To Till or Not to Till?

In 1840, American painter Grant Wood said, “When tillage begins, other arts follow. The farmers therefore are the founders of human civilization.” Today, many farmers recognize that tillage – or the practice of plowing or turning soil to sow crops – lacks efficiency and has unwanted environmental effects, prompting researchers to ask, “What happens when tillage ends?”

Mark Alley, the W.G. Wysor Professor of Crop and Soil Environmental Sciences, has devoted his research to answering this question.

“Every time we till the soil we lose organic matter,” explains Alley, president of the American Society of Agronomy, who adds that parts of Virginia have been tilled for up to 400 years. “No-till farming adds organic matter to the surface of soils. It increases the water-holding capacity of the soil, improves water filtration, adds nutrients, and creates a better environment for crops.”

Alley and his colleagues are studying how no-till farming of agronomic crops improves carbon sequestration, the process of storing carbon to improve soil quality and reduce greenhouse gas emissions. “When looking at the long-term effects of continuous, no-till farming from zero to 14 years, we find a steady increase in carbon levels at the surface,” he says.

"No-till farming adds organic matter to the surface of soils. It increases the water-holding capacity of the soil, improves water filtration, adds nutrients, and creates a better environment for crops," says Mark Alley.

Virginia Tech researchers have sampled data on the impact of no-till farming on carbon sequestration from 63 farms throughout the commonwealth and reported their findings to the Chicago Climate Exchange, a voluntary cap-and-trade system that allows agricultural producers to buy and sell carbon credits. According to Alley, producers in Virginia and the mid-Atlantic region can now participate because of the data collected in Virginia and neighboring states.

“This allows the agricultural sector to participate in the global conversation about environmental sustainability,” he says.

This global conversation involves more than just carbon, a hot-button issue. No-till farming does not require as much machinery and therefore cuts fuel costs. In addition, recent scholarship has shown that no-till farming can reduce the loss of nitrogen from soil to water, where excessive nitrogen levels are an environmental concern.

“We know that soil organic matter has about 5 percent nitrogen content,” Alley says. “By increasing the amount of organic matter in the soils, we are also increasing the pool of nitrogen available to agronomic crops. In effect we are sequestering nitrogen, too.”

Over the past six years, Virginia Cooperative Extension has mobilized its agents around the state to educate farmers about the advantages of no-till farming. Although the practice reduces the cost of equipment and fuel, it requires more management, and therefore, more training.

“In 2009, Extension agents will be leading a grower-to-grower mentoring program that will connect Virginia farmers who have adopted no-till practices with those who have not,” Alley says.

Although more than 50 percent of Virginia farmers have already switched to no-till farming, Extension personnel hope they can increase that number through the mentorship program and other efforts that emphasize the benefits to farmers, such as carbon sequestration.

“Carbon sequestration improves soil quality and efficiency of production,” Alley says. “The latter is the real economic drive for farmers.”

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A researcher collects samples of hairy vetch (Vicia villosa), a cover crop that improves soil quality and stymies weed growth.

Paul Davis, agriculture and natural resources agent for the New Kent County Virginia Cooperative Extension Office, measures vetch and rye grown together to boost carbon and nitrogen sequestration rates.