Based on mulching experiments through triple cropping in dry-land of seasonal arid region of southwest plateau ,the water effects of different treatments were studied .The results showed that straw and plastic film mulching played a very important role in increasing and reserving soil water .The dual mulching mode with plastic film and straw displayed prominent function ,root region was proved to be key region on crop consuming water and soil reserving water . The changes of farmland water were divided into 3 layers:0~30 cm soil layer that was the active changing layer for soil water content and the obvious changing layer for reserving soil water ,30~80 cm soil layer that was the subordinate active changing layer for soil water content and the significant changing layer for reserving soil water ,and 80~100 cm soil layer that was the relative steady changing layer for soil water content and the relative general changing layer for reserving soil water .Furthermore ,mulching cultivation could impel the crop consuming water converted into effective crop transpiration consuming water from useless evaporation consuming water ,and the availability of farmland water was promoted clearly . Thus ,the study on water effects of mulching through triple cropping patterns in dry-land will allow the enhancements of multiple crop index ,water use efficiency and water production potentiality in seasonal arid area of southwest plateau .%在西南高原季节性旱区进行田间试验，研究不同覆盖栽培条件下“旱三熟”种植模式的农田土壤水分效应。研究表明，秸秆、地膜覆盖尤其是秸秆地膜二元覆盖有明显蓄集和保存土壤水的作用，土壤保蓄水度平均提高60．63％，覆盖能有效减少田间水分的无效蒸发，平均减少181．93 mm ，使作物蒸腾系数和水分利用效率提高，平均提高19．84％和23．5％，而使作物耗水系数减小，平均减少18．26％，根区是作物耗水与土壤保蓄水的关键区域；农田水分变化沿土层可划分为3个层次，即0～30 cm土层为土壤水分变化活跃层和土壤贮水变化明显层、30～80 cm土层为土壤水分变化次活跃层和土壤贮水变化显著层、80～100 cm土层为土壤水分变化相对稳定层和土壤贮水变化缓慢层。覆盖栽培可促进作物耗水量由田间无效蒸发耗水向有效的田间作物蒸腾耗水转化，使农田水分的有效性显著提升。
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