施氮量对麦后直播棉氮素吸收利用的影响

Effects of nitrogen application rates on nitrogen uptake and utilization of direct-seeded cotton after wheat harvest

以早熟棉中棉所50为材料进行麦后直播棉花试验,研究施氮量(0、60、120、150、180、240kg N·hm^(-2))对棉株氮素吸收、利用和分配的影响.结果表明:增施氮肥提高了麦后直播棉不同生育阶段的氮吸收量,以盛花到见絮期的氮积累增量最大,并且改变了不同生育期间氮吸收比例,使棉花出苗到盛花期的氮吸收比例降低,盛花到吐絮期的氮吸收比例升高;增施氮肥还降低了生育后期中上部位果枝氮浓度的下降速率.麦后直播棉氮素和生物量累积以中下部果枝为主,在150-180 kg N·hm^(-2)施氮量下棉花产量、氮肥表观利用率、各果枝部位干物质和氮在生殖器官中的分配比例较高,氮浓度和氮累积量动态特征参数比较协调.高于180kg N·hm^(-2)的施氮量导致棉花中部和下部果枝生殖器官生物量和氮素累积量、产量增幅和氮肥利用率降低,而低于150 kg N·hm^(-2)施氮量降低棉花整株干物质和氮经济系数,不利于高产形成.综合分析,150~180kg N·hm^(-2)施氮量可作为长江流域下游棉区麦后直播棉的推荐施氮量.

An experiment was carried out to study the effects of different nitrogen application rates（0,60,120,150,180 and 240 kg N·hm^-2 on the nitrogen uptake,utilization and distribution of short season cotton cultivar（CCRI-50） which was directly seeded after wheat harvest.Results showed that nitrogen application increased the nitrogen uptake of cotton at different growth stages,with the highest increment at the peak flowering-boll opening stage.Nitrogen application changed the percentages of nitrogen uptake among different growth stages.The percentages of nitrogen uptake decreased from seedling to peak flowering stage,but increased from peak flowering to boll maturing stage.In addition,nitrogen application reduced the decreasing speed of nitrogen concentration in middle and upper fruiting branches at later growth stages.Direct-seeded cotton had nitrogen and biomass accumulation in the lower and middle reproductive branches.With the nitrogen application of150-180 kg·hm^-2,the lint yield,NARE（nitrogen apparent recovery efficiency） and the economic coefficient of biomass and nitrogen were relatively higher,and the eigenvalues of dynamic model of nitrogen content and nitrogen accumulation were relatively coordinate.Excessively high nitrogen application（over 180 kg N·hm^-2 decreased biomass and nitrogen amount of reproductive organ in lower and middle branches,narrow rise of yield,and lower nitrogen use efficiency.However,excessively low nitrogen application（lower than 150 kg N·hm^-2 also resulted in lower economic coefficient of biomass and nitrogen and yield.These results suggested the optimum nitrogen application rate 150-180 kg N·hm^-2for direct-seeded cotton after wheat harvest in lower reaches of Yangtze River.