Forage, Nitrogen, and Phosphorus Yield Dynamics of Cool-Season Annual Forages Overseeded onto Tifton 85 Bermudagrass

摘要

'Tifton 85' bermudagrass [Cynodon dactylon L. (Pers.) X C. transvaalensis Burt Davy] is a warm-season forage used on southeastern U. S. dairy concentrated animal feeding operations (CAFO). Cool-season annual forages need to be identified that can be overseeded into Tifton 85 and remove the greatest quantity of P or N while minimizing suppression of bermudagrass spring regrowth. During 3 yr we overseeded six grass, five legume, and two Brassica spp. on a dairy CAFO Tifton 85 field on a Windthorst fine sandy loam (fine, mixed, active, thermic Udic Paleustalf) containing 83 mg plant-available P kg(-1) soil. Hairy vetch (Vicia villosa Roth.), barley (Hordium vulgare L.), oat (Avena sativa L.), and rye (Secale cereale L.) yielded the most (entry x year interaction P < 0.05) dry matter (DM) during at least 2 of the 3 yr, with the grasses and some legumes reducing (entry x year interaction P < 0.05) spring first-harvest Tifton 85 DM yields by 41 to 80%. Cumulative cool-season and first-harvest Tifton 85 P yields increased (entry x year interaction P < 0.05) in some combinations and years compared to Tifton 85 alone, while N yields rose up to 173% when legumes were overseeded, depending on year and combination (entry x year interaction P < 0.05). Results indicate that overseeding some cool-season winter annual forage species onto dormant Tifton 85 can increase N for CAFO feed but only occasionally will it improve P removal.