Excess Rain Could Reduce Yields 34%, Similar to Drought

A muddy field in Missouri. ( Farm Journal )

As you sit in your home office or shop, waiting for the monsoon of spring weather to pass by, you’re likely anxious. With each calendar day that passes you get closer and closer to having to make tough decisions: do you change crop maturity—change crops altogether?

If rain keeps falling, farmers will be faced with an unfortunate reality: yield loss—that will possibly be substantial. Excessive rainfall on corn can be as damaging as drought.

“Some years excessive rainfall reduced U.S. corn yield by as much as 34% relative to the expected yield,” according to University of Illinois research. “Data suggest that drought and excessive heat caused a yield loss of up to 37% during some years.”

The study used county-level USDA insurance data and overlaid it with historical weather data to quantify the effect of too much or too little rainfall on final yield. However, the overall impact of excessive rain varies by region.

“Heavy rainfall can decrease corn yield more in cooler areas and the effect is exacerbated even further in areas that have poor drainage,” said Yan Li, former University of Illinois postdoctoral researcher in a recent news release.

Aside from delayed planting, excessive rain can diminish crop yields in a variety of ways. So, farmers who have corn in the ground should be weary of restricted root growth, oxygen deficiency, nutrient loss and the potential for delayed harvest if rainy conditions continue into the fall.

Climate prediction models indicate farmers in the Corn Belt are likely to continue experiencing intense rainfall this spring. You’ll likely need to scout to make sure seeds or seedlings survive the deluge.

“Wait five days after the event that caused the issue to assess your stand to determine what percent of the crop may recover,” advises Jared Webb, Dekalb agronomist.

Check the calendar to find out how much yield is still available. If there is 70% of a stand left in a field and the calendar indicates there’s only 70% yield potential, it’s better to stick with what’s out there. In addition, keep an eye on weather forecasts to see if there could be more rain coming that could drown out more plants, which could make replanting virtually useless.

“First figure out what your stand is—how many plants per acre, is it even across the field or patchy?” says Dean Grossnickle, Syngenta agronomist. “Look at the time of year, can you replant to corn again or do you need to switch to soybeans? What herbicide did you use—are soybeans even a viable alternative?”

If replant is the best option, experts recommend keeping the same maturity for corn or soybeans as long as possible. It’s also important to wait for the field to be ready, just because the top ½” is dry doesn’t mean below ground is. Traveling over fields too early could lead to sidewall compaction and poor root growth throughout the season.