| Weather has great influence on crop growth and agricultural production,because it depends on the transpiration of crops in this period,and it can also be an indicator of farmland irrigation decision.In order to better analyze the optimal irrigation system of cotton drip irrigation under mulch under the guidance of meteorological information in southern Xinjiang,a field experiment was conducted in 2019-2020.Three stages of experimental irrigation time were set,which were irrigation when the difference between daily crop evapotranspiration and precipitation(ET_C-P) was 25 mm,30 mm and 35 mm,and the corresponding irrigation quota was 30 mm,36 mm and 42 mm respectively.The effects of different irrigation treatments on soil moisture and salt were studied on the basis of the field experiment,the DSSAT model calibrated and verified by the field experiment was optimized and simulated.driven by the meteorological data from 2017 to 2018,with irrigation time of 25 mm,and 7 different irrigation quotas were set.24 mm,27 mm,30 mm,33 mm,36 mm,39 mm and 42 mm respectively.The combination of irrigation time and irrigation quota was constantly adjusted by DSSAT model,and then the irrigation system of cotton with high efficiency and water saving was obtained.The main research results are as follows:(1) According to the meteorological information,cotton drip irrigation under mulch in southern Xinjiang,the soil moisture content of vertical sections of each experimental treatment soil increased first and then decreased with the increase of soil depth during the growth period of cotton,and reached the maximum at 60 cm of soil layer.The soil salinity of the three experimental treatments decreased with the increase of irrigation quota,which indicated that large irrigation quota could promote soil desalination.(2) Irrigation was carried out according to the foundation.Because of the high irrigation quota,the plant height,stem diameter,leaf area index and total dry matter mass of cotton in T3 treatment were higher than those in T1 and T2 treatment,which indicated that higher irrigation quota was beneficial to maintain the vegetative growth of cotton plants.T1 and T2 treatments had no significant difference in cotton yield and quality,but both were higher than T3 treatments.Water use efficiency decreased with the increase of irrigation quota and total water consumption,among which T1 treatment was the highest,T2 treatment was the second and T3 treatment was the smallest,which indicated that the combination of high frequency irrigation and small irrigation quota could improve cotton yield and water use efficiency in southern Xinjiang.(3) Based on the 2-year meteorological data driven DSSAT model,through the analysis of 7 irrigation simulation schemes,the cotton yield showed a trend of first increasing and then decreasing with the increase of irrigation quota in the same irrigation time,showing a quadratic parabola shape,while the water use efficiency decreased with the increase of irrigation quota.Under the same irrigation quota,the combination of high frequency irrigation and small irrigation quota can improve cotton yield and water use efficiency.(4) According to the analysis of DSSAT model simulation results,comprehensive irrigation quota,yield,water use efficiency and other indicators,when the difference between daily crop evapotranspiration and precipitation in cotton field reaches 25 mm for irrigation,irrigation is carried out 11 times in cotton growth period,and irrigation quota is 280～314 mm,irrigation water use efficiency can be improved,which can be used as the optimal irrigation system for cotton under mulch drip irrigation in southern Xinjiang. |
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