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Predicting Corn Dry Down with a Web Based Tool



Hybrids of the recommended relative maturity, which were planted in the first part of May are now approaching maturity.

Hybrids of the recommended relative maturity, which were planted in the first part of May are now approaching maturity. Once the corn reaches physiological maturity a black layer is formed at the base of the kernel and no additional weight will be added. Black layer usually occurs when the grain moisture content reaches 30 to 32% moisture, but can vary from 25 to 40% moisture depending on the hybrid and the season. A freezing event, like that experience on Monday night in some parts of the state, might cause the death of the leaves and affect further grain filling. A short duration frost when temperatures are at or just below freezing can kill leaves but not the stalk. If the leaves are killed, but not the stalk, carbohydrates can still move from the stalk to the ear.

Figure 1. Predicted grain moisture content of an 89-day relative maturity corn hybrid, planted on May 12 at Prosper, ND, 2020. The Corn Drydown Calculator was developed by Iowa State, 2019.

The Corn Growing Degree Day Decision Support Tool, can help to determine how close your corn crop is to maturity. This tool tracked the development of the corn we planted May 14 quite well, with an 89 RM hybrid we sampled today (Tuesday September 8th) coming in at 34% moisture, very close to the moisture we would expect at physiological maturity. The decision support tool predicted that this hybrid would reach blacklayer on September 9th.

Reaching maturity is important as it means that the crop has maximized the amount of weight that it has packed into its kernels. The grain then needs to dry in the field to the point that it can be harvested and be economically dried for storage and marketing. Predicting the rate of drying in the field is more complex than predicting corn development. Factors that affect the rate of field drying include: the initial moisture content of the grain, air temperature, relative humidity, rainfall, dew, wind speed and kernel characteristics. I have found the web-based tool developed by Iowa State University called the Corn Dry Down Calculator to be very helping in predicting how quickly the corn will dry. Using this tool, I found that the hybrid described above, will reach 18% moisture by the first part of October (Figure 1). The moisture decline in September is very rapid, demonstrating the value growing a hybrid that matures by the middle of September when temperatures are still high enough to drive high rates of field drying.


Joel Ransom

Extension Agronomist, Cereal Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.