Cover Crops Reduce Nitrates Without Hurting Yield

By: WallacesFarmer

Results of a five-year study at various locations across Iowa show cover crops added to a corn-bean rotation have no negative effect on yield while significantly reducing the nitrate concentration in subsurface water.

Conducted by Iowa Learning Farms, Iowa State University Extension and Practical Farmers of Iowa, this study helps dispel the commonly held belief that cover crops reduce the yield of cash crops following cover crops in fields.

Throughout the 22 site-years of yield data, there was no significant difference in cash crop yields between control strips without cover crops and those planted with cover crops. The report notes that planter settings may impact yield if not properly managed to accommodate residue from the cover crops.

Significant nitrate reduction, unchanged yields
Iowa soils are highly vulnerable to nitrate loss between April and June when natural nitrate production exceeds typical crop demands. In this study, analysis of water samples from those three months showed a statistically significant reduction in nitrate concentration in the cover crop strips.

The data collected for water quality was comprised of 17 site-years. The most significant reductions were measured in the single species treatments: 61% reduction for rye and 23% for oats when compared to the no cover treatment in the same field.