关键词: 玉米, 增密, 矮秆, 倒伏率, 籽粒容重, 出籽率

Abstract:

【Objective】 The aim of this study was to investigate the differences in the effects of increasing planting density on the dynamic change of agronomic traits, yield and its components among maize cultivars with different plant heights, and to clarify the stable yield mechanism of dwarf maize cultivar under high density for providing a theoretical basis for exploring the high-yield potential of maize and breeding dwarf maize cultivars with high-yield under high planting density.【Method】 A two-factor experiment was conducted during the 2023 and 2024 maize growing seasons. Three maize cultivars with different plant height were used as test materials: tall-stalk variety Xianyu 335 (XY335), medium-stalk variety Zhengdan 958 (ZD958), and dwarf-stalk variety MY73. Nine planting densities were set: 60 000 (D1), 67 500 (D2), 75 000 (D3), 82 500 (D4), 90 000 (D5), 97 500 (D6), 105 000 (D7), 112 500 (D8), and 120 000 plants/hm². The effects of planting density on agronomic traits related to plants, leaves, ears, kernels, and yield of maize cultivars with different plant height were investigated. Analysis of variance was used to statistically evaluate the significance of differences in each index among different cultivars at the same density and among different densities for the same cultivar. The dynamic changes in leaf area index (LAI) were analyzed using the BiHil model.【Result】 The density ranges for achieving high yields of XY335, ZD958 and MY73 across the two-year experiment were 60 000-67 500, 67 500-82 500, and 82 500-97 500 plants/hm², respectively. The average of the highest yields of MY73 over two years was 11.1% and 6.8% significantly higher than that of ZD958 and XY335, respectively. There were no significant differences in lodging rate among the three cultivars under the low-density of D1 and D2. Starting from the D3 density, the lodging rate of the dwarf-stalk variety MY73 was significantly lower than that of the tall-stature variety XY335 and the medium-stature variety ZD958 with increasing planting density, and the lodging rates of ZD958 and XY335 increased significantly, with their two-year average lodging rates ranging from 10.4% to 66.6% and from 11.6% to 82.8%, respectively. In contrast, MY73 exhibited no lodging in 2023, and only lodged at the D9 density in 2024 with a lodging rate of 1.1%. Affected by lodging and other factors, the number of effective ears per unit area of dwarf-stalk cultivar MY73 gradually increased with increasing density, while those of tall-stalk XY335 and medium-stalk ZD958 increased firstly and then decreased. Under high planting density, the number of effective ears per unit area of MY73 was significantly higher than that of XY335 and ZD958. With density increasing, the plant height and LAI of all cultivars gradually increased. MY73 had the smallest increase in plant height and the largest increase in LAI, and its plant height was significantly lower than that of XY335 and ZD958 under all densities. The kernel setting rate, harvest index, shelling percentage, and grain bulk density of MY73 were significantly higher than those of XY335 and ZD958 under all densities, with the harvest index of MY73 remaining stable around 0.6 under all densities. After increasing density, the kernel setting rate, kernel weight per ear, and harvest index of all cultivars gradually decreased, and MY73 showed the smallest decrease relative to the other two cultivars. Compared with density D1, the average decreases in kernel setting rate, kernel weight per ear, and harvest index of MY73 across all densities over two years were 44.0% and 30.5%, 39.5% and 29.4%, and 96.3% and 94.6% smaller than those of XY335 and ZD958, respectively.【Conclusion】 The coefficient of variation of the yield and its components, and plant agronomic traits of MY73 was smaller with increasing planting density, and the magnitude of reduction of green leaf area per plant for MY73 was also smaller with growth period progress. MY73 exhibited lower lodging rate, and higher number of effective ears per unit area, kernel-setting rate, grain bulk density, shelling percentage, harvest index, and grain yield, when the density exceeded 97 500 plants/hm². These characteristics constitute the key mechanism for the high and stable yield of the dwarf-stalk cultivar MY73 under high planting density in this study.

Key words: maize, density increase, dwarf stalk, lodging rate, grain bulk density, shelling percentage