稻田以水带氮肥（尿素）深施技术研究

本研究将稻田氮肥施用方法与水分管理结合起来。施肥前对稻田停止灌水晾田数天，尽可能控制土壤处于水不饱和状态，再把氮肥表施，然后立即浅层灌水，让氮肥随水下渗带入土层中，达到氮肥深施的目的，简称为“以水带氮肥深施技术”。研究结果表明，此技术可将表施的60%以上的尿素氮带入土层中，减少了肥料氮素的损失，提高了氮肥的增产效果和氮素利用率，对水稻省肥增产的作用十分显著，可作为氮肥经济合理施用技术之一，在具有排灌条件的稻田中推广应用。

Deep Placement of N-fertilizer (Urea) Topdressed to Unsaturated Paddy Soil with Reflooded Water

The paper offers a very simple, practical and efficient technique for deep placement of urea topdressed in irrigated rice fields. The technique combines N fertilizer application method with soil moisture regime control. The specific way to use the technique is that urea as N fertilizer was topdressed on rice fields, where moisture regime had become unsaturated by cutting off the water supply and draining, then irrigation should be immediately done after application of urea to make the fertilizer deep placement in reduced zone with downward infiltrating water. The results obtained in the study, which consists of soil column experiment, pot experiment and field experiment, show that fertilizer nitrogen efficiency can be substantially increased with the technique, which resulted in more than 60% of topdressed urea deep-placed in reduced zone and minimized its N-losses. As compared the technique with conventional broadcasting N fertilizer on flooded rice field, 1.5 kg N/mu (22.5 kg N/ha) can be saved to get the comparable high yield (around 7.4 t /ha) and significantly higher yield can be obtained at an equal N level of 7.5 kg/mu.