| Object:Film-mulched drip irrigation is the main production-increasing technology for cotton in Xinjiang,China,but long-term use and low recovery rate have resulted in serious pollution from residual film,which has become one of the main factors limiting the sustainable development of cotton in Xinjiang.Filmless cotton can solve the problem of residual film pollution from the source,but its water and fertilizer loss is rapid,and it loses the effect of warming and moisturizing.We assume that the optimal irrigation volume under early-maturing varieties,high-density,and deep drip irrigation can compensate for the negative effects of filmless on cotton growth.Methods:This study was conducted at the Scientific Observation and Experimental Station of Crop Water Efficient Water Use（Shihezi）（45°38′N,86°09′E）of the Ministry of Agriculture from 2019 to 2020,the early-maturing land cotton variety‘Xinluzao 74’was used as a test material（The growth period was 120 d）.The drip irrigation belt was buried at a depth of 15cm.5 irrigation water treatments（W1,2649 m3/hm2;W2,2925 m3/hm2;W3,3201 m3/hm2;W4,3477m3/hm2;W5,3753 m3/hm2）were set up.Carry out research on soil moisture content,temperature,salinity and p H value,canopy structure,light distribution,temperature and humidity,dry matter accumulation and distribution,yield changes and its response to drip irrigation in the root zone.Results:The main results are as follows:1.Some parameters were evaluated,including the change of moisture,temperature and salt concentration in the root zones.The results showed that the soil water content was ranked in order of W5（W4,W3,W2）before the full flowering period>W1.There was no significant difference between the treatments after the full flowering period,but 21.2%-35.0%lower than that before the full flowering period（P<0.05）.Soil temperature W4was 0.3%-1.2%higher than other treatments（P>0.05）.The soil p H was lower in the W4treatment;the soil layer of 0-30 cm before the initial flowering period and>10-20 cm after the full boll period were 0.1%to 0.8%and 0.6%to 1.3%lower than other treatments,respectively（P>0.05）.The soil electrical conductivity was 6.4%to 19.4%higher than other treatments in the 0-30 cm soil layer under W3treatment（P<0.05）.The correlation analysis showed that soil temperature had a significant negative correlation with soil moisture content and a significant positive correlation with soil conductivity in 20 cm soil layer,and soil conductivity had a significant or extremely significant negative correlation with soil p H value in 0-30 cm soil layer at flowering stage.2.The response of canopy microenvironment to irrigation amount and the relationship between canopy microenvironment and root microenvironment of cotton were studied.The results showed that with the increase of irrigation water,the canopy PAR permeability decreased by 4.1%-18.7%.Leaf area index and mean tilt angle in W4treatment were 1.4%-22.3%and 0.3%-8.7%higher than those in other treatments,which were significantly different from those in W1and W2treatment.The average temperature of the canopy is 0.2%-2.2%lower than other treatments,and the humidity is 0.6%-2.9%higher than other treatments.Correlation analysis showed that the canopy PAR transmittance had a very significant negative correlation with soil water content,leaf area index,leaf inclination,and canopy humidity,and a very significant positive correlation with canopy temperature.The salinity accumulation in the 20 cm soil layer was significantly negatively correlated with the minimum canopy temperature,PAR light transmittance and leaf inclination.3.The response of dry matter accumulation and allocation and yield to irrigation amount and the effect of root and crown micro-environmental factors on yield of cotton were studied.The results showed that with the increase of irrigation water,The total dry matter of cotton and the dry matter weight of buds and bolls increased by 7.6%-45.9%and 22.0%-54.1%.The seed cotton yield in 2020 increased by45.6%-65.5%,compared with 2019（P<0.05）.W4treatment was higher with 4.1%-10.3%increment,compared with other treatments（P<0.05）.The total number of bolls per unit area and the weight of a single boll increased by 4.2%-11.4%and 2.2%-4.1%in W4treatment,compared with other treatments（P<0.05）.The cotton fiber quality did not reach a significant difference.The optimal regression equation of cotton root and crown microenvironment index（Xi）on yield（Y）for deep drip irrigation filmless:Y=27218.720-125.705X55-723.081X60-919.771X68+25.386X99+170.137X104-1854.187X113+552.406X120.The coefficient of determination R2is 0.993.It can be seen from the regression equation that the soil temperature in the root zone of the 30-40 cm soil layer at the bud stage,the leaf area index at the bud stage,the soil p H value of the 10 cm soil layer at the initial flowering stage,the PAR light transmittance of the canopy at the later full boll,and the boll opening canopy temperature and humidity have a direct effect on yield traits,and the effect is significant.Conclusion:Therefore,under the conditions of film-free high-density and deep drip irrigation,when the drip irrigation amount is 3477 m3/hm2,it is beneficial to create a suitable temperature,salinity environment and canopy structure in the root zone（especially>10-20 cm soil layer）for cotton growth.,light distribution,temperature and humidity environment,and then promote the accumulation and distribution of dry matter in the shoots of cotton plants,while not significantly reducing the quality of cotton,the yield of seed cotton reaches 4873 kg/hm2,achieving the goal of clean and efficient cotton production in arid areas. |
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