Increased plant density and reduced N rate lead to more grain yield and higher resource utilization in summer maize

Planting at an optimum density and supplying adequate nitrogen(N) to achieve higher yields is a common practice in crop production, especially for maize(Zea mays L.); however, excessive N fertilizer supply in maize production results in reduced N use efficiency(NUE) and severe negative impacts on the environment. This research was conducted to determine the effects of increased plant density and reduced N rate on grain yield, total N uptake, NUE, leaf area index(LAI), intercepted photosynthetically active radiation(IPAR), and resource use efficiency in maize. Field experiments were conducted using a popular maize hybrid Zhengdan 958(ZD958) under different combinations of plant densities and N rates to determine an effective approach for maize production with high yield and high resource use efficiency. Increasing plant density was clearly able to promote N absorption and LAI during the entire growth stage, which allowed high total N uptake and interception of radiation to achieve high dry matter accumulation(DMA), grain yield, NUE, and radiation use efficiency(RUE). However, with an increase in plant density, the demand of N increased along with grain yield. Increasing N rate can significantly increase the DMA, grain yield, LAI, IPAR, and RUE. However, this increase was non-linear and due to the input of too much N fertilizers, the efficiency of N use at NCK(320 kg ha^(–1)) was low. An appropriate reduction in N rate can therefore lead to higher NUE despite a slight loss in grain production. Taking into account both the need for high grain yield and resource use efficiency, a 30% reduction in N supply, and an increase in plant density of 3 plants m^(–2), compared to LD(5.25 plants m^(–2)), would lead to an optimal balance between yield and resource use efficiency.