Effects Of Aerated Irrigation On Root Zone Microenvironment And Growth Of Cotton Under Drip Irrigation

Objective:Through two years of experiments,this study aims to propose a reasonable aerated irrigation mode suitable for cotton fields with mulched subsurface drip irrigation in Xinjiang,and provide scientific guidance and theoretical basis for the ecological sustainable development of water-saving irrigation agriculture in arid oasis.Methods:Taking cotton under mulched subsurface drip irrigation as the research object,the Venturi aerated irrigation method was used to conduct separate and combined aeration（seedling AS,bud AB,flowering and bolling AF,bud+flowering and bolling ABF,seedling+bud+flowering and bolling AW aerated with water）at the main water-demanding growth stages of cotton.The experiment was set up with CK as the control treatment,a total of 6 treatments.Results:（1）Aerated irrigation can increase soil oxygen content and improve the microenvironment of root zone.With the advancement of the growth period,the soil oxygen content gradually increased,and the soil respiration rate and soil temperature had the same trend of increasing first and then decreasing.Under aerated irrigation,soil oxygen content,soil respiration and temperature increased significantly by 36.5%-42.3%,26.2%-78.3%and 13.7%-26.9%,respectively.Compared with other treatments,the peak values of soil respiration rate and soil temperature were delayed by 9 days,which prolonged the aeration effect and improved the soil environment.（2）Aerated irrigation can improve the photosynthetic rate of cotton.The net photosynthetic rate,transpiration rate and stomatal conductance of cotton under aerated irrigation were significantly higher than those under conventional irrigation,and the intercellular CO₂ concentration was significantly reduced.Among them,the photosynthetic characteristics of aeration at flower and boll stage were significantly higher than those at other growth stages.The net photosynthetic rate increased by 22.68%,the transpiration rate increased by 41.19%,the stomatal conductance increased by 33.42%,and the intercellular CO₂ concentration decreased by 16.22%.The seedling stage was the second,and the bud stage was the lowest.（3）Aerated irrigation can promote the growth and development of cotton.Aerated irrigation has different effects on the growth and development of cotton at different growth stages.On the whole,aerated irrigation treatments in different periods have promoted the growth of cotton aboveground parts to varying degrees.Aeration at bud stage had significant effects on plant height,stem diameter and leaf area index of cotton.Aeration at seedling stage only had significant effects on stem diameter.Aeration at flowering and boll stage had significant effects on stem diameter and leaf area index.（4）Aerated irrigation is beneficial to the accumulation of dry matter.Aeration at seedling stage,bud stage and flowering and boll stage had significant effects on cotton stem,leaf and bud/boll.Aerated irrigation at flowering and boll stage significantly increased the dry matter accumulation of stems,leaves and buds/bolls by 29.26%,11.15%and 33.41%,respectively.（5）Aerated irrigation can improve the quality of cotton,increase cotton yield and water use efficiency.On the whole,the quality indexes of AF treatment were the best.The correlation between cotton quality indicators and yield was:fiber length>elongation>breaking strength>micronaire>uniformity index.Aerated irrigation has a positive effect on improving the quality indexes of cotton.Compared with CK treatment,the micronaire value of AS,AB,AF,ABF and AW decreased by 5.43%,3.46%,8.89%,7.12%and8.30%,the fiber length increased by 5.74%,2.50%,9.57%,7.60%and 9.29%,the breaking strength increased by 1.79%,3.14%,10.53%,7.30%and 8.22%,the elongation increased by 1.17%,1.23%,10.16%,5.79%and 9.05%,and the uniformity index increased by 2.96%,1.88%and 4.11%.3.91%and 4.07%,respectively.The yield of aeration at seedling stage was higher,the water use efficiency was lower,and the yield of aeration at bud stage was the lowest compared with other aeration treatments.Aeration at flowering and boll stage not only obtained the maximum yield,but also had the highest water use efficiency.There was no significant difference in yield between aeration at seedling stage+bud stage+flowering and boll stage and aeration at flowering and boll stage.Conclusion:Although the aeration effect can not be superimposed according to the growth period and has a delay,aeration irrigation at different growth stages can improve the microenvironment of cotton root zone,improve the photosynthetic characteristics of cotton,promote the growth of cotton above ground part,is conducive to the accumulation of dry matter,play a certain effect of increasing production,and can effectively improve the quality and water use efficiency of cotton.In this experiment,considering the above indicators,the study suggests that aerated irrigation at the flowering and boll stage of cotton is the optimal aerated irrigation mode.