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  • 1
    ISSN: 1573-0867
    Keywords: China ; Loess Plateau ; maize ; 15N ; Nitrogen ; urea ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field trials were carried out to study the fate of15N-labelled urea applied to summer maize and winter wheat in loess soils in Shaanxi Province, north-west China. In the maize experiment, nitrogen was applied at rates of 0 or 210 kg N ha−1, either as a surface application, mixed uniformly with the top 0.15 m of soil, or placed in holes 0.1 m deep adjacent to each plant and then covered with soil. In the wheat experiment, nitrogen was applied at rates of 0, 75 or 150 kg N ha−1, either to the surface, or incorporated by mixing with the top 0.15 m, or placed in a band at 0.15 m depth. Measurements were made of crop N uptake, residual fertilizer N and soil mineral N. The total above-ground dry matter yield of maize varied between 7.6 and 11.9 t ha−1. The crop recovery of fertilizer N following point placement was 25% of that applied, which was higher than that from the surface application (18%) or incorporation by mixing (18%). The total grain yield of wheat varied between 4.3 and 4.7 t ha−1. In the surface applications, the recovery of fertilizer-derived nitrogen (25%) was considerably lower than that from the mixing treatments and banded placements (33 and 36%). The fertilizer N application rate had a significant effect on grain and total dry matter yield, as well as on total N uptake and grain N contents. The main mechanism for loss of N appeared to be by ammonia volatilization, rather than leaching. High mineral N concentrations remained in the soil at harvest, following both crops, demonstrating a potential for significant reductions in N application rates without associated loss in yield.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: Loess soil ; Nitrogen ; Simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Periodic N-min measurements were used to validate a simple model describing N regime of cropped Loess soils over the winter half-year. The model comprises of submodels for N mineralization, nitrate transport and N uptake by plants. The description of mineralization is based on kinetic studies in the lab by means of incubation experiments. The transport model is as described earlier4 avoiding an explicite modeling of water movement through soils. Plant uptake for this period was modelled only roughly. The agreement between measurement and simulation is for about 90% of all cases within the confidence interval of the measured values. Possible reasons for the observed deviations are discussed.
    Type of Medium: Electronic Resource
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