitive variety took up less ammonium and acidified less the culture solution flowing through the root sysstem with a residence time of a few hours. Minor elements concentration in the tops of the rice plants did not seem to be greatly influenced by aluminium with the notable exception of manganese, the uptake of which was clearly depressed by increasing aluminium concentration. Attempts were made at using the speciation of the nutrient solutions with or without aluminium complexation by fluoride in order to rank the various ionic forms of aluminium according to their toxicity. It seems that the well-known result of primary toxicity due to the free Al-ion is also true for rice but that some toxicity is associated with the AlSO4-ion.
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  • 63
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    Plant and soil 117 (1989), S. 275-286 
    ISSN: 1573-5036
    Keywords: bronzing ; chloride ; iron toxicity ; magnesium ; Nigeria ; phosphorus ; potassium ; rice ; sulfate ; sulfur ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rice plants with bronzing, collected from fields in central and southern Nigeria, where the soils consisted of Tropaquent, Tropaquult and Tropaquept, showed higher iron and lower potassium, phosphorus, and magnesium concentrations than plants with little or no bronzing. Pot experiments with the soils indicated that the severity of the bronzing was affected not only by the iron concentration in the shoots but also by the potassium concentration. The application of chloride compounds to the soil increased severity of the bronzing and lead to deterioration of growth, whereas the application of sulfate compounds was beneficial. The application of potassium sulfate reduced the severity of bronzing and increased the dry matter production of rice plants grown in the field. The concentration and accumulation of potassium in the shoots increased when the bronzing severity decreased and the iron concentration was decreased by the dilution effect caused by the increased dry matter production.
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  • 64
    ISSN: 1573-5036
    Keywords: Ammonification ; Clay soil ; Exchangeable ammonium ; Grassland ; Incubation ; Kinetics ; Nitrate ; Nitrification ; N cycle ; N mineralization ; Soil Moisture ; Soil temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Net mineralization of N and net nitrification in field-moist clay soils (Evesham-Kingston series) from arable and grassland sites were measured in laboratory incubation experiments at 4, 10 and 20°C. Three depth fractions to 30 cm were used. Nitrate accumulated at all temperatures except when the soil was very dry (θ=0.13 cm3 cm−3). Exchangeable NH4-ions declined during the first 24 h and thereafter remained low. Net mineralization and net nitrification approximated to zero-order reactions after 24 h, with Q10 values generally 〈1.6. The effect of temperature on both processes was linear although some results conformed to an Arrhenius-type relationship. The dependence of net mineralization and net nitrification in the field soil on soil temperature (10 cm depth) and moisture (0–15, 15–25, 25–35 cm depths) was modelled using the laboratory incubation data. An annual net mineralization of 350 kg N ha−1 and net nitrification of 346 kg N ha−1 were predicted between September 1980 and August 1981. The model probably overstressed the effect of soil moisture relative to soil temperature.
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    Plant and soil 86 (1985), S. 425-439 
    ISSN: 1573-5036
    Keywords: Ammonium ; Chloride ; Growth ; Inhibition ; Monod model ; Nitrification ; Soil ; Sulphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Following the addition of 0–75 μmole N g−1 as ammonium chloride or ammonium sulphate to a sandy loam soil the nitrate formed was measured daily for a period of 15–17 days. The nitrate produced as a function of time was described using the Monod equation for microbial growth. An optimisation technique is described for obtaining, from the nitrification time course data, the maximum specific growth rate, the affinity constantant and an index limited by the concentration of ammonium in soil solution. Additions of more than 7.3 μmoles N g−1 soil as ammonium chloride were found to inhibit nitrification. The inhibition was interpreted as being caused by osmotic pressure or by chloride ion. A similar effect was not found with ammonium sulphate, because the salt concentration in the soil solution was restricted by the precipitation of calcium sulphate. The model developed was capable of accounting for nitrate production in the soil under non-steady state conditions of substrate concentrations and nitrifier biomass.
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  • 66
    ISSN: 1573-5036
    Keywords: Bacteria ; Fungi ; Mineralization ; Nitrification ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Microbial numbers in the forest floor and mineral soil (Al horizon) under large individual western hemlock (Tsuga heterophylla) and western redcedar (Thuja plicata) trees were compared. The lower pH and base saturation of hemlock samples was associated with higher fungal spore counts while cedar samples had higher total microbial counts and populations of ammonium oxidizing bacteria. Nitrogen mineralization rates were greater in laboratory incubations of hemlock soil but nitrification was only observed in incubations of cedar soil. These differences in nitrogen mineralization and nitrification are aspects of species-specific nutrient cycling regimes.
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  • 67
    ISSN: 1573-5036
    Keywords: Ammonification ; Groundwater pollution ; Hydrolyzable-N ; Nitrification ; Phosphatase ; Urease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The aim of this work has been to determine the effect of sterilized and non-sterilized, acrobically or anaerobically digested sewage sludges on urease and phosphatase activities, on populations of nitrite oxidizers and on some chemical properties in laboratory conditions and for long incubation periods. Both urease an phosphatase activities were affected when anaerobic sludges were added to the soil. The inhibitory effects on both enzyme activities attributed to the presence of heavy metals were probably masked by the additional source of organic matter both with acrobic and anaerobic sludges. The level of the NO 2 − oxidizer populations was higher in the aerobic than in the anaerobic sludge amended soil. Ammonia-N concentration were increased when the soil received sludges reflecting a higher mineralization rate probably due to a stimulation of the indigencous ammonia producing microorganisms since differences between non-sterilized and sterilized treatments were minimal or absent. Nitrate-N concentrations increased in amended soils and care must be taken to restrict as much as possible the downward movement of nitrate in order to minimize ground-water pollution.
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  • 68
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    Plant and soil 85 (1985), S. 219-227 
    ISSN: 1573-5036
    Keywords: Leaching ; Nitrification ; Nitrogen fertilizer ; Salinity ; Urea hydrolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We studied the transport and transformation of urea under steady-state conditions in two soils and at three water salinities (1.0, 5.0, and 10.0 dS/m) using laboratory soil columns. A mathematical model that considers diffusion, convection, adsorption and first-order kinetic transformation of nitrogen was used to describe measured effluent concentration of the two nitrogen species. Increasing salt levels in the applied water decreased the hydrolysis of urea in the two soils studied with first-order rate coefficients decreasing from 0.015 to 0.009 h−1 in the fine sandy loam, and from 0.075 to 0.015 h−1 in a silty loam. Similarly, the nitrification rate decreased by 50% and 70% in the two soils as salinity increased. The rate coefficients measured in the leaching studies were much smaller than measured in incubation-type experiments. Calculated half-lives for urea and NH 4 + provided a method interpreting the kinetic rate coefficients as a function of the experimental conditions.
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  • 69
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    Plant and soil 83 (1985), S. 47-53 
    ISSN: 1573-5036
    Keywords: EUF-N fractions ; Nitrification ; NO3 leaching ; Slurry-N ; Dicyandiamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Increasing quantities of slurry (30, 60 and 90 m3/ha as well as 60 m3/ha + DIDIN) were applied to two sandy soils both in September and in December 1982. During the 1982/83 winter EUF-N was determined in soil horizons (0–30 cm, 30–60 and 60–90 cm). EUF-NO3 and EUF-Norg clearly reflected the different quantities of slurry applied. The retarding effect of DIDIN on nitrification could also be demonstrated by means of the EUF-N contents. Due to the mild and humid climate prevailing in the winter of 1982/83 slurry-NO3 of the September applications had obviously been leached out of the 0–60 cm soil layer in all treatments by February and even out of the 60–90 cm layer by March 24. Translocation of NO3 was also observed for slurry applied in December. But in this case on March 24 the EUF-NO3 contents in the 60–90 cm layer still reflected the quantities of slurry applied four months earlier. After slurry application the EUF-Norg fraction of a soil initially consists mainly of NH 4 + which is rapidly oxidized to NO3 and transferred in this form to deeper layers. As a consequence a rapid decline in EUF-Norg fraction is observed. It could therefore be expedient to consider the Norg and EUF-NH 4 + fractions separately when slurry applications are concerned.
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  • 70
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    Nutrient cycling in agroecosystems 12 (1987), S. 53-65 
    ISSN: 1573-0867
    Keywords: balance sheet ; 15N ; urea ; rice ; vertisols ; soil organic carbon ; nitrogen losses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A glasshouse experiment was conducted to study the balance sheet of15N labelled urea at three rates (zero, 31.48 and 62.97 mmol N pot−1) applied to rice under flooded conditions with two moisture regimes (continuous and alternate flooding) using three Australian vertisols differing in organic carbon level. Walkley-Black organic carbon values for the three soils were 0.65, 2.13 and 3.76 for the low carbon (LC), medium carbon (MC) and high carbon (HC) soils respectively. Rice dry weight and nitrogen uptake was significantly affected by N fertilizer rates, water regimes and soils. Alternate flooding gave much lower dry weight and nitrogen uptake than continuous flooding and the LC soil gave lower dry weight and nitrogen uptake than for the MC and HC soils. Recovery of15N labelled urea fertilizer in the rice plant was low (15.4 to 38.4%) and the15N urea not accounted for in the plant or soil and presumed lost was high (36.2 to 76.0%). Recovery was lower and loss higher under alternate flooding and for the LC soil. There was no effect of fertilizer rate. The results obtained stress the need for careful management to reduce losses of nitrogen fertilizer, particularly for soils low in organic carbon.
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  • 71
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    Nutrient cycling in agroecosystems 13 (1987), S. 13-29 
    ISSN: 1573-0867
    Keywords: rice ; algicide ; pH ; alkalinity ; urea fertilizer ; NH3 volatilization ; N loss ; fertilizer efficiency ; algae ; terbutryne
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract When urea or ammoniacal-N fertilizers are applied to the floodwater of a rice crop, fertilizer use efficiency is often reduced because there are substantial losses of NH3 by volatilization. As pH rises the potential loss increases exponentially due to the increasing dominance of volatile NH3 gas in equilibrium with NH 4 + . We postulate that the daytime pH rise is caused mainly by photosynthesis of algae and Cyanobacteria, and that addition of a suitable photosynthetic inhibitor, concurrently with fertilizer, should suppress the pH rise, thus conserving N in the form of the non-volatile NH 4 + . We selected terbutryne (2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine) as the most promising inhibitor. In rice floodwater fertilized with urea the addition of terbutryne dampened the diurnal fluctuation in pH for 6 days and significantly increased the ammoniacal-N (AN) concentration measured in the floodwater. The concentration of ammonia gas in the air in equilibrium with the water,ϱ 0, which is proportional to the gaseous flux of NH3 at a given wind speed, was substantially reduced by terbutryne addition. Maximum values were reduced by over 50%. Terbutryne reduced the calculated cumulative NH3 emission by 43%, relative to the fertilizer (N + P) control. Terbutryne also suppressed photosynthetic oxygen production. Therefore, it may reduce N fertilizer losses by inhibiting nitrification, an aerobic process, so retarding subsequent denitrification losses of gaseous nitrogen and nitrogen oxides.
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    Nutrient cycling in agroecosystems 15 (1988), S. 101-109 
    ISSN: 1573-0867
    Keywords: rice ; urea supergranules ; sulfur-coated urea ; placement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Conventional as well as modified nitrogen sources and application methods were evaluated under rainfed lowland conditions in heavy clay soils of Bihar, India for 4 years. Modified nitrogen sources, viz. sulfur-coated urea (SCU) and urea super-granules (USG) were tested against prilled urea (PU) under four levels of N (0, 29, 58 and 87 kg N/ha) in the wet season. A high yielding nonphotoperiod sensitive, long duration variety ‘Pankaj’ was grown in all the four years. Point placement of USG and basal incorporation of SCU resulted in significantly higher panicle numbers per square meter, 100 grain weight and grain yield at all the levels of N tested. The unfilled grain percentage was lower in USG and SCU treatments. Regression analysis using a multifertilizer response model (MRM) showed that rice responded significantly to PU in three years out of four years, to SCU in four years and USG in three years. Economic analysis viz. input and output analysis based on the price of fertilizer (1 kg N as PU at $0.5; USG and SCU costing 10% more than PU), rough rice (ranging from 18.0 to 20.0 $ per ton) and labour wages at 1.0 $ per man day unit, also showed that USG and SCU are more input efficient than PU.
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    Nutrient cycling in agroecosystems 18 (1988), S. 213-220 
    ISSN: 1573-0867
    Keywords: urea ; organic residues ; residual N ; rice ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The organic materials of vetch straw, isotopically labeled with15N and unlabeled, rice straw and15N-enriched urea were applied to rice in a greenhouse experiment to evaluate the release of available N during the decomposition of vetch material and its uptake by rice, and to measure the effect of organic materials on the efficiency of urea-N utilization by rice. Measurements were made at three sampling stages during the growth period. As expected, vetch material decomposed readily and furnished a continuous supply of N for the growth of rice, although only 18.1% of vetch-N was utilized by the rice crop. However, this was not sufficient to support the survival of all tillers until harvest. After harvest, 70% of vetch-N still remained in paddy soil. The influence of organic materials on urea-N absorption by rice became apparent at about the stage of panicle initiation. The highest urea-N uptake by rice was 42.2% in vetch straw-mixed soil. Otherwise, rice straw retarded urea-N uptake by rice. Nitrogen distribution data indicated that the vetch material would stimulate urea-N uptake by rice plants. The residual effect of vetch material was evaluated by planting Sudan grass immediately after rice was harvested. Only 4.4% of residual vetch-N was utilized in 20 weeks. This low percentage of N uptake and its low availability ratio demonstrated the poor residual effects of this leguminous material.
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  • 74
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    Nutrient cycling in agroecosystems 21 (1989), S. 1-6 
    ISSN: 1573-0867
    Keywords: Corn ; tomato ; rice ; nitrate ; glutamine synthetase ; ammonium assimilation ; glutamate dehydrogenase ; asparagine synthetase ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant growth, ammonium assimilating enzyme activity, and free ammonium in tissue of different plant species were compared in the presence of either NO3 or NH4 forms of N at two pH levels in solution culture. Tomato and corn growth, but not rice growth, was reduced when NH4 was the sole form of N in the solution culture. Ammonium toxicity was more severe at low than higher pH. Glutamate dehydrogenase activity in roots of the three plant species was higher in the presence of NH4 than NO3 nitrogen. Asparagine synthetase activity was very low in roots of the three species regardless of the N form supplied. Glutamine synthetase activity in roots and shoots of rice was much higher than in tissue of tomato and corn. Glutamine synthetase activity in rice increased sharply in the presence of NH4, and much less free NH4 was detected in green tissues compared to tomato plants. Glutamine synthetase appears to be a key factor to detoxify NH4 in the leaves of rice.
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  • 75
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    Irrigation and drainage systems 1 (1987), S. 277-286 
    ISSN: 1573-0654
    Keywords: irrigation ; tubewells ; constraints ; cropping systems ; rice ; equity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The constraints on the effectiveness of twenty one deep tubewell schemes in Tangail, Mymensingh and Jamalpur Districts were studied. Major problems were the difficulty of constructing small earthworks (aqueducts), inconsistencies in credit provision, and the non-availability of HYV rice varieties with appropriate characteristics to exploit the irrigation. Research on farmer's cropping choice is reported, and conclusions aer drawn on issues of equity and project identification.
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  • 76
    ISSN: 1573-5087
    Keywords: cytokinins ; cis-zeatin derivatives ; rice ; grain development ; GC/SIM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rice grains at various growth stages were analysed for endogenous free-base, riboside, ribotide and glucoside cytokinins on the basis of GC/MS and GC/SIM using deuterium-labeled internal standards. Cytokinins identified were trans- and cis-zeatins, trans- and cis-ribosylzeatins, isopentenyladenosine, isopentenyladenosine monophosphate, trans- and cis-ribosylzeatin monophosphates, trans- and cis-zeatin-O-glucosides, trans- and cis-ribosylzeatin-O-glucosides and zeatin-9-glucoside (trans/cis geometry was not determined). The highest amounts of cytokinins were recorded at the early growth stage, namely either heading, anthesis or milk stage, suggesting that cytokinins may play important roles in the development of the grain. Cis isomers of zeatin derivatives were always present and more abundant than trans isomers. It seemed unlikely that cis isomers were released from t-RNAs during the extraction procedure.
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  • 77
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    Plant and soil 94 (1986), S. 369-382 
    ISSN: 1573-5036
    Keywords: Azido nitro benzene ; Nitrapyrin ; Nitrification ; Nitro and nitroso aromatic compounds ; Organic nitrogen ; Phenolic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The conversion of substantial amounts of ammonia nitrogen into organic nitrogen as a direct result of nitrification at neutral pH-values, was monitored in soil suspensions amended with ammonium nitrogen. The influence of the chemolithotrophic nitrifying bacteria was verified by applying nitrapyrin as a selective inhibitor in control experiments. In addition, the role of phenolic compounds was examined by adding α naphthol. The factors influencing the nitrification processi.e. pH, NH 4 + −N, NO 2 − −N, NO 3 − −N were measured during a 60 days incubation period. Nitrification started to be active after 5 and 10 days in the normal and the naphthol spiked soil suspensions respectively; it was inhibited in the nitrapyrin controls. Parallel with nitrification, formation of organic nitrogen was observed. The humic matter fractions were extracted and analyzed by I.R. spectroscopy which revealed the valence vibration ranges of nitro and nitroso groups fixed in different positions on aromatic compounds, both for normal and naphthol spiked samples. High resolution gas chromatography combined with mass spectroscopic analysis indicated the formation of nitrosonaphtholes. In addition a novel organic nitro compound was identifiedi.e. an azido nitro benzene. No nitrogen was fixed in the samples treated with nitrification inhibitor. A mechanism for the fixation of nitrite nitrogen during nitrification is proposed.
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    Plant and soil 94 (1986), S. 383-399 
    ISSN: 1573-5036
    Keywords: Nitrapyrin ; Nitrification ; Organic nitrogen formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The formation of mineral nitrogen species and of organic nitrogen was studied in three different types of soils in relation to the application of the nitrification inhibitor nitrapyrin. The results indicate that nitrification brings about a deficit in total mineral nitrogen and a concomitant surplus in non biomass organic nitrogen. This phenomenon increases with increasing levels of applied ammonium nitrogen and soil organic matter. The phenomenon is considered to be due to the reaction of the transient nitrite formed with soil phenolic compounds and appears to be of significance in all soils in which nitrification occurs, even neutral to alkaline and low carbon soils.
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  • 79
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    Plant and soil 94 (1986), S. 401-409 
    ISSN: 1573-5036
    Keywords: Immobilization ; Labelled fertilizer ; Mineralization ; Mineral nitrogen incorporation %15Natom excess ; Nitrapyrin ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of nitrification on the status of soil organic nitrogen is examined by applying NH 4 + -15N to the soil in the absence and the presence of a selective inhibitori.e. nitrapyrin. Parallel with nitrification, formation of organic nitrogen from the added fertilizer was followed. In the soil examined (pH 6.5, 4% organic carbon),ca. 55% of the fertilizer-N was immobilized during the 60 days incubation period, as a consequence of the nitrification process. Nitrification not only appeared to contribute to the binding of added mineral nitrogen onto soil organic matter, but also to re-immobilization of mineralised soil nitrogen.
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  • 80
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    Plant and soil 97 (1987), S. 37-45 
    ISSN: 1573-5036
    Keywords: Ammonium ; Chloride ; Inhibition ; Nitrification ; Osmotic pressure ; Sorbitol ; Sulphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A short term nitrification assay (〈18 h) was used to assess the effect of high concentrations of different solutes on the rate of nitrate production. High solute concentrations were found to inhibit nitrification and the degree of inhibition was related both to the osmotic pressure of the soil solution and the osmoticum used. Ammonium chloride, ammonium sulphate and sorbitol were used as sources of osmotic pressure. The results showed that, with ammonium salts, no inhibition was observed with pressures less than 2 atm. Above these values, the severity of the inhibition followed the order ammonium chloride〉ammonium sulphate〉sorbitol up to the maximum osmotic pressure studied (25 atm). With ammonium chloride, a pressure of 3.5 atm. was sufficient to cause a 90% inhibition of nitrification rate. The inhibition produced by mixtures of ammonium chloride and sorbitol, each mixture generating an osmotic pressure of 5 atm. in the assay, was also investigated. The results suggest that inhibition by Cl-ion is disproportionate to its contribution to the osmotic pressure of the soil solution. The recovery of the nitrification rate, following exposure to high osmotic pressure solutions, was also investigated. It was found that the recovery of the nitrification rate was only partial, with the extent of the recovery diminishing as the severity of the initial osmotic stress applied increased. These results suggest that both reversible and irreversible mechanisms are involved in the inhibition of nitrification.
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    Plant and soil 97 (1987), S. 189-200 
    ISSN: 1573-5036
    Keywords: Immobilization ; Leaching ; Nitrification ; 15N ; N fertilizers ; Winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field experiments with winter wheat (Triticum aestivum L.) were conducted in two years at two locations using15N-enriched (NH4)2SO4 on Smolan silt loam (Pachic Argiustoll) and Ost loam (Typic Arguistoll) soils. The objective was to relate differences in crop utilization of fertilizer to movement and transformations of the N in a complete factorial experiment having fall and spring applications, banded and broadcast, with and without nitrapyrin. Plant uptake of the 60 kg N/ha applied varied from 31% to 62% with greatest uptake when fertilizer was banded in the spring without nitrapyrin and least uptake from fall and spring broadcast treatments using nitrapyrin. Analysis of single factor effects showed greater crop contents of fertilizer N for spring than fall applications. That was related to immobilization of the applied N. Much more fertilizer N was in inorganic forms during the period of rapid wheat growth with spring applications than with fall. Banding the fertilizer at a depth of 0.05 m resulted in greater plant uptake than broadcasting or banding it on the soil surface. A significant portion of the applied N was immobilized near the point of application. That limited the downward movement of the N placed on the surface, making it less available to plant roots than the N placed 0.05 m deep where soil moisture was more favorable. Use of nitrapyrin resulted in lowered amounts of fertilizer N as NO3-until mid-May for fall treatments and until harvest with spring treatments. That appeared to be the reason for lowered plant uptake when nitrapyrin was used.
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  • 82
    ISSN: 1573-5036
    Keywords: Denitrification ; Leaching ; Legumes ; Nitrification ; Nitrogen ; Tillage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen (N) dynamics were studied in conventional and no-tillage agroecosystems on the Georgia Piedmont. Nitrogen inputs in the form of ammonium nitrate (95 kg-N/ha) and winter legume (crimson clover) residues were compared. The legume provided adequate N for summer crop (grain sorghum) production, but water use by the legume reduced the ability of sorghum to utilize the N. Legume N inputs became availabe to plants more gradually than fertilizer inputs. Weed growth and potential denitrification activity were higher in legume-N treatments than in fertilizer-N treatments. Tillage affected the timing of N avaialbility more than the total amount of available N. Summer crops took up more N under conventional tillage while winter crops took up more N under no-tillage. Denitrification activity was higher under no-tillage but was not a significant output from the agroecosystems. Leaching losses of N differed seasonally between treatments but were not significant in any of the agroecosystems.
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  • 83
    ISSN: 1573-5060
    Keywords: Oryzasativa ; rice ; japonica variety ; indica variety ; O. glaberrima ; O. rufipogon ; wild rice ; cytoplasm substitution line ; cytoplasmic male sterility ; sporophytic type
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary It is shown that the restorer gene Rf j extracted from the Japanese rice variety Akebono is effective on pollen restoration in the cytoplasm substitution line having the nucleus of Oryza glaberrima and japonica or indica cytoplasm of O. sativa, and is of the sporophytic type. The Asian perennial type of the wild rice species O. rufipogon is considered to be the progenitor of O. sativa. Two substitution lines having the cytoplasm of a perennial strain of O. rufipogon from Sri Lanka and the nucleus of O. glaberrima with or without the gene Rf j in homozygous condition have been bred by means of successive backcrosses. These lines have now reached the BC5 generation. Plants of the lines resemble morphologically the recurrent parent, but do not show pollen restoration, indicating that the cytoplasm of the rufipogon strain induced male sterility and that the gene Rf j does not act as the restorer.
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  • 84
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    Euphytica 34 (1985), S. 577-585 
    ISSN: 1573-5060
    Keywords: Oryzasativa L. ; rice ; Xanthomonas campestris pv. ; oryzae ; bacterial leaf blight ; resistance ; induced mutations ; seleetion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Dry seed lots of a rice cultivar, Harebare, susceptible for bacterial leaf blight (BLB), were exposed to thermal neutrons with and without pre-treatment of seed for boron-enrichment, and to gamma-rays. M1 plants of each of the treatments were grown and their seeds were separately harvested. M2 populations were raised in rice fields of a farmer in a region where BLB is epidemic every year, and M2 and control plants which expressed resistant reactions to BLB were selected. M3 and control lines as plant progenies of the selected M2 plants were raised in the same rice fields as in M2 generation in order to investigate their BLB resistance and other agronomically important traits. Variances for disease severity of M2 populations were significantly larger than those of the control population. whereas their means were not singificantly different from that of the control population, suggesting induction of mutations toward both resistance and susceptibility to BLB. Mean disease severity values of the M3 lines from selected M2 plants were significantly smaller than those of the control lines, indicating gains of selection in M2 for quantitative resistance against BLB. Thermal neutrons, especially with boron-enrichment pre-treatment were effective to induce mutations for resistance against BLB. Some M3 mutant lines with quantitatively enhanced resistance against BLB were not modified in other agronomic traits from those of the original cultivar. Significance of the induced quantitative resistance in breeding programmes for BLB resistance is discussed.
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    Euphytica 39 (1988), S. 207-212 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; callus culture ; NaCl-tolerance ; salt tolerance ; organogenesis ; peroxidase activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary NaCl-tolerant calli were selected from two Japonica and two Indica rice (Oryza sativa L.) cultivars on basal media containing 6,000, 9,000, 12,000 or 15,000 ppm NaCl. Frequency of callus formation decreased with the increase of NaCl in the medium, especially in Indica. About half of the calli of Japonica cultivars selected on NaCl-ammended media survived 20,000 ppm NaCl but none of the Indica callus survived. In Japonica, more plants were regenerated from calli selected on all concentrations of NaCl media than from NaCl-free medium. Concentration of Cl- in callus increased dramatically with increased NaCl content but peroxidase activity decreased.
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    Plant and soil 101 (1987), S. 141-143 
    ISSN: 1573-5036
    Keywords: Aeschynomene ; green ; manure ; Rhizobium ; rice ; stem-nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A preliminary investigation was conducted in 1 m2 microplots using two stem nodulatedAeschynomene species,A. afraspera andA. nilotica, to evaluate their beneficial effects as green manure on the yield and the nitrogen content of rice.A. afraspera andA. nilotica yielded 7.5 and 9.2 kg m−2 of fresh matter, (42.3 and 53.2 g N m−2 respectively) in 7 weeks growth. Green manuring increased grain yield by more than 80% over the control and by 45% over rice fertilized with 10 g N-urea m−2. The nitrogen content of grain and straw was significantly higher in treatments with Aeschynomene green manure than in other treatments.
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  • 87
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    Plant and soil 101 (1987), S. 235-240 
    ISSN: 1573-5036
    Keywords: anabaena ; axenic culture ; cyanobacteria ; germination ; nostoc ; plant growth regulators ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A screening of 133 cyanobacterial strains in logarithmic growth phase was done to study their effects on rice germination and growth. In unialgal, non axenic culture 30% of the strains had no effect, while 70% of the strains had a negative effect on germination. In contrast, growth of rice was stimulated by 21% of the isolates and inhibited by 12%. Although 57% of the unicellular strains had a positive effect and many Nostoc strains had a negative one, it was not possible to correlate specific effects with taxonomic groups. Among the eight strains showing a stimulatory effect on growth only Anabaena 77S19 remained effective in axenic culture. Partitioning Anabaena 77S19 exudates into three fractions revealed that the organic fraction was more inhibitory. From this work it is concluded that presoaking rice seeds in a cyanobacterial culture should be done with caution or avoided altogether.
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  • 88
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    Plant and soil 93 (1986), S. 347-357 
    ISSN: 1573-5036
    Keywords: Dew ; Grasslands ; Nitrification ; Nitrogen ; Semiarid ecosystems ; Soil texture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The depth distributions of rates of net nitrogen mineralization and nitrification were measured in a series of field and laboratory incubations. Field studies suggested that the highest rates of mineralization and nitrification occurred in the surface 2.5 cm such that forty to sixty percent of the N mineralization in 20-cm soil column occurred in the surface 2.5cm. Some upward nitrate movement occurred but laboratory studies suggested that surface rates were not an artifact of nitrate mobility alone. Microclimatic data indicate that either dew or upward movement and condensation of soil water vapor may drive biological activity at the soil surface. High rates of N mineralization even in dry horizons were sustained as long as water was stored within the 0-to 20-cm depth. High rates of nitrification were found in all incubations, and field measurements showed NO 3 − to be the predominant form of inorganic N, despite previous characterization of the shortgrass steppe as an NH 4 + -dominated system.
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  • 89
    ISSN: 1573-5036
    Keywords: Nitrification ; Organic matter ; Sulphur cycle ; Sulphur oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of wheat straw and pressed sugar beet pulp on sulphur oxidation were determined in a loam soil amended with 1% (w/w) elemental sulphur. Wheat straw stimulated the oxidation of elemental sulphur over the first 2 to 3 weeks of the incubation period, resulting in an increase in LiCl-extractable sulphate. After 4 to 7 weeks incubation however, the only significant increase in soil sulphate followed the 1% straw addition, while at week 7 sulphate concentrations in the 0.25% and 5.0% straw amended soils were lower than the control. Pressed sugar beet pulp (1% w/w) initially stimulated the oxidation of elemental sulphur in the soil, but by weeks 3 to 7 of the incubation period rates of oxidation in pulp-amended soils were lower than the control. Towards the end of the incubation period however, sulphate concentrations in the amended soils exceeded the control values, significantly so by week 11. The concentration of thiosulphate and tetrathionate also increased in soils receiving sugar beet pulp. Nitrification was inhibited in soils in which sulphur oxidation was actively occurring. Although possible alternatives are mentioned, such inhibition appears to result from a decrease in soil pH brought about by the oxidation of elemental sulphur to sulphuric acid.
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  • 90
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    Plant and soil 97 (1987), S. 445-450 
    ISSN: 1573-5036
    Keywords: Dentrification ; Enzyme assays ; Most probable numbers ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three methods for assaying nitrification and denitrification were compared in agricultural field plots in the Southeastern USA. Nitrification was measured using the chlorate inhibition enzyme assay, by measuring (NO 3 − −N) production in controlled incubations and by most probable number (MPN) determinations. Denitrification was measured by the phase I enzyme assay, by incubation of soil cores and by MPN determinations. The methods were compared in terms of their representation of seasonal patterns and treatment differences. The enzyme assays were most effective for showing treatment differences because they measure maximum potential enzyme biomass activity which is an integrated product of treatment effects. The incubation methods required minimal alteration ofin situ soil conditions but were confounded by other biological processes and by high spatial and temporal variabiltiy. MPN determinations were time consuming and were least effective for illustrating treatment differences and seasonal patterns.
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  • 91
    ISSN: 1573-5036
    Keywords: Ammonium ; Disease suppression ; Gaeumannomyces graminis var.tritici ; Liming ; N fertilizer sources ; Nitrate ; Nitrification ; Triticum aestivum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil pH, NH 4 + and NO 3 − concentrations in soil, and take-all root rot of winter wheat grown in the field were measured concurrently from sowing to anthesis in order to relate disease development to liming and N fertilization practices. Experimental variables included soil pH (5.5 and 6.0) and three N sources (NH4NO3, (NH4)2SO4, NH4Cl) banded with the seed at sowing in factorial combination with the same three N sources topdressed in the spring. Take-all severity was increased by increasing soil pH and by fertilization with NO 3 − . Disease severity on crown roots increased exponentially following spring N fertilization and was affected more by soil pH and N-form than was severity on seminal roots. Grain yield ranged from 4.70 Mgha−1 with spring NH4NO3 at soil pH 6.0 to 7.65 Mgha−1 with spring NH4Cl at soil pH 5.5. Sixty-six percent of the variability in grain yield was explained by the number of take-all infected crown roots per tiller at anthesis.
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  • 92
    ISSN: 1573-5036
    Keywords: Barley (Hordeum disticum) ; Denitrification ; Green house experiment ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary To examine the effect of barley roots on denitrification, a pot experiment was designed to compare N2O production and denitrification in soils with and without barley plants. Denitrification, N2O resulting from denitrification and nitrification, and respiration were estimated by incubating pots with soil with and without intact plants in plastic bags at high moisture levels. C2H2-inhibition of nitrous oxide reductase (partial pressure of 10 kPa C2H2) was used to determine total denitrification rates while incubations with ambient air and with C2H2 at partial pressures of 2.5–5 Pa were used to estimate the amounts of N2O released from autotrophic nitrification and from denitrification processes. Other sources of N2O were presumed to be negligible. Potential denitrification, nitrification and root biomass were measured in subsamples collected from four soil depths. A positive correlation was found between denitrification rates and root biomass. N2 was the predominant denitrification product found close to roots; N2O formed by non autotrophic nitrifiers, assumed to be denitrifiers originated in soil not affected by growing roots. Apparently, roots promote denitrification because they consumed oxygen, thereby increasing the anaerobic volume of the soil. The ratio of actual to potential denitrification rates increased over time, especially in the presence of roots.
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  • 93
    ISSN: 1573-5036
    Keywords: Ammonium oxidation ; Clusters ; Modelling ; Nitrification ; pH effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The time course of nitrate production is different in different soils; in some soils, nitrate is produced at a constant rate while in others, this rate increases with time, often exponentially. Mechanistic models, based on the Monod equations, cannot account for a constant rate of nitrification. All such mechanistic models make the implicit assumption that the nitrifying organisms are distributed uniformly as single cells throughout the soil volume, while in reality, the cells might be expected to occur in small clusters formed by repeated cell division. This paper examines the effects of allowing the ammonium oxidising cells to occur in evenly distributed clusters of cells of equal volume. One effect of clustering would be the lowering of soil pH around the cluster, caused by differences in the rates of acid production and diffusion. The effects of this pH depression were examined using a mathematical model. In general, it was found that the effect of clustering was to reduce the rate of ammonium oxidation. In extreme cases, in which the fraction of the soil volume occupied by the cells was assumed to be small, the model predicted a constant rate of ammonium oxidation with time in contrast to the increasing rate with time predicted by a model based on a uniform single cell distribution. The clustering model was therefore capable of reproducing the different time courses of ammonium oxidation reported in the literature. The differences between the time courses of ammonium oxidation predicted using the two different assumptions was affected by the initial pH of the soil. This observation suggested a possible experimental test of the clustering hypothesis.
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  • 94
    ISSN: 1573-5060
    Keywords: Oryza ; rice ; Wx protein ; amylose content ; gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary To get an insight in the gene regulation at the waxy locus of rice, the Wx gene product (Wx protein) controlling the synthesis of amylose was examined by electrophoretic techniques. Among nonwaxy rice strains, two different alleles, Wx a and Wx b, were found at the waxy locus. Wx a drastically enhanced the quantitative level of Wx protein as well as the amylose content in endosperm starch as compared with Wx b. The alleles acted additively in triploid endosperms. This implies that regulatory elements responsible for the Wx gene expression are on the same chromosome. The distribution patterns of Wx a and Wx b in five species of Oryza revealed that the regulatory changes are closely related to racial differentiation within a common rice species (O. sativa), suggesting that Wx b might have been selected for through the difference in grain quality during domestication.
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  • 95
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    Euphytica 35 (1986), S. 751-760 
    ISSN: 1573-5060
    Keywords: Photoperiod sensitivity ; rice ; Oryza sativa L. ; plant height ; flowering duration ; heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The degree of photoperiod sensitivity was studied in the F5 and F6 of three crosses between sensitive and insensitive rice cultivars under field conditions. Photoperiod sensitive lines could be identified as nonflowering lines in a February-seeded nursery. These lines had a short critical daylength (i.e. late flowering date). The strongly sensitive lines also had a high degree of photoperiod sensitivity, measured as the ratio of the difference in growth duration for two seeding dates to the difference in seeding dates in the main wet season. Some lines, however, with a relatively high degree of sensitivity and a longer critical daylength, were able to flower in the February-seeded nursery. In the cross KDML 105 × IR42, photoperiod sensitivity showed a bimodal distribution, suggesting major gene control. In Latisail × IR28 and KDML 105 × IR50, the inheritance was not clear. In KDML 105 × IR42, 37 out of 97 F5 lines were strongly sensitive and in KDML 105 × IR50, 7 out of 95 F5 lines were strongly sensitive. Thus the choice of the insensitive parent greatly influenced the number of strongly sensitive lines recovered. Degree of photoperiod sensitivity was positively correlated with plant height in the wet season. In the dry season this was not observed, because the sensitive lines flowered earlier.
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  • 96
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    Euphytica 35 (1986), S. 1023-1028 
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; tissue culture ; streptomycin resistance ; callus clone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Callus tissues were initiated from seed, radicle and anther cultures of rice (Oryza sativa L.) in order to study the effect of streptomycin on callus growth. Our results showed that the addition of 250 μg/ml or more streptomycin to the culture medium caused a significant inhibition of callus proliferation. The degree of inhibition depended upon the genotype, the drug concentration and the tissue source of callus. Selection of resistant cell lines began with seed and immature embryo cultures grown on various levels of streptomycin. The fastest growing sectors of callus were subcultured for additional selection. In this way, a total of 11 comparatively vigorous callus clones were isolated after 7 or 12 subcultures. Some of these clones exhibited a significant increase of resistance index when compared with unselected starting material. After 5 or 6 selection cycles, 79 plantlets were regenerated from resistant callus, but none grew to maturity because all were white (albino).
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  • 97
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphorus ; potassium ; rice ; low temperature ; reproductive stage ; flag leaf ; auricle distance ; spikelet sterility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Spikelet sterility induced by low temperature at the reproductive stage of rice increased further with the increase of nitrogen supply. Spikelet sterility in Fujisaka-5 did not increase due to low temperature when nitrogen supply was increased from 10 to 40 ppm and at 80 ppm nitrogen supply it was less affected than IR36. Total nitrogen content in the leaves increased with the increase of nitrogen supply and was forced to be associated with the spikelet sterility induced by low temperature. Based on auricle distance between the last two leaves, the most sensitive stage to low temperature damage differed in Fujisaka-5 and IR36. Spikelet sterility induced by low temperature for 10 days was very high in both the varieties and the effect of nitrogen was not clear. The effect of phosphorus on the spikelet sterility induced by low temperature at reproductive stage was not clear except that at the highest phosphorus (P) level (10 ppm) the spikelet sterility increased both in Fujisaka-5 and IR36. Spikelet sterility induced by low temperature at the reproductive stage of rice decreased with the increase of Potassium (K) supply in both Fujisaka-5 and IR36. With an increase of potassium supply, nitrogen (N) content decreased in the leaves and panicles and spikelet sterility induced by low temperature decreased with an increase of the K to N ratio in the leaves and panicles. The results suggest that potassium might play a major role to counteract the low temperature damage at the reproductive stage of rice.
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  • 98
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    Plant and soil 120 (1989), S. 165-170 
    ISSN: 1573-5036
    Keywords: Azolla ; phosphorus ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The trials to use Azolla as a green manure for rice culture were made in the Niger basin.Azolla pinnata (Niger isolate) was used for the experiments. The effect of phosphorus on the growth and N2-fixation was examined in the field and in the laboratory. The growth rate and N content were maximum with P 3.1 ppm culture solution under laboratory conditions. The threshold P content for the growth was 0.5–0.6% in the dry matter. Maximum N content was 4.1% in the laboratory culture. In the field culture, the effect of P fertilizer on the growth and N yield of Azolla was tested. The split application of 6.5 kg P ha−1 per 13 days was most effective in stimulating the growth of Azolla. One kg of P as triple superphosphate produced 3.66 kg N in the Azolla. Maximum growth rate and N content in the field trials was 4.3 days (doubling time) and 2.3%, respectively. The lower productivity in the field in comparison with the laboratory culture was considered to be due to higher temperature and light intensity. the growth of Azolla was suppressed in the hot season in the Niger basin. The growth rate and N content were reduced during the high temperature period over 30°C on an average. The effect of inoculation of Azolla on rice yield was tested in the field experiment. The grain yield was increased 27% by Azolla incolation over the treatment without Azolla inoculation in — N fertilizer treatments. While the growth of Azolla with rice plants did not attain saturated density (1.8 kg fresh weight m−2), the effect on the grain yield was comparable to 40 kg N ha−1 as urea.
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  • 99
    ISSN: 1573-5036
    Keywords: Acidification ; Air pollution ; Aluminium ; Ammonium sulphate ; Nitrification ; Nutrient leaching ; Pinus nigra var.Maritima ; Potassium deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary As a result of air pollution, considerable deposition of ammonium sulphate occurs on vegetation and soil in the vicinity of chicken farms and fields dressed with animal slurry. A clear relation exists between this ammonium sulphate deposition and the distance to certain agricultural activities. Field investigations and ecophysiological experiments both show that the needles ofPinus nigra var.maritima (Ait.) Melville take up ammonium and excrete potassium, magnesium and calcium. This often results in potassium and/or magnesium deficiencies and may lead to premature shedding of needles. The high levels of nitrogen in the needles are strongly correlated to fungal diseases. Whether the observed cation leaching will result in disturbed nutrient budgets depends mainly on soil conditions. Leaching of K, Mg and Ca from the soil, caused by ammonium sulphate, may further inhibit nutrient uptake. Field investigations show a clear correlation between increased ratios of NH4 to K, Mg and Ca in the soil solution and the damage to pine forests.
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  • 100
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    Plant foods for human nutrition 36 (1986), S. 119-137 
    ISSN: 1573-9104
    Keywords: rice ; legume mixtures ; utilization of protein ; energy ; zinc ; iron and copper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Protein, energy and mineral utilization were examined in growing rats fed cooked, dry legume seeds in combination with polished rice. The legumes tested included 3 varieties of common beans, black, white and brown (Phaseolus vulgaris), lentils (Lens esculenta) and peas (Pisum sativum). The rice:legume mixtures (1:1 N ratio) were the only dietary sources of protein, Zn, Fe and Cu. The rice:black bean mixture was also tested at a 4:1 N ratio. Nutrient utilization was studied by balance trials and mineral utilization was further assessed by tissue analyses. True protein digestibility (TD) and energy digestibility of the rice:legume (1:1) mixtures were high. Biological value (BV) varied only little but was lowest in the rice:lentil mixture. The rice:brown bean mixture had the lowest amount of utilizable protein (UP). The (1:1) rice:legume mixtures did not adversely affect Fe status, as measured by liver Fe content and blood hemoglobin and hematocrit, or Cu status, as measured by liver Cu content and plasma ceruloplasmin. However, femur zinc content indicated a sub-optimal Zn status. Increasing the dietary N from rice in combination with black beans resulted in a substantial improvement of BV, NPU and Zn status of the animals but had a negative effect on UP and Fe status of the rats.
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