Crop Rotation

Plant Management-Crop Rotation

	By adding commodities such as corn, small grains, forage and beef cattle to cotton systems,SARE-funded researchers at Texas Tech University cut water use by 23 percent and saw higher profits. Photo by David L. Doerfert

Devising an appropriate plant rotation is an effective way to manage water resources. Since farmers began growing grain in the Great Plains, they’ve used long periods of fallow to conserve water for their wheat and other cash crops. The fallow system relies on the tenet that leaving the land bare over a year or more allows water to accumulate in the soil.

Farmers now commonly leave crop residues on the surface to protect the soil. Yet, a number of SARE projects examine crop alternatives to fallow to achieve better profits and soil benefits while conserving water.

SARE-funded Montana State University researcher Perry Miller tested Austrian winter peas as a fall-planted cover crop grown throughout the winter, the typical fallow. He hoped to prove the nitrogen-building benefits of the crop, which also provides a second cash crop – a protein-rich forage for cattle.

Adding peas during the fallow period captures water, guards against erosion and feeds biomass to the soil. The rotation “is a much more sustainable practice, and economically positive, too,” Miller said.

In the Nebraska High Plains, researchers also are testing peas – as a forage or a grain crop – in wheat systems. Like the Montana researchers, they are responding to growers who want to improve their soil management and reduce their fertilizer and herbicide costs but not deplete soil moisture. Depending on soil moisture, growers may decide mid-season whether to harvest peas as a forage, saving 30 percent more soil moisture, or wait and harvest it as a grain.

Rather than the typical wheat/fallow system that yields a crop every other year, a team of University of Nebraska researchers are studying alternative dryland cropping systems with SARE funding.

“As we’ve looked to increase the intensity of the system – to two crops in three years – this water relations work has become very important,” said University of Nebraska researcher David Baltensperger. “We have become very excited about the potential for cool-season, short-growth crops that use less water and allow more time to accumulate water prior to planting wheat to replace fallow in the High Plains.”

Baltensperger’s colleague, Drew Lyon, has developed a flexible dryland cropping system that encourages producers to decide whether to plant a short-season crop or stay in fallow based on soil moisture availability just before planting. Some growers are planting cool-season oil crops such as brown mustard, canola and camelina, whose seeds are crushed for biofuel. The seeds contain 20 percent more oil than soybeans.

“They are short-season crops with most of their growth in the cool-season, high-rainfall period, with tremendous market potential,” Baltensperger said.

Cotton is a significant water-user. In Texas, about one-quarter of the total U.S. cotton supply comes from the state’s High Plains region. Yet, water levels are declining in the Ogallala aquifer, the main water source for northern Texas growers. Scientists such as Texas Tech University researcher Vivien Allen are seeking water-conserving alternatives to monoculture cotton.

Armed with a SARE grant, Allen developed an innovative cotton, cattle and forage rotation that reduced water use by about 23 percent. Of great interest to farmers, that system – which features the perennial, drought-tolerant forage old world bluestem – also doubles profitability. The forage, seeded in half of the alternative plot, required no irrigation for five months of the year, driving down average irrigation over four years to 372 mm compared to 481 mm in the continuous cotton system.

In early the 1900s, when Texas farmers began drilling wells into the Ogallala aquifer, cotton proved a reliable, profitable crop. As water levels in the Ogallala drop, however, cotton farmers face a few tough choices: run out of water, drill deeper and extract water at greater cost, or diversify. Much of the High Plains region, including parts of Nebraska, Colorado, Wyoming, Oklahoma, Kansas, New Mexico, South Dakota and Texas, relies on the Ogallala for water.

“When we began to irrigate, we took a 10-million-year-old resource and virtually expended it in 100 years,” Allen said. “We need a cover on the land because of erosion, and that cover needs water.”

Allen’s new rotations were so promising that Allen and her management team won a $6.2 million state grant to demonstrate water-conserving farming strategies across the Texas High Plains. Responding to public interest in the dropping water level in the Ogallala aquifer, Allen’s team, the Texas Alliance for Water Conservation, is using the opportunity to further test those systems across 4,000 acres on 26 farms and ranches. Under the state project, producers will test diversified systems and the conservation team will measure their water use. For instance, some farmers will rotate pasture grasses with cotton for forage or grazing; others will over-seed cool-season cereal crops into cotton for eventual harvest.

“The declining aquifer greatly affects us,” said Monty Dollar, an NRCS conservation agronomist and member of Allen’s team. “Irrigation water is instrumental in producing profitable yields that sustain our operations. Yet, we’ve got to learn to live with less water. We’re going to find out if we can do that.”

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