Impacts of Varying Row Ratio Arrangements on Plant Performance, Stand Yield, and Comprehensive Benefits in Soybean-Maize Strip intercropping

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.