Sustainable Agriculture News

Bio-energy Prairies Minimize Nitrate Losses over Corn Systems

Bioenergy-based cropping systems are on the rise, with the goal of producing 136 billion liters of ethanol per year by 2022. This means that more and more producers with subsurface-drained (tile-drained) lands in the U.S. Midwest are shifting some of their land to meet the bio-energy industry’s needs.

In these landscapes, subsurface drainage waters are the primary pathway for transport of nitrate and phosphorus from agricultural fields to surface water bodies. Therefore, infield and edge-of-field practices to minimize nitrogen and phosphorus losses have seen extensive research.

Despite these efforts, little attention has been paid to side-by-side comparisons of annual bio-energy cropping systems (e.g., corn systems) and perennial systems—in particular, reconstructed prairies that are fertilized to maximize biomass production.

In research appearing in the September-October 2015 issue of the Journal of Environmental Quality, a team compared nitrate and phosphorus losses to subsurface drainage waters among prairie- and corn-based bio-energy cropping systems at Iowa State University’s Comparison of Biofuel Cropping Systems research site.

In this four-year study, nitrate concentrations in drainage waters under prairies were 1- to 195-times less than concentrations in corn systems, even when nitrogen fertilizer was applied to the prairies. Losses of nitrogen as nitrate were also equivalent to just 1% of the nitrogen added as fertilizer, whereas corn–soybean rotations or continuous corn systems had losses equivalent to 3 to 38% each year.

However, use of cover crops in continuous corn also limited nitrate losses to just 0 to 15% of added nitrogen fertilizer. The findings suggest that both prairies and corn systems can supply feedstock to the bio-energy industry while minimizing nitrate losses in subsurface drainage waters.

Source: American Society of Agronomy