To optimize the soybean-maize intercropping system in the Huang-Huai-Hai region, this study aimed to evaluate the effects of different row ratio configurations on crop agronomic traits, canopy structure of the population, yield components, edge effects, and overall economic benefits. The goal was to identify suitable row ratio configurations, thereby improving land resource use efficiency and economic returns.

Three row ratio configurations were implemented: 4 rows of soybean intercropped with 2 rows of maize (4:2), 6 rows of soybean intercropped with 4 rows of maize (6:4), and 4 rows of soybean intercropped with 4 rows of maize (4:4), using monoculture soybean (SCK) and monoculture maize (MCK) as controls. Crop dry matter accumulation, leaf area index (LAI), relative chlorophyll content (SPAD), canopy light transmittance, and yield components were measured. The inner and outer row sampling approach was adopted to evaluate edge effects and overall economic benefits.

Compared with monoculture, intercropping significantly decreased per-plant dry matter accumulation in maize during the filling, milking, and maturity stages, and in soybean during the full flowering, full pod, grain filling, and full maturity stages. Among the row ratio configurations, maize exhibited maximum per-plant dry matter accumulation under the 4:4 pattern, whereas soybean achieved its highest accumulation under the 6:4 pattern. Row ratio configurations significantly influenced inter-row variations in dry matter accumulation and yield for both crops. Maize yield followed the order 4:4 pattern>4:2 pattern>6:4 pattern, representing reductions of 15.22%, 18.02%, and 12.62% relative to MCK, respectively; soybean yield followed the order 6:4 pattern>4:4 pattern>4:2 pattern, corresponding to reductions of 55.99%, 50.43%, and 56.00% compared with SCK, respectively. Intercropped maize exhibited pronounced edge advantage, with border row maize yields significantly exceeding those of inner rows. Within the intercropping system, both maize and soybean demonstrated lower canopy light transmittance, LAI, and SPAD values compared with their monoculture counterparts. Maize canopy light transmittance, LAI, and SPAD values followed the consistent ranking: 4:4 pattern>4:2 pattern>6:4 pattern; soybean canopy light transmittance followed 4:4 pattern>6:4 pattern>4:2 pattern, while its LAI and SPAD values mirrored the ranking pattern observed in maize. Maize LAI was significantly influenced by row ratio configuration, whereas no significant inter-row variations were detected for maize SPAD values or for soybean LAI and SPAD values. In evaluations of economic returns and intercropping advantages, the 4:4 pattern configuration demonstrated superior performance, achieving the highest values for land equivalent ratio (LER), relative crowding coefficient (K), and economic benefits. Maize in intercropping exhibited higher LER and K values relative to soybean, with the maize competition ratio (CR_m) being significantly greater than that of soybean (CR_s) (CR_m>1, CR_s<1), demonstrating maize's competitive dominance in interspecific competition.

Although intercropping reduced per-plant dry matter accumulation, LAI, and SPAD values for both crops compared with monoculture, it significantly increased the land equivalent ratio (LER) and overall economic benefits. Under the experimental conditions, the 4:4 pattern exhibited more optimal canopy architecture, with maize demonstrating pronounced edge advantage. This system maintained maize yield while generating additional soybean income, thereby achieving the synergistic enhancement of total productivity and economic returns.

Climate change has led to global warming, with frequent occurrences of high temperatures and droughts, and high temperatures often accompany droughts during production. This study aimed to explore the physiological mechanism of the compound stress of high temperature and drought in different growth periods affecting the yield and photosynthetic characteristics of summer maize.

DH605 was selected as the experimental hybrid. High temperature treatment (T), drought treatment (D) and the compound stress (T-D) treatment were set in different growth periods. In 2019, it was carried out at the third leaf stage (V3), the sixth leaf stage (V6) and flowering stage (VT); In 2020, it was carried out at the third leaf stage (V3), the twelfth leaf stage (V12) and flowering stage (VT). This experiment took natural temperature and normal moisture treatment as control (CK). The effects of high temperature and drought compound treatments on yield, photosynthetic characteristics, dry matter accumulation and distribution of summer maize were studied, and the differences of photosynthetic characteristics and yield between single treatment and compound treatment were compared.

After the combined stress treatment of high temperature and drought in different growth stages, the LAI and SPAD of summer maize decreased significantly, which affected the net photosynthetic rate (P_n) and it decreased significantly. Among that, the compound stress during the VT period had the most significant effect on P_n. The P_n under T-D treatment in the VT period decreased by 39.0% on average compared with CK, while the net photosynthetic rate of summer maize after the combined treatment of high temperature and drought decreased more than that under single stress such as high temperature and drought. The combined treatment of high temperature and drought caused the photosynthetic performance of summer maize to decrease, and it led to the decrease of dry matter accumulation capacity and distribution ratio of summer maize to grains, which in turn led to a significant decrease in yield. In 2019, the output of T-D at V3, V6, and VT decreased by 27.4%, 18.3%, and 66.5%, respectively, compared with CK; in 2020, the output of T-D treatment at V3, V12, and VT decreased by 14.5%, 14.6% and 68.7%, respectively, compared with CK.

After the combined stress of high temperature and drought, the leaf area index and chlorophyll content was decreased, gas exchange was inhibited, leading to the decrease of photosynthetic performance, and thus hindered the accumulation and distribution of photosynthetic compounds, resulting in a significant yield reduction of summer maize. The combined stress of high temperature and drought during the flowering stage had the greatest impact on the yield and photosynthetic characteristics of summer maize, and the combined stresses had greater impacts than that of single stress.