by John Toft, CCA and Latham’s Regional Manager in Nebraska
While walking fields recently, I’ve seen corn leaves that are yellowing around the leaf margins. The yellowing starts at the tip of a leaf, extending along its edges to the base of the leaf. In more severe cases, the edges are brown.
Corn and soybeans are showing signs of potassium deficiency this growing season. Most of the potassium deficiency I’ve seen so far this season is not due to planting in too-wet soil conditions or compaction, although this certainly could be a reason in some cases. Instead, I’m seeing more potassium deficiencies where there is an extremely dry soil surface and where root activity has been slow. Dry conditions typically limit root growth, which explains why soils can have good levels of potassium but nutrients don’t get to the plants. It also helps explains why, in some fields I have observed, the K deficient symptoms are occurring in the best-drained soils in the field while the more poorly drained areas look better.
Dry surface soils express K deficiency most often. Ridge-till, no-till situations and side wall compaction will sometimes show symptoms in dry years. Irrigation or simply rainfall is a great way to jumpstart the root systems and help the plant develop through the K deficiency.
It’s important to understand why if and why there is a potassium deficiency because K is an essential nutrient for plant growth that has a large impact on overall yield. Potassium controls transpiration and respiration, as well as the uptake of certain nutrients including nitrogen and magnesium.
The type of nutrient deficiency determines soil management strategies. Some people side-dress potash or various forms of K. Others try foliar products. One word of warning is that some of these products can be harmful to the plant at certain stages of growth. A grower should select a low salt form of K and avoid anything with KCl or KSO4 for foliar applications. A better and safer means is to address the situation by applying potassium before planting 2013.
Walk your fields now and note where you’re seeing signs of potassium deficiency, so you can be sure to test and possible treat those areas before the 2013 crop is planted. Another leaf tissue sample can provide helpful information, too. You can see if there are other nutrient deficiencies in your field. Tissue sampling is one service provided through Latham’s Seed-to-Soil program.