控释氮肥侧条施用对宁夏引黄灌区稻田氮素损失的影响机制

Ningxia Yellow River Irrigation Region is one of the largest gravity irrigated areas in the Northwest China. With the rice production intensification improving, excessive application of nitrogen fertilizer leads to low fertilizer use efficiency and serious water environment pollution in the watershed. Long-term Yellow River warping and cultivation formed a special farmland soil type - irrigation silting soils. There were a lot of researches on nitrogen loss ways in the paddy rice field, however, it was yet not involved on nitrogen transformation and losse mechanisms with side bar fertilization technology based on controlled released nitrogen fertilizer(CRNF). Field experiment was conducted to study effects of side bar fertilization technology based on CRNF application on rice yield and nitrogen transformation mechanisms, and clarify the characteristics of nitrogen gaseous and leaching losses dynamic in different rice growth stages, and evaluation the nitrogen balance in the paddy rice system of the irrigation silting soils field, and reveal these key factors that influenced on nitrogen losses and its running mechanism with side bar fertilization technology based on CRNF, and then propose a theoretical basis for the new fertilization technique with high yield and quality of rice and reduction of nitrogen losses in Ningxia Irrigation Region. These results could provide theoretical references for similar high-yield paddy rice and environmentally friendly fertilization techniques.

宁夏引黄灌区是我国西北大型引黄自流灌区，水稻生产集约化程度不断提高，氮肥过量施用导致肥料利用率低和流域水环境污染，长期的引黄淤灌和耕作形成了该区特殊的农田土壤类型-灌淤土。该区域稻田氮素损失途径已有大量研究，而基于控释氮肥侧条施用措施下灌淤土稻田的氮素转化和损失机制研究尚未涉及。项目采用田间定位试验的方法，探讨控释氮肥侧条施用对水稻产量和氮素转化机制的影响，明确氮素在水稻生育期气态和淋洗损失动态规律，评价灌淤土稻田系统氮素平衡特征，揭示基于控释氮肥的侧条施用下影响氮素损失的关键因子和作用机制，为宁夏灌区水稻优质高产和降低氮素损失的新型施肥技术提供理论依据。研究结果可为同类地区水稻优质高产和环境友好型施肥技术提供理论参考。

针对宁夏引黄灌区稻田氮肥过量和不合理施用导致氮肥利用低和面源污染严重的问题，采样田间小区试验和15N同位素示踪研究了控释氮肥侧条施用对稻田氮素转化和损失的影响。结果表明，控释氮肥施用量与常规施肥比较降低25%-40%的条件下，水稻子粒产量并没有降低，氮肥利用率比常规施肥处理提高了31.2%。控释氮肥处理水稻生育期内田面水和淋溶水中的TN浓度均低于常规施肥，延迟了田面水中TN浓度峰值出现的时间。常规处理全生育期氮素淋洗损失总量为24.57 kg/hm2，控释氮肥各处理素淋洗损失总量在11.54～17.35 kg/hm2，总氮淋失量比常规施肥降低了47.78%，硝态氮是氮素淋洗损失的主要形态。常规施肥处理氨挥发损失主要发生在分蘖和拔节期，氨挥发损失量达55.02 kg/hm2，占到施肥量的18.34%，控释氮肥侧条施肥显著降低了氨挥发损失通量61.3%，氧化亚氮排放损失比例较小。控释氮肥侧条施用通过降低水稻收获后土壤中的氮素残留，提高植株对氮素的吸收比例，同时减少淋洗和气态排放损失量，提高了氮肥的当季利用效率。综合考虑水稻产量和氮素损失因素，宁夏引黄灌区兼顾控释氮肥侧条施用适宜用量在180～225 kg/hm2之间。项目共发表研究论文10篇，其中SCI论文3篇，制定地方标准2项，申报发明专利2件，培养在读研究生1名，参加3次国内外学术会议，对项目研究成果进行了推介和展示。