The spring rush of planting is catching up to the soybean crop in some fields, says University of Kentucky grain crops specialist.
"Surface compaction and sidewall compaction was most likely caused by planting when fields were a little too wet," Lee says. "The compacted soil has restricted root growth on soybeans."
Lee says up until now, there has been enough water to keep most nutrients within the root zone and soybeans looked fine. But as the soybeans reach full pod development (R4), the plants are rapidly accumulating nitrogen and potassium.
"The restricted roots are not taking up enough nutrients to sustain plant growth. Plants turn yellow," Lee says. "Timely rainfall now will help move nutrients into the root zone. Yield losses from compaction could be very minor or very severe, depending on rainfall, soil fertility within the root zone and severity of compaction."
Fertilizers at this point will likely have little impact on yields, Lee adds.
"As more soybeans get closer to full pod and beginning seed development, I expect we will see more yellow soybean," he says.