Study On Nitrogen Balance Of Soil-forage Maize System

Forage maize-Italian ryegrass is one of the most widely forage planting systems, which is the main forage for beef and cattle in Chuanxi plain. The quantitative research on the nitrogen utilization and nitrogen migration of the system by soil (including nitrogen input and output by water) and forage of at the area of Xinjin county of Sichuan province. This study can provide the theory basis for improving fertilization of Nitrogen rationality, decreasing nitrogen residual in soil, analyzing the migration path of nitrogen and reducing the cost of forage grass production, which has a very important practical value for the production of livestock husbandry of this area. The main conclusions are as follows:(1) The forage corn and above-ground biomass were28643.57kg·hm-2and26756.82kg hm-2.The demand of nitrogen were328.43kg@hm-2and317.39kg·hm-2, the percentage was75.07%and72.54%of the total nitrogen input respectively.(2) The amount of NO3--N, NH4--N and TN were24.92,80.6and772.43kg·hm-2in the0-50cm soil layers after planting forage maize. Comparing with before planting, the amount of NO3--N reduced by71.07%, while NH4+-N and TN improved by50.82%and5.51%respectively.(3) After planting forage maize, the NO3--N and NH4+-N residues in soil and nitrogen surface runoff improved3.67times,13.52%and1times respectively and the concentration of TN dropped by8.71%with fertilization condition compared without fertilization condition. The amounts of nitrogen gas volatilized and residual of nitrogen in soil were126.69kg·hm-2and103.69kg·hm-2respectively, which were accounting for51.44%and42.10%of total nitrogen applied.(4) The settlement of TN, TIN, NO3--N and NH4+-N in total atmospheric nitrogen wet deposition were19.67,13.38,10.92,2.46kg·hm-2respectively. The TN, TIN, NO3--N and NH4+-N in soil surface runoff nitrogen were0.083,0.074,0.069kg·hm-2and0.005kg·hm-2 respectively. The leach of NO3--N, NH4+-N and TN in soil were1.521,0.098and1.826kg. hm-2respectively.(5) The rainfall had positive relationship with nitrogen wet settlement and nitrogen leached, but negative correlation with the concentration of NH4--N, NO3--N and TIN in rain.(6) The production of forage grass dry matter from the Forage Maize-Italian Ryegrass planting system can reach38960kg·hm-2·a-1and the system needs a lot of nitrogen to maintain high yield for forage grass. The production of Italian Ryegrass increased significantly when a great quantity of nitrogen was put into it in the growing season. But if nitrogen fertilization was applied for forage maize in the growing season again, the utilization efficiency of nitrogen fertilization was very low and the losses of that were significant. In the case of livestock excrements returning to field, we should control the input of inorganic nitrogen fertilizer, which could meet nitrogen requirement of the planting system.