Effects of Irrigation and Nitrogen Application on Canopy Structure and Yield in Summer Maize

Zhengdan958 was used in the experiment, the effect of irrigation and nitrogen regimes on canopystructure and grain yield of summer maize was studied. The results showed that irrigation increased the SPAD whiledecreased the transmittance of summer maize. But it had no significant effect on grain yield. Under no irrigation con-ditions(W0), nitrogen application significantly increased the SPAD in all leaves and the leaf area index(LAI) of theear layer, thus improved the grain yield of summer maize. The highest yield was obtained at the nitrogen rate of 375kg/ha under no-irrigation condition, which was 39.5% higher than no-nitrogen treatments. While under irrigationconditions(W1), nitrogen application significantly increased LAI in all parts of the plant, and improved the SPAD.Nitrogen application also improved the leaf angle in ear layer, but decreased the transmittance. The treatment of ni-trogen rate 225 kg/ha got the maximum yield under irrigation condition. Nitrogen partial productivity decreased withthe increase of nitrogen rate, and the treatment of nitrogen rate 375 kg/ha obtained the minimum at both water condi-tions. Taking yield and nitrogen use efficiency into account, the appropriate nitrogen rates in this region were from225 to 300 kg/ha for high yielding maize production. However, the decision for irrigation might depend on the pre-cipitation and its distribution in a peculiar year.