Several factors can contribute to corn seedlings showing various shades of yellowing and/or interveinal leaf striping. Usually, the yellowing is due to restricted or damaged roots caused by cool soil and air temperatures, saturated soils, compaction, and root damage from insects, diseases, or chemicals (Figure 1). Inhibited roots, regardless of cause, can reduce the plant’s ability to uptake nutrients, such as nitrogen (N), zinc (Zn), and sulfur (S).
Saturated soils from heavy spring rains can reduce soil oxygen levels which can slow crop growth and uptake of nutrients. Compaction formed from tilling, harvesting, and planting in wet soil conditions can remain over several seasons and block root growth.
When corn plants are small, the impact on corn yield potential from yellowing is generally of little concern. Corn plants between the V3 and V5 growth stages are transitioning from being dependent on the seed to acquiring energy from photosynthesis and nutrient uptake from the roots. During these stages, any yellowing is generally related to unfavorable environmental conditions and can diminish as conditions improve. However, if the roots are restricted from compaction or damaged by insects, diseases, or chemicals, there may be a negative impact on yield potential depending on the seriousness and damaging levels of the causes.
Soil warming encourages microbial activity and breakdown of organic material, which releases additional nutrients that can help plants recover from a nutrient deficiency. Deeper root growth could allow roots to reach water-soluble nutrients, such as S and N, that may have leached deeper into the soil with wet conditions. As soils dry out from saturation, oxygen content can increase and allow for better plant growth.
A wait-and-see approach can be taken during the vegetative stages. Should a nutrient deficiency actually exist, consideration should be given to sidedressing and foliar applications of nutrients (Figure 3, right). If the symptoms persist into the growing season, a tissue analysis at silking stage can help determine nutrient imbalances.
Correcting the problem for the current season may not be feasible, but soil preparation for next season can include fertilizer applications based on soil test recommendations and compaction alleviation or prevention.
Bly, A. 2014. Yellow corn. iGrow. South Dakota State University Extension. http://igrow.org.
Nafziger, E. 2013. Purple and yellow corn plants. The Bulletin. University of Illinois Extension. http://bulletin.ipm.illinois.edu.
Nielsen, R.L. 2008. Early planted corn feeling “under the weather”. Purdue University Extension. http://www.agry.purdue.edu.
Sawer, J. 2011. Yellow corn plants. Integrated Crop Pest Management News. Iowa State University Extension. http://www.extension.iastate.edu.
Web sources verified 3/15/18 12151743255