垄覆膜集雨对苜蓿草地土壤水分动态及利用效率的影响

摘要

我国西北黄土高原干旱半干旱区年降雨稀少和土壤水分周期性亏缺,导致人工草地生产力低下、水分利用效率低.本试验在旱作条件下,将垄覆膜集雨措施应用于紫花苜蓿种植,研究了沟垄宽比和覆膜方式对2年龄苜蓿草地土壤水分动态及水分利用效率的影响.结果表明:垄覆膜集雨在集雨前期(4月中旬至6月上旬)显著提高0～20 cm土层土壤含水量,在集雨中后期(6月中旬至9月下旬)显著提高0～120 cm土层平均含水量,越冬期增加土壤水分入渗能力,提高20～120 cm土层平均含水量;且垄覆膜处理的集雨效率高于土垄处理.随着生育时期的延伸,垄覆膜处理0～120 cm土壤平均贮水量呈先降后升的趋势,土垄处理0～120 cm土壤平均贮水量呈由高到低的趋势;在苜蓿生长后期垄覆膜处理的蓄墒能力显著高于土垄处理.垄覆膜处理的平均水分利用效率为34.91 kg·mm-1·hm-2,为对照(平作,CK)的2.25倍,土垄处理的平均水分利用效率为28.47kg·mm-1·hm-2,为CK的1.83倍,垄覆膜相对土垄处理平均水分利用效率提高22.62%:垄覆膜处理以沟垄宽比为60 cm:60 cm和60 cm:75 cm的水分利用效率最高.%The productivity and water use efficiency of cultivated pastures are low in arid and semiarid areas of the Loess Plateau due to low annual rainfall and periodical deficit of soil moisture.In this study, the rainwater harvesting system via plastic film-covered ridge was applied in production of biennial Medicago sativa grassland in dryland.And the impact of ditch/ridge ratio and mulching patterns on the trends and use efficiency of soil moisture were determined.Results showed that rainwater harvesting by plastic film-covered ridge significantly improved soil moisture content in 0～20 cm soil at early stage of rainwater harvesting (from the middle ten-day of April to the first ten-day of June).It also greatly enhanced average soil moisture content in 0～120 cm soil at mid-late rainwater harvesting stage (from the middle ten-day of June to the last ten-day of September).During winter, rainwater harvesting via plastic film-covered ridge increased soil infiltration capacity and improved average soil moisture content in 20～120 cm soil.Further, the rainwater harvesting efficiency of plastic film-covered ridge was higher than that of compacted bare ridge.The moisture storage in 0～120 cm soil with rainwater harvesting via plastic film-covered ridge initially dropped, and then rose during the growth period of M.sativa.At late growth stage, soil moisture storage with rainwater harvesting via plastic film-covered ridge was evidently higher than that via compacted bare ridge.Average water use efficiency with plastic film-covered ridge was 34.91 kg · mm-1 · hm-2, which was 2.25 times that of CK (flat field without ridge and mulch).Average water use efficiency with compacted bare ridge was 28.47 kg · mm-1 · hm-2, which was 1.83 times that of CK.Average water use efficiency of plastic film-covered ridge increased by 22.62％ compared with that of compacted bare ridge, and the highest ones were in plastic film-covered ridges with 60 cm/60 cm and 60 cm/75 cm ditch/ridge ratios.