| Drought and low rainfall and uneven seasonal distribution are one of the key factors restricting the development of apple industry.Mulching is a widely used water storage and conservation measure in arid and semi-arid areas,which can increase rainfall infiltration,reduce soil evaporation and realize the cross-season utilization of water.Based on the Baishui Apple Test Station of Northwest Agricultural and Forestry University,this study set up the management mode of grass mulching,straw nulching and cloth mulching in the dwarf apple orchard,and studied the characteristics of soil available water space-time change,rainfall infiltration and soil moisture decay law,soil evaporation and water utilization efficiency through long-term positioning monitoring,and investigated the growth status of fruit trees and fruit yield.In order to provide theoretical basis and technical support for the optimization of apple cultivation technology in drylands.The following key results are based on three years of research data:(1)The variation characteristics of soil available water content under different precipitation years were clarified.The variation range of soil available water content in normal years was greater than that in under-water years.Mulching increased the variation range of soil available water compared with clean tillage.There were significant differences in root distribution layer and root expansion layer in normal rainfall years(P < 0.05).During the growth period of fruit trees in different precipitation years(March to October),the soil available water content decreased first and then increased.The available water supplement was less than consumption in the under-water years,and the opposite was observed in the normal years.Compared with clean tillage,straw mulching and cloth mulching could increase the available water storage and reduce soil water deficit in different precipitation years.Grass mulching increased the effective water storage of root rare layer in normal years,but the water deficit of root main distribution layer in different precipitation years was greater than that in clean tillage.(2)The water storage effect of different covering measures is clarified: After typical rainfall,mulching can promote rainfall infiltration.The fitting results show that for every 1mm increase in rainfall,the infiltration depth and infiltration amount under straw mulching,cloth mulching and grass mulching are 0.3389,0.2277,0.1534 cm and 0.0632,0.0437,0.0373 mm higher than those under clean tillage,respectively.According to the fitting formula,when the rainfall is less than 6.17 mm,the rainfall infiltration under straw mulching is lower than that under clean tillage.With the increase of rainfall,the water storage capacity of straw mulching increases.When the rainfall is greater than 95.72 mm,the rainfall infiltration depth under straw mulching is the largest.Mulching affected the attenuation rate of soil moisture after rain.Straw mulching and cloth mulching could significantly reduce the loss rate of soil moisture after different types of rainfall(P < 0.05).The loss rate of soil moisture under grass mulching was higher than that under clean tillage after light rain and moderate rain.(3)The preservation effect of different mulching measures is defined: Covering can reduce soil temperature during growth period,soil evaporation,and evaporation fluctuation after rain.The soil evaporation of different treatments was in the order of clear tillage > grass mulching > straw mulching > cloth mulching.The evaporation reduction efficiencies of grass mulching,straw mulching and cloth mulching during the vigorous evaporation period were38.81 %,48.03 % and 50.41 %,respectively.The effects of daily average temperature and rainfall on soil evaporation are different in different precipitation years.The effect of temperature on soil evaporation in normal years is greater than that in under-water years,while the effect of rainfall on soil evaporation in normal years is less than that in under-water years.Covering in different precipitation years can weaken the response of soil evaporation to temperature and rainfall.(4)The effects of different mulching measures on the growth,yield and water use efficiency of fruit trees were revealed.Mulching can optimize the structure of fruit branches,increase the number of short branches and the proportion of short branches,and improve the yield and water use efficiency of fruit trees.Compared with clean tillage,the yield of fruit trees under straw mulching and cloth mulching increased by 10.26 % and 11.04 % in underwater years and 9.10 % and 8.67 % in normal years,respectively.In conclusion,straw mulching and cloth mulching both have the effect of water preservation and increase production,but when the rainfall is small,straw mulching will blocking rainfall infiltration,furthermore,straw in Loess have the low quantity and high price,economic benefits are lower than cloth mulching,therefore,cloth mulching is the most appropriate coverage measures in the dwarf apple orchard. |
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