Optimal nitrogen distribution in maize canopy can synergistically improve maize yield and nitrogen utilization efficiency while reduce environmental risks

Abstract

Under the premise of 0 increase in nitrogen input and environmental friendliness, optimizing planting density to improve canopy nitrogen distribution is conducive to balancing the contradiction between resource consumption and yield increase, and promoting a cleaner production model of high yield and high efficiency in maize. We studied the effects of nitrogen application on grain yield, grain nitrogen concentration, grain protein concentration, nitrogen utilization efficiency, and vegetative organ nitrogen uptake, distribution, remobilization, economic returns and environmental benefit of two high-yielding maize hybrids under different planting densities (7.5 ×10⁴ plant ha⁻¹ and 12.0 × 10⁴ plant ha⁻¹) and nitrogen applications (0, 180, 360, and 540 kg N ha⁻¹) during 2019–2020. The results showed that the maize yield, grain nitrogen concentration and grain protein concentration reached the maximum of 22.7 t ha⁻¹, 1.9 %, 12.7 % corresponding to planting density of 12.0 × 10⁴ plant ha⁻¹ and nitrogen application of 360 kg ha⁻¹. The economic returns were also maximized which was 5.4 × 10³ USD ha⁻¹. Nitrogen utilization efficiency decreased with increasing nitrogen application, while increased with increasing planting density. The nitrogen accumulation and remobilization of plants had a positive response to nitrogen application and planting density. Higher yields were obtained due to higher vegetative organs of pre-silking nitrogen accumulation and stalk nitrogen remobilization and high nitrogen accumulation in the middle leaf. Under this high-yielding condition, both reactive nitrogen losses and greenhouse gas emissions of the optimal combination were 6.1 % lower than the low-yielding combination. Therefore, under high planting density, selecting suitable hybrids, defining the appropriate nitrogen application and optimizing nitrogen distribution in maize canopy can achieve high-yield and efficient production of maize while reduce environmental risks. This study highlights the importance of optimizing canopy nitrogen distribution in maize, and likewise provides new insights into mitigating the negative environmental effects of agricultural production.