Effects of Soil Texture on the Growth of Young Apple Trees and Soil Microbial Community Structure Under Replanted Conditions

A two-year field experiment was carried out in order to study the occurrence degree and mechanism of apple replant disease(ARD)in the apple orchards with different soil textures.So we can adopt appropriate controlmeasures according to the severity of ARD.Healthy two-year-old seedlings with consistent growth were selected,of which the root stock was T337 and the scion was Yanfu 3.There were significant differences in biomass between methyl bromide fumigation and replanted treatments,and the difference was the largest in clay loam,followed by sandy loam,and loam,which verified ARD in clay loam was most serious,followed by sandy loam and loam.Based on high-throughput sequencing of fungi in soil samples,fungal richness and diversity were the highest in clay loam,followed by sandy loam,and loam.The relative abundance of Fusarium in SX,SL,FX,FL,WX and WL was 7.33%,19.32%,2.70%,4.24%,10.71%and 23.87%,respectively.Based on Real-time quantitative analysis,there were significant differences in the number of Fusarium oxysporum and Fusarium solani between methyl bromide fumigation and replanted treatments,i.e.,clay loam>sandy loam>loam.Fusarium was the main pathogen causing ARD.This shows that ARD is the most serious under replanted clay loam condition.High-throughput sequencing technology was used to prove the difference in Fusarium was one of the important reasons for ARD under different soil textures.This technology provides a new idea for the prevention and control of ARD.

Effect of biochar applied with plant growth-promoting rhizobacteria(PGPR)on soil microbial community composition and nitrogen utilization in tomato

Plant growth-promoting rhizobacteria(PGPR)represent an important microbial community group and have beneficial effects on plant growth and development.A pot experiment was conducted to study the effect of biochar applied with PGPR on the soil microbial community composition and nitrogen use efficiency(NUE)of tomato,which could provide a theoretical basis for rational fertilization.Six treatments were designed:no nitrogen(N),PGPR,or biochar control(CK);biochar without N or PGPR(BCK);N without PGPR or biochar(U);N and PGPR without biochar(UP);N and biochar without PGPR(UB);and N,PGPR,and biochar(UBP).The tomato yield in the UP treatment was 9.09% lower than that in the U treatment,whereas that in the UB treatment was 19.93% higher than that in the U treatment.The tomato yield in the UBP treatment was 32.45%,45.69%,and 10.44% higher than those in the U,UP,and UB treatments,respectively.Biochar combined with PGPR increased the relative abundance of Nitrospira and Bradyrhizobium in the soil.At the tomato maturity stage,the soil NO_(3)^(-)-N content in the UBP treatment was 87.12%,88.12%,and 31.04% higher than those in the U,UP,and UB treatments,respectively.The NUE in the UP treatment was 4.03% lower than that in the U treatment,and that in the UBP treatment was 13.63%,17.66%,and 10.77% higher than those in the U,UP,and UB treatments,respectively.This study showed that biochar combined with PGPR can improve soil microbial community structure and increase the NUE of tomato.