Twelve winter cover crops were planted in Citra and Live Oak, FL, in 2004, to evaluate their potential for use as living mulches in organic vegetable production: black oat, rye, annual ryegrass, hard fescue, two cultivars of white clover, berseem clover, crimson clover, subterranean clover, arrowleaf clover, barrel medic, and a hybrid disc × strand medic cultivar. The best canopy development and weed suppression occurred with black oat, rye, and annual ryegrass. In 2005, black oat, two rye cultivars, and annual ryegrass were evaluated as living mulches in broccoli at Citra and Live Oak, using organic production methods. ‘Florida 401’ (FL 401) rye was tallest, black oat was intermediate, and ‘Wrens Abruzzi’ (WA) rye and ‘Gulf’ ryegrass were of similar height and were the shortest living mulches. Biomass harvested at 12 and 13 wk after planting at Citra and Live Oak, respectively, was greatest with FL 401 rye. At Live Oak, the three other mulches had similar amounts of biomass; however, at Citra, black oat biomass was greater than that of WA rye, and biomass of ryegrass was lowest. The greatest weed infestation occurred with the weedy control. Weed biomass was highest with the weedy control, intermediate with ryegrass, and lowest with rye and black oat. However, the biomass of the weedy control was lower than that of the living mulches plus any associated weeds. Marketable broccoli yield was highest with the weed-free control. Yields with black oat, WA rye, and ryegrass were similar to that of the weedy control, whereas yield with the FL 401 rye was lower than with the weedy control. Suppression of living mulches by mowing at 3 and 7 wk after planting had no effect on broccoli growth or yield.
Nomenclature: Annual ryegrass, Lolium multiflorum Lam.; arrowleaf clover, Trifolium vesiculosum Savi, barrel medic, Medicago truncatula Gaertn., berseem clover Trifolium alexandrinum L., black oat, Avena strigosa Shreb., broccoli, Brassica oleracea L. var. italica Plenck., cereal rye, Secale cereale L., crimson clover Trifolium incarnatum L., disc × strand medic hybrid, Medicago tornata (L.) Mill. × Medicago littoralis Rohde ex Loisel., hard fescue, Festuca longifolia Thuill., subterranean clover, Trifolium subterraneum L., white clover, Trifolium repens L