遮荫条件下氮肥运筹对棉花生长和氮素积累的影响

【目的】果棉间作下棉花贪青晚熟现象明显,霜前花率低,产量下降严重,而合理的氮肥追施可以调控作物生育进程,优化各器官生物量和氮素的积累分配。为此,本文探讨果棉间作下棉花适宜的氮肥追施模式,以期为间作棉合理施氮提供理论依据。【方法】以中棉所49为材料,采用裂区设计,主区为遮荫50%(S50)与不遮荫(CK),副区为3个氮肥追施方式,即N1(氮肥前移)、 N2(正常追肥)、 N3(氮肥前移比例大于N1),总施氮量N 320 kg/hm2,随机追施量为160 kg/hm2,追施时期与比例见表1。研究其对棉花生物量、 氮素动态累积特征的影响。【结果】遮荫50%(S50)与不遮荫(CK)相比,营养器官生物量理论最大值和最大生长速率较大; 生殖器官生物量理论最大值、 最大生长速率和生长特征值较小; 总氮快速积累提前5~8 d; 单株铃数、 单铃重和衣分显著降低,皮棉产量平均减少35.61%。遮荫50%时,以N1处理地上部营养器官和生殖器官生物量进入快速增长期的起始日和结束日、 最大生长速率出现日提早,生殖器官生物量理论最大值表现为N1＞N2＞N3; 氮积累量理论最大值、 快速积累持续时间及生长特征值最大; 有利于营养器官对氮的净吸收、 净转移和对棉纤维的贡献; 单株铃数、 单铃重最高,皮棉产量比N2、 N3提高18.90%和29.07%。不遮荫时,以N2处理地上部营养器官生物量的最大生长速率和生长特征值最大; 氮积累量理论最大值、 氮快速积累持续时间及生长特征值也最大; 皮棉产量比N1、 N3提高13.03%和23.67%。【结论】遮荫50%条件下,氮肥追施适度前移(N1),即提前至盛蕾期(6月中下旬)开始追肥,在盛铃期(8月上旬)前结束,可改善遮荫条件下棉花快速生长期的生长特征值,显著增加生物量和氮素积累量,有利于营养器官对氮的净吸收、 净转移和对棉纤维的贡献,最终增加单株铃数、 单铃重和产量。

Effects of nitrogen application on growth and nitrogen accumulation of cotton under shading condition

Objectives] Late maturation is often happened in cotton intercropped with fruit, which causes lower pre-frost lint percentage, the yield is declined seriously. Reasonable nitrogen fertilizer topdressing could regulate and control the growing process of cotton, optimize accumulation and distribution of biomass and nitrogen in organs. The study will provide theory basis for reasonable nitrogen application for the intercropping cotton. [Methods] The cotton cultivar was Zhangmain 49, the feild experiment was performed with split plot design. The main areas were 50% shading ( S50 ) and not shading ( CK). The split areas were N1 ( earlier topdressing), N2 ( normal topdressing) and N3 (more proportion of earlier topdressed nitrogen than N1). Total nitrogen was 320 kg / hm2 , half of them was topdressed with irrigation. The details of topdrossing date and amont was listed in Table 1. Effects of the nitrogen application on dynamic accumulation characteristics of biomass and nitrogen under the shading were studied. [Results] Compared with CK, the theoretical maximum biomass and growth rates of the vegetative organs were higher, while the theoretical maximum biomass, growth rates and growth eigenvalues of reproductive organs biomass were smaller under half shadding. The rapid accumulation of total nitrogen arose 5 -8 d in advance, boll number, boll weight and lint percentage were reduced significantly, lint yield was reduced by 35. 61% in average under the shading of 50% . Under the 50% shading, the start and finish of the rapid growth rates of the vegetative and reproductive organs under N1 were ahead, and the theoretical maximum biomass of the reproductive organs were in order of N1 > N2 > N3. The theoretical maximum nitrogen accumulation, the lasting days of rapid nitrogen accumulation and growth eigenvalues are the largest in N1, which was bonefited to the net absorption, the net transfer of nitrogen and contribution to the fiber nitrogen for vegetative organs, and the lint yield is higher than those of N2 and N3 by 18. 90% and 29. 07% . Under CK, the maximum growth rates and growth eigenvalues of aboveground vegetative organs biomass of N2 are the largest, and the theoretical maximum of nitrogen accumulation, the lasting days of the rapid nitrogen accumulation and growth eigenvalues were the largest, too. Boll number and boll weight were the highest, and the lint yield is 13. 03% and 23. 67% higher than those of N1and N3. [Conclusions] In condition of 50% shading, the ealier nitrogen topdressing (N1), namely, beginning at the full budding stage (in the middle and last ten days of June), ending before the full boll stage (in the first ten days of August), could improve the eigenvalues of the rapid growth period under the shading, increase cotton biomass and nitrogen accumulation significantly, be helpful to net nitrogen absorption, net transfer and contribution to the cotton fiber in vegetative organs, and increase boll number per plant, boll weight and yield finally.