Timing is Everything on Corn Yields this Year
By Chad Lee
A county agent sat in the buddy seat on a combine and watched the yield monitor swing from 300 bushels per acre to zero and back again. One hundred forty miles away, a farmer videoed his yield monitor starting at 260 bushels per acre in the low areas and dropping to zero as the combine climbed to higher elevations. These are just two examples of what we are seeing across Kentucky this year. It is a reminder of just how important water to corn yield was this season, but also, how important the timing of that water was this year.
From June 8 to July 15, most of Kentucky was short on rainfall by as much as 3 inches in some areas (Figure 1). Shifting the calendar to June 20 to August 20 shows that Kentucky was closer to normal in rainfall, except in far western Kentucky. The monthly precipitation for western Kentucky further defines just how dry May and June were for that part of the state (Figure 2). Our corn crop agrees with these weather maps. Much of our corn was pollinating in the early part of July, especially corn in western Kentucky. For corn that pollinated later, because of later planting dates, that corn pollinated in less stressful conditions and has better yields.
Figure 1. Kentucky rainfall departure from normal for June 8 to July 15, 2022 (left) and (Figure 2.) from June 20 to August 20, 2022 (right). Graphics courtesy of the Kentucky USDA-NASS Office.
Figure 3. Western Kentucky Monthly Precipitation Departures from Normal. Data obtained by Matt Dixon with UKAg Weather Data Center from the MRCC database: https://mrcc.purdue.edu/CLIMATE/
The Kentucky USDA-NASS is projecting corn yields to be 149 bushels per acre, down 22% from the record yield in 2021. In my much, much less scientific conversations with farmers around Kentucky, the number is probably close to that. Given the amount of corn pollinating during the water deficits in June and July, this is an amazing number.
About 66% of the Kentucky corn crop underwent water stress during the worst possible time. The only management option that would have helped at this time was irrigation. If a farmer could not irrigate, then no management was going to fix this problem. Once pollination was damaged, corn cannot make up the yield difference. Some plants might have produced larger kernels, but that larger seed size was not enough to make up the yield.
To repeat, no crop management method, except for irrigation, was going to overcome the extent of dry weather the corn crop faced this summer. As farmers look at this year’s yields and ponder next year’s decisions, there are some key points to consider:
1. The timing of rainfall relative to corn growth and development was more important than any other management factor this year.
2. This is a bad year to compare one field to the next. The water and crop growth timing was slightly different from field to field and from low spot to high spot in the same field.
3. This is a bad year to assess a new hybrids. See bullet point 1. Differences in hybrid yields this year has more to do with timing than genetics.
4. This is a bad year to compare late-maturing hybrids to early-maturing hybrids. In some parts of the state, 118-day corn will do better than 110-day corn. In other parts of the state, the reverse is true. See bullet point 1.
5. This is a bad year to look at planting date. Early planting was better in some areas and late planting was better in others.
6. This was a great year to test products promoted to alleviate stress… if you had a check strip or two in the same field. You cannot compare one field to the next. See bullet point 2.
7. This is a good year to reconsider marketing strategy and determine just what percent of the expected crop can be marketed ahead for the 2023 harvest.
This year was a difficult one in which to grow a corn crop. If the USDA NASS estimate of 149 bushels per acre is correct, then the yields are a testimony to excellent hybrids and crop management. However, the timing to the dry weather was such that everyone should be very cautious about using the results from this year to apply to decisions in the future.
Thanks to David Knopf and Matthew Dixon for allowing me to use their weather data and graphics. Thanks to Conner Raymond for reviewing this article.
Resources:
MRCC Database: https://mrcc.purdue.edu/CLIMATE/
USDA NASS Kentucky website: https://www.nass.usda.gov/Statistics_by_State/Kentucky/index.php
USDA NASS Kentucky Crop Progress and Conditions page: https://www.nass.usda.gov/ Statistics_by_State/Kentucky/Publications/Crop_Progress_&_Condition/index.php
USDA NASS National Crop Progress page: https://www.nass.usda.gov/Publications/ State_Crop_Progress_and_Condition/index.php
