Optimization of biochar and nitrogen fertilizer in rice cultivation

Abstract

To optimize the biochar and nitrogen fertilizer, an experiment was conducted based on CCD. The high and low levels of biochar were 0 and 40 t.ha−1 and 0 and 300 kg.ha−1 of nitrogen fertilizer, respectively. Grain yield, nitrogen losses, and NUE were measured as the dependent variables. The optimal amount of biochar and nitrogen fertilizer was calculated based on three economic, environmental, and economic-environmental scenarios. In site 1, the highest grain yield was obtained at 40 t.ha−1 of biochar and 300 kg.ha−1 of the nitrogen fertilizer. In site 2, it was obtained at 20 t.ha−1 of biochar and 300 kg.ha−1 of the nitrogen fertilizer. The lowest nitrogen losses were obtained in 40 t.ha−1 of biochar and 0 kg.ha−1 of the nitrogen fertilizer in the two sites. In both sites, the highest NUE was obtained in 20 t.ha−1 of biochar and 150 kg.ha−1 of the nitrogen fertilizer. In site 1, the optimum amount of independent variables in the economic scenario was 29.49 t.ha−1 of biochar and 239.39 kg.ha−1 of the nitrogen fertilizer. In the environmental scenario, the optimum amount of biochar and nitrogen fertilizer equaled 40 t.ha−1 and 55 kg.ha−1, respectively. The optimum amount of these in the economic-environmental scenarios was 20 t.ha−1 of biochar and 97 kg.ha−1 of the nitrogen fertilizer. In site 2, the optimum amount of biochar and nitrogen fertilizer in economic, environmental, and economic-environmental scenarios equaled 23.8 t.ha−1 of biochar and 263.6 kg.ha−1 of the nitrogen fertilizer, 40 t.ha−1 of biochar and 97 kg.ha−1 of the nitrogen fertilizer, and 19.4 t.ha−1 of biochar and 133.3 kg.ha−1 of the nitrogen fertilizer, respectively.