有机无机肥配施提高麦-稻轮作系统中水稻氮肥利用率的机制

采用盆栽试验，研究了有机无机肥配施对麦-稻轮作系统中水稻氮素累积动态和土壤氮素供应动态的影响，并从微生物学角度探讨了有机无机肥协同提高水稻氮肥利用率的机制.结果表明：有机无机肥配施处理的土壤微生物生物量碳、氮和矿质态氮在水稻分蘖期前低于化肥处理，而在抽穗期至灌浆期显著高于其他处理.土壤氮素供应动态与水稻吸收利用氮素规律吻合程度最高，促进了水稻产量、生物量和氮素累积量的增加，显著提高了水稻的氮肥利用率.其主要机制是有机无机肥配施促进了土壤微生物繁殖，使其在水稻生育前期固持了较多的矿质氮，在水稻生育中、后期这些氮素逐渐被释放以供水稻吸收利用，较好地满足了水稻各阶段生长发育对氮素养分的需求.

Mechanisms for the increased fertilizer nitrogen use efficiency of rice in wheat-rice rotation system under combined application of inorganic and organic fertilizers

A pot experiment was conducted to study the effects of combined application of organic and inorganic fertilizers on the nitrogen uptake by rice and the nitrogen supply by soil in a wheat-rice rotation system, and approach the mechanisms for the increased fertilizer nitrogen use efficiency of rice under the combined fertilization from the viewpoint of microbiology. Comparing with applying inorganic fertilizers, combined application of organic and inorganic fertilizers decreased the soil microbial biomass carbon and nitrogen and soil mineral nitrogen contents before tillering stage, but increased them significantly from heading to filling stage. Under the combined fertilization, the dynamics of soil nitrogen supply matched best the dynamics of rice nitrogen uptake and utilization, which promoted the nitrogen accumulation in rice plant and the increase of rice yield and biomass, and increased the fertilizer nitrogen use efficiency of rice significantly. Combined application of inorganic and organic fertilizers also promoted the propagation of soil microbes, and consequently, more mineral nitrogen in soil was immobilized by the microbes at rice early growth stage, and the immobilized nitrogen was gradually released at the mid and late growth stages of rice, being able to better satisfy the nitrogen demand of rice in its various growth and development stages.