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Effects of Bacillus Subtilis on Growth Characteristics and Mechanism of Cotton under Mulch Drip Irrigation in Arid AreaCN



Abstract:Salinization of field soil causes stress to crop growth and development process,which further causes decrease of crop quality and yield,and seriously restricts agricultural production and regional economic development.Based on microbial regulation technology,this paper aims to improve soil microenvironment and promote crop growth and yield.By combining the application of Bacillus subtilis with drip irrigation technology under film in arid area,the growth characteristics and growth promotion mechanism of cotton under film drip irrigation in Xinjiang were studied under the coupling of Bacillus subtilis application amount(0,1.5,3,4.5,6 kg/mu)and irrigation amount(260,290,325 m3/mu).The main conclusions are as follows:(1)The cotton growth index(plant height,stem diameter and LAI),biomass,cotton yield and water use efficiency of cotton treated with Bacillus subtilis were all higher than those treated with CK,and with the increase of Bacillus subtilis dosage,all indexes showed a trend of increasing first and then decreasing.Compared with CK,Bacillus subtilis treatment increased the total dry matter by 8.31%-46.86%,the dry matter weight of vegetal organs by 1.52%-33.67%,the dry matter weight of reproductive organs by 16.75%-603.86%,the yield by 1.71%-21.91%,the water use efficiency by-0.8%-11.75%,and the irrigation use efficiency by 1.71%-21.90%.When Bacillus subtilis content was 1.5 and 3 kg/mu,the cotton grew better,and the cotton yield and water use efficiency were higher.(2)The application of Bacillus subtilis can effectively improve the soil water retention and water retention,which is conducive to the cotton root to fully absorb water.The soil water content of cultivated layer(0-20 cm)fluctuated greatly after the application of Bacillus subtilis,and the average soil water content of the whole growth period treated with Bacillus subtilis increased by 2.6%~25.1%compared with CK.The soil water consumption and daily water consumption intensity were also increased by Bacillus subtilis treatment.The total water consumption in the growth period was increased by 9.8%~16.5%compared with the actual irrigation amount,and by 2.8%~9.0%compared with CK.When Bacillus subtilis content was 3 kg/mu,soil average volumetric water content,water consumption and daily water consumption intensity all showed the highest values.(3)The Bacillus subtilis coupled with the irrigation amount can reduce the salt content and affect the transport and distribution of soil salt.The treatment with Bacillus subtilis showed desalination at the harvest stage,the desalination rate ranged from 2.8%to 22.0%,and the desalination effect was the most obvious when the content of Bacillus subtilis was 3 kg/mu and the irrigation amount was 325 m3/mu.The effect of Bacillus subtilis combined with irrigation on the distribution of soil available nutrients was obvious.When fertilization and irrigation were consistent,the decrease of soil available nutrient content under Bacillus subtilis treatment was significantly greater than that under CK treatment.Among them,the available nutrients decreased significantly when the Bacillus subtilis content was 1.5 and 3 kg/mu,and the appropriate Bacillus subtilis application amount improved the absorption and utilization of available nutrients in cotton,and provided sufficient sources of nutrients for crop growth during the growth period.(4)The application of Bacillus subtilis significantly increased the number of OTUs and αdiversity index(Shannon index,Chaol index)of soil bacteria in the root zone,and increased firstly and then decreased with the increase of Bacillus subtilis application.Combined treatment with Bacillus subtilis and irrigation promoted the abundance of growth-promoting bacteria such as Gemmatimonadetes and Bacteroidota in the soil(0-20 cm),and increased the relative abundance of nitrogen fixation,denitrification,biocontrol and phosphorolytic genus in the soil.With the advance of growth period,the distribution of soil bacterial community in the root zone became more and more uniform,and the community structure became more and more stable in the harvest period,which indicated that the application of B acillus subtilis had a certain timing-effectiveness.Soil enzyme activities were significantly affected by the coupling of Bacillus subtilis and irrigation.The activities of SC,URE and PHO decreased with the increase of the application amount of B acillus subtilis,while CAT increased with the increase of the application amount of Bacillus subtilis.Appropriate application of Bacillus subtilis and irrigation could improve soil enzyme activities.(5)Based on Logistic and regression models,the growth model of cotton under drip irrigation with Bacillus subtilis coupled with irrigation was established.In addition,the effects of various factors in soil microenvironment on yield were analyzed by using grey correlation analysis.The correlation between irrigation amount and yield is very obvious.The correlation between the amount of Bacillus subtilis application rate and the yield was the least,which was medium correlation.The correlation degree of various factors(Gemmatimonadetes,CAT,NH4+,P.SC,URE,PHO,NO3-)in soil microenvironment was extremely strong or strong.In conclusion,Bacillus subtilis can improve soil microenvironment and affect crop growth and yield by affecting soil bacterial community structure and richness,improving soil water retention and soil nutrient transformation,alleviating salt stress,etc.However,more application amount will lead to a decrease in the effect.In this experiment,the application amount of mild saline-alkali subsurface Bacillus subtilis is suggested to be 3 kg/mu,and the irrigation amount is 325 m3/mu.The research results provide theoretical basis and method support for solving the problems of soil saline-alkali and secondary saline-alkali in arid area by using microbial technology,improving land use efficiency and crop economic benefits,and realizing sustainable land use in arid area.
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    (D) Agriculture

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