Expect Lower Test Weight in Wet Corn

Low weights shouldn't be a surprise.

Published on: Nov 3, 2009
A relationship Sonny Beck of Beck's Hybrids, Atlanta, pointed out years ago is definitely a potential concern this year. He noted that when grain moisture was higher, test weights tended to be lower. When corn is drier, as it has been in Indiana in most of the past seasons, until this one, test weights tend to be higher. Typically some hybrids in a company's line-up of hybrids will top 60 pounds per bushel coming out of the field. That may be a tall order this year. 

There can be a relationship between low test weight and grain quality. That can also impact how well corn stores, and how long it can be kept safely in grain bins on the farm. Iowa farmers experienced low test weight as a general trend in the '08 season. Iowa State University Extension specialists note that based on how well that corn stored this past year, normal shelf life for low test weight corn is about half of what you would normally expect if corn has normal test weights.

Bob Nielsen, Purdue university Extension corn specialist, agrees that it's a fact that high grain moisture typically results in low-test weight corn. It's obviously the most obvious reason corn coming out of the field so far at 20 to 30% moisture levels has fairly low test weight. There are actually formulas that allow you to correct for the decrease in test weight reportedly caused by high moisture content.

However, increased moisture readings isn't the only cause this year, Nielsen believes. Because of what else happened this season, test weights might be on the low side whether corn was coming out of the field wet or not.

Believe it or not, there was drought stress in parts of northern Indiana. That contributes to lower test weight, he notes. There were also late-season foliar diseases, primarily gray leaf spot and northern corn leaf blight, that brought an early end to the plant's ability to utilize photosynthesis to the utmost potential.

Dave Nanda, the Indianapolis-based corps consultant, reports northern corn leaf blight was rampant, especially in central Indiana, by early to mid September. He blames its development on ideal weather conditions for the disease.

Below normal temperatures throughout September also affected the plant's ability to make starch, Nielsen adds. It helped pull the rug out from under successful completion of grain fill in some fields. The result is kernels that don't have the optimum amount of starch that genetics would allow.

The latest-maturing fields may have been finished by early October frost and freezes. The cause was actually leaf or whole plant death due to frost. That's most noticeable in the very latest planted fields that were still relatively immature in early October.

Finally, the explosion of ear molds can result in light-weight, chaffy grain. Many reports of ear molds continue to pour in. Overall, it was not a good year for high test weight.