灌水与施氮对夏玉米冠层结构及产量的影响

以郑单958为材料，在大田条件下研究不同水、氮处理对夏玉米冠层结构及产量的影响。结果表明，试验条件下，灌水使植株叶绿素含量（SPAD）增加、透光率减小，对产量无显著影响。施氮对冠层结构和产量的影响因灌水处理而不同，在不灌水条件下，增施氮肥增加叶片SPAD，提高穗位层叶面积指数（LAI）和产量，以施氮量375 kg/hm²时产量最高，较不施氮处理提高39.5%；在灌水条件下，增施氮肥增加各层LAI和SPAD，而使透光率减小，产量以施氮量225 kg/hm²时最高。氮肥偏生产力随施氮量增加呈明显下降趋势。从产量及氮肥高效利用看，高产玉米适宜的施氮量在225～300 kg/hm²之间，灌水与否取决于不同降水年型。

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 canopy structure and grain yield of summer maize was studied. The results showed that irrigation increased the SPAD while decreased the transmittance of summer maize. But it had no significant effect on grain yield. Under no irrigation conditions(W0), nitrogen application significantly increased the SPAD in all leaves and the leaf area index(LAI) of the ear layer, thus improved the grain yield of summer maize. The highest yield was obtained at the nitrogen rate of 375 kg/ha under no-irrigation condition, which was 39.5% higher than no-nitrogen treatments. While under irrigation conditions(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 nitrogen rate 225 kg/ha got the maximum yield under irrigation condition. Nitrogen partial productivity decreased with the increase of nitrogen rate, and the treatment of nitrogen rate 375 kg/ha obtained the minimum at both water conditions. Taking yield and nitrogen use efficiency into account, the appropriate nitrogen rates in this region were from 225 to 300 kg/ha for high yielding maize production. However, the decision for irrigation might depend on the precipitation and its distribution in a peculiar year.