Forage Performance and Soil Quality in Forage Systems under Organic Management in the Southeastern United States

Interest is increasing in organic forage production and sod-based rotations in the southeastern United States, but research-based information is limited. A replicated field study was established to evaluate productivity and soil quality changes in five organically-managed forage systems over 2 yr. Systems included four regionally-adapted perennial systems and one warm- and cool-season annual rotation: (i) alfalfa (Medicago sativa L.), (ii) red clover (Trifolium pratense L.), (iii) alfalfa/orchardgrass (Dactylis glomerata L.), (iv) red clover/orchardgrass, and (v) an annual system of wheat (Triticum aestivum L.)/crimson clover (T. incarnatum L.) followed by sorghum-sudangrass [Sorghum bicolor x S. bicolor var. sudanense (Piper) Stapf.]. Soil quality was compared to two annual vegetable systems, one managed organically and one managed conventionally. Poultry litter was applied to organically-managed systems in September 2010 (9 Mg ha(-1)) and in September 2011 (4.5 Mg ha(-1)). Mean annual forage yield was greatest from wheat/crimson clover and sorghum-sudangrass (12.4 Mg ha(-1) yr(-1)), intermediate from red clover, red clover/orchardgrass, and alfalfa/orchardgrass (10.0-10.3 Mg ha(-1) yr(-1)), and least from alfalfa (7.6 Mg ha(-1) yr(-1)). Soil C (total and particulate organic matter-C) increased over 2 yr in all forage systems which were similar, and was in most cases significantly lower in vegetable systems. Soil N (total and particulate organic matter- N) increased in all forage systems and was highest in alfalfa and treatments containing red clover, and lowest in vegetable systems. Results suggest these short-term forage systems are viable options for regional organic rotations.