Subscribe and stay up-to-date with the latest news and great offers from DEKALB, Asgrow and Deltapine.
Don't miss out on the latest agronomic news.
Local agronomic alerts.Delivered straight to your inbox.
Diagnosing nutrient stress effects on corn ears, leaves, and stalks can help determine the effects of management decisions for the current corn crop and any adjustments to consider for the next season. Environmental conditions play a big role in determining the nutrient status of corn plants and corn yield potential even under high fertility management programs. Many late-season symptoms may have multiple causal factors.
Patterns of aborted or missing kernel and other ear abnormalities reflect nutrient, sugar, and protein limitations to the kernels during grain fill.1 Tip dieback/tip back is incomplete kernel development at the tip of the ear, due to poor pollination or kernel abortion.2 Stress conditions (heat, moisture, hail, foliar, insects, disease, or nitrogen deficiency) may cause a shortage of nutrients that lead to kernel abortion. Kernels at the tip of the ear are most sensitive to stress. Kernel abortion may also be caused by intervals of cloudy conditions after pollination or plant shading from very high plant populations. Aborted kernels are yellowish in color while poor pollination can be distinguished by kernels or ovules appear dried up and shrunken.
Favorable growing conditions can result in an ear setting greater than normal number of potential kernels per row. Although all the ovules, particularly those at the ear tip, may not be filled, the total number of kernels per ear may be greater than the normal number. If ears are consistently filled to the tip it may be an indicator that plant populations should be pushed higher to maximize yield potential.2
Late-season nitrogen (N) deficiency symptoms include firing or dropping of lower leaves which will appear first on lower leaves as yellowing and tissue necrosis in a V pattern (Figure 1). Phosphorus (P) deficiency can interfere with pollination, resulting in incomplete kernel set. Potassium (K) deficiency can cause lightweight ears with poorly filled, shrunken kernels. Potassium deficiency symptoms on corn leaves appear first on lower leaves as chlorotic and necrotic leaf margins, in contrast to the V pattern associated with nitrogen deficiency (Figure 2).
A good diagnostic resource to identify potential causes of ear abnormalities is the article Abnormal Corn Ear Development at http://www.roundupreadyplus.com/Pages/Article.aspx?article=Abnormal-Corn-Ear-Development.
Nitrogen deficiency can cause stalks to weaken when the demand for carbohydrates to fill kernels cause the plant to remobilize or cannibalize nutrients from stalk tissues. Potassium deficiency can result in weak stalks that are prone to lodging. Potassium also plays a role in helping prevent stalk rot diseases and maintain photosynthesis. Potassium increases root growth, improves drought tolerance, maintains turgor pressure that helps reduce water loss and wilting, builds cellulose, reduces lodging, helps translocate sugars and starches and helps retard the diseases and nematodes.
Recent research on nutrient uptake and utilization in corn indicates that current corn products take up nearly 30% more nitrogen (N) from the soil after flowering than older products.3 New research also shows that the timing of nutrient uptake in high management corn systems differs between nutrients and may have implications for nutrient management.4
Some late-season nutrient deficiencies may show diagnostic symptoms earlier in the season rather than near maturity. It is a good idea to look for causes of deficiencies throughout the season:
By late in the season, there is nothing that can be done to lessen the impact of nutrient deficiencies. However, it is the perfect time to rate your current nutrient management program and consider if changes may be necessary for next season. The end-of season cornstalk test can be used to evaluate whether the crop had too much or too little N for optimal yields. Soil testing should also be performed to assess total nutrient availability and indicate whether additional fertilizer is needed to maximize crop growth next season.5
Fall is also a good time to sample for soil nitrate and assess nitrogen management practices. Soil samples should be taken from representative areas of each field and to a depth of two feet to adequate measure residual nitrate.6
Monitoring the nutrient status of corn with in-season plant tissue sampling can help identify nutritional deficiencies. Generally, the corn ear leaf at silking should be sampled when N, S, Mg, and Zn levels are tested.7
Sources: 1 Thomison, P and A. Geyer. 2007. Abnormal corn ears ACE-1. Ohio State University. 2 Thomison, P. 2010. “Tip dieback�? and “zipper ears�? in corn. C.O.R.N. newsletter. Ohio State University. 3 Ciampitti, I.A. et al. 2013. Maize nutrient accumulation and partitioning in response to plant density and nitrogen rate: macronutrients. Agronomy Journal 105:3 783-795 4 Bender, R.R. et al. 2013. Modern corn hybrids’ nutrient uptake patterns. Better Crops With Plant Food (94:7-10). 5 Laboski, C. 2010. Considerations when using the end-of-season stalk nitrate test. Wisconsin Crop Manager 17(26):113-114. 6 Rehm,G., et al. 2007. Using the soil nitrate test in Minnesota. 7 Kaiser, D. E. et al. 2013. Plant analysis sampling and interpretation FO-3176-B. University of Minnesota. 140828150836