Effects Of Biochar On Soil Nutrient And Gaseous Nitrogen Losses In Facility Vegetable Production

In recent years,with the adjustment of rural industrial structure,the agricultural economy develops rapidly.Environmental pollution problems have increasingly become serious with the increased application of nitrogen fertilizer.The excessive nitrogen fertilizer application have resulted in waterbody eutrophication,as well as substantial loss of nitrogen through ammonia volatilization and N₂ O emission.Biochar is an emerging soil conditioner.It has been reported that properly managed application of biochar can reduce gaseous nitrogen loss,and increase the soil nutrient content and crop yield.In this study,we selected bamboo biochar and dead pig biochar as soil conditioners,and carried out a field experiment in a vegetable greenhouse.We investigated the effect of biochar type,application rates(10 t hm^-2 or 20 t hm^-2)and application patterns(one or two applications of 20 t hm^-2)on crop yield,plant uptake of nitrogen,concentrations of soil nitrate nitrogen,ammonium nitrogen,and other soil physical and chemical properties in an Ipomoea aquatica Forsk-Brassica chinensis rotation system.Soil ammonia volatilization and N₂ O emission rates were monitored using the closed intermittent air-flow chamber and static chamber and gas chromatography,respectively.It is expected that the data collected would provide a helpful guidance for optimal application of biochar in field conditions.The main results are as following:1.In the Ipomoea aquatica Forsk crop season,the 20-0-DPB treatment significantly（p <0.05）increased the Ipomoea aquatica Forsk crop yield and soil pH,whereas the other biochar treatments had no significant effect on soil pH.The 20-0-DPB and 10-10-DPB treatments significantly（p <0.05）increased the yield of Brassica chinensis crop,whereas the 20-0-BB and 10-10-BB treatments significantly（p <0.05）reduced the Ipomoea aquatica Forsk crop yield.The 20-0-DPB and 20-0-BB treatments significantly（p <0.05）increased Ipomoea aquatica Forsk root nitrogen concentration,but they had no significant effect on Brassica chinensis root nitrogen concentration.The 10-10-DPB treatment significantly（p <0.05）increased Brassica chinensis root nitrogen concentration.The biochar treatments had no significant effect on soil nitrate concentration or vegetable shoot nitrogen concentration.2.Compared with the control,application of 20 t·hm^-2 dead pig biochar once significantly（p <0.05）reduced soil ammonia volatilization by 50.61% in the rotation system.Bamboo biochar and dead pig biochar applied twice at 10 t·hm^-2 each time only significantly（p <0.05）reduced soil ammonia volatilization in the Ipomoea aquatica Forsk season,whereas no significant effect on soil ammonia volatilization during the rotation.Application of bamboo biochar at 20 t·hm^-2 once significantly reduce（p <0.05）the total amount of N₂ O emissions from the soil by 26.61% in the rotation.To reduce soil ammonia volatilization and N₂ O emissions,the one off application of 20 t·hm^-2 of biochars was more effective than the two split applications.In conclusion,20 t·hm^-2 of the biochars applied once was more effective in increasing the crop yield and soil pH,and reduce soil ammonia volatilizationand N₂ O emission.One off application of biochar at this rate appears to be more economical and environmentally friendly than the two split applications do.