Effect of combined application of humic acid and nitrogen fertilizer on nitrogen uptake, utilization and yield of winter wheat

Studies on the effects of combined humic acid and nitrogen fertilizer application on nitrogen (N) uptake, utilization and yield of winter wheat can provide theoretical basis for increasing the productivity of N fertilizers and reducing N fertilizer pollution in the winter wheat-summer maize rotation cropping system. A field experiment was conducted in 2014 at Wolong District in Nanyang City, Henan Province, an area with a predominant winter wheat and summer maize rotation cropping system and drab soils. The experiment was consisted of 6 treatments-no N fertilizer (only P and K fertilizers), conventional fertilization (P and K fertilization with N application rate of 180 kg·hm^-2), single humic acid (3 000 kg·hm^-2), conventional fertilization plus humic acid, conventional fertilization with 15% less N plus humic acid and conventional fertilization with 30% less N plus humic acid. The characteristics of yield and N fertilizer utilization of winter wheat under different fertilization modes were analyzed. The results showed that combined application of humic acid and N fertilizers increased winter wheat yield, and promoted N accumulation and utilization rate. Among treatments, the treatment of conventional fertilization with 15% less N plus humic acid treatment had the best effects. Winter wheat yield, grain N content, grain N accumulation, aboveground total N accumulation, N use efficiency and net income increased. Compared with conventional fertilization, yield increased by 4.96%, N use efficiency by 23.42% and net income by 2.18%. However, the 30% less N treatment reduced winter wheat productivity and revenue. Thus, on the basis of the application of humic acid, the appropriate dose of N fertilizer was recommended to ensure high productivity and income. The conventional fertilization with 15% less N plus humic acid was the best fertilization mode in the study area. The results are beneficial for improving productivity efficiency of agricultural, resources and environmental protection.