Optimizing planting density for enhanced maize yield and resource use efficiency in China. A meta-analysis

Reasoned increases in planting density are key measures to enhance maize yields. However, most existing studies on maize planting density based on long time spans often fail to account for diverse microclimates. The impact of planting density on yield components has not also been well investigated in major production regions of China. Therefore, we conducted a meta-analysis of 1951 data pairs from 160 published papers (2013–2023) to assess the effects of increasing planting density on maize yield, yield components, phenotypic traits, and resource utilization and to determine optimal density increase ranges for different environments. The results showed that increasing planting density improved the leaf area index by 23.4%, plant height by 1.8%, aboveground dry matter accumulation by 15.9%, water use efficiency by 3.8%, nitrogen use efficiency and 34.2%, and grain yield by 10.0–11.0%. Dense planting also increased the maize ear number per area by 34.3% but decreased grain number per ear by 12.5%, 1000-grain weight by 7.2%, and harvest index by 2.4%. Notably, the density increase range emerged as the primary factor influencing yield and its components, with changes in grain number per ear the most significant contributor to yield variations. A 25–50% density increase range was identified as optimal, resulting in an 11.5–13.4% yield increase. Average local planting densities were 63,496 plants·ha^–1 in the Northwest, 58,928 plants·ha^–1 in the Huang-Huai-Hai region, 58,234 plants·ha^–1 in the Northeast, and 51,761 plants·ha^–1 in the Southwest. Here, we show for the first time that the optimal density increase range varied by region: 25–50% for the Northeast, >50% for the Huang-Huai-Hai and Southwest, and 0–25% for the Northwest. These findings highlight the importance of tailoring planting density to local conditions, offering a scientific basis for optimizing maize production across diverse regions in China.