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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of two versions of the acetylene inhibition/soil core method for measuring denitrification loss from an irrigated wheat field (1999)
    Springer
    Biology and fertility of soils 29 (1999), S. 328-331 
    Details
    ISSN: 1432-0789
    Keywords: Key words Acetylene inhibition ; Soil core technique ; Denitrification ; Irrigation ; Nitrous oxide entrapment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Two versions of the acetylene inhibition (AI)/soil core method were compared for the measurement of denitrification loss from an irrigated wheat field receiving urea-N at a rate of 100 kg ha–1. With AI/soil core method A, the denitrification rate was measured by analysing the headspace N2O, followed by estimation of N2O dissolved in the solution phase using Bunsen absorption coefficients. With AI/soil core method B, N2O entrapped in the soil was measured in addition to that released from soil cores into the headspace of incubation vessels. In addition, the two methods were also compared for measurement of the soil respiration rate. Of the total N2O produced, 6–77% (average 40%) remained entrapped in the soil, whereas for CO2, the corresponding figures ranged from 12–65% (average 44%). The amount of the entrapped N2O was significantly correlated with the water-filled pore space (WFPS) and with the N2O concentration in the headspace, whereas CO2 entrapment was dependent on the headspace CO2 concentration but not on the WFPS. Due to the entrapment of N2O and CO2 in soil, the denitrification rate on several (18 of the 41) sampling dates, and soil respiration rate on almost all (27 of the 30) sampling dates were significantly higher with method B compared to method A. Averaged across sampling dates, the denitrification rate measured with method B (0.30 kg N ha–1 day–1) was twice the rate measured with method A, whereas the soil respiration rate measured with method B (34.9 kg C ha–1 day–1) was 1.6 times the rate measured with method A. Results of this study suggest that the N2O and CO2 entrapped in soil should also be measured to ensure the recovery of the gaseous products of denitrification by the soil core method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050560
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  • 2
    Electronic Resource
    Electronic Resource
    Denitrification and total fertilizer-N losses from an irrigated cotton field (2000)
    Springer
    Biology and fertility of soils 31 (2000), S. 270-278 
    Details
    ISSN: 1432-0789
    Keywords: Key words Acetylene inhibition ; Denitrification ; Cotton ; Nitrous oxide entrapment ; 15N-balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In a 2-year field study, denitrification loss was measured from an irrigated sandy-clay loam under cotton receiving urea-N at 158–173 kg ha–1. An acetylene inhibition-soil core method was employed for the direct measurement of denitrification, considering also the N2O entrapped in the soil. Taking into account the N2O evolved from soil cores and that entrapped in the soil, a total of 65.7 kg N ha–1 and 64.4 kg N ha–1 was lost due to denitrification during the 1995 and 1996 cotton-growing seasons, respectively. Most (〉70%) of the denitrification loss occurred during June–August, a period characterized by high soil temperatures and heavy monsoon rains. On average, 35% of the denitrification-N2O was found entrapped in the soil and the amount of entrapped N2O was significantly correlated with head space N2O concentration and with water-filled pore space. 15N-balance during the 1996 growing season revealed a loss of 71.8 kg N ha–1. It was concluded that a substantial proportion of the fertilizer-N applied to irrigated cotton is lost under the semiarid subtropical climatic conditions prevailing in the Central Punjab region of Pakistan and that denitrification is the major N loss process under irrigated cotton in this region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050656
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  • 3
    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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  • 4
    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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    Paper (German National Licenses)
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