膜下滴灌条件下滴水量和滴水频率对棉田土壤水分分布及水分利用效率的影响

通过两年的田间试验，研究了滴水量和滴水频率对膜下滴灌棉田土壤水分分布及棉花水分利用效率的影响.结果表明： 从整个生育期来看，当滴水量(375 mm)相同时，高频滴灌(每3天1次)处理0～20 cm土层含水率较高而深层土壤湿润不够；低频滴灌(每10天1次)处理有利于水分的下渗和侧渗，深层土壤含水率较高，但水分补给不及时，表层土壤偏低；总体上中频滴灌(每7天1次)处理有利于水分在土壤剖面中的均匀分配.当滴水频率相同时，滴水量越大，土壤含水率越高，40 cm以下土层含水率也越高.不同处理的棉田耗水规律基本一致，苗期较低，平均不高于1.7 mm·d^-1，蕾期开始上升至花铃期达到最高，日均耗水量可达8.7 mm·d^-1，吐絮期回落到1.0 mm·d^-1左右.总耗水量与降水和滴水量密切相关，而与滴水频率无关；滴水频率对棉花水分利用效率无显著影响，但水分利用效率随滴水量的增大而显著降低.少量滴灌(300 mm)虽然可以获得较高的水分利用效率，但减产严重，过量滴灌(450 mm)无显著增产效应，水分浪费严重.在当地棉田自然条件下，采用中量(375 mm)+中低频(每7天或10天1次)的滴灌模式为宜.

Effects of irrigation amount and frequency on soil water distribution and water use efficiency in a cotton field under mulched drip irrigation.

A 2-year (2009 and 2010) field experiment was carried out to investigate the effects of irrigation amount (300, 375, and 450 mm) and irrigation frequency (once every 3-, 7-, and 10 days) on the soil water distribution and cotton water use efficiency (WUE) under mulched drip irrigation in North Xinjiang. When the irrigation amount was 375 mm, irrigation once every 3 days induced a higher water content in surface soil (0-20 cm) in the whole growth season of cotton but made the deeper (below 40 cm) soil not moistened enough. Irrigation once every 10 days benefited the irrigation water penetrated downward or sideways and made the deeper soil have a higher water content; however, this drip irrigation did not replenish water in time, and made the surface soil water content lower. Overall, drip irrigation once every 7 days benefited the uniform distribution of irrigation water in soil profile. Under the same irrigation frequencies, the larger the irrigation amount, the higher the soil water content. The cotton water consumption in all treatments had the similar pattern, i.e., lower at seedling stage (averagely <1.7 mm·d^-1), increased gradually since squaring stage and reached the maximum at full bloom stage (about 8.7 mm·d^-1), and decreased at open-boll stage (about 1.0 mm·d^-1). Under the natural condition, the total cotton water consumption had close correlation with irrigation amount but poor correlation with irrigation frequency, and the cotton WUE decreased significantly with increasing irrigation amount. When the irrigation amount was 300 mm, the WUE was higher but the yield production decreased markedly,whereas excessive irrigation(450 mm)had no significant yield-increasing effect but wasted water. It was suggested that irrigation with an amount of 375 mm and a frequency of once every 7- or 10 days could be an appropriate drip irrigation mode for the local cotton field under natural condition.