Effect of Planting Density and Nitrogen Rate on Dry Matter Accumulation and Yield Formation of Super Highly-yielding Summer-sowing Maize

In order to clarify the effects of planting density and nitrogen fertilization rate on dry matter accumulation and yield formation of summer-sown maize,a field experiment was carried out at Gaocheng County,Hebei Province in 2013,using a summer-sown maize cultivar,Nongdan 902. The experiment was designed as split plot arrangement,with planting density as main plots( 5. 25 × 104,6. 00 × 104,6. 75 × 104,7. 50 × 104,and 8. 25 × 104 plants per ha) and nitrogen fertilization rate as split plots( N 300,375,450 kg / ha). the results showed that,the interactions of planting density and nitrogen fertilization rate on dry matter accumulation and yield traits were not significant( P 0. 05). Under the same nitrogen fertilization rate,the amounts of dry matter accumulation and ears per hectare increased,but the harvest index,grains per ear and 1000 grain weight decreased with the increasing density.And the amount of post-silking dry matter accumulation,the contribution percentage of post-silking dry matter to total dry matter accumulation,and grain yield firstly increased,and then decreased with the increase of density. The influence of planting density on the length of aborted part of the ear and grains per ear was the biggest,and that on grain rows per ear was the smallest. Under the same planting density,the dry matter accumulation at all growing stages( except jointing),post-silking dry matter accumulation,harvest index,grain yield and the three yield components all increased with the increase of nitrogen fertilization rate and reached the maximum at the nitrogen rate 375 kg / ha,then decreased when the nitrogen fertilization rate increased from 375 kg / ha to 450 kg / ha. Under the condi-tions of this study,the highest grain yields of maize,12 797. 3,12 425. 5 kg / ha,were achieved in the treatments with the planting density 6. 75 × 10~4,7. 50 × 10~4/ ha,and nitrogen fertilization rates 375 kg / ha,respectively,in which the three yield components were coordinate.