A Farmer’s Best Defense Against Drought
By XiaoZhi Lim
BU News Service
In the summer of 2012, during the worst drought in twenty years, Danforth, Illinois, went for six weeks without rain but the corn in Hoekstra Farm grew tall and green. The corn in the neighboring fields was almost a foot shorter. While farmers across the Corn Belt watched their crops shrivel and die, Harold Wilken of Hoekstra Farm made enough money from his crops that summer to pay a bonus rent to his landowner.
Wilken did not use special drought-resistant seeds, and his fields did not get more rain than his neighbors’. What Wilken did, for the last eight years farming at Hoekstra, was take extra care of the soil in his fields.
Wilken is not the only farmer paying special attention to his soil. Although researchers have long tried to address drought by creating drought-resistant plants, more and more farmers, soil scientists and university extension staff are starting to realize that healthy soil is more effective in dealing with ruinous dry spells.
For the last two decades, scientists from major biotech companies like Monsanto and DuPont focused their research on engineering drought-resistant seeds. The idea of a plant that can survive on significantly less water was an attractive solution that required no extra effort from the farmers.
But drought-resistant seeds have limitations. Corn, for example, is particularly vulnerable. It must have sufficient water during a critical seven-day period within the growing season, if not it will be unable to produce kernels.
Because of these limitations, a growing number of farmers are staying with traditional methods, focusing on their soil, not seeds. Healthy soil can retain moisture, providing a steady supply of water when rainfall is sporadic and helping crops survive until the next rain. It has a loose, pliable structure and contains about three to five percent organic matter. Organic matter, which comprises carbon-based material like compost or manure, acts like a sponge. According to soil scientists, organic matter can hold up to over six times its weight in water. A loose, crumbly soil structure allows water to infiltrate deep, to be slowly released until the next rain.
At Hoekstra Farm, Wilken has a rigorous soil fertility program. He spreads manure on his fields to maintain organic matter content and uses a complex crop rotation to replenish essential plant nutrients. In 2011, he planted alfalfa on his corn fields, wheat in 2010 and soybeans in 2009. Different crops use up different nutrients in the soil, so by changing crops for three years, Wilken replenished the soil’s nutrients before planting corn again. Additionally, plants with deep roots like alfalfa can loosen up the soil and enhance water infiltration right before planting a water-demanding crop like corn, according to Joe Pedretti, an organic education specialist with the Midwest Organic and Sustainable Education Service.
During the winter, Wilken plants cover crops such as oats and alfalfa to protect his soil from being eroded by the wind. According to Eileen Kladivko, a professor of agronomy at Purdue University, farmers usually don’t harvest the cover crop, but kill it during the spring with either herbicides or ploughing it down. In this way, the cover crop returns to the soil as organic matter.
Alvin Smucker, a professor of soil biophysics at Michigan State University, has developed a membrane that can be placed in the root zone of plants to retain water. Dubbed SWRT for Sub-surface Water Retention Technology, Smucker’s membranes are made of polyethylene. An installation machine inserts folded membranes into the soil one foot apart and in two layers, 14 and 22 inches deep, where the membrane opens up in the shape of a trough. According to Smucker, the corn in his fields with the SWRT yielded 170 percent more than the control corn crops. The test fields had “at least double the water capacity than the control soil,” said Smucker.
Challenges remain, especially because soil health takes a long time to build. The practices that help soil become resilient to drought don’t pay out in the short term, usually taking several years depending on how healthy the soil is. In contrast, genetically-engineered seeds like DuPont’s Aquamax tend to attract more attention because brown, withered Aquamax corn does turn green again when rain finally comes, according to Mark Rhorbach, a sales associate for seeds involved in field tests. But even genetically-engineered seeds can only take so much stress: if the rain just doesn’t come, the crop won’t survive. Rhorbach agreed that paying attention to soil health and using methods like planting cover crops can help reduce the effects of drought in ways that Aquamax can’t.
As for Wilken, the forecasts for drought in the coming years don’t daunt him. “We’re not doing anything different this year than last year,” said Wilken. “It takes moisture, and it takes good soil. All the genetics in the world will not replace Mother Nature.”