Late-Season Dry Weather and Soybean Prospects
Excerpt from Emerson Nafziger
IPM Bulletin Post
September 12, 2013
Why would a few hours of decreased photosynthetic activity in a day, which would usually lower corn yields, have less effect in soybean? Soybean plants tend to have a little more leaf area than they normally need for maximum photosynthesis, and because they can’t move sugars away from the leaves fast enough, they typically form starch during the day to tie up the extra sugar. While much of that starch is converted back to sugar and goes to good use, small reductions in photosynthesis over the course of a day may not decrease the available supply of sugars enough to hurt yields. This is especially true if pod numbers are less than normal, which means less demand for sugars.
The amount of seedfilling that the soybean crop is able to do when it’s dry during the second half of the season is directly related to two things: 1) how many seeds are present to fill; and 2) how long the crop is able to maintain enough active canopy to fill seeds.