Effect of Row Spacing Pattern on Yield and Plant Height Uniformity in Highly-densed Summer Maize

In comparison with treatments of row spacing of 40 cm,50 cm,60 cm,70 cm and 40 + 80 cm,the treatment of row spacing of 50 cm ranked first with increase of 5.15%-5.77% in yield,and 40 cm was followed under about 70 000 plant/ha planting condition.There was no significant difference among row spacing of 40 cm,40 + 80 cm,60 cm and 70 cm.The optimum planting pattern was 50 cm row spacing with ratio of row space to plant space of 1.82 ∶ 1 for highly-densed summer maize.There was a trend of increase in grain number per hectare,grain weight and plant height uniformity with row spacing reduced,which compensated to some extent the negative effect on grain number per ear and 1 000-grain weight.There was no significant difference for layer and number of secondary roots among treatments.