CORN Newsletter: 2008-30, September 8, 2008

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C.O.R.N Newsletter 2008-30
September 8, 2008 - September 16, 2008

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Field Drying and Corn Harvest Timing
by Peter Thomison


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There are plenty of corn fields that are green with kernels in the late dough and early to dent stages in parts of Ohio that received timely rains and where corn was planted late. However, near drought conditions and recent dry weather in much of the state have accelerated maturation in many corn fields. Corn will normally dry approximately 3/4 to 1% per day during favorable drying weather (sunny and breezy) during the early warmer part of the harvest season from mid September through late September. By early to mid October, dry-down rates will usually drop to ½ to 3/4% per day. By late October to early November, field dry down rates will usually drop to 1/4 to 1/2% per day and by mid November, probably 0 1/4% per day. By late November, drying rates will be negligible.

Estimating dry down rates can also be considered in terms of growing degree days (GDDs). Generally, it takes 30 GDDs to lower grain moisture each point from 30% down to 25%. Drying from 25 to 20 percent requires about 45 GDDs per point of moisture. In September we average about 10 to15 GDDs per day. In October (as weather cools) the rate drops to 5 10 GDDs per day. However, note that the above estimates are based on generalizations, and it is likely that some hybrids vary from this pattern of drydown. Dr. Bob Nielsen at Purdue has written an excellent overview of grain drying (referenced below) that includes a discussion of hybrid characteristics that influence the rate of grain drying.

Agronomists generally recommend that harvesting corn for dry grain storage should begin at about 23 to 25% grain moisture. Allowing corn to field dry below 20% risks yield losses from stalk lodging, ear rots, and insect feeding damage. Growers this year should be prepared for stalk lodging problems (associated with drought stress) that may slow harvest and contribute to yield losses. The loss of one "normal" sized ear per 100 feet of row translates into a loss of more than one bushel/acre. In fact, an average harvest loss of 2 kernels per square foot is about 1 bu/acre! According to an OSU ag engineering study, most harvest losses occur at the gathering unit with 80% of the machine loss caused by corn never getting into the combine. Growers need to consider the impact of premature plant death on corn maturation. Within fields, significant variation in grain moisture may exist among plants that died prematurely and those that matured more normally.
Reference
Nielsen, R.L. (Bob). 2008. Field drydown of mature corn grain. Corny News Network, Purdue Univ. [On-Line]. http://www.agry.purdue.edu/ext/corn/news/timeless/GrainDrying.html

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

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