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  • 1
    Electronic Resource
    Electronic Resource
    Microbial biomass and mineralization-immobilization of nitrogen in some agricultural soils (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 157-163 
    Details
    ISSN: 1432-0789
    Keywords: Available N ; Fumigation method ; N immobilization-remineralization ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The chloroform fumigation-incubation method (CFIM) was used to measure the microbial biomass of 17 agricultural soils from Punjab Pakistan which represented different agricultural soil series. The biomass C was used to calculate biomass N and the changes occurring in NH4 +-N and NO3 −-N content of soils were studied during the turnover of microbial biomass or added C source. Mineral N released in fumigated-incubated soils and biomass N calculated from biomass C was correlated with some N availability indexes. The soils contained 427–1240 kg C as biomass which represented 1.2%–6.9% of the total organic C in the soils studied. Calculations based on biomass C showed that the soils contained 64–186 kg N ha−1 as microbial biomass. Immobilization of NCO3 −-N was observed in different soils during the turnover of microbial biomass and any net increase in mineral N content of fumigated incubated soils was attributed entirely to NH4 +-N. Biomass N calculated from biomass C showed non-significant correlation with different N availability indexes whereas mineral N accumulated in fumigated-incubated soils showed highly significant correlations with other indexes including N uptake by plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257595
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  • 2
    Electronic Resource
    Electronic Resource
    Quantification and potential availability of non-symbiotically fixed 15N in soil (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 32-38 
    Details
    ISSN: 1432-0789
    Keywords: Hydrolysable N ; Mineralizable N ; N2-fixation ; Priming effect ; Plant available N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Non-symbiotic N2 fixation was studied under laboratory conditions in two soils from Pakistan (Hafizabad silt loam and Khurrarianwala silt loam) and one from Illinois, USA (Drummer silty clay loam) incubated in a 15N-enriched atmosphere. N2 fixation was greatest with the Drummer soil (18–122 μg g−1 soil, depending upon the soil treatment) and lowest with the Khurrarianwala soil (4–81 μg g−1 soil). Fixation was increased by the addition of glucose, a close correlation being observed between the amount of glucose added and the amount of N2 fixed in the three soils (r = 0.96). Efficiency of N2 fixation varied with soil type and treatment and was greatest in the presence of added inorganic P. Application of Mo apparently had a negative effect on the amount and efficiency of N2 fixation in all the soils. The percentage of non-symbiotically fixed 15N in potentially mineralizable form (NH 4 + -N released in soil after a 15-day incubation period under anaerobic conditions) was low (2%–18%, depending upon the soil treatment), although most of the fixed N (up to 90%) was recovered as forms hydrolysable with 6N HCl. Recovery in hydrolysable forms was much greater for the fixed N than for the native soil N, indicating that the former was more available for uptake by plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260729
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  • 3
    Electronic Resource
    Electronic Resource
    Transformation of 15N-labelled leguminous plant material in three contrasting soils (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 54-60 
    Details
    ISSN: 1432-0789
    Keywords: Biomass N ; Humus fractions ; Hydrolyzable N ; Legume N ; Mineralizable N ; N-mineralization ; 15N-labelled material
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two soils from Pakistan (Hafizabad silt loam and Khurrarianwala silt loam) and one from Illinois, USA (Drummer silty clay loam) were incubated with 15N-labelled soybean tops for up to 20 weeks at 30°C. Mineralization of soybean 15N was slightly more rapid in the Pakistani soils, and after 20 weeks of incubation, 50%, 53%, and 56% of the applied 15N was accounted for as (NH4 ++NO3 −)-N in Drummer, Hafizabad, and Khurrarianwala soils, respectively. Potentially mineralizable N (determined by anaerobic incubation) varied between 1.5% and 10% of the applied 15N in the three soils at different stages of incubation; somewhat higher percentages were mineralizable in the Pakistani soils than in the Drummer soil. From 3.7% to 9% of the applied 15N was accounted for in the microbial biomass. From 10% to 32% of the applied N was recovered in the humic acid and fulvic acid fractions of the organic matter by sequential extraction with Na4P2O7 and NaOH; from 12% to 49% was recovered in the humin fraction. Of the three soils, Drummer soil contained more 15N as humic and fulvic acids. In all cases, the 15N was approximately equally distributed between the humic and fulvic acid fractions. A significant percentage of the humin 15N (52%–78%, equivalent to 8%–34% of the applied 15N) occurred in non-hydrolyzable (6 N HCl) forms. Of the hydrolyzable 15N, 42%–51% was accounted for as amino acid-N followed in order by NH3 (17%–30%), hydrolyzable unknown forms (20%–22%), and amino sugars (6%–2%). The recovery of applied 15N for the different incubation stages was 87±22%. Recovery was lowest with the Khurrarianwala soil, presumably because of NH3 volatilization losses caused by the high pH of this soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260516
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of 15N-labelled microbial biomass in soil in situ and extraction of biomass N (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 180-185 
    Details
    ISSN: 1432-0789
    Keywords: Extractability ratios ; Microbial biomass ; N immobilization-remineralization ; Priming effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A Pakistani soil (Hafizabad silt loam) was incubated at 30°C with varying levels of 15N-labelled ammonium sulphate and glucose (C/N ratio of 30 at each addition rate) in order to generate different insitu levels of 15N-labelled microbial biomass. At a stage when all of the applied 15N was in organic forms, as biomass and products, the soil samples were analysed for biomass N by the chloroform (CHCl3) fumigation-extraction method, which involves exposure of the soil to CHCl3 vapour for 24 h followed by extraction with 500 mM K2SO4. A correction is made for inorganic and organic N in 500 mM K2SO4 extracts of the unfumigated soil. Results obtained using this approach were compared with the amounts of immobilized 15N extracted by 500 mM K2SO4 containing different amounts of CHCl3. The extraction time varied from 0.5 to 4 h. The amount of N extracted ranged from 27 to 270 μg g−1, the minimum occurring at the lowest (67 μg g−1) and the maximum at the highest (333 μg g−1) N-addition rate. Extractability of biomass 15N ranged from 25% at the lowest N-addition rate to 65%a for the highest rate and increased consistently with an increase in the amount of 15N and glucose added. The amounts of both soil N and immobilized 15N extracted with 500 mM K2SO4 containing CHCl3 increased with an increase in extraction time and in concentration of CHCl3. The chloroform fumigation-extraction method gives low estimates for biomass N because some of the organic N in K2SO4 extracts of unfumigated soil is derived from biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292580
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  • 5
    Electronic Resource
    Electronic Resource
    Transformations in soil and availability to plants of15N applied as inorganic fertilizer and legume residues (1985)
    Springer
    Plant and soil 86 (1985), S. 3-13 
    Details
    ISSN: 1573-5036
    Keywords: Fertilizer N ; Humus components ; Immobilization-remineralization of N ; Microbial biomass ; N transformations ; N uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A pot experiment was conducted to study the transformations of organic and inorganic N in soil and its availability to maize plants. Inorganic N was in the form of15N labelled ammonium sulphate (As) and15N labelledSesbania aculeata (Sa), a legume, was used as organic N source. Plants utilized 20% of the N applied as As; presence of Sa reduced the uptake to 14%. Only 5% of the Sa-N was taken up by the plants and As had no effect on the availability of N from Sa. Losses of N from As were found to be 40% which were reduced to 20% in presence of Sa. Losses of N were also observed from Sa which increased in the presence of As. Application of As had no effect on the availability of soil or Sa-N. However, more As-N was transported into microbial biomass and humus components in the presence of Sa. Plants derived almost equal amounts of N from different sourcesi.e., soil, Sa and As. However, more As-N was transported into the shoots whereas the major portion of nitrogen in the roots was derived from Sa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185020
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  • 6
    Electronic Resource
    Electronic Resource
    Transformation of14C labelled plant components in soil in relation to immobilization and remineralization of15N fertilizer (1985)
    Springer
    Plant and soil 86 (1985), S. 15-25 
    Details
    ISSN: 1573-5036
    Keywords: C transformation ; Fertilizer N ; Humic components ; Hydrolysable C ; Hydrolysable N ; Immobilization-remineralization of N ; Microbial biomass ; N transformations ; Stabilization of C and N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Uniformly14C labelled glucose, cellulose and wheat straw and specifically14C labelled lignin component in corn stalks were aerobically incubated for 12 weeks in a chernozem soil alongwith15N labelled ammonium sulphate. Glucose was most readily decomposed, followed in order by cellulose, wheat straw and corn stalk lignins labelled at methoxyl-, side chain 2-and ring-C. More than 50% of14C applied as glucose, cellulose and wheat straw evolved as CO2 during the first week. Lignin however, decomposed relatively slowly. A higher proportion of14C was transformed into microbial biomass whereas lignins contributed a little to this fraction. After 12 weeks of incubation nearly 60% of the lignin14C was found in humic compounds of which more than 70% was resistant to hydrolysis with 6N HCl. Maximum incorporation of15N in humic compounds was observed in cellulose amended soil. However, in this case more than 80% of the15N was in hydrolysable forms. Immobilization-remineralization of applied15N was most rapid in glucose treated soil and a complete immobilization followed by remineralization was observed after 3 days. The process was much slow in soil treated with cellulose, wheat straw or corn stalks. More than 70% of the newly immobilized N was in hydrolysable forms mainly reepresenting the microbial component. Serial hydrolysis of soil at different incubation intervals showed a greater proportion of 6N HCl hydrolysable14C and15N in fractions representing microbial material.14C from lignin carbons was relatively more uniformly distributed in different fractions as compared to glucose, cellulose and wheat straw where a major portion of14C was in easily hydrolysable fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185021
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  • 7
    Electronic Resource
    Electronic Resource
    Uptake by wheat plants and turnover within soil fractions of residual N from leguminous plant material and inorganic fertilizer (1986)
    Springer
    Plant and soil 95 (1986), S. 97-108 
    Details
    ISSN: 1573-5036
    Keywords: Fertilizer15N ; Humus components ; Immobilization-remineralization of N ; Legume residue15N ; Mineralizable N ; N balance ; N transformations ; N uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The availability and turnover in different soil fractions of residual N from leguminous plant material and inorganic fertilizer was studied in a pot culture experiment using wheat as a test crop. Plants utilized 64% of the residual fertilizer N and 20% of the residual legume N. 50–60% of the N taken up by plants was recovered in grain and 4–8% in roots. After harvesting wheat up to 35% and 38% of the residual legume N and fertilizer N, respectively was found in humic compounds. A loss of humus N derived from legume and fertilizer was found during wheat growth but the unlabelled N increased in this fraction. Biomass contained 6% and 8% of the residual legume and fertilizer N, respectively when both were available. The mineralizable component contained upto 28% of both the residual legume and residual fertilizer N. Only a small percentage of the soil N (3–4%) was observed in biomass whereas the mineralizable component accounted for 7–14% of the soil N. In this fraction legume derived N increased during wheat growth whereas unlabelled N increased in both the mineralizable component and microbial biomass. Some loss of N occurred from residual legume and fertilizer N. Nevertheless, a positive total N balance was observed and was attributed to the addition of unlabelled N in the soil-plant system by N2 fixation. The gain in N was equivalent to about 38% of the plant available N in the soil amended with leguminous material. The additional N was concentrated mainly in the mineralizable fraction and microbial biomass, although some addition was also noted in humus fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02378856
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  • 8
    Electronic Resource
    Electronic Resource
    Evaluation of acid permanganate extraction as an index of soil nitrogen availability (1984)
    Springer
    Plant and soil 79 (1984), S. 249-254 
    Details
    ISSN: 1573-5036
    Keywords: Acid KMnO4 extraction ; Chemical index ; Incubation ; Mineralizable N ; Mineral N ; N uptake ; Soil ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A chemical measure of soil nitrogen (N) availability has been evaluated. The method involved the estimation of initial mineral N, plus mineralizable N released with 0.05N KMnO4 in 1NH2SO4. The results obtained correlated highly significantly with the N uptake by wheat plants (r=0.72,P〈0.01).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182347
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