Growth, photosynthesis and yield of soybean in ridge-furrow intercropping system of soybean and flax

It is of practical significance to control the excessive vegetative growth of soybean during the rainy season, which causes a reduction in yield. In this study, we adopted soybean flax ridge-furrow intercropping system in order to constrain soybean's excessive vegetative growth by interspecific competition between intercrops and estimated the growth, photosynthesis and yield of soybean. Two-year-experiment was conducted in 2018 and 2019 in the experimental farm of KIM IL SUNG University. Soybean seeds were grown in ridges and flax seeds were in furrows between ridges. During the co-growth stage, the early growth of soybean intercropped with flax was depressed by interspecific competition. At 45 days after soybean sowing, just before flax harvest, the average height and stem diameter of intercropped soybean plant were 22.5 cm and 0.7 mm shorter than those of sole cropped soybean plant, respectively. At the reproductive growth stage, the height of intercropped soybean plant was still 18.5 cm shorter than sole cropped soybean, while other agronomic parameters, including leaf area index (LAI), dry matter per plant, photosynthetic rate and chlorophyll contents, were greater for intercropped soybean. This led to higher yield of soybean (118.5%) and land equivalent ratio (LER) (203.5%) in ridge-furrow intercropping, as compared to sole cropping. Our results suggest that ridge-furrow intercropping system can be an effective way to constrain soybean's excessive vegetative growth during the rainy season and improve soybean seed yield and LER.