- Agronomic: rye, soybeans
- Crop Production: conservation tillage
- Education and Training: demonstration, on-farm/ranch research, workshop
- Energy: energy conservation/efficiency
- Natural Resources/Environment: soil stabilization
- Pest Management: allelopathy, chemical control, mulches - killed, physical control, mulching - vegetative
- Production Systems: transitioning to organic, organic agriculture
- Soil Management: soil analysis, nutrient mineralization, organic matter, soil quality/health
- Sustainable Communities: local and regional food systems, sustainability measures
The demand for organic grains is increasing. Farmers making the transition to organic production cite weed management as their biggest challenge. The objective of the project was to determine if an organic no-till system was feasible in the Southeast US. Experiments were held throughout the state. A rye (Secale cereal) cover crop (‘Rymin’) was planted in late fall and rolled/crimped or flail-mowed prior to planting to create a weed suppressing mulch with potential allelopathic properties. To augment weed control, one pre-emergence and two post-emergence weed management tactics were evaluated. Compared with conventionally treated check plots, the rolled rye system resulted in equivalent soybean yields at most of our locations. Rye biomass levels played a critical role in weed suppression.
In a separate experiment, we planted 14 legume cover crop varieties, including berseem clover, subterranean clover, sweet clover, crimson clover, hairy vetch, common vetch, winter pea and blue lupine, and we planted 6 varieties of rye. Cover crop stands have been evaluated, and all the legume cover crops have been rolled on two to three different dates from early April to early May in order to see how rolling and planting match up with full-bloom for cover crop kill. Corn was no-till planted into the rolled cover crops.
Demand for organic corn and soybeans in North Carolina is growing. Braswell Milling in Nashville, NC estimates they need at least 500,000 bushels of organic corn and 7,000 tons of organic soybean meal each year to supply their organic egg farms. A group of farmers in eastern North Carolina have incorporated as Eastern Carolina Soy Products, LLC to build a soybean crusher that will process up to 400,000 bushels of organic soybeans each year. Although demand for organic grains is high, NC producers cannot take advantage of these opportunities. North Carolina currently imports a majority of its organic corn and soybeans to meet market demand. Weed management in organic soybeans and adequate fertility for organic corn are the biggest challenges in developing a sustainable organic grains rotation system.
Currently, weed management in organic soybean production relies heavily upon multiple secondary tillage passes over the field each season. Increased tillage can result in increased soil erosion (Beale et al., 1955) and soil compaction (Raper et al., 2000), increased fossil fuel requirements (Hargrove, 1990), increased CO2 release (Paustian et al., 1998), increased labor costs (Weersink et al., 1992), increased equipment costs (Weersink et al., 1992) and decreased soil residue cover (Hargrove, 1990).
Some cover crops such as rye have demonstrated allelopathic (releases weed inhibiting chemicals) properties (Barnes et al., 1987). A newly designed chevron roller can be utilized to effectively kill the rye and create a thick biomass layer on the soil surface. By planting soybeans into such a biomass layer, weed growth can be greatly inhibited. This system has been successful at the Rodale Institute in the Northeast, but it has not been investigated for the Southeast region. With the increased research and development of organically certified herbicides (Tworkoski, 2002), use of corn gluten (shown to possess weed suppressive qualities (Christians 1993)) and high residue cultivation equipment (Paarlberg et al., 1998), more options have become available to successfully implement no-till organic grain production.
Many farmers interested in organic grain production farm in NC’s Tidewater region; an area of poorly drained, high organic matter soils. Most organic grain farmers in the state would like a cover crop to contribute significantly to the nitrogen budget of their corn crop. In organic systems, reliance on manures for nitrogen isn’t sustainable due to increasing phosphorus levels and concerns of environmental contamination (Bulter et al., 2005). Crimson clover is typically recommended for adding large amounts of biomass with high nitrogen content. However, crimson clover is inhibited on poorly drained soils (Yenish et al., 1996; Cavigelli et al., 2007). Hairy vetch is also a significant contributor of nitrogen and known to tolerate wet soils (Anderson et al., 1990). In an attempt to incorporate no-till into a full rotation system, farmers have identified the need to further investigate the limitations of crimson clover on poorly drained soils and the potential use of hairy vetch, a cover crop more tolerant to wet soils but rarely used in North Carolina grain rotations.
We utilized research stations and on farm trials to compare no-till organic soybean systems utilizing different combinations of the following tactics: planting soybeans into a rye cover crop compared to planting into no cover crop; planting soybeans into a rolled down rye cover crop compared to planting into an undercut rye cover crop; planting soy with a 7 inch band of corn gluten over the crop row, use of post crop emergence clove oil organic herbicides with sprays directed under crop foliage and the use of one pass of a high residue cultivator to control weeds between crop rows.
We also proposed a multi-location investigation of nitrogen contribution by crimson clover and hairy vetch cover crops grown on poorly drained soils preceding corn as part of the no-till organic grain rotation.