It is that time of year and with the weather conditions we’ve had the last 30 day we should expect to see purple corn, yellow corn, and maybe even some tattered leaves. Mostly the mosaic of corn color is a product of the weather; cooler and wetter. Over the last 30 days, rainfall has been 150 to 200% above normal and temperatures have be a couple degrees cooler than normal across Iowa.
Nitrogen and potassium deficiencies, herbicide injury, and soil compaction can all contribute to yellow leaf tissue while purple leaf tissue is a symptom of phosphorus deficiency or problems that result in reduced plant sugar translocation within the plant. However, yellow and purple plants can also be attributed to cooler and wetter conditions that slow root and plant growth rates which in turn diminishes the ability of the plant to take up nutrients. No, this doesn’t necessarily mean there is a nitrogen, phosphorus, or potassium deficiency.
Another complication in addition to cool and wet weather is that many fields have corn plants in the 2nd to 4th leaf stage. This is the timeframe where corn plants transition from the radicle and seminal roots to the rapidly developing nodal root system. Even with ideal weather conditions it is common with a keen eye to be able to notice plant yellowing briefly during this transition.
The end result, take the holiday weekend to go fishing and hope warmer, drier weather prevails. As warmer, sunny weather will increase root and plant growth rates and plant color will turn green again.
Mark Licht Associate Professor
Dr. Mark Licht is an associate professor and extension cropping systems specialist with Iowa State University Extension and Outreach. His extension, research and teaching program is focused on how to holistically manage Iowa cropping systems to achieve productivity, profitability and en...