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  • Articles  (6)
  • Mineralization  (6)
  • 1990-1994  (6)
  • 1955-1959
  • Geosciences  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Short-term and long-term effects of bacterivorous nematodes and nematophagous fungi on carbon and nitrogen mineralization in microcosms (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 249-256 
    Details
    ISSN: 1432-0789
    Keywords: Microcosm ; Arable soil ; Bacteria ; Bacterivorous nematodes ; Nematophagous fungi ; Carbon and nitrogen ; Mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A microcosm experiment was carried out to quantify the effects of organisms at various trophic levels on C and N mineralization after the addition of crop residues to arable soil. The effects of the bacterivorous nematodes Rhabditis sp. and Acrobeloides bütschlii and of the nematophagous fungi Arthrobotrys oligospora und Drechmeria coniospora on soil respiration and N mineralization were measured over 6 months at 20°C. In the presence of nematodes, C mineralization was increased during the first month and subsequently reduced; N mineralization was increased during the first 2 months and then reduced. The results support the assumption that nematodes influence C mineralization mainly indirectly by affecting bacterial activity, and N mineralization mainly directly by mineralizing bacterial biomass. A. oligospora contributed directly to C mineralization. The effect of both fungi on N mineralization was indirect and resulted from the reduction in the numbers of nematodes. The results showed that the effects of nematodes and nematophagous fungi and the mechanisms behind the effects may vary strongly in time, and are correlated with the type of organic matter decomposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00383977
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of acetylene provided by wax-coated calcium carbide on transformations of urea nitrogen applied to an irrigated wheat crop (1993)
    Springer
    Biology and fertility of soils 16 (1993), S. 86-92 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen immobilization ; Mineralization ; Nitrification ; Nitrification inhibitor ; Acetylene ; CaC2 ; 15N enrichment ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of acetylene (provided by wax-coated calcium carbide, CaC2) on N transformations in a red-brown earth was measured in a field experiment with irrigated wheat by determining the change in the concentration and 15N enrichment of the organic N and mineral N pools with time. The study was conducted in the Goulburn-Murray Irrigation region of south-eastern Australia using 0.3 m by 0.3 m microplots fertilized with 15N-labelled urea (10 g N m-2; 5 atom% 15N). Acetylene was effective in slowing the nitrification of both unlabelled and labelled N. Nitrate derived from the added fertilizer reached a maximum 19 days after sowing in the treatment without CaC2, whereas little nitrate accumulated in the 8 g CaC2 m-2 treatment. There was significant immobilization of the urea N by 19 days after sowing in all treatments, but the extent of immobilization was not affected by the acetylene. The addition of acetylene slowed net mineralization of labelled and unlabelled N from the organic N pool, and resulted in increased accumulation of both unlabelled and labelled N in wheat tops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369408
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of active roots on the decomposition of soil organic materials (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 121-126 
    Details
    ISSN: 1432-0789
    Keywords: Biodegradation ; Nutrient levels ; Mineralization ; Rhizosphere ; Microenvironment ; Root exudates ; Priming effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of one form of soil organic matter, such as living roots or root exudates on another form of soil organic matter, such as dead roots or incorporated litter and litter leachates, has been studied from various perspectives over the last 25 years. The effect seems to be either positive (priming) or negative (conserving). The present review concentrates on the conserving effect, measured as a decrease in 14CO2 released, in both field and greenhouse/growth chamber studies. The field experiments suggested that certain physical conditions in the soil, such as less available moisture or restricted aeration which led to lower microbial activity, explained the conserving effect of living roots on soil organic matter. Although more detailed greenhouse/growth chamber studies confirmed the conserving effect per se, it appears that biological rather than physical factors could better explain the reduction in the rate of decomposition of 14C-labelled plant residues in the presence of roots. However, a complex picture has emerged through a variety of postulates, all proposed in attempts to explain the conserving effect. Finally, the most recent studies have argued that the decrease in decomposition of labelled organic matter in planted soil is probably more apparent than real. A decrease in respired 14CO2 could be explained by an incorporation of 14C derived from old roots into the rhizosphere microbial populations of the living roots. To make any further progress on the fundamental question of how soil organic matter moves along its continuum from a living to a refractory state, the microenvironment needs to be examined at periodic intervals. New developments in improved histochemical and electron-probe microanalyses look promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336247
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of soil texture and structure on carbon and nitrogen mineralization in grassland soils (1992)
    Springer
    Biology and fertility of soils 14 (1992), S. 126-134 
    Details
    ISSN: 1432-0789
    Keywords: Grassland ; Mineralization ; Soil texture ; Soil structure ; Physical protection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The hypotheses that disruption of soil structure increases mineralization rates in loams and clays more than in sandy soils and that this increase can be used to estimate the fraction of physically protected organic matter were tested. C and N mineralization was measured in undisturbed, and in finely and coarsely sieved moist or dried/remoistened soil. Fine sieving caused a temporary increase in mineralization. The relative increase in mineralization was much larger in loams and clays than in sandy soils and much larger for N than for C. The combination of remoistening and sieving of the soil gave a further increase in the mineralization flush after the disturbance. Again, the extra flush was larger in loams and clays than in sandy soils, and larger for N than for C. In loams and clays, small pores constituted a higher percentage of the total pore space than in sandy soils. The fraction of small pores explained more than 50% of the variation in the N mineralization rate between soils. There was also a good correlation between the small-pore fraction and the relative increase in N mineralization with fine sieving. For C, these relations were not clear. It is suggested that a large part of the organic matter that was present in the small pores could not be reached by microorganisms, and was therefore physically protected against decomposition. Fine sieving exposed part of this fraction to decomposition. This physically protected organic matter had a lower C: N ratio than the rest of the soil organic matter. The increase in N mineralization after fine sieving can be regarded as a measure of physically protected organic matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336262
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of pretreatment of soil samples on N mineralization in incubation experiments (1992)
    Springer
    Biology and fertility of soils 14 (1992), S. 135-139 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen ; Mineralization ; Soil pretreatment ; Incubation experiment ; Freezing/thawing ; Long term field experiment ; Farmyard manure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We studied the effects of pretreating soil samples (field-fresh, drying at 40° and 105°C, freezing/thawing) on N mineralization in an incubation experiment and on the dynamics of the organic N fraction extracted by K2SO4 solution. The soil samples were collected from plots in a long-term field experiment with the application of mineral fertilizer and farmyard manure. Compared with the field-fresh soil samples, freezing/thawing resulted in higher NO 3 − -N contents while the NH 4 + -N and the organic N content were increased by drying at 105°C. During the incubation period N mineralization was highest after the samples were dried at 105°C and a little lower in those dried at 40°C. After freezing/thawing the order of magnitude of N mineralization remained the same. The difference in organic N between the beginning and the end of the incubation experiment and the mineral N content at the end of the experiment were correlated significantly. Despite this correlation, however, the change in the organic N content underestimated the N mineralization rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336263
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  • 6
    Electronic Resource
    Electronic Resource
    Carbon and nitrogen turnover in two acid forest soils of southeast Australia as affected by phosphorus addition and drying and rewetting cycles (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 212-218 
    Details
    ISSN: 1432-0789
    Keywords: Mineralization ; Microbial biomass ; Drying and rewetting ; P addition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of adding P and of drying and rewetting were studied in two acid forest soils from southeast Australia. The soils were a yellow podzolic with a low soil organic matter content (3.75% C) and a red earth with a high organic matter content (13.5% C). C and N mineralization and microbial C and N contents were investigated in a laboratory incubation for 151 days. Microbial C and N were estimated by a hexanol fumigation-extraction technique. Microbial C was also determined by substrate-induced respiration combined with a selective inhibition technique to separate the fungal and the bacterial biomass. The results obtained by the selective inhibition technique were not conclusive. Adding P to the soil and drying and rewetting the soil reduced microbial N. This effect was more pronounced in rapidly and frequently dried soils. Microbial C was generally less affected by these treatments. Compared with the control, the addition of P caused a reduction in respiration in the red earth (-13%) but an increase in the yellow podzolic soil (+12%). In the red earth net N mineralization was highest following the addition of P. In the yellow podzolic soil highest N mineralization rates were obtained when the soil was subjected to drying and rewetting cycles. In both soils increased N mineralization was associated with a decrease in microbial N, indicating that the mineralized N was of microbial origin. Nitrification decreased with rapid drying and rewetting. The addition of P promoted heterotrophic nitrification in both soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336325
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