Effects of biochar application after five years on soil biochemical properties and summer maize yield

Biochar application can increase crop yield and improve soil fertility, but consecutive application increases cost, and thus exploring the effect of one-time application of biochar is a great significance for reducing input cost, ensuring high yield of crops and improving soil fertility.In this field experiment, we set up five rates of biochar treatments including biochar 10 t·hm^-2 (T1), 15 t·hm^-2 (T2), 20 t·hm^-2 (T3), 25 t·hm^-2 (T4) and no biochar(CK).The summer maize yield, changes in soil nutrients and soil microbial characteristics after five-years application were examined.The results showed that all biochar treatments increased the soil organic carbon, available phosphorus, available potassium, microbial biomass carbon, nitrogen and enzyme activities.These effects enhanced with the increased rate of biochar application.However, no significant effects by biochar application on soil available nitrogen content were found.Compared with CK, T1, T2, T3 and T4 treatments significantly increased the maize yield by 8.85%, 14.5%, 22.2% and 30.1%, respectively.Correlation analysis showed that the increased summer maize yield was positively correlated with soil microbial carbon and nitrogen, enzyme activities, soil organic carbon, available phosphorus and potassium.Therefore, biochar application after five years still has a significant effect for increasing maize yield and improving soil fertility, and the higher the rate, the greater the after effect.