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  • 1
    Electronic Resource
    Electronic Resource
    Nitrification activity in submerged soils and its relation to denitrification loss (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 16-22 
    Details
    ISSN: 1432-0789
    Keywords: Nitrification activity ; Submerged soils ; Denitrification ; 15N balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrification activity (formation of NO 2 − + NO 3 − per unit soil weight) was measured in the surface layer of 15 presubmerged soils incubated in petri dishes under flooded but aerobic conditions. soils with pH above 5 nitrified quickly, whereas soils with pH below this level did not nitrify or nitrified slowly. The pH values between 7 and 8.5 were optimal for nitrification. Organic-matter levels in the 15 soils of our study did not influence their nitrification activities. In a follow-up greenhouse pot study, after a period of 3 weeks, 15N-balance measurements showed that the loss of N through apparent denitrification did not follow the nitrification patterns of the soils observed in the petri dishes. Apparent denitrification accounted for 16.8% and 18.9% loss of 15N from a soil with insignificant nitrification activity and a soil with high nitrification activity, respectively. These results, thus, indicate a lack of correspondence between the nitrification activities of soil and the denitrification loss of N when the former was measured in the dark and the latter was estimated in the light. Soils that nitrified in the darkness of the incubator did not nitrify in the daylight in the greenhouse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260726
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  • 2
    Electronic Resource
    Electronic Resource
    Biological nitrogen fixation in faba bean (Vicia faba L.) in the Ethiopian highlands as affected by P fertilization and inoculation (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 353-359 
    Details
    ISSN: 1432-0789
    Keywords: Keywords Soil nitrogen balance ; Crop rotation ; Seed yield ; Nitrogen-15 isotope dilution technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  N2 fixation by leguminous crops is a relatively low-cost alternative to N fertilizer for small-holder farmers in developing countries. N2 fixation in faba bean (Vicia faba L.) as affected by P fertilization (0 and 20 kg P ha–1) and inoculation (uninoculated and inoculated) with Rhizobium leguminosarium biovar viciae (strain S-18) was studied using the 15N isotope dilution method in the southeastern Ethiopian highlands at three sites differing in soil conditions and length of growing period. Nodulation at the late flowering stage was significantly influenced by P and inoculation only at the location exhibiting the lowest soil P and pH levels. The percentage of N derived from the atmosphere ranged from 66 to 74%, 58 to 74% and 62 to 73% with a corresponding total amount of N2 fixed ranging from 169 to 210 kg N ha–1, 139 to 184 kg N ha–1 and 147 to 174 kg N ha–1 at Bekoji, Kulumsa and Asasa, respectively. The total N2 fixed was not significantly affected by P fertilizer or inoculation across all locations, and there was no interaction between the factors. However, at all three locations, N2 fixation was highly positively correlated with the dry matter production and total N yield of faba bean. Soil N balances after faba bean were positive (12–58 kg N ha–1) relative to the highly negative N balances (–9–44 kg N ha–1) following wheat (Triticum aestivum L.), highlighting the importance of rotation with faba bean in the cereal-based cropping systems of Ethiopia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000258
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  • 3
    Electronic Resource
    Electronic Resource
    Beneficial effects of blue-green algae and Azolla, excluding supplying nitrogen, on wetland rice fields: a review (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 329-342 
    Details
    ISSN: 1432-0789
    Keywords: Key words Azolla ; Blue-green algae ; Nutrient availability ; Wetland rice ; Ammonia volatilisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The role of blue-green algae (BGA) and Azolla in supplying N to rice fields is well documented. In addition, they also bring about, directly or indirectly, a number of changes in the physical, chemical and biological properties of the soil and soil-water interface in rice fields. For example, BGA liberate extracellular organic compounds and photosynthetic O2 during their growth, while Azolla prevent a rise in the pH, reduce water temperature, curb NH3 volatilisation and suppress weeds; and both of them contribute biomass. On decomposing, they influence the redox activity and result in the formation of different organic acids in soil. All such changes brought about by BGA and Azolla in soil may ultimately influence plant-available nutrients and also soil characteristics. An attempt has been made in this review to highlight these effects of BGA and Azolla in rice fields and discuss their possible implications relating to management and productivity of rice-field systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050501
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  • 4
    Electronic Resource
    Electronic Resource
    Labeled nitrogen fertilizer research with urea in the semi-arid tropics (1984)
    Springer
    Plant and soil 80 (1984), S. 3-19 
    Details
    ISSN: 1573-5036
    Keywords: 15N Nitrogen balance ; Nitrogen fertilizer ; Nitrogen loss ; Phenyl phosphorodiamidate ; Sorghum bicolor L ; Urea ; Urea phosphate ; Urea supergranule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary As part of a research program to determine the fate of N fertilizers applied to dryland sorghum in the semi-arid tropics,15N balance studies were conducted with various N sources in the greenhouse. Two American soils, Houston Black clay (Udic Pellustert) and Windthorst sandy loam (Udic Paleustalf), similar in properties to the Vertisol and Alfisol in the semi-arid tropics of India, were employed. Experiments were conducted with large pots containing 20 or 60 kg of soil which was subjected to several watering regimes. The15N not accounted for in the plant and soil was presumably lost. Losses of N on calcareous Houston Black clay were greatest for broadcast urea, 16%–28%. Amendment of broadcast urea with 2% phenyl phosphorodiamidate, a urease inhibitor, reduced N losses only slightly to 15%–20%. Point placement of urea at a 6 cm soil depth reduced losses to 1%–11%. Granule size had no effect on N loss from point-placed urea. Ammonia volatilization was apparently the main N loss mechanism, since N losses from sodium nitrate were less than 7%, except when the soil surface was waterlogged. N losses on the Windthorst soil averaged 30% from urea and 11% from ammonium nitrate. Amendment of urea with urea phosphate to form a 27% N and 13% P product reduced fertilizer N losses but did not increase grain yield on Windthorst soil. N losses were also less from ammonium nitrophosphate than from urea. Band and point placement of urea 6 cm below the soil surface were equally effective in reducing N loss on Houston Black clay. The findings give credence to the recommendation of deep band placement for urea in the semi-arid tropics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02232935
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  • 5
    Electronic Resource
    Electronic Resource
    Alleviating soil fertility constraints to food production in West Africa: Efficiency of nitrogen fertilizers applied to food crops (1991)
    Springer
    Nutrient cycling in agroecosystems 29 (1991), S. 21-33 
    Details
    ISSN: 1573-0867
    Keywords: Nitrogen ; urea ; calcium ammonium nitrate ; cropping density ; N use efficiency ; slow release ; urease inhibitors ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An overview is provided of the N efficiency research conducted within the West African Fertilizer Management and Evaluation Network (WAFMEN). Factors such as N rate, mode of N fertilizer application and choice of N sources for different agroecological zones of West Africa are discussed in relation to crop yield response. The interactive effects of cropping density and rainfall on N efficiency and yield are examined with particular emphasis on production of millet in Niger. The potential role of new, slow-release fertilizers as well as urea amended with urease inhibitors is mentioned in relation to present and future fertilizer N requirements in West Africa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048986
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  • 6
    Electronic Resource
    Electronic Resource
    4. Reappraisal of the significance of ammonia volatilization as an N loss mechanism in flooded rice fields (1986)
    Springer
    Nutrient cycling in agroecosystems 9 (1986), S. 79-98 
    Details
    ISSN: 1573-0867
    Keywords: N Fertilizer efficiency ; N balance ; micro-meteorology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The role of ammonia volatilization as a nitrogen loss mechanism in lowland rice (Oryza sativa L.) has recently been extensively reevaluated using techniques that do not disturb the field environment. This paper summarizes methodologies used in this research and discusses findings from recently conducted micrometeorological studies on ammonia volatilization. Factors affecting ammonia loss and the contribution of this process to the overall nitrogen loss from lowland rice systems are also outlined. Suggestions for future research are included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048696
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  • 7
    Electronic Resource
    Electronic Resource
    The role of fertilizers in sustaining agriculture in sub-Saharan Africa (1990)
    Springer
    Nutrient cycling in agroecosystems 26 (1990), S. 327-339 
    Details
    ISSN: 1573-0867
    Keywords: Soil fertility ; sustainable agriculture ; food crop production ; marketing ; trade ; policy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract African farmers have relied traditionally on fallowing for up to 15 years to restore soil fertility. Leaving land unproductive for such periods is a luxury many regions cannot afford, given the contemporary decline in per capita food production (1%/year). Thus, alternative soil fertility maintenance measures such as agroforestry, novel intercropping systems, residue conservation, the use of manure, soil amendments, and fertilizer have recently been given greater emphasis. The Food and Agriculture Organization (FAO) estimates that 75% of the increase in regional food production must come from intensive production. However, fertilizer use in sub-Saharan Africa is only one tenth of the world average. The small size of fertilizer markets in most countries is an important contributing factor in relatively high farm-gate prices and low fertilizer use. There is significant scope for improving the efficiency of fertilizer procurement and distribution in the region. Most countries can substantially reduce farm-gate prices by changing to higher analysis formulas, relaxing specifications, importing in bulk and bagging locally, and improving systems of distribution. Various options of fertilizer production are discussed in this context. Intensification in areas where environmental constraints are limited and surplus production can be marketed may alleviate the demographic pressures to cultivate marginal land where increased land and labor productivity is unlikely. Although substantial effort should be made to research sustainable farming system options for marginal lands, efforts in the more resilient environments should concentrate on increased crop production, using inputs where feasible. Provisions should be made for adequate support in the infrastructural, institutional, and policy spheres to transform these regions into granaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048771
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  • 8
    Electronic Resource
    Electronic Resource
    Urease activity and inhibition in flooded soil systems (1980)
    Springer
    Nutrient cycling in agroecosystems 1 (1980), S. 191-202 
    Details
    ISSN: 1573-0867
    Keywords: 15N ; rice soils ; urea fertilization ; ammonia volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ammonia volatilization is an important mechanism of N loss from flooded rice soils. Inhibition of urease may delay the formation of conditions favorable to NH3 volatilization in the floodwater, thus giving the soil and plant a better chance to compete with the atmosphere as a sink for N. The experiments reported here were designed to identify the site of urea hydrolysis in flooded soils and to attempt selective urease inhibition with some of the inhibitors reported in the literature. Studies with three flooded soils using15N-labeled urea showed that 50–60% of the urea was found in the floodwater, despite incorporation. This floodwater urea is hydrolyzed largely at the soil—floodwater interface and subsequently returns to the floodwater (〉 80%) or is retained by the soil (〈 20%). Of the following urease inhibitors (K-ethyl-xanthate; 3 amino-1-H-1, 2, 4-triazole; phenylphosphorodiamidate) added at 2% (w/w of urea), only the latter was able to delay the appearance of NH3 (aq) in the flood-water and thus delay NH3 volatilization. Use of an algicide addition to the floodwater depressed NH3 (aq) levels during the entire period studied, but in the presence of PPD the algicide had little additional effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053131
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  • 9
    Electronic Resource
    Electronic Resource
    Fate and efficiency of N fertilizers applied to pearl millet in Niger (1990)
    Springer
    Plant and soil 125 (1990), S. 221-231 
    Details
    ISSN: 1573-5036
    Keywords: calcium ammonium nitrate (CAN) ; 15N ; urea ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field studies were conducted in Niger using 15N-labeled fertilizers to assess the fate and efficiency of fertilizer N in pearl millet (Pennisetum glaucum [L.] R.Br.) production. Total plant uptake of fertilizer N was low in all cases (20%–37%), and losses were severe (25%–53%). The majority of N remaining in the soil was found in the 0- to 15-cm layer though some enrichment at lower depths was found when the N fertilizer was calcium ammonium nitrate (CAN). In a comparison of urea placement methods (band, broadcast, or point placement), no significant differences in 15N uptake or yield were noted though point placement did exacerbate 15N loss. The mechanism of N loss is believed to have been ammonia volatilization. Yields were similar whether urea or CAN was used, but 15N uptake from CAN was higher. A statistical model was developed relating millet yield and N response to midseason rainfall. In drought years, no N response was found, whereas in years of good rainfall a response was found of 15 kg grain for each kilogram of N applied (at 30 kg N ha-1 rate).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010660
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  • 10
    Electronic Resource
    Electronic Resource
    Labeled nitrogen fertilizer research with urea in the semi-arid tropics (1984)
    Springer
    Plant and soil 80 (1984), S. 21-33 
    Details
    ISSN: 1573-5036
    Keywords: Carthamus tinctorius L ; Double-cropping ; Fertilizer application ; Nitrogen balance ; Nitrogen fertilizer ; Safflower ; Semi-arid tropics ; Sorghum bicolor L ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field studies were conducted on Indian Vertisol to determine the fate of15N-labeled fertilizers applied to dryland sorghum in two successive rainy seasons. In the 1981 season, a split-band (SB) urea application of 74 kg N/ha, half amounts placed 5 cm deep and 8 cm from opposite sides of plant rows at 4 and 19 days after emergence, was superior to preemergent applications of either surface-applied (S) or incorporated (I) applications at the same rate; 907 mm of rainfall fell during the sorghum growing period. Percentages of applied N recovered in the soil-plant system after the sorghum harvest were 94%, 74%, and 72%, respectively, for the SB, I, and S application methods. Substantial quantities, 39%, 45%, and 42% of the added N for the SB, I, and S tretments, respectively, remained in the soil after the final harvest. Plant utilization of added urea-N was greater in 1980 when rainfall during the growing season was 212 mm less than in 1981. S or I applications of urea at 74 kg N/ha, with above-ground plant15N recoveries of 48.0% and 48.6%, respectively, were also equally as efficient during 1980. Residual soil N derived from fertilizer was of little value for a sorghum crop in the following rainy season and for a safflower crop in the post-rainy season in a double-cropping system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02232936
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