Effects of nitrogen rate, applying time on cotton growth and soil mineral nitrogen content | 氮肥用量与施用时期对棉花生长发育及土壤矿质氮含量的影响

Chinese. 探讨不同氮肥用量与施用时期对棉花生长发育及土壤矿质氮含量的影响，为棉花合理施用氮肥提供理论依据。以不施氮肥为对照，采用2种氮肥用量（150，300 kg/hm2）与不同施用时期（播前全部基施、1/2播前基肥+1/2蕾期追肥、1/3播前基肥+1/3蕾期追肥+1/3花铃期追肥）进行组合的田间小区试验，分析氮肥用量和施用时期对棉花产量、棉铃生长发育及各生育时期土壤矿质氮含量的影响。在供试区土壤较为瘠薄的情况下，与不施氮肥相比，施用氮肥使棉花产量、株有效铃数、成铃率、单铃质量分别显著增加44.8%~80.0%，1.0~2.3，4.3%~8.1%和0.66~1.36 g，且高氮处理低氮处理。氮肥施用时期对棉花产量有显著影响，低氮处理中以1/2基肥+1/2蕾期追肥方式获得相对高产（2.99 t/hm2）；高氮处理中以播前1/2基肥+1/2蕾期追肥或播前1/3基肥+1/3蕾期追肥+1/3花铃期追肥方式处理的棉花产量较高，分别为3.36 ，3.40 t/hm2。高氮分施可显著提高棉花株有效铃数、成铃率及单铃质量，2次分施可明显提高株有效铃数与成铃率，而3次分施更有利于单铃质量的增加。施用氮肥可显著提高各生育期0~40 cm土层土壤矿质氮含量，且高氮处理低氮处理。氮肥全部基施使苗期土壤矿质氮含量显著提高，但在生育后期含量较低，分施处理则使生育中后期土壤矿质氮含量显著提高。此外，氮肥用量与施用时期对氮肥农学效率也有显著影响。在土壤养分瘠薄的地区，在施用磷钾肥基础上增加氮肥用量是提高棉花产量的有效措施，并可以通过不同氮肥用量与施用时期耦合的策略对棉花产量、品质及肥料利用进行平衡调控。

English. Cotton growth and soil mineral nitrogen conditions during cotton growth and development period under different nitrogen rates, and applying time were studied to provide some theory for reasonable application of nitrogen fertilizer on cotton. With no nitrogen fertilizer as control, the influences of nitrogen fertilizer on cotton yield, boll’s growth and development, and soil mineral nitrogen content were analyzed through the field experiment of low and high nitrogen rate (150, 300 kg/hm2) at different applying time (all as basal fertilizer, 1/2 basal fertilizer+1/2 bud topdressing,1/3 basal fertilizer+1/3 bud topdressing+1/3 flower topdressing, respectively). In the poor test areas, on the basis of P and K fertilizer application, in comparison with the control, cotton yield, the effective bolls’ number, boll ratio and boll weight were significantly improved by 44.8% to 80.0%, 1.0 to 2.3 plant-1, 4.3%-8.1% and 0.66-1.36 g, respectively, by applying nitrogen fertilizer. And effects of high N treatment were stronger than low N treatment. Influence of nitrogen applying time on cotton yield was significant. Under low nitrogen rate, basal fertilizer+bud topdressing treatment got higher yield of 2.99 t/hm2; under high nitrogen rate, basal fertilizer+bud topdressing treatment or basal+bud+flower topdressing treatment got higher yield of 3.36 t/hm2 and 3.40 t/hm2, respectively. The cotton effective bolls, available boll’s ratio and boll’s weight were significantly increased by applying high rate nitrogen fertilizer; the effective boll’s number and available boll’s ratio were significantly improved by spliting with two times, and boll’s weight was more benefited from spliting with three times. The soil mineral nitrogen content of 0-40 cm depth of soil was significantly increased by application of nitrogen fertilizer, and effects of high nitrogen treatment was stronger than low N treatment. Seedling soil mineral N content was significantly increased with applied all nitrogen as basal fertilizer, but lower levels in the late growth stage, and the soil mineral N content in the late growth stage was increased significantly by split fertilization. In addition, nitrogen agronomic efficiency (NAE) was also influenced significantly by the nitrogen rate and applying time. In barren areas, on the basis of P and K fertilizer application, increasing nitrogen fertilizer was still an effective measure to improve cotton production, and it’s possible to use the different strategies by coupling nitrogen rate and applying time to balance the cotton yield, quality and nitrogen efficiency.