Enhancing Soil Nitrogen Availability and Rice Growth by Using Urea Fertilizer Amended with Rice Straw Biochar

Urea fertilizer as a nitrogen source is used widely and globally. However, N loss through ammonia volatilization from applied urea has become a major drawback to agriculture. A pot experiment was conducted to determine the effect of rice straw biochar on (1) total N, soil exchangeable NH4+, and available NO3- (2) uptake of N, P, and K in rice plants. The treatments evaluated were: (S: Soil only, U: soil + 175 kg ha(-1) urea, B1: soil + 175 kg ha(-1) urea + 5 t ha(-1) rice straw biochar, B2: soil + 175 kg ha(-1) urea + 10 t ha(-1) rice straw biochar, CB1: 50% soil + 50% commercial biochar potting media and CB2: 100% commercial biochar potting media). The addition of rice straw biochar at 5-10 t ha(-1) in the pot experiment significantly increased the soil total N availability by 33.33-46.67%. Treatments B1 and B2 also had significantly increased exchangeable NH4+, NO3-, P, and K in the soil over U. The soil availability nutrients increment in soil was attributed to the higher adsorption capacity of the rice straw biochar. Increment in soil nutrient availability such as N, P, and K increased the plant height, tiller number, greenness, and panicle number because of effective rice plant absorption. This resulted in dry matter production increment in line with plant nutrient uptake and use efficiency. Rice straw biochar at 5-10 t ha(-1) can improve the productivity of rice plants by increasing N retention in soil.