氮肥运筹对机插双季稻产量、氮肥利用率及经济效益的影响

摘要

【目的】随着劳动力成本的提高，机械插秧是降低水稻生产劳动强度的必要措施之一，研究适应该技术的氮肥施用时期和比例，对推广该技术，实现机插双季稻稳产高产具有重要意义。【方法】以早稻和晚稻为试验材料，进行机插双季稻氮肥施用田间试验。在同一施氮量下，设置氮素基肥∶分蘖肥∶穗肥比例为8∶2∶0（N8∶2∶0）、7∶2∶1（N7∶2∶1）、6∶2∶2（N6∶2∶2）、5∶2∶3（N5∶2∶3）、4∶2∶4（N4∶2∶4）、3∶2∶5（N3∶2∶5）和不施氮肥（CK）7个处理。调查了早稻和晚稻产量形成、氮素吸收以及氮肥利用特征，讨论了氮肥后移与产量、产量形成及肥料利用率的关系。【结果】机插早、晚稻基肥∶分蘖肥∶穗肥比例分别为6∶2∶2和5∶2∶3处理水稻高产的群体结构最合理，有效穗、穗粒数、结实率与千粒重的乘积最大，协调产量的各因子达最佳值。同时发现，机插早、晚稻穗肥比例与有效穗数呈极显著负相关，与穗粒数呈正相关，与结实率呈抛物线关系。施氮处理机插早、晚稻的籽粒和秸秆氮含量及氮素累积量较 CK处理均有所增加，其中随着穗肥比例的增大，早、晚稻的籽粒和秸秆氮含量均呈现增加的趋势，而氮素累积量均呈先增后减的趋势。无论机插早稻（施氮量为180 kg/hm2）还是晚稻试验（施氮量为195 kg/hm2），随着穗肥比例的增大，氮肥贡献率（NCR）、氮肥农学利用率（NAE）、氮肥吸收利用率（NRE）、氮肥偏生产力（PFPN）以及经济效益均呈先增后减的趋势，其中早稻 N6∶2∶2处理 NCR、NAE、NRE、PFPN和经济效率均达最大值，晚稻 N5∶2∶3处理均达最大值；而早、晚稻氮肥生理利用率（NPE）随着穗肥比例的增大均呈现逐渐减少的趋势。【结论】在施氮量和分蘖肥比例相同的条件下，机插早、晚稻施基蘖肥与穗肥比例分别为6∶2∶2和5∶2∶3时，有利于水稻高产和氮肥高效，是较为理想的施肥模式。%Objectives]Machine-transplanted seedling has become one of the important ways for decreasing labor cost in rice cultivation. Studying the optimized N application is crucial for achieving high N use efficiency and stable and high yield of double-cropping rice.[Methods]Field experiments were conducted on a double-cropping rice using mechanical transplanting. Under the same nitrogen application rate and with no- nitrogen fertilizer as control (CK), six ratios of N fertilizer amount in basal: tillering: earring were designed as: 8 : 2 : 0 (N8 : 2 : 0), 7 : 2 : 1 (N7 : 2 : 1), 6 : 2 : 2 (N6 : 2 : 2), 5 : 2 : 3 (N5 : 2 : 3), 4 : 2 : 4 (N4 : 2 : 4), 3 : 2 : 5 (N3 : 2 : 5). The rice yield, and N absorption and use efficiency were investigated, the relationships among them were discussed.[Results]With the N ratio of basal: tillering: panicle of 6 : 2 : 2 for early rice, and 5 : 2 : 3 for late rice, the rice had more reasonable population structure, higher effective panicle number, more grain number per panicle, higher seed-setting rate and 1000-grain weight, and the optimal coordination of each factor. The N ratio in panicle fertilizer had a significantly negative correlation with the effective panicle number, but a positive correlation with the grain number per panicle, and had a parabolic relation with the seed-setting rate. For early and late rice, the N contents of both grain and straw and N accumulation amount in all N fertilizer treatments increased compared with those of CK treatment, where in the N contents of both grain and straw took on a rising trend with the increase of panicle fertilizer proportion, while the N accumulation amount first went up and then dropped down. Whether machine-transplanted early rice (N 180 kg/hm2) or late rice (N 195 kg/hm2), along with the increase of panicle fertilizer proportion, nitrogen contribution rate (NCR), nitrogen agronomic efficiency (NAE), nitrogen recovery efficiency (NRE), nitrogen partial factor productivity (PFPN) and economic benefit all increased first and then decreased, each reaching up to a maximum for early rice in the N6∶2∶2treatment and for late rice in the N5∶2∶3treatment, respectively. However, the physiological nitrogen efficiency (NPE) went down for early and late rice with the increase of panicle fertilizer proportion.[Conclusions]Under the same amounts of total N application and allocated proportion for tillering fertilizer, the N ratio of basal to tillering to panicle fertilizer N of 6 : 2 : 2 for early rice and 5 : 2 : 3 for late rice contributed to high yield of rice and high N utilization efficiency, and could be used as an ideal mode of nitrogen fertilizer application.