Effects of biochar produced from rice straw and oil cake on soil nutrients, growth, yield and nutrient content of wheat (Triticum aestivum L.)

A pot experiment was conducted to assess the comparative effects of biochar and conventional inorganic NPK fertilizers on wheat growth and nutrient content as well as certain soil chemical and nutritional properties. Biochar produced from oil cake and rice straw were mixed with soils at rates of 0, 1, 2, 3, 4 and 5% (w/w) and inorganic NPK fertilizer was also mixed separately with soils at rates of 0, ¼, ½, ¾ and 1 of the recommended rate. Biochar increased the fresh weight and dry weight of wheat plant parts significantly. The root biomass and grain yield with oil cake biochar (OCB) were relatively higher than with rice straw biochar (RSB). Biochar application at a 4-5% rate produced maximum wheat root, straw and grain yield which were comparable to the recommended inorganic 1 NPK rate. The study revealed that oil cake biochar (OCB) was more effective in increasing soil organic carbon (OC), whereas rice straw biochar (RSB) was found to be more effective in raising soil pH, soil electrical conductivity (EC) and decreasing soil exchangeable acidity. A similar effect on soil cation exchange capacity (CEC) was also observed with both types of biochar. The soil available ammonium N (NH4 +-N), Olsen P and K content increased with increasing rates of both biochar and inorganic NPK in soils after the harvest of plants. Applying biochar at a rate of 5% resulted in the highest effect on the soil’s chemical and nutritional properties. Maximum N, P and K concentrations in wheat root, straw and grain were found at 4-5% biochar rates, which were significantly higher than inorganic NPK fertilizer rates.