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Weather the changing storm

As rainfall patterns change across Illinois and growing seasons lengthen, here’s what you need to know to prepare soil for 6-inch rains and capture bigger gains from longer growing seasons.

Illinois farmers know one thing for sure: Corn yields are increasing — to the tune of 2 bushels per year, on average.

In yield plots, gains appear even bigger. Says Joel Wipperfurth, director of ag technology for WinField United, their Illinois-based Answer Plots show yields from five different seed companies are higher than ever. Eight years ago, in all Illinois plots, only three replications hit 300 bushels. Last year, nearly 147 replications hit 300 bushels.

Bigger yield means bigger risk, begging a bigger question: How do you manage 300 bushels’ worth of inputs when the weather is, at best, volatile? And how can knowing more about weather trends help you manage those inputs — and adapt your soil?

“You can’t put 300 bushels’ worth of inputs down in the fall and expect them to be taken up in the spring and be there,” Wipperfurth says. “When you get a quarter inch of rain, soil can handle it. When you get 5 inches of rain, soil can’t handle it, and it runs off.”

Wipperfurth, like many of his colleagues in the nutrient and weather businesses, say changing weather patterns in Illinois and beyond mean farmers need to prepare their soils to take up more water — and retain it during droughts.

“What if you knew that the next 10 years would be about preparing your soil structure to receive 6-inch rainfalls, and that to capture yield, it would be about retaining that 6-inch rainfall — without leaching nutrients away?” Wipperfurth asks.

Identifying the trends
Eric Snodgrass, Agrible co-founder and atmospheric scientist at the University of Illinois, agrees and says there are big underlying trends in weather — and knowing about them could help farmers mitigate risk.

“Year-to-year variability is always high,” he says. “But big trends shift you incrementally throughout the years you farm.”

Snodgrass sees two big trends in Illinois:

• Rainfall. Illinois has seen a statistically significant change in rainfall patterns over the past 70 years. The state still gets 40 inches a year, but it comes in big events, followed by longer dry spells. That makes tile more important, Snodgrass says. It also makes nutrient application and retention even more critical — along with soil health, so soils can absorb and retain moisture when needed.

Season length. Illinois has seen a 10- to 20-day increase in frost-free season length over the last 40 years. “We’re able to be more productive because the weather’s letting us do it,” Snodgrass says.

Specific to the lengthening frost-free seasons, he says the effect is greatest in the Northern states, where the growing season has grown by nearly a month. Upshot: More Dakota farmers now grow soybeans instead of barley.

Back in Illinois, Snodgrass says the frost-free season length is similar to what it was during the 1930s, when plenty of weather records were broken. There’s been a significant shift away from the growing season of the 1960s.

“The last time the U.S. lost a crop to frost was maybe 1974,” he adds.

And rainfall? Illinois still gets about 40 inches annually, a figure that hasn’t changed since 1980. In many years, those 40 inches came in deluges followed by drought, particularly across southern Illinois.

“There’s a high probability that we’ll get our 40 inches from four big events,” Snodgrass says. “That doesn’t mean it’ll happen this year; we could get them in an inch and a tenth at a time. But the underlying trend is still there.”

This season, Snodgrass points to two places in the Corn Belt with completely opposite water resources. Much of the Mississippi and Ohio river valleys are in flood, while places in Texas and Oklahoma haven’t had a rainfall since 2017.

In Illinois, that means any rain through the end of May will fall on saturated soil — meaning those weather patterns have already disrupted the 2018 planting season. Snodgrass says to watch for setups in the upper atmosphere that result in really strong flow out of the Gulf of Mexico, which can pump enormous amounts of moisture into the Midwest. Already in January and February, better than 15 inches of rain fell in Arkansas, while parts of Illinois saw 6- and 8-inch rains.

Offsetting weather risk
What to do this year? Build soil structure through cover crops, reduced tillage and reduced compaction. Wipperfurth says improving soil structure keeps rain from carrying off topsoil, and it increases water-holding capacity in the soil — important when there are longer periods between rainfalls. 

“It’s a long battleship when you’re talking about soil fertility and soil structure,” Wipperfurth says. “If you’re going to start turning way down there in the soil, you have to start today.”

More weather variability also means fewer operating days, which puts pressure on equipment to be right-sized. Wipperfurth suggests current weather patterns may require you to run two planters. Or maybe you’d be ahead to have multiple autonomous 20-hp tractors running when conditions are moderate, instead of one big four-wheel-drive tractor running when it’s a little too wet.

“When the labor is no longer the limiting factor, farmers will make in-season input applications multiple times in a season,” he predicts.

And when you know the weather trend is for higher amounts of rainfall, hold off on inputs until the plant needs it. “Put off your decisions!” Wipperfurth says. “Just put enough nitrogen out there until you get to the next point where you need to make the next decision.”

Wipperfurth’s rallying cry is that farmers need to measure what they’re trying to manage, through tissue sampling, nitrate sampling and crop modeling. A variety of agronomic companies offer mapping programs to help offset soil loss and increase soil health.

Working with WinField United, the Land O’Lakes Sustain program maps elevation and lets you analyze the number of tons of soil you can lose at different combinations of management. “If you know you lose a ton of soil that’s valued at $100 per acre, then $30 an acre for a cover crop doesn’t look so bad,” Wipperfurth says.

At the end of the day, it’s about managing the risk — and understanding the weather trends.

“Weather changes put a lot of pressure on operational excellence and on your ability to make hay,” he says.

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