Effects of Reduced Fertilization and Biochar Application on Nitrogen Leaching from Tobacco-growing Soils

In order to clarify the effects of fertilizer reduction and biochar application on nitrogen leaching loss in different tobacco planting soils, laboratory soil column experiments were conducted to study different fertilization treatments (conventional fertilization, fertilizer reduction by 30%, fertilizer reduction by 30%+5% biochar, no fertilization) on leaching loss of available nitrogen (N) from brown soil, red soil, and purple soil. The results showed that the leaching intensity of all forms of N was strong in the early stage of leaching, and gradually decreased with time. The leachate contained mainly total soluble N and nitrate N. Compared with conventional fertilization, the total amount leached of soluble N, nitrate N, and ammonium N decreased by 12.0% to 21.8%, 8.9% to 22.5%, and 12.7% to 25%, respectively. Fertilizer reduction and biochar application significantly delayed the leaching time of available nitrogen in the three soils, and decreased the total soluble nitrogen and nitrate N in leachate by 26.6% to 35.4%, and 36.5% to 59.2%, respectively. In conclusion, fertilizer reduction and biochar application can decrease the leaching loss of total soluble N and nitrate N from these soils.