| The moisture stored in the 0～200 cm profile of the soil before sowing plays an important role in the production of winter wheat in drylands.However,the Loess Plateau region lacks water resources,and the natural climate is arid and less rainy.At the same time,the temporal and spatial distribution of precipitation is seriously misaligned with the growth period of winter wheat.The summer fallow period accounts for 2/3 of the annual precipitation,resulting in the winter wheat growth in this region often suffering from drought stress.Adopting annual surface mulching cultivation measures can make efficient use of limited precipitation resources,and the soil water retention effect during the summer fallow period is very important to the yield of winter wheat.This study relies on the long-term positioning field experiments of different anniversary mulching measures in Yongshou County,Shaanxi Province.This experiment has set up four treatments: straw mulching(SM),plastic film mulching(PM),ridge-furrow plastic mulching(RM+FS)and no mulching control(CK).By measuring and calculating important indicators such as soil moisture,soil temperature,soil evaporation,and precipitation utilization efficiency under different mulching methods during the summer rest period,the aim is to quantitatively study the relationship between soil water storage and soil temperature and precipitation during the summer fallow period.In order to find the best mulching cultivation method for dryland winter wheat production,and provide a new approach and theoretical basis for stable and high-yield and environment-friendly agricultural development technology of dryland winter wheat The main conclusions of this experimental study are as follows:1.The study shows that the precipitation in this area is mainly concentrated in the summer fallow period,which accounts for 60% of the annual precipitation.The change of water content in the surface layer of soil from 0 to 20 cm is closely related to the increase of precipitation.Taking mulching measures can effectively improve the stability of soil response to water,and the stability of straw mulching is higher than that of plastic film mulching and ridge-furrow plastic mulching.Taking mulching measures during the summer fallow period can effectively reduce the evaporation of water from the soil surface,and the daily evaporation of the soil surface with the straw mulching method is the lowest.2.The study found that compared with no mulching,straw mulching in the annual mulching planting measures of dryland winter wheat has a significant cooling effect on the topsoil in the summer fallow period,while the use of plastic film mulching measures will have a certain warming effect.The study further showed that there were differences in soil temperature between day and night for each treatment,and the cumulative soil temperature at night was higher than that in the daytime.Although the difference of soil temperature at noon of different mulching treatments is greater than that at other times,on the whole,there is little difference in soil temperature under different mulching methods at each time(CV value is between 0.8%～2.8%).The diurnal variation of the surface temperature of the straw mulching method is more gentle than other mulching methods,so the straw mulching method can effectively stabilize the diurnal variation of the soil temperature.3.There was no significant difference in soil water storage volume of 0～200 cm of soil for each treatment after winter wheat was harvested(the start of the summer fallow period).Over time and the increase in precipitation during the summer fallow period,before the next winter wheat sowing(the end of the summer fallow period),the soil water storage of 0～200cm soil under mulching measures was significantly higher than that in the no mulching treatment.During the summer fallow period,precipitation can supplement the consumption of soil moisture by the growth of wheat in the previous season,which is beneficial to the planting of wheat in the next season.Adopting surface mulching methods can enhance the soil profile to preserve precipitation during the summer fallow period and the average leisure efficiency can be increased to 65% or more,and the moisture storage and water retention effect of straw mulching is the best.The water content difference of soil profiles under different treatments increased with the advancement of the summer fallow period and the deepening of the soil layer.Taking mulching measures was beneficial to increase the water content of the deep soil.Among them,the average water content in the 110～170 cm soil layer of straw mulching treatment increased most obviously.4.The cumulative soil temperature and soil water storage are related in a quadratic function,and the cumulative precipitation during the summer fallow period is linearly related to the soil water storage.The retention and storage capacity of each treatment soil to precipitation during the summer fallow period is different,among which the straw mulching treatment has the best effect.The specific embodiment is that for every 1 mm precipitation during the two-year summer fallow period,the water in the treated SM,PM,RM + FS and CK soil increases by 0.66 mm,0.65 mm,0.64 mm and 0.51 mm respectively.There is a large gap between the contribution of soil cumulative temperature and cumulative precipitation to soil water storage during the summer fallow period.The contribution of cumulative precipitation to soil water storage in the treatment with mulching measures was greater than that in the treatment without mulching.The relationship between soil water storage and soil temperature and precipitation in different mulching methods during the summer fallow period showed that,the straw mulching method has the best water storage and moisture retention capacity and the best effect of inhibiting evaporation during the summer slack.So it is suitable for popularization and application in the winter wheat planting area of the Weibei dry plateau on the Loess Plateau. |
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