Managing for resiliency in the face of drought

“Nobody’s really loving life right now,” Arnall says. “Everybody is just moving through with the hopes to get through 2022 to 2023.”

Dealing with drought isn’t new. As long as humans have been farming, we’ve worried about water. “There’s a drought somewhere every year,” says CCA Fred Vocasek, a senior lab agronomist at ServiTech Laboratories in Kansas. Soil conditions can easily slip into the too-dry realm even in humid climates. In more arid climates, though, like much of the High Plains, Southern Plains, and the West, a drought may be just a day away.

What is new, however, is how climate change is affecting the hydrologic cycle, causing longer, hotter and more frequent heat waves, longer and more frequent droughts with rapid intensification, and, simultaneously, more extreme rainfall events. What’s also new are our abilities to track some of these effects via satellite, to model and forecast them, and to efficiently manage nutrients and employ other conservation measures to help mitigate these changes.

It’s now the offseason for some crops and early season for others. It’s a good time to advise farmers what changes they might undertake to make their farms more resilient.

Defining Drought Conditions

Droughts are periods of unusually dry weather. The first classification used by the U.S. Drought Monitor is D0, abnormally dry. Then it goes from moderate (D1) to severe (D2) to extreme (D3) to exceptional (D4). A location in the abnormally dry category can go to normal within 24 hours with one good slow, soaking rain that fills 50 to 60% of pore space in the soil, says Katie Lewis, a professor of soil chemistry and fertility at Texas A&M AgriLife Research and Texas Tech University. (Fifty to sixty percent of pore space filled with water is ideal. Much below 50 can lean into deficit conditions; much above can cause root diseases or even flooding.)

On the flip side, a site can go from normal to drought conditions virtually overnight as well, especially as lower-than-normal precipitation meets a heat wave with high winds and/or high solar radiation, causing high evapotranspiration rates. That’s known as a flash drought. Flash droughts happen frequently, especially in the central and western U.S. “If not predicted and discovered early enough, changes in soil moisture that accompany flash drought can cause extensive damage to agriculture,” according to the National Integrated Drought Information System (Drought.gov). Flash droughts may be shorter lived than prolonged droughts, but they can still cause massive crop losses.

In early September, prolonged drought conditions were affecting 80% of the High Plains (North and South Dakota, Nebraska, Kansas, Colorado, and Wyoming), according to the Drought Monitor. That’s up from three months and a year prior but down from the start of the calendar year. Just over 60% of the South (Oklahoma, Texas, Arkansas, Louisiana, Mississippi, and Tennessee) was in drought conditions, up significantly from 2021. And 88% of the West was under drought conditions, which is actually less than it was three months ago, at the start of the calendar year, and one year ago.

When we think about droughts, we tend to think back to the last bad season, says Jim Schepers, a retired soil scientist with the USDA-ARS and emeritus professor at the University of Nebraska. “Farmers will always remember a bad event, whether it’s grandpa telling the young bucks how damn bad it got” or they themselves lived through it, he says. This year has reminded farmers of a really bad drought in 2011 and 2012.

Between 1998 and 2014, much of the U.S. was in drought. In the Southern Plains, the worst period started in fall 2010, but were followed by one of the hottest, driest summers in history for the region, according to NOAA. In Texas, 2011 marked the driest year on record. Grain production was half of normal levels and cost more than $7 billion in crop and livestock losses. In other parts of the Plains and West, the drought peaked in 2012. Since then, droughts have popped up all across the region, worse in some places than others at a given time.

In 2020, a reconstruction of past droughts showed that the droughts of the 21st century—especially if you count the exceptionally dry period from 2000 through 2018 as one large drought—may rival past severe droughts, like those of the 1950s and 1930s, the latter of which includes the infamous Dust Bowl. That study found that despite the severity, duration, and spatial coverage of those severe droughts, they pale in comparison to the megadroughts that struck the High Plains between AD 850 and 1500, some of which lasted more than 100 years (see sidebar). Now, though, a follow-up study in March 2022 in Nature Climate Change has shown that the current drought period from 2000 through 2021 (not even including 2022) is the driest 22-year period since at least AD 800.

Droughts in the future could surpass megadroughts of the past due to rising global temperatures. Rising temperatures intensify the hydrologic cycle. Higher temperatures can lead to both more drought and more extreme rainfall events. Higher temperatures lead to droughts by drying out the soils and plants, which causes the plants to release less moisture into the air, leading to less rain. Similarly, higher temperatures can lead to extreme rainfall events because warmer air leads to more evaporation and warmer air can hold more water vapor, leading to more intense rains. These are complicated feedback loops. Intensification of the El Niño–Southern Oscillation meteorological pattern is also leading to more hydrologic changes. This winter, for example, we’re likely to see a rare third consecutive year of La Niña conditions, which leads to the southwestern U.S.—which is already in the midst of a severe drought—being drier than normal. The prevailing wisdom is that projected increases in temperatures are likely to lead to more frequent and more extreme droughts, so we better figure out how to adapt.

Where irrigation isn’t an option, farmers might choose to plow under or bale their crops rather than harvest them, like many did last summer. It’s a calculated decision, Arnall says. “If I have about $20 worth of nitrogen, $20 worth of potassium, and $10 worth of phosphorus, can I get back those inputs if I bale it?” he says. Baling the crop removes it, and its nutrients, offsite. If they do bale it, farmers might consider leaving more residue—like chopping crops higher—to take advantage of the nitrogen that is in the lower stalks for the next year.

Earlier in the growing season, another option for managing nutrients under a changing climate is to time fertilizer application when conditions are optimal, Vergopolan says. Such a nutrient management strategy can be a conservation measure since applying only what is needed at the right time and in the right amount can protect air and water quality, maintain or improve soil quality, and limit greenhouse gas emissions. To help determine when conditions are optimal, during the growing season, farmers can check soil moisture levels using gravimetric methods, soil probes, or dielectric sensors. “If conditions are too dry, nitrification is not going to happen. But plants also are not going to absorb the fertilizers if the soil is too wet,” she says.

An even easier way midseason to determine whether more fertilizer would be helpful is to employ “check strips,” Arnall says. Check strips are rows in the field that are enriched with nitrogen, whereas the rest of the field is not. The idea is that when the nitrogen-rich strip shows up during the growing season, you know the rest of the field is becoming deficient, he says. It’s an early warning system. Usually in drier years, for wheat, farmers don’t need as much nitrogen as wetter years. “We’ve been utilizing the enrich strips in wheat since the early 2000s in Oklahoma,” Arnall says. “We have a lot of sensors and other technologies, but the visual of seeing it as you drive by your field—or not seeing it—is highly valuable.” Such a simple tool can save tremendous amounts of fertilizer—and money.

Ways to Increase Resiliency

Even more ideal is making fields more resilient. “What we do now can potentially influence 5 to 10 years down the road,” Lewis says. Many different conservation practices can help, she says, such as crop rotations, reduced tillage, and potentially cover crops. “Any conservation-type practice that’s going to improve the soil from chemical, biological, physical perspectives, those are going to better help the soil withstand drought events in the future.”

Many farmers already rotate their crops. One potential way rotation can help in droughts, though, is in fertilizer management. For example, “if you have a drought one year, instead of planting soybeans, you might decide to plant corn again the second year because you have so much residual nitrogen, and nitrogen is expensive,” Schepers says. That decision should be made in fall for spring crops, he says.

Cover crops are a hotly debated option for dealing with droughts, Arnall says. Cover crops reduce evapotranspiration, so they can be helpful over time, Lewis says. But they also remove water from the field (taking it up as they grow). So you risk removing moisture from the field as you grow cover crops and then not having enough for your cash crop, Arnall says. Whether cover crops will work basically depends on whether you’re in a high-rainfall region, he says. It also depends on what you’re growing, he adds. For example, cotton leaves a “bare scorched earth,” so alternating with grazed wheat or using cover crops can be really helpful.

For those irrigating, Schepers says, another option is to install center-pivot irrigation. Research in Nebraska has shown that using center-pivot irrigation instead of furrow irrigation results in using half as much water and reducing nitrogen by up to one-third, he says.

Despite the weather and climate issues, these are “promising times” for farmers in that they have more tools at their disposal than ever before, Vergopolan says. If you think about where we were 5 or 10 years ago, and where we might be 5 or 10 years from now, she says, it’s exciting to have new prospects for monitoring and dealing with droughts.