Objectives Efficient and reasonable application of nitrogen (N) is vital for high yield and green development of agriculture. Suitable plant density and N application rate in summer maize production were studied to provide theorical and technical support of high-productivity and high-efficiency cultivation in summer maize.

Methods Field experiments were conducted in Suqian, Yancheng, and Yangzhou, Jiangsu Province, using maize cultivar of Jiangyu 877 as the tested material. The treatments including two planting densities of 60000 plants/hm² (D1) and 82500 plants/hm² (D2), and four N modes of zero N (N0), N 300 kg/hm² of conventional urea (N1), N 225 kg/hm² of conventional urea (N2), and N 225 kg/hm² of slow-release fertilizer (N3). The yield, accumulation and distribution of dry matter and N, and N use efficiency in response to interactions of plant densities and N modes were investigated.

Results Planting densities and N rates significantly affect the yield and N absorption and utilization of summer maize. At the same N rate, single plant yield was higher at D1 than that at D2, while the population yield was higher at D2. In comparison with N2, the average population yields of N1 and N3 were increased by 11.3% and 10.9% under D1, and by 7.4% and 9.0% under D2, respectively. The population yields of N1 and N3 were similar under D1 and D2. The population yield of D2N3 in Suqian achieved 9214 kg/hm², which was the highest among all treatments. The N accumulation and translocation for population were higher at D2 than those at D1. The total accumulation of dry matter and N of N3 at D1 were similar to those of N1, and both were higher than those of N2. At D2, the total dry matter accumulation in N3 was higher than that in N1, but N accumulation of N3 was similar to that of N1. The profit of different N treatments under D2 was higher than that under D1, and D2N3 got the highest profit among all the treatments.

Conclusions Based on the yield and nitrogen absorption and utilization in the three sites, plant density of 82500 plants/hm² with slow-released fertilizer of N 225 kg/hm² can improve the grain yield and N use efficiency, reduce the production cost, and increase profit of summer maize in Jiangsu Province.