Combines were running near Mt. Vernon in Posey County last week. Mike Allyn, his brother, Matt, and dad, David, were harvesting dryland bottom fields wedged between both the Wabash River and the Ohio River. Moisture was dry enough that they could bin some of the corn, but they knew moisture levels would increase when they got to irrigated fields and then upland fields later this month. Yet they're hoping by then that moisture contents will be reasonable. They're also banking on being able to move through down corn and harvest nearly all of it with their new cornhead, the latest series from Deere, with a low profile and other features that make it suited for pulling in as much down corn as possible, even without after-market corn reels of any type attached to the cornhead.

If you live in central or northern Indiana, maybe you've started selling earlier fields. Or maybe you're still waiting for moisture content to drop on corn maturing in the field so you can hold down energy costs for drying. The risk, of course, is what the back half of the season may be like. You have to factor in potential harvest losses for the last field you will harvest if you decide to wait on field drying, says Bruce Erickson, a Purdue University ag economist and coordinator of the Top Farmer Crop Workshop held at Purdue each July.

A big factor is temperature, since it impacts field drydown losses greatly, he notes. Bob Nielsen, Purdue's Extension corn specialist, conducted a study sometime back that concluded you could expect corn grain still standing in the field to lose about 0.4 points of moisture per day if daily temperatures averaged 55 to 60 degrees F. That means corn might go from 23.3% moisture to 22.8% moisture in one 24-hour period.

If temperatures were warmer, say 70 to 75 degrees for a daily average, Nielsen estimates you could expect 0.7 points of moisture loss per day. So if corn tested 24% one day it should drop to 23.3% the next day. A week of nice weather at those temperatures would really knock down moisture.

Field drying is free- but only sort of. If you wait to start harvest or start, then suspend harvest to let a field dry, and high winds knock it over or it's inundated by stalk rot, and you don't have the newest style cornhead like the Allyns, harvest losses could mount rather quickly.

Based on earlier studies it appears harvest losses increase at about 1 per week, on average, beginning during the second in October. If the corn is still standing in November, harvest losses generally rise to an extra 2% per week.

You're the only one who can weigh these various factors and arrive at a decision that makes economic sense for you, Erickson believes. To help in sorting through this process, try a computer model Erickson ad Luc Valentin developed. Find it at: www.agecon.purdue.edu/topfarmer/update.asp