Response of Water Radiation Utilization of Summer Maize to Planting Density and Genotypes in the North China Plain

Increasing the planting density of summer maize to improve the utilization efficiency of limited soil and water resources is an effective approach; however, how the leaf water-use efficiency (WUEL), yield, and RUE respond to planting density and genotypes remains unclear. A 2-year field experiment was performed in the North China Plain (NCP) to investigate the effects of planting density (high, 100,000 plants ha−1; medium, 78,000 plants ha−1; and low, 56,000 plants ha−1) and genotypes (Zhengdan 958 and Denghai 605) on the leaf area index (LAI), photosynthetic characteristics, dry-matter accumulation, WUEL, and RUE of maize. The objective was to explore the effect of density and genotype on the WUEL and RUE of maize. Increasing planting density boosted LAI, light interception, dry-matter accumulation, and spike number but reduced the chlorophyll content, net photosynthetic rate, transpiration rate, and 1000-kernel weight. Both high and low planting densities were averse to RUE and yield. Zhengdan 958 increased the WUEL by 19.45% compared with Denghai 605, but the RUE of Denghai 605 was 18.19% higher than Zhengdan 958, suggesting that Denghai 605 had a greater production potential as the planting density increased. Our findings recommend using 78,000 plants ha−1 as the planting density with Denghai 605 to maintain summer maize yields in the NCP.