生命科学学院知识库

全球变暖加剧了气候的变化，导致全球平均温度升高和降水分布不均，再加上农业可用水资源的日益匮乏，提高作物水分利用效率(WUE)和增加作物产量就成了农业生产面临的首要问题。土壤覆盖可以有效的减少土壤水分蒸发，从而改善土壤水分含量，增加作物产量；灌溉也是增加作物产量的一种措施，但如何更有效的利用灌溉用水，还有待进一步研究。本研究收集了来自122篇文献中的1483个数据，利用Meta分析研究不同土壤覆盖处理、不同土壤灌溉处理和不同水平滴灌处理对几种作物产量和水分利用效率的影响。研究目的是(1)量化不同土壤覆盖处理对玉米产量、水分利用效率和蒸散量的影响；(2)量化不同灌溉处理对作物(棉花、玉米、高粱、辣椒、番茄、卷心菜、秋葵和黄瓜)产量和灌溉水分利用效率(IWUE)的影响；(3)量化不同水平滴灌处理对作物(棉花、卷心菜和甜瓜)产量和灌溉水分利用效率的影响，从而选择出不同作物的最优滴灌处理水平；(4)评估在不同土壤类型下，土壤覆盖、土壤灌溉和不同水平滴灌处理的产量效应；(5)估算降水和温度对覆膜处理增产效应的影响，即在何种降水和温度条件下覆膜处理的增产效应会消失。研究结果表明：
1）与平作不覆盖(对照，CK)相比，秸秆和地膜覆盖都显著的增加了玉米产量和水分利用效率(除了秸秆垄作SMR)。地膜覆盖比秸秆覆盖的增产效应更显著，特别是在寒冷和干旱的环境中。四种覆盖处理中，覆膜垄作(PMR)的产量最高；且相比于粉砂壤土，该处理在粘壤土中的增产效应更高。相比较CK处理，秸秆覆盖和地膜覆盖均增加了土壤湿度，且地膜覆盖的效果更好；同时地膜覆盖还改善了玉米生长早期的土壤温度。
2）传统地面灌溉(漫灌、沟灌、喷灌等)能够有效地增加作物产量，但其用水量大，灌溉水分利用效率较低。滴灌处理不仅能显著地增加作物产量，还能有效地提高作物的灌溉水分利用效率，且滴灌+地膜覆盖处理的产量效应最高。不同土壤类型下，滴灌(不覆盖)处理的作物产量效应之间无显著差异。
3）相比较充分(即100%)滴灌，不充分滴灌不仅能够有效的节省灌溉用水，而且能够进一步提高作物的灌溉水分利用效率，也不会对产量造成严重的影响，从而在降低农业生产成本的基础上达到较高的经济效益。其中棉花、甜瓜和卷心菜的最优滴灌水平分别为0.8I、0.75I和0.6I (I：100%充分滴灌下的灌溉量)。不同土壤类型下，不同水平滴灌(不覆盖)处理的作物产量效应也无显著差异。
4）随着生育期降水量和平均温度的增加，地膜覆盖对玉米产量的积极效应逐渐降低。当地区的生育期降水量大于770mm，生育期平均温度大于24°C时，覆膜在这些地区的增产效应趋于0。而秸秆覆盖的增产效应不随生育期降水量和温度的变化而变化，因此可以作为水热条件较好地区的覆盖方式。本研究的结果可以为农业应对全球变化提供科学依据。

Global warming has intensified climate change, and result in higher global mean temperature and uneven distribution of precipitation. Moreover, the increasing scarcity of available water resources for agriculture, therefore increase crop water use efficiency (WUE) and crop yield have become the primary issues in agricultural production. Soil mulching can reduce the soil evaporation, improve soil moisture content and increase crop yield; Irrigation is also a practice to increase crop yield, but how to use irrigation water more effective remains to be further study. In this study, we collected 1483 observations from 122 published papers and used meta-analysis to investigate the effect of different soil mulching, different soil irrigation and different levels of drip irrigation on crop yield and water use efficiency. The aim is to (1) quantify the effects of different soil mulching on maize yield, water use efficiency and evapotranspiration; (2) quantify the effects of different soil irrigation on crop (cotton, maize, sorghum, pepper, tomato, cabbage, okra, and cucumber) yield and irrigation water use efficiency (IWUE); (3) quantify the effects of different levels of drip irrigation on crop (cotton, cabbage, and muskmelon) yield and irrigation water use efficiency in order to select the most optimal drip irrigation level for different crop; (4) evaluate the yield effects of different soil mulching, different soil irrigation, and different levels of drip irrigation in different soil types; and (5) estimate the effects to plastic mulching by precipitation and temperature, i.e., under which precipitation and temperature conditions do the positive effects of plastic mulching on maize disappear. The results show that:
1) Compared with no mulch + flat (CK), both straw mulch and plastic mulch were significantly increased maize yields and WUE (except for SMR), and that plastic mulch was more effective than straw mulch in increasing yields, particularly in cold and dry environments. PMR has the highest yields and is more effective in clay loam than in silt loam soils. Straw mulch, but particularly plastic mulch, increased the soil moisture compared to the CK treatment, while plastic mulch increased soil temperature, mainly in early stages of maize growth.
2) Traditional irrigation (flood irrigation, furrow irrigation, and sprinkler irrigation) can effectively increase crop yield, but due to the large amount of water use, the irrigation water use efficiency was lower. Drip irrigation can not only significantly increased crop yield, but also effectively improved crop irrigation water use efficiency, and the yield effects of drip irrigation and plastic mulch was the highest. There was no significant difference in crop yield effects of drip irrigation (no mulch) under different soil types.
3) Compare with 100% drip irrigation (1.0I), the deficit irrigation can not only effectively save irrigation water, but also further improve the crop irrigation water use efficiency, and it will not cause serious impact on crop yield, thus achieving higher economic benefits on the basis of reducing the cost of agricultural production. The optimal drip irrigation levels of cotton, muskmelon and cabbage were 0.8I, 0.75I and 0.6I (I, the water consumption under 100% full drip irrigation), respectively. There was also no significant difference in crop yield effects of different deficit irrigation (no mulch) under different soil types.
4) The positive effects of plastic mulch on maize yield diminished with increasing mean growing-season temperature and precipitation, reaching zero when the growing-season precipitation was greater than 770 mm and the mean growing-season air temperature exceeded 24°C. But the straw mulch has not significant change across the precipitation and temperature gradients, including when the benefits of plastic mulch reached zero, thus it can be used as a mulch practice in better hydrothermal conditions.The result of this study can provide a scientific basis for agriculture to response to global changes.