| Biochar-Based microbial fertilizer is a new type of fertilizer made of biochar as a carrier to fix microorganisms with specific functions.The use of carbon-based microbial fertilizers can enhance crop yields,improve the soil environment and,to a certain degree,reduce the use of chemical fertilizers,thus achieving high-quality green agricultural development.In this study,23 plant growth-promoting rhizobacterias（plant growth-promoting rhizobacteria,PGPR）with growth-promoting functions were selected.Through experiments on plant culture of tomato seedlings,PGPRs with significant growth-promoting effects and capable of assisting tomato seedlings to resist salt stress were screened,and then investigate the effect of biochar on the growth and adsorption capacity of PGPR.To prepare for the production of carbon-based microbial fertilizers that can serve to increase the yield of tomatoes in the process of growing them in facilities.The main conclusions of this paper are as follows:（1）In the culture experiment of tomato seedlings,a total of 6 PGPRs exhibiting excellent growth-promoting effects were screened by combining biomass and root data of tomato seedlings,namely Bacillus F,Halomonas hydrothermalis P-21,Pantoea D1-28,Paraburkholderia D2-1,Chryseomicrobium amylolyticum L-29,and Chryseomicrobium imtechense Z-34,respectively,in which tomato seedlings treated with Bacillus F increased aboveground dry weight,belowground dry weight,root surface area,and root volume by15.73%,86.94%,131.62%,and 139.43%,respectively,relative to the control group.The tomato seedlings treated with Halomonas hydrothermalis P-21 showed increases of 62.15%,27.87%,and 59.92%in aboveground dry weight,underground dry weight,root surface area,and root volume,respectively,compared to the control group;the tomato seedlings treated with Pantoea D1-28 showed increases in aboveground dry weight,underground dry weight,root surface area,and root length,respectively,compared to the control group.The aboveground dry weight,belowground dry weight,root surface area,and root length of tomato seedlings treated with Pantoea D1-28 increased by 10.05%,100%,115.88%,and 43.96%,respectively,compared to the control;the aboveground dry weight and belowground dry weight of tomato seedlings treated with Paraburkholderia D2-1 increased by 14.97%,and 49.54%,respectively,compared to the control;the aboveground dry weight and belowground dry weight of tomato seedlings treated with Chryseomicrobium amylolyticum L-29 treated tomato seedlings increased 47.68%,121.35%and 159.97%in aboveground dry weight,root surface area and root volume,respectively,compared to the control group.The aboveground dry weight,belowground dry weight and root surface area of tomato seedlings treated with Chryseomicrobium imtechense Z-34 increased by 18.09%,48.14%and 91.52%,respectively,relative to the control.（2）In the experiment of PGPR to assist tomato seedlings to resist salt stress,Pantoea D1-28 was found to exhibit its growth-promoting effect even under salt stress conditions.At a Na Cl concentration of 40 mmol·L-1,aboveground fresh weight,belowground fresh weight,root area,and root volume of tomato seedlings treated with Pantoea D1-28 increased by 54.03%,32.90%,44.69%,and 67.00%,respectively,compared with the control group;at a Na Cl concentration of 80 mmol·L-1,the aboveground fresh weight,belowground fresh weight,root area,and root volume of tomato seedlings treated with Pantoea D1-28 The aboveground fresh weight,belowground fresh weight,root area and root volume of tomato seedlings treated with Pantoea D1-28 at Na Cl concentration of 80 mmol·L-1 increased by 69.55%,126.21%,70.33%and77.59%,respectively;aboveground fresh weight,belowground dry weight,root area and volume of root heel of tomato seedlings treated with Pantoea D1-28 at Na Cl concentration of120 mmol·L-1 increased by 73.56%,37.85%and 91.97%,77.66%,respectively.（3）The effect of different biochars on PGPR growth varies at different growth periods.In a study on the effect of two different biochars on the growth of PGPR,it was found that the addition of biochar to the medium promoted the growth rate of Pantoea D1-28 during the logarithmic growth period,but did not increase the biomass of Pantoea D1-28 by the logarithmic growth period;hemp straw charcoal did not affect the growth of Pantoea D1-28;Both biochars did not affect the growth of Bacillus F.This indicates that both cornstalk charcoal and hemp straw charcoal are not toxic to Bacillus F and Pantoea D1-28.（4）Biochar has good adsorption to PGPR.In the adsorption study of two biochars on PGPR,it was found that the adsorption rate of both biochars on PGPR was the fastest within 1hour and the process stopped by 24 hours.The maximum adsorption rates were 72.79%for Pantoea D1-28 and 70.02%for Bacillus F.The maximum adsorption rates were 72.13%for Pantoea D1-28 and 69.31%for Bacillus F for hemp straw charcoal. |
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