Effects of biochar-based fertilizers on nutrient leaching in a tobacco-planting soil

Biochar is a soil amendment for increasing soil quality and decreasing nutrient leaching. However, there is little information on the impact of biochar-based fertilizer (BF) on soil nutrient leaching in agricultural soils. We conducted a soil column leaching experiment to study the effects of BF on the leaching of total nitrogen (TN), total phosphorus, and total potassium (TK) in tobacco soils. The distribution characteristics of NH4+-N, available P, and available K in soil profiles were analyzed after the application of BF. Biochar was prepared by pyrolysis of flue-cured tobacco stems. It was applied at four levels, 0%, 3%, 9%, and 15% (w/w), respectively, to the compound fertilizer. Compared with the control, the leaching loss of soil TN decreased by 8.36%, 6.72%, and 6.45%, and the loss of soil TK decreased by 9.18%, 9.31% and 11.82% in the 3%, 9%, and 15% BF treatments, respectively. However, BF had no significant effect on the P leaching due to the low movement of P in the soil profile. In addition, the BF addition increased the immobilization of NH4+-N, available P, and available K in the soil profile. These results indicate that addition of BF to a tobacco-planting soil reduced nutrient leaching, and suggest that BF could be an effective method of applying biochar to agriculture fields.