Effects of Biochar Addition on Nitrogen Leaching Loss in the Vegetable Soil

Leaching loss from vegetable production systems was one of the mainly polluters to lake eutrophication in China, which could be attributed to poor soil nitrogen retention capacity caused by intensive cultivation. It was hypothesized that biochar addition to soils used for vegetable production could reduce leaching loss by improving soil nitrogen retention. A pot experiment was conducted with soil collected from a vegetable field in the Tailake region. Three levels of biochar (0, 1%, 5%) were added into the soil in the no nitrogen and nitrogen conditions. The soil ammonium nitrogen content was increased due to biochar addition from 5.64 mg/kg to 12.47 mg/kg and 20.28 mg/kg to 34.54 mg/kg in the no nitrogen and nitrogen conditions, respectively. Volume and nitrate concentration of leachate was significantly decreased in soils amended with biochar by 17%-58% and 6%-35%, respectively. Biochar addition could increase soil water retention capacity and residence time of nitrate nitrogen for pakchoi uptake. It was suggested that biochar could be used as a potential soil amendment to improve soil nitrogen retention and reduce nitrogen leaching for vegetable production. Therefore, the contribution of vegetable production systems to lake eutrophication could be decreased by biochar addition. 