Premature Plant Death Will Cost Yield Loss

CROP WATCH: When plants died will determine amount of yield loss.

Published on: Sep 23, 2013

Some fields are already shelled, so you don’t have to worry about beating the frost. If the field died prematurely, however, you may wonder why yields weren’t quite as good as you thought. Premature death can happen if plants are affected by insects, disease, hail or nutrient deficiencies, not just frost.

Bob Nielsen, the Purdue University Extension corn specialist, helped prepare information that is in the Purdue Corn & Soybean field guide. The guide is published in pocket form in print, and is now available as an app for the App store or Purdue’s Education Store for $13.99. The app so far works only on iPads.

If the milk line was half way down the plant and only the leaves died, it’s estimated the yield loss will be 6%. If the whole plant dies, it could be 12%. If the whole plant died with kernels half way down the milk line, the corn would likely be at 40% moisture. It would not yet be black-layered.

When plants died will determine amount of yield loss.
When plants died will determine amount of yield loss.

The Crop Watch ’13 Contest field experienced dry weather and a nitrogen deficiency in August. Whether it was a real nitrogen deficiency due to lack of N in the soil or the inability of roots to pull N out of the soil due to dry weather is unclear. The result is the same – the leaves showed N deficiency and dried up early.

Let’s see how this might affect yields. Our original field checks using the normal method of estimating yield in 1/1000th acre produced a yield of 189 bushels per acre. Factoring in lower yields on the ends and the amount of land devoted to the ends, the whole field average dropped five bushels per acre to 184.

Next, Nielsen says the formula overestimates yield when grain fill is not favorable and kernels don’t do as deep or get as plump as they could have. It can range from 10 to 20%. Suppose the formula overestimated by 10%. Now the yield of dry corn is down to 166 bushels per acre.

How far did yields fall?- Did August hurt yields as much as some think, or will they be a pleasant surprise?
How far did yields fall?- Did August hurt yields as much as some think, or will they be a pleasant surprise?

Finally, suppose leaves dying early put another yield hit on the crop. If it’s 6%, that means the average yield is another 10 bushels lower, or 156 bushels per acre.

To look at the field, it looks better than that. Early yield reports are indicating corn is better than farmers expected given the dry August. Time will tell. What once looked like 200 bushels plus corn, even on August 1, was hit hard if it only makes 154 bushels per acre.

You still have time to enter the yield guessing contest. Refer to the most recent issue of Indiana Prairie Farmer for details, or email your guess to tbechman@farmprogress.com. Your guess must include your name, cell phone number, address and number of acres of each crop you raise.

The deadline for email entries is 11:59 p.m. EDT on October 15.