University of Illinois crop specialist Fabian Fernandez says over the last two weeks he's observed several fields and received numerous reports of potassium (K) deficiency symptoms in corn and soybean yields. Since many farmers have not seen this before, he is offering some education on whether or not symptoms are those of K deficiency or nitrogen deficiency (see following pictures).
Potassium deficiency symptoms in corn develop on the edges of older leaves, typically starting at the tip, while the new growth appears normal. (Photos courtesy of the University of Illinois Plant Clinic.)
Potassium deficiency symptoms in soybean develop on the edges of older trifoliates, while the new growth appears normal.
Fernandez says symptoms showing up in so many fields reflect two general conditions:
- insufficient supply due to low soil-test K levels, and
- reduced K availability due to less-than-ideal soil conditions and slow root activity.
"The best action at this point is to look for clues that may help with determining how best to solve or minimize any future K deficiency. Take note of the general condition of the roots and the physical condition of the soil, and collect soil samples for K analysis from adjacent areas with seemingly normal growth and K-deficiency symptoms. If the deficiency is not extreme and is caused by dry conditions, the crop likely will recover with little or no yield reduction once there is sufficient rain," says Fenandez. "Most fields have areas that are more severely affected than others; it would be advisable to mark those areas with a handheld global positioning system (GPS) and go back after harvest to sample the soil and to target the area with variable rate applications if deemed necessary."
Read more about potassium-deficiency at this link.