Effects of biochar application on potting media chemical properties, arbuscular mycorrhizal fungi spore density, growth and nutrient uptake of sorghum (Sorghum vulgare L.)

Two sets of laboratory incubation and pot experiments were conducted to characterize the chemical properties and to evaluate arbuscular mycorrhizal fungi (AMF) abundance, growth and nutrient uptake of sorghum grown in biochar–amended soil-sand potting media. Both experiments used pasteurized sand and two acid soils (Ultisol and Entisol) as the base substrate with rice hull char (RHC), coconut sawdust char (CSC), peanut hull char (PHC) and corn cob char (CCC) as potting amendment. A soil and sand without biochar served as the control. Application of PHC in Ultisol-based potting mix had shown marked increase in pH, electrical conductivity (EC), total N, total P, exchangeable K, Ca and Mg and decreased exchangeable acidity and Al. Similarly, PHC application in Entisol-based potting mix increased pH, total organic carbon (OC), total N, total P, exchangeable K and a significant decrease in exchangeable acidity and Al. On the other hand, CSC application in Ultisol- and Entisol-based potting mix resulted in higher EC and exchangeable Na values. Application of PHC and CSC in Entisol-based mix depressed plant height and biomass production. In Ultisol-based potting mixes, improved P concentration and uptake was obtained from PHC and RHC addition. Except for RHC, biochar application had reduced spore counts. Among biochar evaluated, PHC had the most superior influence on the chemical properties of potting mixes. However, increased in pH and P due to PHC and CSC application posed a detrimental effect on plant growth, biomass production and AMF abundance.