The yield formation of soybean is related closely to the photosynthesis and dry matter accumulation
and distribution, out ratio (OR) and contribution ratio (CR) of every organ after blooming. In this study, effects
of spraying uniconazole at V5 and R1 stages, respectively, on the LAI, Leaf greenness, dry matter accumulation
and distribution of soybean after blooming. OR and CR of every organ were examined to explore the yield
forming mechanism. Spraying uniconazole increased LAI and Leaf greeness after blooming, delayed theirs
degradation effectively and prolonged leaf longevity. Spraying uniconazole at V5 stage significantly increased
dry matter accumulation and the effect of 75 mg/L treatment was the best for Zhechun 3(early-maturing soybean
cultivar), the effect of 30 mg/L treatment was the best for Gongxuan1 (late-maturing soybean cultivar). Spraying
uniconazole at R1 stage could increase dry matter accumulation and the effect on Zhechun 3 was significantly
higher than on the contrast, the best concentration of uniconazole was 100 mg/L, but there was no significant
difference between uniconazole treatments for Gongxuan 1 and the contrast. Spraying uniconazole could
significantly increase the ratio of dry leaf weight and dry root weight at podding stage and increase the ratio
of dry pod weight at maturity. Spraying uniconazole could significantly increase OR and CR of the root and leaf.