Evaluation of Organic Forage Production Systems for the Southeast.

There is increasing interest in the Southeast in organic dairy and other organic grazing livestock production as a way to increase the viability of family farms. However, there is limited research and extension information derived from studies in organic systems from this region to help conventional farmers transition to organic or to help beginning farmers establish their operations. This is especially true in the area of forage management for organic livestock producers, an important issue considering that the USDA National Organic Program specifies that 30% of dry matter intake for dairy cows or other ruminant livestock must be supplied through grazing, and that animals must graze throughout the length of the grazing season. While there has been extensive forage research in the U.S. Southeast, recommendations derived from this research are of questionable relevance to organic producers considering that studies have been largely conducted under conventional management with the use of herbicides for weed control and ample readily-soluble conventional fertilizers. In Fall 2010, we established a randomized complete block plot experiment with four replicates at The University of Tennessee’s Organic Crops Unit to evaluate the performance of forage species and mixtures under organic management.  Forage systems evaluated included four perennial mixtures and one mixture of warm and cool-season annuals: (1) alfalfa (Medicago sativa L.) monoculture, (2) red clover (Trifolium pratense L.) monoculture, (3) alfalfa-orchardgrass (Dactylis glomerata L.) mix, (4) red clover-orchardgrass mix, and (5) wheat (Triticum aestivum L.)-crimson clover (Trifolium incarnatum L. ) mix followed by sorghum-sudangrass (Sorghum bicolor x S. bicolor var. sudanense (Piper) Stapf.). Forages were seeded in early October 2010 at the highest seeding rates within the range of rates recommended by the University of Tennessee (as is common practice among organic producers) and managed according to USDA National Organic Program Guidelines. At the first forage harvest in mid-April 2011, herbage yield was highest from the wheat-crimson clover (5,752 kg dry matter ha^-1) and red clover-orchardgrass mixtures (4,518 kg ha^-1), intermediate from the alfalfa-orchardgrass mixture and red clover monoculture (3,522 and 2,804 kg ha^-1, respectively), and least from the alfalfa monoculture (637 kg ha^-1). Alfalfa production was greatly reduced at the first harvest due to incidence of sclerotinia stem and crown rot (Sclerotinia trifoliorum). At the second harvest in early June 2011, herbage yield was highest in the red clover monoculture (3,452 kg ha^-1) which was statistically similar to the red clover-orchardgrass mixture (3,274 kg ha^-1) and greater than the alfalfa monoculture (3,075 kg ha^-1) or alfalfa-orchardgrass mixture (2,934 kg ha^-1). The proportion of nonsown species in herbage dry matter was similar among perennial mixtures at the first harvest, with 36 to 52% of dry matter accounted for by nonsown species (primarily annual ryegrass (Lolium multiflorum Lam.), but also henbit (Lamium amplexicaule L.) and common sowthistle (Sonchus oleraceus L.)). In contrast, less than 2% of dry matter was attributable to nonsown species in the wheat-crimson clover mixture. At the second harvest, the percentage of nonsown species remained high in the alfalfa-orchardgrass and red clover-orchardgrass mixtures (~ 58% of dry matter), but was greatly reduced in the alfalfa and red clover monocultures (< 10% of dry matter). Forage quality, soil fertility, and soil quality analyses are ongoing and will be reported.