New study shows benefits of rotating with soybeans

First-of-its-kind checkoff study shows the environmental benefits of soybean-corn rotation, beyond the single-rotation studies of the past

The study’s preliminary findings show corn-soybean rotations emit three times less harmful nitrous oxide (N2O) than continuous-corn rotations. One pound of N2O emissions is equivalent to 300 pounds of carbon dioxide emissions.

Compared with prior studies that focused solely on individual crops, the USB and soybean checkoff funded this study to quantify the benefits of the use of soybeans in crop rotations by U.S. farmers.

SES, a research firm specializing in agriculture natural resources management, conducted the study using a model to simulate biochemical and plant growth over a 12-year period. SES analyzed nine different variables, including:

• three crop rotations – continuous-corn, corn-corn-soybean and corn-soybean
• three locations – Lincoln, Neb.; Springfield, Ill.; and Lumberton, N.C.
• three tillage scenarios – no-till, minimum-till and minimum-till soybeans/disking corn

The study focused on three environmental effects: nitrogen, greenhouse gas (GHG) emissions and carbon sequestration.

NItrogen

Continuous-corn rotations resulted in as much as three times as much nitrogen leaching as corn-soybean in Lincoln. Nitrogen leaching for continuous-corn in Springfield and Lumberton proved to be double that of the corn-soybean rotation.

GHG Emissions

No-till and minimum-till resulted in negative GHG emissions for all three crop rotations at all three locations. The corn-soybean rotation showed the lowest GHG emissions under intense tillage.

Carbon Sequestration

Due to corn containing greater amounts of biomass than soybeans, continuous-corn and corn-corn-soybean rotations remove as much as double the carbon from the atmosphere and store it in the soil, compared with corn-soybean rotations using no-till or minimum-till.

“This study definitely shows the benefits of including soy in rotations with corn or even other crops,” says Patrick Splichal, SES vice president and lead researcher on this project. “Whatever U.S. farmers can do to show they’re reducing nitrogen and phosphorus going into the watershed or that they’re reducing GHG emissions and sequestering carbon in the soil is definitely of benefit to all U.S. farmers.”