灌溉水盐度和施氮量对棉花产量和水氮利用的影响

淡水资源不足和盐渍化是干旱半干旱地区农业生产的重要限制因素，因此提高水、 肥利用效率和作物产量，减少根区盐分积累和地下水污染风险是这些地区水分养分优化管理的重要目标。通过田间试验研究了滴灌条件下灌溉水盐度和施氮量对棉花产量和水、 氮利用率的影响。试验设置灌溉水盐度和施氮量两个因素，灌溉水盐度（电导率，EC）设3个水平，为0.35（淡水）、 4.61（微咸水）和 8.04（咸水）dS/m，分别用SF、 SM和SH表示；施氮（N）量设4个水平，为0、 240、 360和480 kg/hm2，分别以N0、 N1、 N2和N3表示。研究结果表明，棉花干物质重、 氮素吸收量和氮肥利用率受灌溉水盐度、 施氮量及二者交互作用的影响显著。咸水灌溉处理（SH）棉花干物质重、 氮素吸收量、 产量和氮肥表观利用率均显著降低，而微咸水灌溉（SM）对棉花氮素吸收量和氮肥表观利用率影响不大，但干物质重和产量有所降低。施氮肥可显著促进棉花生长，增加干物质重、 氮素吸收量和产量，但随着灌溉水盐度的增加，其促进效应明显受到抑制。微咸水和咸水灌溉会导致水分渗漏增加、 蒸散量降低，增施氮肥则可显著降低水分渗漏、 增加蒸散量。微咸水灌溉水分利用率最高，其次是淡水灌溉，咸水灌溉最低；增施氮肥则可显著提高水分利用率。因此滴灌条件下，高盐度的咸水不宜用于灌溉。而短期的微咸水灌溉不会对棉花产量和水、 氮利用率产生严重的负面影响；同时，合理的配施氮肥也有助于促进棉花生长，提高棉花产量和水分利用率。

Effects of water salinity and nitrogen rate on yield, WUE and NUE of cotton under drip irrigation with saline water conditions

In arid and semi arid regions, fresh water scarcity and salinity are the serious and chronic problem for agricultural production. The purposes of optimal water and nutrient management are to maximize water and fertilizer use efficiencies and crop production, and to minimize salt accumulation in root zone and groundwater pollution in these regions. In this study, field experiments were conducted to investigate effects of irrigation water salinity and N application rate on yield, water use efficiency (WUE) and nitrogen use efficiency (NUE) of cotton under drip irrigation conditions. The experimental design was a 3 4 factorial with three water salinity levels (EC 0.35, 4.61, and 8.04 dS/m; denoted as SF, SM and SH, respectively) and four N application rates (0, 240, 360, and 480 kg/ha; denoted as N0, N1, N2, and N3, respectively). Results show that the biomass, N uptake, and NUE of cotton are significantly affected by irrigation water salinity, N rate and their interactions and are decreased significantly by the saline water irrigation with the high salinity level (8.04 mS/cm). There are no significant differences for cotton N uptakes and NUEs between SM and SF treatments, while the biomass and yield of the SF treatment are higher than those of the SM treatment. The growth of cotton is promoted by the N fertilization and the biomass, N uptake, and yield are increased, while those effects are decreased with irrigation water salinity level increasing. Water drainage is increased and evapotranspiration is reduced significantly with the increase of irrigation water salinity level, while water drainage is decreased and evapotranspiration is increased significantly with the increase of nitrogen rate. The treatment of SM has the highest WUE, and the treatment of SH has the lowest WUE. WUEs of three water salinity treatments are increased with nitrogen application rate increasing. Therefore, saline water with EC value more than 8 dS/m is not suitable for drip irrigation, but short period saline water irrigation with EC value less than 5 dS/m does not have a severe adverse effect on yield, NUE and WUE of cotton under drip irrigation conditions. Moreover, optional N application can promote cotton growth and increase yield and WUE of cotton.