Rough Weather Ahead:
Predicted Increases in Storms and Temperatures Make Conservation More Vital Than Ever
The past couple of years of unpredictable weather, relentless spring storms and summer hot spells may well be a harbinger of seasons to come – a new reality of extreme weather conditions that will likely change the way you farm.
“We’re seeing a shift toward spring precipitation and more intense precipitation in those spring storms, and models also predict that we’re going to be drier in the summer,” warns Jerry Hatfield, Laboratory Director of the USDA-ARS National Laboratory for Agriculture and the Environment in Ames. “What we saw in 2011, we’re going to see a lot more of that.”
“When it rains, it’s going to rain really heavily, but not necessarily as often,” continues Hatfield. “That’s going to cause us some real issues – we’re going to have to manage our soils and crops to be able to cope with these extreme variations in precipitation. Conservation practices are going to have to handle that as well.”
That may not be as easy as it sounds, notes farmer Jim Andrew. Starting in 1974, Andrew and his father spent a decade building 3.5 miles of tile-drained terraces on the family farm near Jefferson. He says terraces built for the 10-year floods envisioned in the ‘70s and ‘80s have been challenged severely in recent years.
“We’ve surpassed those standards to where we can get rains that fill up behind the terraces or even overtop them,” Andrew says. “But you can only go so far. You get to the point where it’s impregnable, but so expensive you can’t afford to build it.”
Andrew points out that seeing sediment build up along his terraces’ backslopes from rill erosion in his fields inspired him to switch to continuous no-till 15 years ago. Hatfield applauds the move, noting that no-till is a key conservation strategy that doesn’t involve pushing up bigger structures.
“Let’s start with managing the up-field areas above the terraces rather than saying, ‘let’s build taller terraces,’” suggests Hatfield. “If we do that, I think the longevity and efficiency of our terraces will be maintained for a long time. Let’s do everything we can to maximize water infiltration above those terraces. Where I see terraces overtopped is where I see bare soil, where there’s no infiltration – the water just screams across the field and the terraces get overtopped.”
That fast-flowing runoff water also carries silt to the base of terraces’ backslopes, filling in the back of the terrace, choking drain inlets and creating a silty, river bottom-type soil with low infiltration, he adds. No-till reduces that downhill flow by boosting infiltration rates throughout the field. Continuous no-till helps restore good soil structure and leaves crop residue on the surface that diffuses the pounding, soil-sealing energy of raindrops, he says.
Improving infiltration does more than reduce erosion, Hatfield notes.
“We have to maintain the soil condition so it absorbs every raindrop that falls,” he says. “With less-frequent rainfalls, the only way we’re going to have enough moisture is to infiltrate and
Stored water may also be even more vital as temperatures rise, cautions Elwynn Taylor, professor of agricultural meteorology at Iowa State University. As temperatures climb, water demand increases exponentially, he explains.
“At 94 degrees, the crop demand for water is about two times as high as it is at 84 degrees,” Taylor says. “At those temperatures in Iowa, we’d probably need something on the order of four inches of water per week. Even a crop with ideal soil and ideal moisture would fall behind – very few root systems, even healthy ones, can maintain that kind of water use for more than a couple of days.”
Taylor adds that rising night-time temperatures are actually an extreme weather phenomenon that most people don’t even notice, though they can be devastating to crops. In fact, he points out, a season in which night-time temperatures are just two degrees higher than normal can seriously impact soybean and corn productivity.
Soil temperature is another challenge, adds Hatfield. There, residue can again come to the rescue.
“On a hot June day, with small plants out there, at a one-inch depth under bare soil it may be 100 degrees, and under residue it might be 85 or less,” he notes. “Plus, the moisture content of that bare soil surface may be close to zero, whereas the soil under the residue layer may be moist enough to support biological activity.”
It’s anyone’s guess what temperatures and rainfall patterns will look like this year, next year, or 10 years down the road. But Taylor says climate research points to increasing volatility in weather and crop yields.
Don’t panic, he advises. “Be rational about this,” Taylor says. “Keep records on your farm. Know which year you planted what, and what your yield was. Know your volatility – how consistent was your yield with your county, your crop reporting district and your state?”
Seek out the tools that can help you farm in a more volatile, extreme environment – drought-tolerant varieties, consistent yielders, equipment that allows you optimal seed placement and more residue cover. And continually evaluate and improve your conservation practices.
“Start looking at the field landscape and asking, ‘Am I doing everything I can from the bottom of the slope to the top of the slope to prevent the destructive force of water?’” suggests Hatfield. “Think about managing your soil and managing the water you have so you can maximize your soil’s buffering capacity so the crop suffers less.
“It starts with residue,” he adds. “It starts with building up the soil and creating the reservoir.”