Utilizing Cover Crop Mulches to Reduce TIllage in Organic Systems in the Southeast.

Cover crop roller-crimper trials have been conducted across the southeastern U.S. during the past decade.  Regional climatic conditions make the system particularly attractive but also pose their own challenges.  Winter annual cover crops productivity can exceed 8 Mg ha^-1 (dry weight) for rye (Secale cereale L.) in Alabama and Georgia, 6 Mg ha^-1 for hairy vetch (Vicia villosa Roth)  and crimson clover (Trifolium incarnatum L.) in North Carolina, 9 Mg ha^-1 for blue lupin (Lupinus angustifolius L.) in Georgia, and 7 Mg ha^-1 for rye/legume mixtures in the region.  Productivity at this level provides mulch levels sufficient for substantial weed control; and when utilizing legumes, most of the nitrogen necessary for corn.  Hairy vetch in some cases contributes more than 200 kg N ha^-1. These high residue levels also necessitate the use of planting equipment adapted to conditions more demanding than typical reduced tillage systems.  Cover crops also impact soil water and temperature relations.  Soil water can be depleted due to cover crop transpiration in low rainfall environments.  On sandier soils, typical of the Coastal Plain that stretches from Texas to Virginia, rolling several weeks prior to planting facilitates recharge of soil moisture, while residues increase infiltration and reduce evaporation.  Though the system shows promise, known and unexpected interactions need further research.  Increased grasshopper pressure on vegetables in Alabama, severe lodging of soybeans in North Carolina, damping off diseases of peanuts in Georgia, and others highlight the myriad of mechanisms whereby roller-crimped cover crops can impact crop yields.  The system needs coordinated region-based research to fully develop recommendations for farmer implementation.