For a while it looked like this was the year farmers would find out how much soybean genetics and improved production methods had helped to improve soybean yields. Instead, August turned dry once again, making this the fourth consecutive year in Indiana when soybeans in most locations have had less than ideal conditions during the critical reproductive phase.
Technically, August had enough rain for most areas in 2012, but the damage was already done – especially to earlier varieties – by a fast-maturing crop and extreme heat and drought prior to early August.
Now spots are appearing in fields, especially on slight rises or side slopes, which indicate that some soybeans are running out of gas. The plants are turning yellow in relatively small areas, but it's a sign that the crop needs water. In soils where it has more trouble getting to moisture, the drain stress is putting on soybeans is more obvious.
According to the Purdue University Corn & Soybean Field Guide, stress during reproduction is most costly from R3, which is beginning pod set, though R6, which is the stage where soybeans reach full maturity. Threshold levels for treatment for beetles or another damaging insect is higher than compared to earlier in the season when plants were in the vegetative state.
Spots on higher ground which were starting to turn yellow a few days ago were a tell-tale sign that the crop needs water and is shutting down early. On more poorly drained, black soils in these fields, however, soybeans still seem to be hanging on. The question will be what kind of seed the plants form in each area. Last year seed was large from later-maturing soybeans because when the rains came, it was the only way left that soybeans could compensate. This year it's possible that the seed will be smaller, especially without more rain soon.