Skip Navigation

Cover Crops

Mulching Cover Crop Mixtures to Increase Weed Suppression, Soil Nitrogen Availability, Soil Moisture and Grain Yield

Sam E. Wortman, John L. Lindquist, Rhae A. Drijber , Mark L. Bernards and Charles A. Francis,

Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, 68583-0915.


   Many studies have demonstrated the weed suppressive potential and fertility contributions of individual cover crop species, but the value of diverse cover crop mixtures has received less attention. Moreover, there is increasing interest in conservation tillage strategies for cover crop termination. The objective of this study was to determine the effects of cover crop diversity and termination method on weed suppression, soil nitrogen availability, soil water content and grain yield in an organic cropping system. A field experiment was conducted in 2009 and 2010 near Mead, NE where spring-sown mixtures of 2, 4, 6 and 8 cover crop species were included in a sunflower – soybean – corn crop rotation. Cover crops were planted in late-March, terminated in late-May using a field disk or undercutter and main crops were planted within one week. Cover crop termination with an undercutter only decreased weed biomass by 4% (±2.5%) relative to the no cover control at 34 days after planting main crop (DAP) in 2009.  However, the combined effects of increasing cover crop diversity and termination with an undercutter increased weed suppression at 23 DAP in 2010; weed biomass in the undercut 8 species mixture was reduced by 46% (±12.6%) relative to the no cover control. Undercutting cover crops increased soil nitrogen availability (3.2 ppm ± 0.2) relative to incorporation with a disk (2.2 ppm ± 0.2) at 29 DAP in 2010. All cover crop mixtures reduced soil water content prior to main crop planting, while cover crop termination with an undercutter increased soil water by as much as 7.3% (± 0.2%) compared to the field disk during early main crop growth. Most importantly, cover crop termination with an undercutter increased corn and soybean yields by as much as 32% (±7%) and 34% (±16%) compared to the no cover control, respectively.

For more information contact:

Sam Wortman

sam.wortman at

Research Poster (MOSES 2011)

Wortman et al. 2010 Increased weed diversity, density and above-ground biomass in long-term organic crop rotations

Significance to Organic Ag

Research Poster (MOSES 2010)