Overseeding Cool-Season Forages In Coastal Burmudagrass Pastures On Dairies In North Central Texas to Recycle Phosphorus.

Dairies in north-central Texas containing high-phosphorus soils resulting from the application of waste water and manure can recycle nutrients by over-seeding Coastal bermudagrass (Cynodon dactylon (L.) Pers.) fields with cool-season annual forages. Ryegrass (Lolium multiflorum Lam.), barley(Hordeum vulgare L.), rye (Secale cereale L.), triticale (Triticum secale L.), oats (Avena sativa L.), wheat (Triticum aestivum L.), hairy vetch (Vicia villosa Roth), burr medic (Medicago polymorpha L.), arrowleaf clover (Trifolium vesiculosum Savi.), rose clover (Trifolium hirtum All.), crimson clover (Trifolium incarnatum L.), turnips and rape (Brassica spp.) were evaluated for winter forage quality and yields. Species were no-tilled into 1.5 X 5 m plots in early fall of 2004, 2005 and 2006. Cool-season grass and brassica plots received 56 kg ha-1 nitrogen in mid winter. Species were individually harvested in the spring when the cool-season grasses were in boot stage and the forbs flowered. Rainfall totals from October through May were 589 mm in year 1 (2004-2005), 359 mm in year 2 (2005-2006) and 675 mm in year 3 (2006-2007). Dry matter yields and P yields for the cool-season forages over-seeded in Coastal were affected by year x species interaction (P < 0.0001). Cool-season grasses were the most productive in DM yield and P extraction in years 1 and 3 (26 to 41 kg ha-1 P ). Year 2 DM yields were not significant in the Coastal overseed due to lack of sufficient rainfall. Hairy vetch was the most productive legume resulting in an additional 4 to 13 kg ha-1 of P per year. Overall, cool-season forages can extract an additional 2 to 41 kg ha-1 of phosphorus per year in growing seasons that have sufficient rainfall. Bermudagrass production was reduced by over-seeding in year 1 and year 3 (P < 0.0001). Overall, cool-season forages can extract an additional 2 to 41 kg ha-1 of phosphorus per year in growing seasons that have sufficient rainfall. Growing seasons that have sufficient rainfall to grow cool-season annual forages result in a loss of Coastal (10-70%) in the first cutting.