Response of light use efficiency and grain yield of maize to planting density and nitrogen application rate

Objectives A rational planting density and judicious use of chemical fertilizer input are effective ways to improve crop yields and fertilizer use efficiency in the rainfed region. We studied the effect of planting densities, N fertilizer application rate, and their interaction on light use efficiency (LUE) and yield, to provide data support for a more efficient use of the light resources.

Methods Split plot experiments were conducted over three consecutive years (2017−2019) with a maize hybrid cultivar, Zhengdan 958 (ZD958). The main plot was assigned to four planting densities (M4.5, 45000 plants/hm²; M6.0, 60000 plants/hm²; M7.5, 75000 plants/hm²; M9.0, 90000 plants/hm²), and the subplots were occupied by three N application rates (120, 180 and 240 kg/hm²). The maize leaf area index (LAI), P_n, LUE, above ground biomass, and grain yield were determined.

Results The maize grain yield, dry matter, LAI, P_n, and LUE were significantly influenced over the three years. The average LUE in 2017, 2018, and 2019 was 1.58%, 1.99%, and 2.20%, respectively. The grain yield, biomass, LAI, P_n, and LUE were significantly affected by planting density. The highest average LUE (2.07%) and grain yield (12219 kg/hm²) were obtained under the planting density of 75000 plants/hm². N application rate also affected biomass and LAI significantly. The highest LUE was 1.87% at the N rate of 180 kg/hm². There were similar interaction effect of planting density and N rate on grain yield, biomass, LAI, and P_n. However, the highest LUE of 2.16% was recorded under M7.5+N240, and the effect of planting density on LUE was greater than that of N rate, which was 9.93% and 6.01%, respectively.

Conclusions In semi-humid rainfed agricultural regions, both plant density and the interaction of density and N rate, significantly improved the light use efficiency of maize, and the effect of plant density is greater than N application rate. Therefore, a relatively high planting density (75000 plants/hm²) and N application rate (180 to 240 kg/hm²) are recommended for efficient use of light and optimum maize grain yield.