Integrating Annual and Perennial Forages in Organic Vegetable Cropping Rotations.

In integrated crop-livestock systems, annual or perennial grasses and legumes can serve not only as cover crops, but also as forage crops through either mechanical harvest or grazing. These dual-use cover crops can still provide agronomic benefits to cash crops in rotation and soil quality benefits with aboveground biomass removal, but this has not been well-explored, especially for organic vegetable cropping systems. A four-year field study at the University of Tennessee evaluated crop performance and soil quality in organic cropping systems, including cover-crop based vegetable rotations either with or without spring tillage (i.e., conventional versus reduced-tillage systems), cover-crop based vegetable rotations with forage harvest of aboveground cover crop biomass, and vegetable crops in rotation with short-term perennial grass and legume species. Measures of soil quality (total carbon (C), total nitrogen (N), particulate organic matter C and N (POM-C, POM-N, and permanganate oxidizable-C (POx-C)) generally indicated improved soil quality during two years of perennial forage production as compared to vegetable production with conventional tillage, whereas soil quality from the reduced tillage vegetable system was intermediate. Soil quality gains from forage production were relatively short-lived following rotation to vegetable production with conventional tillage; total C in forage-vegetable rotation systems was higher than continuous vegetable production one year following transition (12.7 vs. 11.8 g C kg^-1 soil, respectively), but statistically similar two years post transition. A similar trend was observed for total N and POx-C. Data on cover crop, forage, and vegetable crop performance will be presented.