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Check corn stalks for ability to stand this fallPosted Wednesday, September 8, 2010, at 3:49 PM
Corn harvest has begun in a few isolated locations and as harvest progresses there are some issues to watch for. Corn has been stressed to some degree this year by the excess moisture and periods of high temperatures. These conditions are very conducive to the development of diseases. As the crop reaches physiological maturity, it stops actively growing and uses its energy to fill the ear. At the same time, any disease infections can take off and infect the plant's crown and stalk tissues. We are also seeing various levels of leaf disease that may make the situation worse. Out of all of these issues the result can be weakened stalks. As the corn plant matured, the seeds will pull nutrients from the stalks to complete their development.
To check for stalk deterioration, grab a plant at chest height and pull it toward you until it is at an angle and let go. If the stalk snaps back and stands up, it is strong. If it is weak it falls over. You can also test the stalk integrity by pinching the base of the stalk. If you find weak stalks in your fields, you may want to harvest those fields first. Associated with the weak stalks may be ears that tend to fall off. If this is occurring in the field, it would be another reason to harvest that field earlier. Another factor to consider is the moisture of the grain. If there are problems with stalk deterioration and the corn is still at higher moisture, one would need to consider whether the costs of drying grain would be offset by the cost of anticipated harvest losses.
Another issue with some corn harvested is a lower than expected test weight. Test weight, which is technically "bulk density", is a complex measurement, including factors such as slipperiness of the seedcoat, kernel shape, endosperm density, and even the size of the embryo. There are hybrid differences, but growing conditions also affect the test weight. In general, correlations between yield and test weight are not very high. It is possible that the rapid filling in 2010 resulted in slightly lower density of starch packing into the endosperm than normal. This directly lowers test weight and may or may not result in lower kernel weights. It is kernel weight that determines yield. Yield per acre is the product of kernel number and kernel weight. If kernels are sound and of normal weight, but test weights are below normal, there should be little to worry about.
Test weight also affects pressure plate readings on yield monitors. It will be important to calibrate yield monitors for this year's conditions and check the calibration periodically. The variation between fields and hybrids may be greater this year than in past years.
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As our local University of Missouri Agronomy Extension Specialist, Crook has been writing a column for the print edition Agriculture page for the past three years and we will now be sharing it on our web version. Crook has a bachelor and masters degree in agronomy from University of Missouri and received his doctorate in Agronomy from Kansas State University. He was in soybean variety development research for 22 years for various seed companies and has been Saline County's agronomy specialist for 10 years.