Effects Of Biochar Combined With Plant Growth Promoting Rhizobacteria (PGPR) On Crop Growth And Soil Physical,Chemical And Biological Properties

Microbial fertilizers are used in agriculture more and more,but their effect is unstable because the colonization of the microbes in them is affected by soil properties greatly.So it is of great significance to study the scientific application methods of microbial fertilizers to improve their utilization rate.The effects of biochar combined with plant rhizosphere growth-promoting bacteria on crop growth and soil physical,chemical and biological properties were studied by pot experiments.The feasibility of using biochar as a carrier of plant rhizosphere growth-promoting bacteria and its difference with traditional microbial fertilizer carrier were studied.The test results are as follows:1.Effects of biochar combined with Plant growth promoting rhizobacteria(PGPR)on growth and physiological characteristics of tomato.The effect of biochar combined with PGPR on yield increase was better than that of single application of biochar and PGPR.Compared with treatments U,the yield of treatments UB was 19.93% higher.Compared with treatments U,the yield of UP was 9.09% lower.The yield of UPB treatments was 32.45% higher than that of U treatments,45.69% higher than that of UP treatments,and 10.44% higher than that of UB treatments.Nitrogen use efficiency of UPB was 13.63 percentage points higher than that of U,17.66 percentage points higher than that of UP and 10.77 percentage points higher than that of UB.The chlorophyll content of UPB was 18.78% higher than that of U,41.45% higher than that of UP,and 22.86% higher than that of UB.The results showed that biochar as a carrier of growth-promoting bacteria increased nitrogen use efficiency,tomato photosynthetic capacity,dry matter accumulation and thus fruit yield.2.Effects of biochar combined with Plant growth promoting rhizobacteria on physiological and biochemical characteristics of soil.The content of available nutrients in all treatments decreased gradually during the growing period,and the addition of biochar could effectivelyslow down the loss of nutrients.On the basis of adding biochar,the application of PGPR effectively increased the content of nitrate nitrogen in soil.Nitrate nitrogen content in UPB treated soil increased by 15.97% in the whole growth period on the average,compared with that in UB treated soil.Biochar combined with growth-promoting bacteria could effectively increase urease activity in tomato rhizosphere soil,but the catalase activity in soil decreased significantly.The urease activity of UPB treated soil was increased by 34.20%,44.78% and 13.51%respectively compared with that of U,UP and UB.The catalase activity of UPB treatments soil decreased by 25.21% and 31.18% compared with that of UP treatments,but there was no significant difference between UB and UPB treatments.The results showed that biochar could effectively improve soil physical and chemical properties and improve soil fertility as a carrier of growth-promoting bacteria.3.Effects of biochar combined with PGPR on microbial community diversity in tomato rhizosphere soil.The microbial community diversity of tomato rhizosphere soil was improved by biochar combined with growth-promoting agent,and the relative abundance of Nitrospira and Bradyrhizobium was significantly increased(p=0.008).The effect was better than that of single application.The results showed that biochar could effectively promote the colonization of exogenous microorganisms in soil and play an active role in the transformation and circulation of nitrogen in soil.4.Effects of biochar and compost combined with PGPR on growth and physiological characteristics of ryegrass.The aboveground dry weight of biochar combined with PGPR treatments(UPB)was 26.29%,45.27% and 6.59% higher than that of U,UP and UB treatments respectively.Compared with U,UP and UC,the above-ground dry weight of UPC was 23.09%,41.58% and 17.31% higher respectively.The biomass of ryegrass of UB treatments was 12.92%higher than that of UC treatments,but there was no significant difference between the treatments of UPB and UPC.Compared with U,UP and UB,the nitrogen use efficiency of UPB was 21.31,29.28 and 7.24 percentage points higher respectively.The nitrogen use efficiency of UPC was18.9,26.87 and 12.92 percentage points higher respectively,compared with that of U,UP and UC,and the difference was significant.The nitrogen use efficiency of UB was 8.09 percentage points higher than that of UC,but there was no significant difference between UPB and UPC.The chlorophyll content of UPB was 15.75% higher than that of UPC,but there was nosignificant difference in carotenoid content between UPB and UPC.The results showed that the biomass and nitrogen use efficiency of ryegrass could be effectively improved by using biochar and compost as carrier of growth-promoting microbial agents,but the synergistic effect between compost and growth-promoting microbial agents was more positive than that of applying them alone.5.Effects of biochar and compost combined with PGPR on soil chemical and biochenmical properties.At the maximum nutrient efficiency stage(jointing stage),the nitrate nitrogen content of UPB was 45.09% and 16.94% higher than UP and UB respectively,and the nitrate nitrogen content of UPC was 39.59% and 39.40% higher than UP and UC respectively,and the difference was significant.There was no significant difference in nitrate nitrogen content between UPB and UPC.The content of ammonium nitrogen in UP soil decreased by 18.74% compared with that in U.The content of ammonium nitrogen in UB,UC,UPB and UPC soil had no significant difference from that in U.There was no significant difference in soil urease activity between UPB and UPC,but soil catalase activity of UPB was 13.49% lower than that of UPC.The results showed that biochar and compost as carriers of growth-promoting bacteria could improve soil physical and chemical properties and soil fertility.6.Effects of biochar and compost combined with PGPR on microbial community diversity in ryegrass rhizosphere soil.Compared with conventional fertilization,the microbial community richness of tomato rhizosphere soil was no significantly different when biochar and compost were used alone or when they were combined with growth-promoting agents.However,the microbial community richness of reygress rhizosphere soil decreased when biochar and compost were used alone on the basis of conventional fertilization.Azoarcus(nitrogen-fixing bacteria)abundance in UPC rhizosphere soil microorganisms was significantly higher than that in UPB.The results showed that compost as a carrier of growth-promoting bacteria had a more positive effect than biochar in the process of nitrogen fixation.