Researchers tested five combinations of three crops – soy, wheat, and corn – and two cover crops – red clover and rye. They also planted a crop of only corn, while minimizing the effects of other management practices such as variable fertilizer and pesticide inputs that interfere with the crop rotation effect. Researchers observed a 33 percent increase in soil carbon by increasing rotational diversity. An indication of soil organic matter, the carbon content of soil is a major factor in its overall health and improves the physical properties of soil. Researchers also found that as crop diversity increased, so did total nitrogen concentrations, a sign of soil fertility.

“The data we present are the first to support the hypothesis that increasing rotational diversity fundamentally changes microbial community structure and activity, with positive effects on aggregate formation and soil organic matter accrual,” Tiemann said. “These findings provide further support for the use of rotational diversity as a viable management practice for promoting agroecosystem sustainability.”

A byproduct of increased pressure on soils due to agricultural intensification is a negative impact on microbial diversity and function. This is a problem worldwide and can lessen soil’s ability to perform important ecosystem functions. Results may include threats to long-term food security, increases in greenhouse gas emission, and a reduction in water quality.