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Ohio State University Extension


C.O.R.N. Newsletter 2009-36

Dates Covered: 
October 19, 2009 - October 27, 2009
Curtis E. Young

Weather Outlook

The trend the last 30 days has been for below normal temperatures and above normal rainfall in much of Ohio. Rainfall was generally 100-200% of normal with normal being 2-3 inches. The exception was in the far north and east which saw at or slightly below normal rainfall.

The outlook for this week is dry and warmer through Thursday, then rain later Thursday into part of Saturday. Rainfall is expected to average 0.50-1.00 inches with isolated 2 or 3 inch totals as the remains of an eastern Pacific hurricane moves across the U.S.

Next week will be colder than normal with more rain later next week into Halloween weekend.

Overall, the trend is for colder than average temperatures and normal to slightly above normal rainfall. This will continue to present issues for clay soils.

Jim will update the Nov-Dec outlooks later this week for future CORN Newsletters.

Field Drying and Scheduling Corn Harvest

The most recent USDA/NASS ( report indicates that corn acreage harvested is considerably behind what's normal for Ohio on this calendar date. As of Sunday October 18, 2009, eight percent of the corn was harvested, compared to 35% last year and 31% for the five-year average. Most Ohio farmers are focusing on completing soybean harvest and wheat planting. Moreover because much of the corn crop has been slow to mature and dry down, many corn growers are planning to wait for corn to dry more in the field before harvest.

Corn will normally dry approximately 1/4-1/2% per day by late October to early November. By mid-to-late November, drydown rates usually drop to about 0-1/4% per day and after Thanksgiving drying rates are usually 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 25-20% requires about 45 GDDs per point of moisture. In a "normal" October, we typically accumulate 5-10 GDDs per day. However, during October this year, we've struggled to accumulate appreciable heat units because of much cooler than normal temperatures.

Agronomists generally recommend that harvesting corn for dry grain storage should begin at about 23-25% grain moisture. Allowing corn to field dry below 20% risks yield losses from stalk lodging, ear rots (and potential mycotoxin problems), and insect feeding damage. In those areas of NW Ohio that experienced very dry conditions in 2009, 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. In such fields, growers 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. Keep in mind that most harvest losses occur at the gathering unit. The table below shows the range of visible corn harvesting losses by source. Average gathering unit losses accounted for about a 1.2 bu/acre loss out of the total 1.5 bu/acre machine loss. The results indicate that approximately 80% of the total machine loss is caused by corn never getting into the combine.

Corn harvest losses by source, Bu/A*

Source   Low Avg. High
Preharvest   0 0.35 2.44
  Ear 0 0.50 4.0
  Loose Kernel 0.02 0.66 3.36
Machine   0.13 1.51 5.02
Total Crop Loss   0.17 1.86 7.47

*From Gliem, J.A., R.G. Holmes, and R.K. Wood. 1989. Current utilization and optimization of existing machinery technology when harvesting feed grains. The Farm Income Enhancement Program. OSU Dept. of Agric. Econ. and Rural Sociology.

Waiting for a field to dry needs to be balanced with increased field loss and the possibility of a wet weather that can restrict field traffic. Growers also need to consider the effects of harvest delays on next year's crops if fall tillage is not completed.

The field yield loss that can be sacrificed to pay for lower drying costs can be estimated using the following formula (from "How long should we wait for corn to dry?" by Paul Carter, Univ. of Wisconsin Pest Management Newsletter, 1992).

Bushels/A sacrificed to pay for drier grain = drying costs (cents/% moisture) x difference in grain moisture % (harvest now vs. waiting) x yield (Bu/A) divided by corn price ($/bu).

1) Preharvest yield = 175 Bu/A
2) Drying cost = $0.04/% moisture above 15% grain moisture**
3) Corn price = $3.50/Bu
4) Grain moisture difference = 25% (now) minus 20% (waiting) = 5%

Bu/A that can be sacrificed to pay for drying costs:
175 x 0.04 x 5 divided by 3.50 = 10 Bu/A

In this example, if a grower elected to delay harvest to naturally dry grain from 25-20% grain moisture, the cost or sacrifice would equal 10 bushels (or $35.00). If waiting for the grain to dry in the field resulted in field harvest losses exceeding 10 Bu/A, the grower would lose more potential income than he would save on drying costs.

**Drying cost was obtained from the 2009 Ohio Enterprise Budget for Corn (online at



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Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.