Effects of nitrogen management modes on yield formation and nitrogen utilization efficiency of summer maize

A field experiment was conducted to study the effects of nitrogen management modes on yield formation and nitrogen utilization efficiency of summer maize,Zhengdan 958.The results showed that the rational nitrogen management could remarkably increase the kernel numbers of ear,kernel weight,bulk density,grain yield,biomass and plant nitrogen accumulation of the summer maize,and the grain yield was increased by 16.4% due to the nitrogen application.There were significant positive correlations between the nitrogen uptakes in stalk,grain and nitrogen application amounts,while split applications of nitrogen in the same application rate had no significant effects on the nitrogen uptake amounts.When the nitrogen application rate was beyond 300 kg/ha with a spilt application at flowering and milky stage,the transfer nitrogen to grain was decreased significantly.Moreover,with the increase of the nitrogen application rates the nitrogen contents and accumulations in maize straw and grain were continuously increased,and extravagant nitrogen absorption happened,therefore the apparent utilization ratio,agronomic efficiency,physiological efficiency,dry matter production efficiency and grain production efficiency of nitrogen were decreased remarkably.The contribution ratio of nitrogen to grain showed a fluctuation from an initial rising to a drop.Under the condition of the experiment,the 300 kg/ha of nitrogen application is the optimum amount for high yield and nitrogen utilization efficiency,and it is reasonable to change split nitrogen applications at different growing stages to the applications at the seeding and 12-leaf stage.