You would imagine that if you harvest corn from a very stressed part of the field and you harvest corn in another part of the field that is halfway decent, halfway being the key word, that the test weight of the higher yielding corn would be considerably higher than the test weight of the corn from the very stressed part of the field.
Richard Stroshine, Purdue University grain quality specialist, says that may not be the case. The test weight might be slightly lower where the crop was stressed and the yield is poor, but it may still be respectable. If so, that's one small consolation in a year when you may be looking for positive news from the field anywhere you can find it.
REASONABLE TEST WEIGHT: The test weight may be either equal to or slightly lower for stressed corn vs. normal corn unless the stressed corn develops ear rots.
Stroshine did a study in 2011 in an irrigated field near Columbus, Ind. He discovered that corn from the corners, which were very stressed by drought last year as well, where water didn't hit, were small. But when he checked test weights from the irrigated and non-irrigated corn, there was only about a two pound per bushel difference. And the test weight from the non-irrigated corners was above 56 pounds per bushel. That means that test weight would not have kept it from being graded as number one corn according to official U.S. grain grading standards.
Stroshine does add one caveat, however. If disease enters the field, such as Aspergillus ear rot, then all bets on test weight are off. Aspergillus flavus is the fungal mold, olive brown in color that develops on ears under the husks. It can produce aflatoxin.
The small grains would be more vulnerable to infection in most instances because they have already been stressed. Most fungal and bacterial diseases of corn are secondary infections and opportunistic. They set up shop after something else has severely hampered the plant's defenses.