Yield components, dry matter, LAI and LAD of soybeans in Northeast China

Pod and seed number are the most important yield components of soybean [Glycine max (L.) Merr.]. Leaf area index (LAI), leaf area duration (LAD) and dry matter accumulation during the reproductive period strongly influence yield components. Our objectives were: to investigate if differences in yield components exist among genotypes differing in both yield and maturity; and to examine the dynamics of dry matter accumulation, LAI, and LAD during the reproductive period for the high-yielding genotypes. Sixteen soybean genotypes within three maturity groups were grown in Hailun, China in a randomized complete block design with three replications, across 2 years. Maturity groups were selected to differ by approximately 7 days in mean days to R7 (5% of pods are mature pod color). Dry matter accumulation, LAI, and LAD were measured at R2, R4, R5, and R6 stages, respectively in each year. Yield, yield components and harvest index were determined at maturity. Late maturity genotypes had higher yield than early ones. Majority of the seed yield and components were positioned in the middle and upper part of the plant. Both pod number and seed number were higher in high-yield genotypes in each group. Seed number per pod contributed to increased yield in the high rainfall year but was not related to the variation in yield of the genotypes evaluated. Significant variations were found for LAI, LAD and dry matter within each maturity group. Higher accumulation of dry matter, higher LAI and LAD during reproductive stages were found to be closely related to high-yield genotypes in each group. No relationship was found between harvest index (HI) and seed yield.