抄録
Soybean plant growth during reproductive stage controls strongly seed yield. Two field experiments were conducted to analyze whether water condition improve soybean plant growth from flowering to the beginning of seed developing stage and which growth factors were related. One experiment was the comparison in plant growth between 2008, a wetter season, and 2009, a drier season. Crop growth rate (CGR) from flowering to beginning seed stage in 2008 was higher than that of 2009 and this was associated with higher mean leaf area index (LAI). Relative growth rate (RGR) in 2008 was as high as that of 2009 and this was associated with higher mean specific leaf area (SLA) in spite of lower net assimilation rate (NAR). The other was the irrigation experiment where we irrigated a half of experimental field during emergence to maturity. Although the differences between the treatments were smaller, CGR, LAI and mean SLA increased by irrigation. These results indicate that the improvement of soil water condition increased CGR with the increase in LAI and keep RGR by high SLA in spite of high total dry weight at flowering and lower NAR during reproductive stage.
