Co-application Of Biochar And Microbes (Trichoderma Harzianum L.and Bacillus Subtilis L.) Improves The Productivity Of Cereal-legume Cropping System And Remediate Cadmium-contaminated Soil

Cadmium(Cd)is an unessential trace element in plants that is ubiquitous in the environment.Anthropogenic activities such as disposal of urban refuse,smelteing,mining,metal manufacturing,and application of synthetic phosphate fertilizersenhance the concentration of Cd in the environment and are carcinogenic to human health.Sole biochar addition or microbial inoculation as a soil amendment helps to reduce cadmium(Cd)toxicity in polluted agricultural soils.Yet the synergistic effects of microorganisms and biochar application on Cd absorption and plant productivity remain unclear.Therefore,two pot experiments were conducted to investigate the combined effect of microorganisms(Trichoderma harzianum L.and Bacillus subtilis L.),biochar(maize straw,cow manure,and poultry manure),and Cd(0,10,and 30ppm)on cereal-legume plant physiology and growth to test how biochar influences microbial growth and plant nutrient uptake,and how biochar ameliorates under Cd-stressed soil.1.From the soybean pot experiment results showed that in comparison to non-Cd polluted soil,the highest reduction in chlorophyll content,photosynthetic rate,transpiration rate,stomatal conductance,water use efficiency,and intercellular CO₂of soybean were observed in Cd₂(30 ppm),which were 9.34,22.95,40.45,29.07,20.67,and 22.55%respectively less than the control Cd₀(0 ppm).Among sole inoculation of microorganisms,highest stomatal conductance,water use efficiency,and intercellular CO₂of soybean were recorded with combined inoculation of both microorganisms(M₃),which were 5.92,7.65,and 7.28%respectively higher than the control,and reduced the Cd concentration in soil,root,and shoot of soybean by 21.34,28.36,and 20.95%,respectively,compared to the control.2.Similarly,co-application of microorganisms and biochar ameliorated the adverse effect of Cd in soybean as well as significantly improved plant biomass,photosynthetic activity,nutrient contents,and antioxidant enzyme activities,and minimized the production of reactive oxygen species and Cd content in plants.Soil amended with poultry manure biochar had significantly improved the soil organic carbon,total nitrogen,total phosphorous,and available potassium by 43.53,36.97,22.28,and 4.24%,respectively,and decreased the concentration of Cd in plant root and shoot of soybean by 34.68 and47.96%,respectively,compared to the control.3.Correspondingly,from maize experiment the highest reduction in the SPAD value,transpiration rate,water use efficiency,stomatal conductance,photosynthesis rate,and intercellular CO₂ of maize were recorded in Cd₂(30 ppm),which were 34.50,40.45,20.66,29.07,22.41,and 22.36%respectively lower than control Cd₀(0 ppm).Sole application biochar,resulted in enhanced SPAD value,transpiration rate,water use efficiency,stomatal conductance,photosynthesis rate,and intercellular CO₂ of maize were recorded in cow manure biochar B₂,which were 20.54,23.80,5.96,13.37,13.50,and 7.27%higher than the control and reduced the Cd concentration in shoot and root of maize by 32.53 and 34.07%,respectively as compared to control.4.Similarly,among sole microorganism's inoculation,the highest SPAD value,transpiration rate,water use efficiency,stomatal conductance,photosynthesis rate,and intercellular CO₂ of maize were recorded in combined microorganisms inoculation M₃which were 10.04,12.29,8.43,5.92,5.26,and 7.72%higher as compared to the control and minimized the Cd concentration in soil,root,and shoot of maize by 10.35,20.15,and23.77%respectively than the control.5.From the current finding it was concluded that co-application of biochar and microorganisms reduced the toxic effect of Cd in cereal-legume(i.e.,maize and soybean)cropping system as well as significantly improved the antioxidant enzyme activities,nutrients availability,plant biomass,photosynthetic activity,and minimizing the synthesis of reactive oxygen species and Cd content in plant.6.These results suggested that co-application of biochar and microorganisms as soil amendments had synergistic effects in improving the adsorption of nutrients and decreasing the Cd uptake in plant,and improving the plant physiology of plant cultivated in Cd-contaminated soils as compared to sole application of biochar or microorganisms.