Effect of N application on N utilization and N balance in spring maize

Field experiment was carried out to investigate N application on plant N uptake and utilization, soil N supply and N balance in spring maize. Results obtained showed that, maize yield increased significantly with the increment of N application rate, and with the trend of decreasing when the nitrogen application rate was higher than N 240 kg/ha. N recovery efficiency decreased with the N application rate. Nitrate content in the soil profile throughout the growth stages showed the trends of decreasing rapidly first, and then rose slowly. Nitrogen application significantly increased nitrate content in all layers of soil profile, and nitrate content rose with N application rate. Appropriate rate of nitrogen promoted plant N uptake and utilization, and plant biomass and yields as well. Over use of N resulted in luxury nitrate accumulation in soils, and therefore enhanced the risk of nitrate leaching into the underground water. At harvest, nitrogen application significantly increased residue mineral N (Nmin) in soils. The residue Nmin in soils rose with N application rate, but the value decreased when N application rate was over N 240 kg/ha. Under the experimental conditions, with the consideration of yield, nitrogen utilization and soil nitrate accumulation, a reasonable amount of nitrogen application should be controlled at about N 180-240 kg/ha.