Assessing the influence of furrow width on growth and yield of soybean in ridge-furrow relay intercropping system with flax

Abstract

Soybean flax ridge-furrow relay intercropping system is a new method of intercropping system to distress excessive vegetative growth of soybean during the rainy season. However, the effects of furrow width for flax on growth and yield of soybean in ridge-furrow relay intercropping system remain unclear. In this study, we investigated that the effects of three treatments (FS1: 10 cm furrow width, FS2: 20 cm furrow width, FS3: 30 cm furrow width) on growth and yield of soybean and clarified informative principal data for soybean flax ridge-furrow relay intercropping system. In a three-year field experiment, soybean was grown in ridges and flax was grown in furrows. At the early vegetative growth stage of soybean, environmental conditions such as water, light, and temperature, in ridge-furrow relay intercropping system, decreased significantly by interspecific competition in comparison with sole cropping system. The differences in environmental conditions between sole cropped and intercropped treatments increased in accordance with increasing width of flax furrow. Especially, soil moisture content, photosynthetically active radiation (PAR), and temperature in FS3 were 39.9%, 29.6%, 4.4 ℃ lower than those of SS, respectively, on average of 3 years. At the reproductive growth stage, expanding furrow width for flax decreased the number of abscised leaves, plant height, leaf area index (LAI), and specific leaf area (SLA) of intercropped soybean, while increased PAR penetration within the canopy and stem diameter. At 130 DAS, average numbers of abscised leaves in FS2 and FS3 were 4 and 5 lower than that of SS, respectively. Plant height of soybean was 0.3 m lower than that of SS in both FS2 and FS3. In LAI, the value of sole cropped soybean varied between 6.8 and 7.2, but it in FS2 and FS3 varied between 3.4 and 4.3. Particularly, LAI in FS2 ranged from 4.1 to 4.3. Average stem diameter of soybean was 0.3 cm higher than that of SS in both FS2 and FS3. PAR penetration at 30 cm below soybean canopy in FS1, FS2, and FS3 was 111.2, 122.5, 133.0% of that in SS, respectively. These led to a higher crop growth rate (CGR), reproductive growth rate (RGR), and grain distribution in intercropped soybean, as compared to sole cropped soybean. Among three treatments, FS2 exhibited the maximum CGR, RGR, and grain distribution. Also, FS2 achieved maximum soybean yield of 4.9 t ha−1 (averaged by 2020, 2021, and 2022) and maximum land equivalent ratio (LER) of 2.1 (averaged by 2020, 2021, and 2022). No significant difference in LER was observed between FS2 and FS3; however, soybean yield in FS2 was significantly higher compared to FS3 across each year. Our results suggest that by selecting the appropriate furrow width, we can constrain the excessive vegetative growth more effectively and increase the yield of soybean under ridge-furrow relay intercropping system with flax.