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

Abstract

‘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 × year interaction P < 0.05) dry matter (DM) during at least 2 of the 3 yr, with the grasses and some legumes reducing (entry × 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 × 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 × 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.