Effects of humic acid nitrogen fertilization on corn yield, nitrogen utilization and nitrogen loss

Objectives In order to promote application of the new type fertilizers, increase crop yield and reduce environmental pollution, the research explored effects of humic acid nitrogen fertilizer on corn yield, nitrogen absorption and utilization, and nitrogen distribution and loss in soil.

Methods The nitrogen isotope tracer technique was used to study the effects of humic acid nitrogen on the nitrogen utilization. Experimental plot soil was circled by specific device. The tested N fertilization treatments were: 1) CK1 (N 0 kg/hm²), 2) CK2 (urea N 225 kg/hm²), 3) HA1 (activated humic acid fertilizer, N 225 kg/hm²), and 4) HA2 (ordinary humic acid nitrogen N 225 kg/hm²). Soil samples in different layers of soil (0-20 cm, 20-40 cm and 40-60 cm) were collected by using earth drilling before planting corn, before fertilization and after the harvest. Ammonia volatilization nitrogen was measured by the static body mothed, and N₂O was measured by static body collecting, vacuum flask cold storage and gas chromatograph determining. After the harvest, vegetative organs and grains were separated. After drying, corn production and vegetative organs’ weights were calculated. The vegetative organs and grain were mechanically ground by ball milling ready for measuring.

Results In grains, the nitrogen amounts from the fertilizers occupied 34.6%-36.2%, and in vegetative organs they occupied 14.6%-17.4%. The utilization rates of common urea and the activated humic acid fertilizer and conventional mixing humic acid fertilizers were 25.1%, 30.9% and 28.5%, respectively, and the loss rates of the nitrogen fertilizers were 38.1%, 19.8% and 27.2%, respectively. The results of application of the activated humic acid fertilizer and conventional mixing humic acid fertilizers compared with common urea were: 1) Maize yields were increased significantly; 2)The total N absorption amounts were increased by 25.8 kg/hm² and 16.3 kg/hm², respectively; 3) The nitrogen utilization rates were increased by 5.8 and 3.4 percentage points, respectively; 4) The nitrogen loss rates were reduced by 18.3 and 10.9 percentage points, respectively; 5) The soil nitrogen retention rates at the 0-60cm depth were increased by 12.5 and 7.5 percentage points; 6) The soil ammonium nitrogen and nitrate nitrogen contents were significantly improved in 0-20 cm and 20-40 cm.

Conclusions Humic acid nitrogen fertilizer could significantly improve the utilization rate of nitrogen fertilizer and maize yield, and significantly increase the N residue in soil at 0-20 cm depth. Humic acid nitrogen fertilizer could increase the inorganic nitrogen contents in soil of 0-40 cm, and retard N moving to deeper layer thereby reduce the nitrogen leaching loss. Application of humic acid fertilizer can improve the distribution of nitrogen in the soil thereby can be better adapted to crop root fertilizer demand characteristics. Humic acid nitrogen fertilizer could significantly reduce N₂O loss and other loss thereby reduce the nitrogen loss. The activated humic acid fertilizer was better than the conventional humic acid fertilizer.