Effect of Acid Modified Biochar on the Growth and Essential and Non- Essential Element Content of Bean, Chickpea, Soybean, and Maize Grown in Calcareous Soil

Biochar (BC) and modified biochar (MBC) were applied at a rate of 10 g kg(-1) to the plants. Both BC and MBC treatments had no significant effect on the growth of chickpea and maize while MBC treatments significantly increased the growth of bean and soybean. The effect of MBC on nitrogen (N) and phosphorus (P) concentrations of the plants is more pronounced compared to BC. Potassium (K) concentrations of soybean were significantly increased by both BC and MBC treatments while K concentration of bean was increased by BC but decreased by MBC. MBC treatment significantly increased the calcium (Ca) concentrations of the plants and magnesium (Mg) concentrations of bean and soybean. MBC treatments significantly increased the sulfur (S) and zinc (Zn) in bean, soybean, and maize. Manganese (Mn) concentration of the plants was significantly increased by MBC treatments as compared to control and BC treatment. Both BC and MBC significantly increased chloride (Cl) concentrations of the plants however significantly reduced silicon (Si) concentrations of bean and maize. Aluminum (Al) concentration of maize was significantly increased by BC and MBC. BC applications had no significant effect on chromium (Cr), cobalt (Co) and vanadium (V). Compared to control, both BC and MBC treatments significantly reduced bean nickel (Ni) concentration. Application of MBC reduced bromine (Br) concentrations of the plants. Arsenic (As) concentration of chickpea increased with BC and MBC treatment. Rubidium (Rb) concentrations of bean and chickpea decreased with BC and MBC treatment. Strontium (Sr) concentrations of the plants were increased significantly by BC and MBC treatment. MBC treatment significantly reduced the soybean bismuth (Bi) concentration. Thorium (Th) concentration of the maize is significantly reduced by biochar treatments while uranium (U) concentrations of the plants were not affected by the biochar treatments. Our results suggests that MBC was superior to BC for mineral nutrition of plants in calcareous soil and reduction in the uptake of some non-essential elements such as Br, Rb, and Th. These promising results now need to be complemented by ?eld and long-term studies.