The Cross Timbers region of north-central Texas, especially the Bosque River Drainage, has a heavy concentration of large dairies. These dairies produce large quantities of effluent, manure and a more easily transported product, manure compost, which can be effectively utilized as a crop fertilizer and soil organic matter enhancer. Properly managed, these products can provide dairies with closed phosphorus and nitrogen nutrient cycles that avoid contaminating surface and sub-soil water. Our research and extension program has undertaken a series of forage studies that determined the P uptake capabilities of these species when moderate amounts of manure compost were incorporated in to soil.

A group of Dairymen (Bosque & Leon Rivers), Agricultural Experiment Station, Texas Cooperative Extension, and Tarleton State University have formed a team to tackle this issue. Funding for this effort has come from two sources:

• EPA 319h through the Texas State Soils & Water Conservation Board. "Vegetative strategies for soil phosphorus reduction and subsequent reduced phosphorus runoff from land receiving dairy manure on the north Bosque River".
• USDA National Integrated Research, Education and Extension Projects. "Strategies for soil phosphorus reduction and subsequent reduced phosphorus runoff from land receiving dairy manure on the north Bosque and Leon Rivers."

These two funding sources support research, outreach and education efforts that look at the entire dairy in an effort to reduce phosphorus losses to the environment. They also support efforts to remediate soils that are already excessively high in phosphorus. The team includes:

1. Three dairies
2. Dr. Barry Lambert (TSU/TAES), dairy nutritionist
3. Dr. Tamilee Nennich (TCE/TAES), dairy nutrient management
4. Dr. Jeff Tomberlin (TCE/TAES), livestock entomologist
5. Dr. David Weindorf (TSU/TAES), soil nutrient management
6. Dr. Jim Muir (TAES), phytoremediation through forage systems
7. Dr. Yoana Newman (TCE), dairy forage systems
8. Dr. Roger Wittie (TSU), native buffer strips
9. Dr. Mark Yu (TSU), P system modeling
10. Dr. Saqib Mukhtar, surface water P runoff

The figure right illustrates our "whole farm" approach to improving dairy waste management.

The results we have on phytoremediation, to date, are summarized in an article that takes a critical look at exact land area requirements (LAR) that dairies and other livestock concentrated/confined animal feeding operations (CAFO) require for distribution of their manure.

• J.P. Muir, S.R. Stokes, T.J. Butler and R.M. Jones. 2001. Selecting forage systems to improve phosphorus cycling within confined animal feeding operations. Proc. American Forage and Grassland Council, Springdale AR, April 22-25, 2001. 10:252-256.

Despite careful management, some fields around CAFO´s end up with excessive phosphorus loads that run the danger of contaminating surrounding bodies of surface water. Anything over 200 ppm (parts per million) of water-soluble phosphorus is considered excessive by environmental agencies. When this happens, phytoremediation (the use of plants to correct soil problems) based on forage production may be the key to correcting this imbalance. The amount of phosphorus removed from the soil is a product of forage yield and forage-P concentration. Although there is no direct correlation, soil-P removal by plants should eventually lower the laboratory soil analysis plant-available-P readings.

Our studies looking at soil-P removal by forages under irrigation include:

• Muir, J.P., S.R. Stokes and E.P. Prostko. 1999. Corn variety performance at Stephenville under irrigation as affected by manure application. Forage Research in Texas http://overton.tamu.edu/frt/.
• Muir, J.P., S. Stokes and E. Prostko. 2001. Production, quality and phosphorus uptake of summer annual grasses grown as alternative silages with diary compost. Prof. Animal Scientist 17:90-94.

• Muir, J.P., S. Stokes and E. Prostko. 2001. Production, quality and phosphorus uptake of summer annual dicots grown as alternative silages with diary compost. Prof. Animal Scientist 17:95-100.

Dryland forage production systems remove soil-P more slowly because yields are lower. Our studies have looked at higher quality legumes and forbs although dryland grass systems would likely remove greater amounts of soil-P. We are currently looking at phosphorus recycling potential of mixed switchgrass/winter legume systems and the following information is already available:

• Muir, J.P. 2001. Effect of dairy compost application, variety and stand age on kenaf forage yield, nitrogen content and phosphorus uptake. Agron. J. 93:1169-1173.

Kenaf is both productive and high in phosphorus.

• Muir, J.P. Forage and seed production from annual and short-lived perennial warm-season legumes fertilized with dairy compost. Crop Science.

Dryland summer annual legumes, such as this velvetbean, are high in P but not very productive. Turfgrass production requires the removal of some topsoil when turf is removed. This makes it an ideal medium for the removal of surface-applied manure that then enhances turf growth and nutrition for years to come.

• Vietor, D.M., E.N. Griffith, R.H. White, T.L. Provin, J.P. Muir, and J.C. Read. 2002. Export of manure phosphorus and nitrogen in turfgrass sod. Journal of Environmental Quality 31: 1731-1738.

Switchgrass makes for a strong, well-rooted filter strip in Texas bottomlands.

The use of filter strips (also called buffer strips) to slow down the run-off of surface-applied manure-P is a way of avoiding contamination of surface water.

• Sanderson, M.A., R.M. Jones, M.J. McFarland, J. Stroup, R.L. Reed and J.P. Muir. 2001. Nutrient movement and removal in a switchgrass biomass-filter strip system treated with dairy manure. J. Environmental Quality 30:210-216.

Feedlots also benefit from tightened management of manure nutrients.