Influence of biochar application on soil amendment and nitrogen utilization efficiency under drip irrigation

The soil in Dengfeng tobacco-planting areas in Henan suffers from quality deterioration and low fertilizer utilization efficiency caused by long-term nitrogen fertilizer application. A field experiment was carried out with biochar at three application rates (600, 1 200 and 1 800 kg/hm²) under drip irrigation combined with a reduced nitrogen application rate. The related indicators of tobacco-planting soils under different treatments were detected. The results showed that biochar application promoted carbon/nitrogen ratio in soil. Comparing with the conventional fertilization method at a nitrogen application rate of 30 kg/hm² (CK2), the microbial biomass carbon and nitrogen contents and the activities of urease and sucrose in soils at the middle and late growth stages of tobacco under drip irrigation were increased by 24.68%-111.62%, 36.10%-136.27%, 1.02%-135.38% and 34.26%-97.46%, respectively, for the three biochar application rates. The optimal soil amendment effect was obtained at the biochar application rate of 1 200 kg/hm², at which the apparent nitrogen utilization efficiency reached 68.01%. Therefore, the application of biochar promotes soil quality and the nitrogen utilization efficiency of tobacco under drip irrigation treatment in Dengfeng tobacco-planting areas.