Effects of Phosphorous and Biochar Application on the Phosphorous Availability, Growth and Yield of Sorghum Inoculated with Phosphate Solubilizing Bacteria

Due to the calcareous nature of our country's soils, the plant phosphorus availability is low.  In order to study the effects of soil microorganisms and biochar application on the phosphorous availability, growth and yield of sorghum and some soil chemical characteristics, a pot experiment as factorial in completely randomized design were conducted. In this research, effects of two treatments of inoculation and non-inoculation of phosphate solubilizing bacteria and two biochar consumption treatments (0 and 1.5% by weight) on the four levels of zero, 25, 50 and 75 mg .kg-1 of P2O5 as triple superphosphate source, in three replications were studied. The results showed that phosphate solubilizing bacteria inoculation and biochar application had a significant increase on the volumes, fresh and dry weight of roots, fresh forage yield and phosphorous, nitrogen, potassium and zinc uptake. Using phosphorus increased the forage weight by increasing the height and diameter of the stems. Phosphorus application also increased soil salinity and decreased soil organic carbon, but bacteria inoculation increased the amounts of organic carbon and decreased soil salinity while biochar application increased both of organic carbon and salinity amounts. None of them had a significant effect on soil acidity. Data showed that although single application of the biochar and or bacteria had significant effects on the phosphorus uptake increases, but combined use of biochar and phosphorus and bacteria with phosphorus and also combination of these three treatments caused sorghum yield increases by increasing of phosphorus uptake. In other words, biochar or bacterial had a positive effect on the phosphorus effectiveness so that the highest plant height, fresh and dry forage, and the highest phosphorus, nitrogen, potassium and zinc uptake were obtained from the combined use of phosphorus solubilizing bacteria, biochar and 50 mg P2O5 per kg of soil.