Utilizing Rolled Rye Mulch for Weed Suppression in Organic No-till Soybeans.

Rising demand for organic soybeans (Glycine max L.) is not being met by North Carolina producers.  While the economic incentives are advantageous, producers interested in transitioning to organic cite weed management as their biggest problem.  Current weed management relies heavily on secondary cultivation.  Concerned about the consequences of cultivation, producers are interested in organic no-till production.  Experiments were planted in 2008 and 2009 at three site locations.  Rye (Secale cereal L. cv. Rymin) was planted as a cover crop in the fall of each year.  Prior to soybean planting, the rye was terminated with a roller/crimper or flail-mower, creating a thick weed-suppressing mulch with potential allelopathic properties.  The mulch was augmented with one of three additional weed control methods.  A pre-emergence granulated corn gluten meal was banded in the soybean row.  A post-emergence clove oil was employed as a directed under-canopy herbicide for in-row control and a high-residue cultivator was used for between-row weed control.  In 2008, rolled rye resulted in pigweed (Amaranthus retroflexus) cover of 3% vs. 13% in flail-mowed rye.  Compared with conventionally treated check plots, the rolled rye system resulted in equivalent soybean yields at sites where biomass was 10854 kg ha^-1 and 9526 kg ha^-1.  A low rye biomass of 6606 kg ha^-1 was insufficient for adequate weed control and soybeans from rolled rye plots yielded 853 kg ha^-1 less than those from conventional plots.  In 2009, rye biomass levels were 8366, 8066, and 4450 kg ha^-1.  Preliminary weed rating data concluded higher weed densities in 4450 ka ha^-1 rolled rye plots.  Weed control and yields so far suggest the roller/crimper is a promising tool for reducing tillage in organic systems.