旱地雨养农业覆膜体系及其土壤生态环境效应

覆膜技术作为一项有效提高粮食产量的重要手段,在中国西北地区雨养农业中得到广泛的推广应用。本文综述了地膜覆盖体系关于作物产量、土壤水分、土壤温度、土壤养分转化和迁移以及微生物数量和活性等方面的研究进展,以期为旱地雨养农业发展和完善覆膜技术体系提供理论支撑。研究表明:玉米、小麦和马铃薯覆膜处理增产显著,其平均增产率分别为26.2%、37.1%和29.8%;同时,增产受到覆膜方式影响,全覆膜处理增产效果最好,其玉米、小麦和马铃薯平均产量分别比半覆膜处理高30.0%、5.1%和26.4%。覆膜下玉米、小麦与马铃薯的水分利用效率分别比不覆膜处理高42.8%、10.9%和92.8%。覆膜处理影响硝酸盐在土体的空间分布,硝酸盐在膜下出现表聚现象;同时覆膜能够提高氮肥利用效率,减少氮素淋溶损失,降低氨挥发。但关于覆膜下反硝化过程的研究结论不一,还需进一步深入的探讨。覆膜对有机碳的影响与气候、土壤、作物、覆膜年限等有关,其研究结论尚有争议。另外,覆膜增加了农田土壤微生物量,改变土壤物理性状。尽管覆膜显著提高作物产量,其对生态环境却可能存在一定的影响,比如"奢侈耗水"现象,温室气体排放增加,土壤有机质耗竭,农膜残留等问题。因此,进一步系统研究覆膜对土壤生态环境的影响机理,完善覆膜技术体系与应用,全面评估覆膜体系的生态环境影响,对其在中国干旱地区农业生产的可持续发展具有重要意义。

Review of plastic film mulching system and its impact on soil ecological envi-ronment in China's rainfed drylands

Plastic film mulching, as an important and effective cultivation mode that improves grain yield, has been widely used in rainfed agricultural areas in Northwest China. This study reviewed crop yield, soil moisture content, soil temperature, soil nutrient transformation and transport, and microbial population and activity under plastic film mulching conditions. The review was designed to provide theoretical support for improving plastic film mulching system in China''s rainfed dry regions. Researches results showed that maize, wheat and potato increased yields significantly under plastic film mulching compared to no mulching condition. Yield increase was influenced by plastic film cover mode, with an average increase rate of 26.2%, 37.1% and 29.8%, respectively. Full-film mulching most significantly increased crop yield. Average yields of maize, wheat and potato were respectively 30.0%, 5.1% and 26.4% higher than ridge and furrow system with ridge mulching. Water use efficiencies of maize, wheat and potato under film mulching increased respectively by 42.8%, 10.9% and 92.8% over no mulching. Film mulching influenced vertical distribution of nitrate in the soil profile, with nitrate accumulation in the topsoil layer under plastic film mulching. Also film mulching improved nitrogen fertilizer use efficiency, and reduced nitrogen leaching and ammonia volatilization. However, there were some different conclusions on denitrification under film mulching system, which required further studies. The influence of film mulching on organic carbon was related to climate, soil, crop and mulching time, which meant that the results were not consistent. In addition, film mulching increased farmland soil microbial biomass and changed soil physical properties. Although film mulching significantly improved crop yields, it certainly affected the ecological environment via such processes as "extravagant water deprivation", increased greenhouse gas emission, soil organic matter exhaustion, mulch film residues, etc. Thus further systematic research on the controlling mechanisms, improvement strategies of film mulching technology and comprehensive evaluation of the effect of film mulching system on ecological environment needed urgent attention for sustainable development of agricultural production in China''s arid areas.