| The research was aimed to study the impact of different soil moisture conditions on soybean yield and the
distribution of biological organs . Soybean pot experiments were done at Heshan Fam in Heilongiang Province in 2009，and the soil moisture content treatments were 15%， 18%，24%， 30%，40% and 48% respectively. The results showed that there was good conical relationship between soil moisture and yield (R2=0.97), and the yield reached the peak with 30% (field capacity, FC). The yield would decrease when soil moisture was less or more than FC, and the range of yield decreasing between 80%~133% of FC was smaller of the soil moisture. The range of constituent elements decreasing with 60% and 133% of FC was bigger. There was good conical relationship between dry weight proportion of beans, bean stem，roots and soil moisture, and R2 were 0.93, 0.89 and 0.91 respectively. Dry weight proportion of beans reached maximum (51.31%) at field capacity; dry weight proportion of bean stem， roots was smaller, 41.06% and 7.63% respectively. Harvest index of soybean reached the maximum 0.59 under field capacity. There was good conical relationship between yield, dry weight proportion of beans，bean stem, roots and soil moisture . The influence law
of soil moisture on constituent elements of yield was the same as that on yield. FC was the optimum soil moisture for soy-bean growth and constituent elements of soybean yield by combination of yield and the constituent elements and compre-hensive analysis. |