Yellow soybeans? That probably isn’t a good sign. What’s happening, exactly?
Dorivar Ruiz Diaz and Ignacio Ciampitti, Extension specialists with Kansas State University, recently discussed four potential culprits in a recent edition of K-State’s “Extension Agronomy eUpdate” newsletter. Here’s what may be happening in those particular fields.
1. Nitrogen deficiency. This may be due to a delay in rhizobial nodule development because of extreme wet, dry or hot conditions. Check lower leaves – if they’re pale green or chlorotic, N deficiency may be the reason. Soybeans that are double-cropped after wheat are also susceptible, and even hail-damaged soybeans are at risk if enough foliage was injured.
2. Iron chlorosis. If soils are overly saturated, temporary symptoms of iron chlorosis is a potential result. Topmost leaves will turn yellow while veins remain green. Highly alkaline pH soils are most susceptible.
3. Potassium deficiency. Unlike iron deficiency, K deficiency is more common later into the season. Look for irregular yellow mottling around leaflet margins. It’s a problem most common when soils are too wet or too dry. Good root growth will solve these problems, unless there’s a true K deficiency.
4. Rooting restrictions. Any number of issues – including wet or dry soil, compaction problems, or even root insects and diseases – will adversely affect growth and could lead to yellowing. “With a restricted root system, the growing plant can’t access the nutrients it needs to make more leaves,” the researchers note. “As a result, nutrient deficiencies can show up in fields where you [otherwise] might not expect them based on a typical soil test.”
Click here for more information about these potential problems.