尿素配施有机物料时土壤不同氮素形态的动态及利用

用盆栽试验研究了尿素配施有机物料时土壤不同氮素形态的动态和利用特征。结果表明：尿素与C／N比高的小麦秸秆配施时，降低了作物吸氮量；与C／N比低的鸡粪配施时，增加了作物的吸氮量。但尿素单施，尿素与小麦秸秆配施，与鸡粪配施的生物量并没有显著的差异。尿素的水解和硝化在14d以前完成。与单施尿素相比，尿素配施秸秆降低了土壤中NH4－N和NO3－N的含量，而配施鸡粪增加了它们的含量，这与作物吸氮量的变化是一致的。土壤中微生物氮也参与了对作物的供氮过程。作物对“老固定态铵”的利用能力很弱，施肥会显著的增加土壤固定态铵的含量，这些“新固定铵”在作物生长期能被吸收利用。几种处理氮肥利用率的顺序为：尿素＞尿素与鸡粪配施＞尿素与秸秆配施。

Dynamics of Various Nitrogen Forms in Soil and Nitrogen Utilization Under Application Urea and Different Organic Materials

The dynamics of various nitrogen forms in soil and characteristics of nitrogen utilization under application of urea and different organic materials were studied with pot experiment. The results showed that crop nitrogen uptake decreased when urea(U) applied with high C/N ratio of wheat straw(WS) and increased when urea applied with low C/N ratio of poultry manure(PM). There were no significant difference in crop biomass among U, U+WS, U+PM treatments. Urea hydrolysis and nitrification completed within 14 days. Compared with U treatment, the application of high C/N ratio of wheat straw significantly decreased amount of NH 4 N and NO 3 N in soil while the application of low C/N ratio of poultry manure increased their content, which were consistent with crop nitrogen uptake. Soil microbial biomass N also involved in nitrogen supply to crop. The utilization of earlier fixed NH + 4 by crop was weak. Soil fixed NH + 4 was increased after application of nitrogen fertilizers, and this kind of fixed NH + 4 could be uptake by crop during growth period. The order of nitrogen recovery rate by crop was: U>U+PM>U+WS.