施氮量对滨海改良盐土棉花钾累积利用的影响

以长江流域大面积种植的转基因棉湘杂棉8号为材料,在江苏省大丰市稻麦原种场(33.2°N,120.5°E)滨海改良盐土上研究施氮量(0、150、300、375、450、600 kg N hm–2)对棉株钾素吸收、利用和分配的影响。结果表明,增施氮肥提高不同生育阶段棉株钾的吸收量,以盛花到见絮期的钾积累增量最大,并改变生育期间的钾吸收比例,使出苗到盛花期的钾吸收比例降低,盛花到吐絮期的钾吸收比例升高;同时,增加施氮还降低生育后期中上部果枝钾浓度的下降速率,但对下部果枝影响较小。随施氮量增加,各部位果枝氮对钾吸收的边际效应(每增施1 kg氮促进钾的吸收量)呈先升高后降低趋势,且果枝部位越高,基于最大边际效应的施氮量越高。在300~375 kg hm–2施氮量范围内,干物质和钾在经济器官中的分配比例提高,钾浓度和钾累积量动态特征参数比较协调,中部和上部果枝氮素对钾吸收的边际效应和钾的皮棉生产效率较高,利于高产形成。高于375 kg hm–2的施氮量导致皮棉产量增幅下降,氮素对钾吸收的边际效应和钾的皮棉生产效率较低;低于375 kg hm–2的施氮量降低干物质和钾经济系数,不利于高产形成。

Effect of Nitrogen Application Amounts on Uptake and Utilization of Potassium in Cotton Grown in Improved Coastal Saline Land Regions

A field experiment using transgenic cotton cultivar Xiangzamian 8 with different nitrogen application amounts(0, 150, 300, 375, 450, and 600 kg N ha^–1)was carried out in the coastal improved saline land region of Dafeng city in 2010 and 2012. Results showed that the nitrogen application increased potassium uptake of cotton at different growth stages, with the highest increment at the peak flowering-boll opening stage, and the percentages of potassium uptake decreased from seedling to peak flowering stages, but increased from peak flowering to boll maturing stages. In addition, nitrogen application lowered the decreasing speed of potassium concentration in middle and upper fruiting branches at later growth stages, but had less influence on lower fruiting branches. The marginal effectof potassium uptake (promoted amount of potassium uptake due to 1 kg increase of N application) showed an upward-downward trend with the increase of nitrogen application rate. The higher the position of fruiting branches grown, the more the nitrogen amount demanded to meet the highest marginal effectof potassium uptake. Under the nitrogen application of 300–375 kg ha^–1, the economic coefficient of biomass and potassium was relatively high, eigenvalues of dynamic model of potassium content and potassium accumulation were relatively coordinate, and the marginal effectof potassium uptake and lint production efficiency of potassium were relatively high in middle and upper fruiting branches. Excessively high nitrogen application resulted in a relatively narrow rise of yield, and the marginal effectof potassium uptake and lint production efficiency of potassium were relatively low; excessively low nitrogen application, however, also resulted in a lower yield, as economic coefficient of biomass and potassium was relatively low.