Infiltration Behavior of Ammonium and Phosphate in Runoff Through Soil Amended with Erythrina arborescens Biochar

Biochar, a promising exogenous material, is of great interest due to its ability to retain soil nutrients. Understanding the nutrient retention and release characteristics of biochar in soil is crucial to avoid environmental risks. In the current study, batch adsorption experiments were used to explore the adsorption capacity of ammonium (NH 4 + -N) and phosphate (PO 4 3− -P) on Erythrina arborescens biochars produced at 300–700 °C. The biochar produced at 600 °C (BC600) was used to conduct the column leaching experiments under different addition ratios (0, 1%, 3%, 5%, and 10%) to evaluate the effects of biochar on nutrient leaching and soil quality over the short period of time. The results found that BC600 at different addition ratios owned the best adsorption ability to NH 4 + -N, and the highest removal rate was up to 49%. Column leaching experiments displayed that compared to pure soil, the introduction of 1% biochar could reduce the cumulative NH 4 + -N in the leachate by 30.7%. The adsorption of PO 4 3− -P on different biochars was poor, and with the increase of biochar addition ratio, the phenomenon of negative PO 4 3− -P removal rate appeared. Column leaching experiments found that when the biochar addition rate was 1%, the cumulative PO 4 3− -P in the leachate was reduced by 12.9% compared to that in pure soil. Meanwhile, the application of BC600 in soil also improved soil pH, electrical conductivity, cation exchange capacity, and organic matter. These findings suggested that the application of Erythrina arborescens biochar with the appropriate ratio in soil could benefit to mitigate nutrient loss.