Effect Of Organic Fertilizer Replacing Part Of Chemical Fertilizer On Soil Character And Cotton Yield Formation

Cotton is one of the most important economic fiber crops in China.Rational fertilization can increase fertilizer utilization rate and cotton yield.Excessive fertilization may not only decrease the fertilizer utilization rate and cotton yield,but also cause a series of environmental problems,such as soil hardening,soil acidification.Therefore,replacing organic fertilizer with chemical fertilizer is of great significance for green production.After field Localized fertilization(started in 2016),partial substitution of chemical fertilizer the experiments were conducted in 2018-19 to understand the impact of organic fertilizer substitution on soil characteristics and cotton yield formation to.This study also exploresd the influence of the different organic fertilizer substitution rates on soil physical and chemical properties,soil enzyme activity related to nitrogen transformation,soil bacterial community structure,cotton growth and development,nitrogen,phosphorus and potassium nutrient uptake,yield and fiber quality.The purpose of this study was to find out the best substitution rate of organic fertilizer instead of chemical fertilizer,so as to green development of cotton in the Yellow River basin regions.The research results are as follows:(1)There was no significant difference in soil physical properties between organic fertilizer replacement treatment and single fertilizer treatment;There was no significant difference in soil organic matter,total nitrogen,alkaline nitrogen,available potassium and pH between the organic fertilizer replacement treatment and mineral fertilizer treatment;In the soil layer of 0-20 cm and 20-40 cm,the content of available P in the soil treated with organic fertilizer alone was significantly higher than that of the soil treated with mineral fertilizer,and the difference among the other treatments was not significant;the content of available P in the soil of 40%,50% organic fertilizer alternative treatment and single application of organic fertilizer treatment was significantly higher than that of chemical fertilizer treatment in the soil layer of 40-60 cm.(2)There was no significant difference in soil urease and hydroxylamine reductase activity between the organic fertilizer replacement treatment and the single application of chemical fertilizer;compared with the single application of chemical fertilizer,the 50% organic fertilizer replacement treatment significantly increased soil protease and nitrate reductase activity;the single application of organic fertilizer treatment significantly increased soil nitrate reductase and nitrite reductase activity.Soil urease activity was significantly positively correlated with soil organic matter and total nitrogen content while,nitrite reductase activity was significantly positively correlated with soil available P and K content.Moreover,soil hydroxylamine reductase was significantly positively correlated with soil organic matter and total nitrogen content.There was no significant difference observed in the alpha index of soil bacteria among different treatments.The increase of soil organic matter content promoted the evenness and diversity of the bacterial community and the increase of soil available phosphorus content promoted the richness and diversity of the bacterial community.However,no significant correlation observed between soil enzyme activity and bacterial diversity index.At the level of bacterial Phylum,Proteobacteria and Actinobacteria are the most dominant bacterial communities among all treatments.PCoA results showed that there was no significant difference in bacterial community structure among different treatments.The findings of Heatmap and RDA revealed that soil nutrients,soil organic matter,total nitrogen,alkaline nitrogen,available potassium and pH could affect the community structure of soil bacteria.(3)The organic substitution(40% and 50%)treatment significantly increased the gradual growth of cotton compared with single fertilization treatment.However,no significant difference observed between the organic fertilizer replacement treatment and the single fertilizer treatment in terms of cotton growth,seed cotton yield,yield components and fiber quality.Finally,the substitution of chemical fertilizer by 50% organic fertilizer increased the biomass accumulation,nutrient accumulation and seed cotton yield to some extent.In summary,Replacing part of chemical fertilizer with organic fertilizer can reduce the amount of chemical fertilizer,and maintain the physical and chemical properties of soil,the activity of enzyme related to soil nitrogen transformation,the structure of soil bacterial community,the growth and development of cotton,the biomass,the uptake of nutrients,the yield,fiber quality;replacing 50% chemical fertilizer with organic fertilizer can increase the biomass and nutrient accumulation of cotton,the yield of seed cotton,and the best substitution effect.