- Yellowish leaves or interveinal leaf striping in corn early in the season is generally caused by reduced nutrient uptake due to restricted root growth.
- Restricted root growth can result from air and soil temperatures, saturated or compacted soils, and root damage.
What to Look For
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).
- Nitrogen deficiency causes the older leaves of the corn plant to turn pale or yellowish-green (Figure 2, left). The deficiency then starts to create a V shape, starting at the tip of the leaf.
- Zinc-deficient plants exhibit interveinal chlorosis on the upper leaves. The veins, midrib, and leaf margin remain green. As the deficiency intensifies, bands (or “stripes”) develop on either side of the midrib and the leaves may turn almost white. Additionally, a Zn-deficient corn plant may be stunted (Figure 2, right).
- Sulfur deficiency appears as a general yellowing of young leaves. The deficiency can be confused with N deficiency. Because S is not as easily mobilized within the plant, younger leaves show the visual symptoms first (Figure 3).
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.
Impact on Crop
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.
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Web sources verified 3/15/18 12151743255