This study aimed to explore the regulatory effects of different plant height combinations of maize varieties on the light distribution and light resource utilization of the population canopy under the soybean and maize strip intercropping pattern.

From 2023 to 2024, four maize varieties with different plant heights were used as experimental materials, including the short-stemmed varieties of MY73 and Denghai 605 (DH605), and the tall varieties of Jingke 968 (JK968) and Xianyu 1466 (XY1466), as well as the soybean variety Qihuang 34. The row configuration of maize and soybean was both 4:4. Different intercropping patterns were set, including intercropping of the same maize variety in all four rows as the control (S-MY, S-DH, S-JK, and S-XY), with 6.75×10⁴ plants/hm² for each of the four rows and intercropping of tall and short varieties (middle row tall variety JK968, edge row short variety MY73: MY-JK-1, MY-JK-2; middle row tall variety XY1466, edge row short variety DH605: DH-XY-1, DH-XY-2), and two types of planting densities were set, with 6.75×10⁴ plants/hm² for each of the four rows (MY-JK-1, DH-XY-1), 6.75×10⁴ plants/hm² for the middle rows, and 8.25×10⁴ plants/hm² for the edge rows (MY-JK-2, DH-XY-2). The plant spacing of soybean in each treatment was the same. The focus was on analyzing the effects of different intercropping patterns on the canopy structure of the population, light distribution, photosynthetic characteristics of maize and crop yield.

The combined planting of maize varieties with different plant height optimized the canopy structure, significantly improved the light transmittance of the spike layer in the maize population, increased the leaf area index and photosynthetic characteristics, and ultimately promoted the increase in total system yield. During the silk production stage, the light transmittance of the spike layer in MY-JK-1 and MY-JK-2 increased by 18.55%-88.22% compared with S-MY and S-JK, and that in DH-XY-1 and DH-XY-2 increased by 39.26%-55.77% compared with S-DH and S-XY. The net photosynthetic rate (P_n) of the four varieties (except MY73) in the tall and short plant combination pattern was all increased. Among them, the P_n of DH605 in the DH-XY-2 pattern is 6.88% higher than that of S-DH, and the P_n of XY1466 in the DH-XY-2 pattern is 10.31% higher than that of S-XY. At the same time, the maximum photochemical efficiency (F_v/F_m) and potential activity (F_v/F_o) of the spike leaf also increased. The yield of maize under the MY-JK-2 pattern increased by an average of 19.44%, 9.58% and 1.66% over two years compared with the S-MY, S-JK and MY-JK-1 patterns, respectively. The average increase of DH-XY-2 over two years was 30.20%, 14.94% and 9.21% compared with the S-DH, S-XY and DH-XY-1 patterns, respectively. The maize yield (12 536.58 kg·hm^-2) and total system yield (14 001.29 kg·hm^-2) under the DH-XY-2 pattern were the highest in both years.

Compared with the intercropping pattern of single maize varieties, the combined planting of maize varieties with different plant heights could optimize the canopy structure of the population, improve the light distribution of the population canopy, and increase the light transmittance of the maize ear position layer and the photosynthetically active radiation at the top of soybean. At the same time, it improved the leaf area index and photosynthetic characteristics of maize, promoted the accumulation of photosynthetic products, and ultimately increased the total system yield. With the increase of edge row density, the maize yield was further enhanced. Under the conditions of this experiment, in the eastern part of the Huang-Huai-Hai region, it was recommended to use the combined planting of short-stemmed DH605 and tall XY1466, with a middle row density of 6.75×10⁴ plants/hm² and an edge row density of 8.25×10⁴ plants/hm².