一次性施肥稻田田面水氮素变化特征和流失风险评估

为评估单季稻一次性施肥模式中氮素径流损失风险,通过田间试验研究了一次性施肥模式中缓释氮肥类型、施用比例和氮肥施用量对田面水氮素含量的影响。结果表明:与尿素分次施肥处理(225 kg N·hm-2)相比,不同缓释氮肥(180 kg N·hm-2)一次性施肥后田面水铵态氮浓度为稳定性肥料(NIU)常规分次施肥(Urea)树脂包膜尿素(RCU)聚氨酯包膜尿素(PCU);氮肥施用量为180 kg N·hm-2时田面水铵态氮浓度随缓释氮肥施用比例增加而下降,但180 kg N·hm-2和144 kg N·hm-2处理间田面水铵态氮含量没有明显差异。尿素分次施肥和一次性施肥处理的稻田氮素径流损失风险都在施基肥后5 d。研究表明,一次性施肥模式通过缓释氮肥的应用和氮肥减量等措施,虽然基肥用量大于尿素分次施肥处理,但没有增加稻田氮素径流损失风险。

Dynamic variation and runoff loss evaluation of nitrogen in the surface water of paddy fields as affected by single basal fertilizer application

To evaluate the risk of nitrogen runoff loss from single fertilization in monocropping systems, field experiments were conducted to determine the effects of the types of slow-release N fertilizer(SRN), the ratios of SRN to urea, and the application amount of N fertilizer on the N concentrations in rice paddy surface water. The results showed that the concentrations of ammonium nitrogen(NH₄⁺-N) in rice paddy surface water after single application of different SRNs(180 kg N·hm^-2), compared to multiple applications of urea(225 kg N·hm^-2), were ranked as follows:nitrification inhibitor urea > conventional multiple application of urea > resin-coated urea > polymer-coated urea. At a rate of 180 kg·hm^-2 for nitrogen fertilizer, the NH₄⁺-N concentration in rice paddy surface water decreased as SRN usage increased. However, no significant difference was seen in NH₄⁺-N in the surface water at rates between 180 kg·hm^-2 and 144 kg·hm^-2. All nitrogen runoff amounts peaked on the fifth day for both single and multiple urea fertilizations. With the combination of SRN and reduced nitrogen fertilizer application, single fertilization did not increase the risk in nitrogen runoff loss, although it required more basal fertilizer than that with multiple fertilizations.