Cover crops are an integral element in no-till conservation systems because they provide important benefits to soils and plants. Covers must produce large amounts of biomass to maximize these benefits (Brady and Weil, 1999). A commonly used cover crop in the southern United States is rye (Secale cereale L.), which can produce 3,000 to 10,000 kg·ha−1 per year (Bowen et al., 2000). Primary benefits of using rye as a cover crop include protection of soil from the impact of rainfall energy leading to reduced soil erosion and surface runoff, decreased soil compaction, and increased infiltration (Kern and Johnson, 1993; McGregor and Mutchler, 1992; Raper et al., 2000a, 2000b; Reeves, 1994). Cover crops also provide a physical barrier on the soil surface, which inhibits weed emergence and growth. In addition to providing a physical barrier, rye has allelopathic properties that provide weed control similar to applying a pre-emergence herbicide (Barnes and Putman, 1986; Hoffman et al., 1996). Additional benefits are associated with improving soil physical/chemical properties as a result of increased soil organic carbon content, resulting in better crop growth.
Rolling/crimping technology has been used to manage mature cover crops by flattening and crimping cover crops such as rye in no-till conservation systems. Crimping cover crop tissue causes plant injury and accelerates its termination or senescence. In no-till conservation systems of the southern United States, termination of cover crops should be performed 3 weeks before planting the cash crop, which is similar to standard burndown recommendations by most agricultural extension services. Results from previous research have shown that when rye rolling was performed at the optimal growth stage of early milk to soft dough, the termination rate for rye was typically above 90% 3 weeks after rolling (Ashford and Reeves, 2003; Kornecki et al., 2006). Nelson et al. (1995) also stated that a later growth stage for rye such as a soft dough might be ideal for mechanical termination. Most agricultural extension services recommend ending the cover crop at least 2 weeks before planting the cash crop to prevent the cover crop from competing for soil moisture. According to Hargrove and Frye (1987), a minimum time for rolling/crimping should be at least 14 d before planting of the cash crop to enable soil water recharge before planting.
Optimum residue conditions for planting a cash crop are usually reached 3 weeks after termination, at which time the residue is dry, crisp, brittle, and easy to penetrate with equipment.
In vegetable production, however, planting must be completed within the recommended dates for a specific climatic region to avoid yield reduction of the vegetable crop. This time restriction may not allow the cover crop to reach the recommended growth stage for termination. To speed up the cover crop termination process, herbicide application has been implemented along with rolling in conservation systems of the Southeast for field and vegetable crops. However, herbicide use is not allowed in organic vegetable production; thus, cover crop management must be done mechanically by cutting/incorporating or through rolling/crimping technology. Different roller designs have been developed to roll and crimp cover crops; however, none have been evaluated in no-till vegetable production systems for which the recommended time for cover crop termination might need to be adjusted to follow the recommended planting date of the cash crop.
The objective of this study was to determine the impact of different roller designs and two different rolling speeds on mechanical termination of a cereal rye cover crop and their effects on soil volumetric moisture content and yield of a no-till sweet corn system.
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