Between the V3 and V5 growth stages, corn transitions from deriving energy directly from the seed to acquiring energy from sunlight through photosynthesis. Visual appearances during these stages offer clues to overall plant health.
Factors to Consider
- Causes of foliar symptoms
- Nutrient deficiency symptoms
- Crop residue
- Soil tests and tissue tests
- Hybrid genetics
- Scout fields early and often. Knowing what is happening in the field is the best way to manage problems. Early detection and diagnosis will allow for solutions to be implemented before significant damage is done to the crop.
- Diagnose visual cues.
• Purple color: Deep reddish or purple coloring may result from anthocyanin pigment formation or may be brought on by cool, wet soil. Anthocyanin pigment is caused by exposure to night air temperatures in the 40s and day temperatures in the 60s. The degree of purpling depends on the hybrid. Cool, wet soils can lead to phosphorus deficiency if the root system is not established enough to absorb sufficient nutrients for an active young seedling. Pigmentation caused by weather will not affect grain yield and will slowly disappear as soil temperatures return to normal.
• Yellow color: Cool, wet soil conditions will enhance yellow coloration in the leaves if there is not enough sunlight and/or heat units for the plant to actively grow and produce energy. If plants remain yellow after a few sunny days, check for nitrogen (N) deficiency.
- Test and take corrective measures. Examine soil test results and make sure proper nutrient rates are recommended and applied. If nitrogen is a limiting factor, it can be sidedressed to alleviate the deficiency. Tissue tests can establish which nutrients are deficient and help determine if symptoms are due to soil deficiency or a problem with plant uptake and metabolism.
- Manage crop residue. Crop residue is a good way to recycle nutrients as long as it is evenly dispersed across the field. Large amounts of residue delay the soil’s ability to warm. These cooler soil temperatures slow corn seedling root growth and penetration and can cause purple seedlings. The problem is compounded by limited nutrient uptake, which happens when mineralization and availability of nutrients are decreased due to slower microbial activity in cool, wet soils. Consider using a starter fertilizer when temperatures are cool and conditions for germination and growth are not optimal.
- Check hybrid genetics. Some varieties are genetically predisposed to have higher levels of anthocyanins (purple coloring), but this does not affect final population, growth or grain yield. If the coloring is uniform through the field, the cause is likely genetic.
During early corn growth, environmental conditions have a huge impact on root systems and their ability to take up nutrients, sometimes leading growers to think their crops have a nutrient deficiency. When deficiency symptoms appear, take time to evaluate the cause. Plants often outgrow early season symptoms as the soils warm and microbial activity releases additional nutrients. Early and correct diagnosis of problems allows producers to manage accordingly. For more information, contact your local Mycogen Seeds commercial agronomist or trusted agronomic adviser.