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

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Title: Utilizing Rolled Rye Mulch for Weed Suppression in Organic No-Tillage Soybeans
Author: Smith, Adam Nelson
Advisors: J. Paul Mueller, Committee Chair
S. Chris Reberg-Horton, Committee Co-Chair
Consuelo Arellano, Committee Member
Abstract: Rising demand for organic soybeans (Glycine max L.), coupled with high price premiums for organic products, has producers interested in making the transition to organic soybean production. However, organic soybean producers and those making the transition cite weed management as their biggest limitation. Current organic weed management relies heavily on cultivation. Cultivation has negative consequences on soil health and producers are interested in organic reduced and no-till production. Rye (Secale cereal L. cv. Rymin) cover crop was evaluated for weed suppression abilities and effects on soybean yield. Experiments were planted in 2008 and 2009 at three site locations. Rye was planted in the fall of each year and killed at soybean planting with a roller-crimper or flail-mower, creating thick weed-suppressing mulch with potential allelopathic properties. The mulch was augmented with one of three additional weed control tactics: pre-emergence corn gluten meal (CGM), post-emergence clove oil, or post-emergence high-residue cultivation. Rolled-crimped and flail-mowed treatments had similar weed suppression abilities. There were no differences between CGM, clove oil, or cultivation at most sites. Rye biomass level was the only independent variable that affected weed control. Rye biomass levels higher than 9,000 kg ha-1 were sufficient in controlling weeds. Organic soybean yields were similar to weed-free soybean yields at rye biomass levels higher than 9,000 kg ha-1. Goldsboro 2008, where rye biomass was 10,854 kg ha-1, the organic rye-only treatment yielded at 2,190 kg ha-1 and the weed-free treatment yielded at 2,143 kg ha-1. Plymouth 2008, where rye biomass was 9,526 kg ha-1, the organic rye-only treatment yielded 2,694 kg ha-1 and the weed-free treatment yielded at 2,809 kg ha-1. On the contrary, at low rye biomass levels (4,450- 6,606 kg ha-1), the organic rye-only treatment yielded 628- 822 kg ha-1 less than the weed-free treatment. High rye biomass levels are critical to the success of this production system. However, at rye biomass levels greater than 10,000 kg ha-1, severe soybean lodging was induced and potentially limited yield potential.
Date: 2010-04-27
Degree: MS
Discipline: Crop Science
URI: http://www.lib.ncsu.edu/resolver/1840.16/6297


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