施氮量对长江流域滨海盐土棉花氮素吸收利用的影响

【目的】长江流域下游棉区棉花种植逐渐向沿海地区集中,但该地区棉花生产中氮肥运筹不合理问题突出,本研究旨在揭示长江流域滨海盐土棉花氮素吸收利用对施氮量的响应特征,以期为该区棉花的合理氮肥运筹提供理论依据。【方法】2010年和2012年在江苏省大丰市稻麦原种场(33.2°N,120.5°E)滨海盐土棉田,以湘杂棉8号棉花品种为材料,设置施氮(N)量0、150、300、375、450、600 kg/hm2试验,研究了长江流域下游滨海盐土条件下,施氮量对棉花产量、不同空间部位生物量和氮素累积分配特征以及氮素利用的影响。【结果】随施氮量的增加,棉花皮棉产量和氮肥表观利用率均呈先升高后降低的趋势,并在301 374 kg/hm2施氮量范围内,皮棉产量和氮素表观利用率达到最高,氮肥农学利用率、氮肥偏生产力和氮素生产效率则随施氮量的增加呈降低趋势。施氮量通过调控棉花不同果枝部位氮含量和氮累积量的动态特征影响氮素和生物量的累积转运,进而影响棉花产量。适宜施氮量(301 374 kg/hm2)下,棉株各部位氮素含量和氮素累积动态特征参数比较协调,有利于光合产物向生殖器官的转运,进而提高产量;过量施氮增加了棉株各部位氮素含量,棉株下部氮素累积速率加快,氮素快速累积期持续时间延长,棉株中部氮素快速累积期持续时间延长,棉株中下部的光合产物以及氮素向生殖器官的分配减少,吐絮期氮素的吸收比例和累积量增大,产量降低;施氮不足则降低了棉株各部位氮含量,加快了各部位氮素含量的降低,减少了氮素累积量,降低了棉株生物量和皮棉产量。【结论】在长江流域滨海盐土地区,棉花生产的推荐施氮量为301 374 kg/hm2,该施氮量下棉花产量和氮肥表观利用率相对较高。超过该适宜施氮量,棉花产量降低归因于棉株中下部光合产物和氮素向生殖器官的转运受到抑制,并且增加了生育后期氮素的吸收比例和累积量,棉花贪青晚熟。低于该施氮量则由于氮素供应不足,氮累积量和生物量减少,导致产量降低。

Effects of nitrogen application rate on the nitrogen uptake and utilization of cotton grown in coastal saline fields of Yangtze River Valley

【Objectives】 Unreasonable nitrogen application has been a main problem in cotton cultivation in the coastal saline land of Yangtze River Valley. The aim for this study was to identify the response of nitrogen uptake and utilization of cotton grown in the coastal saline land of Yangtze River Valley to nitrogen application rate, and provide theoretical support for reasonable nitrogen application in the area. 【Methods】 Field experiments were carried out with different nitrogen application rates(0, 150, 300, 375, 450 and 600 kg/hm2) in coastal saline land in Dafeng(33.2°N,120.5°E), Jiangsu Province in 2010 and 2012. A cotton cultivar, Xiangza No.8, was selected for the study. The cotton yield, biomass accumulation and distribution, nitrogen uptake and utilization were investigated. 【Results】 The lint yield and nitrogen apparent recovery efficiency(NARE) of cotton are increased firstly and then descended with the increase of nitrogen application rate, and reach their high values under 301-374 kg/hm2. The nitrogen agronomic efficiency(NAE), nitrogen partial factor productivity(NPP), and nitrogen production efficiency(NPE) are descended with the increase of nitrogen application rate. The dynamic characteristics of the nitrogen content and nitrogen accumulation amount of cotton plant are changed under the nitrogen application, and affect the accumulation and translocation of biomass and nitrogen to reproductive organs and lastly affect the yield of cotton. The eigenvalues of the dynamic model of the nitrogen content and nitrogen accumulation in 301-374 kg/hm2 nitrogen rates are more harmonious those of the other treatments. In excessive nitrogen supply rates, the nitrogen content and nitrogen accumulation rate in the all fruiting branch parts are increased, the duration of fleetly accumulation of nitrogen is elongated and the reproductive distribution of biomass and nitrogen are descended in low and middle fruiting branch parts, the proportion and amount of nitrogen uptake at the boll maturing stage are increased, and the lint yield is decreased. In deficient nitrogen supply conditions, the nitrogen content in the all fruiting branch parts is reduced, the reduced rate of nitrogen content is increased, the biomass and accumulation amount of nitrogen are reduced, and subsequently the lint yield is reduced. 【Conclusions】 According to the results of the two-year field experiments in the coastal saline land of Yangtze River Valley, N of 301-374 kg/hm2 is considered as an appropriate nitrogen application rate for cotton production in the area. Excessive nitrogen supply will cause yield loss because of the reduces of the reproductive distributions of biomass and nitrogen in low and middle fruiting branch parts, and increase the proportion and amount of nitrogen uptake at the boll maturing stage. Deficient nitrogen supply reduces the lint yield due to the decrease of the nitrogen content in the all fruiting branch parts, and reduces the biomass and accumulation amount of nitrogen.