Effect of row spacing on nitrogen uptake, nitrogen utilization and yield of summer maize

To identify the row spacing suitable for mechanization of maize production in the south of Huanghuai maize region, field experiments were conducted at two experimental sites (Fangcheng and Huixian) in Henan Province in 2012 and 2013, respectively. Three varieties of hybrid maize with different plant heights (high — ‘Xianyu 335’, medium — ‘Zhengdan 958’ and dwarf — ‘512-4’) were planted under two planting densities (low density — 60 000 plants·hm^-2 and high density — 75 000 plants·hm^-2) and five row spacings (50 cm, 60 cm, 70 cm, 80 cm, and 80 cm + 40 cm) conditions. The study determined the effects of row spacing and planting density on nitrogen uptake, nitrogen utilization and yield of maize. The results showed that grain yield of both ‘Xianyu 335’ and ‘512-4’ with 60 cm row spacing was obviously higher than those of other row spacings. Also yield of medium height variety ‘Zhengdan 958’ with 60 cm and 70 cm row spacings was higher than that of others row spacings under low density treatments. The study also showed that under high plant density, grain yield of high-height variety ‘Xianyu 335’ and medium-height variety ‘Zhengdan 958’ with 60 cm row spacing was obviously the highest, followed by dwarf-height variety ‘512-4’ with 50 cm row spacing and treatments with other row spacings. Initially, plant nitrogen accumulation increased with increasing row spacing, reached peak level at 60 cm row spacing, and then decreased. Nitrogen accumulation in plant under 60 cm row spacing was significantly higher than that under 80 cm and 80 cm + 40 cm row spacings in low planting density treatment, while no significant difference among different row spacings under high planting density. Nitrogen accumulation in different maize varieties varied with different row spacings. As for high-height maize variety, nitrogen accumulation was not difference among different row spacings. For medium-height maize variety, nitrogen accumulation in plant of 80 cm row spacing was significantly decreased compared with that of other row spacings. However, nitrogen accumulation in plants of 50 cm and 60 cm row spacing were obviously higher than that of other row spacings. Seed nitrogen accumulation and nitrogen harvest index initially increased with increasing row spacing, reached the highest in 60 cm row spacing, and then decreased. Similarity, nitrogen partial factor productivity was increased firstly, and then decreased with increasing of row spacing, and it was significantly higher in 60 cm row spacing treatment than that in 80 cm row spacing under high density condition, but no obvious difference was found among different row spacings under low density conditions. Compared with other row spacings, nitrogen utilization efficiency and grain yield were relatively higher under 60 cm row spacing condition. In conclusion, 60 cm row spacing was the optimal planting pattern for summer maize in the south of Huanghuai maize region.