Most of the soybean crop remains green or at least has some green leaves. These are still capable of producing sugars to help fill seeds, though day/night temperatures of low 70s/upper 40s are not favorable for seedfilling.
“The return to cool weather likely has helped the crop cope with water shortage by lowering water use rates,” Nafziger said. “But lower water use rates and low temperatures mean lower photosynthetic rates, and so we expect that yield is being added slowly in most soybean fields. This will speed up as it warms up again, but senescence may not be far behind.”
In the Urbana planting date study with Maturity Group 3.6 soybeans, the mid-April and early May plantings are both close to maturity, with little green color left. In the earliest planting, upper pods are starting to dry. In contrast, the early June planting is dark green, with seeds perhaps half-filled. Very early-maturing soybeans planted in early June around that study are yellow, and seeds appear to be well filled, he said.