Density effect and yield stability adaptability of maize varieties in different ecological regions of Henan

【Objective】To study the density effect and stable yield adaptability of maize varieties in different ecological regions of Henan, which could provide reference for screening high-yield and wide-adaptability maize varieties and constructing an optimized layout scheme for summer maize planting density in Henan. 【Method】Field experiments were conducted in 6 ecological regions（environments） of Henan from 2022 to 2023, using a split-plot design. The main treatment was density with 4 levels:60000, 67500, 75000 and 82500 plant/ha（only in 2023）; the sub-treatment was variety, including 14 new maize varieties recently approved in the Huang-Huai-Hai region and Henan. Methods such as variance analysis, high stability coefficient method, AMMI model, GGE biplot analysis, correlation analysis and quadratic polynomial regression model were used to systematically evaluate the adaptability of maize varieties, yield components, and density response characteristics. 【Result】Planting density, environment, varieties, two-way interactions, and three-way interactions all had different degrees of influence on summer maize yield, ear rows, kernels per row and hundred-kernel weight. The environment had high proportion of explanation for summer maize yield variation in 2022 and 2023, which were 27.91% and 43.18%, followed by variety（9.76% and 10.19%）, and density had the smallest proportion（1.54%-2.25%）. Under different environments, the summer maize yield in 2022 was Nanyang ＞ Luohe ＞ Shangqiu ＞ Luoyang ＞ Anyang ＞ Zhoukou, and in 2023 it was Nanyang ＞ Zhoukou ＞ Luoyang ＞ Shangqiu ＞ Anyang ＞ Luohe. Based on the results of the high stability coefficient method, AMMI model and GGE biplot analysis, maize varieties such as Jingke 999, Qiule 368, Zhongkeyu 505 and Zhengdan 5179 had good high-yielding performance and were suitable for planting in Henan. Anyang and Shangqiu had stronger variety discrimination ability than other environments. Yield was significantly（P＜0.05） or extremely significantly（P＜0.01 or P＜0.001） positively correlated with plant height, ear height, ear length, ear rows and kernels per row, and extremely significantly negatively correlated with lodging and breaking rate（P＜0.001）. Reasonable variety selection could increase yield in Henan, but not all regions were suitable for increasing density. The quadratic polynomial regression analysis showed that the optimal planting density for summer maize in Henan was 71823.56 plant/ha, with a theoretical yield of 9358.10 kg/ha. 【Conclusion】Reasonable planting density and variety matching are the keys to improving summer maize yield in Henan. The most suitable planting density in this region is 71823.56 plant/ha, and the high-yield and stable-yield maize varieties suitable for planting are Jingke 999 and Qiule 368.