Tuesday, November 14, 2006
217-27

Phytoremediation of a High Phosphorus Soil by Summer and Winter Hay Harvest.

Veronica A. Ryan1, Lewis Gaston2, Darren Cooper3, and Matt Stephens1. (1) Louisiana State Univ, AgCenter, Dept of Agronomy and Env Mgmt, 104 Sturgis Hall, Baton Rouge, LA 70803, (2) Louisiana State Univ AgCenter, Dept of Agronomy and Env Mgmt, 104 Sturgis Hall, Baton Rouge, LA 70803, (3) Louisiana State Univ, AgCenter, Calhoun Research Station, Calhoun, LA 71225

Long-term land-applications of poultry litter may results in excessively high soil phosphorus (P).  This study examined the potential of common bermudagrass [Cynodon dactylon(L.) Pers.] overseeded with annual ryegrass [Lolium multiflorum  Lam.] and harvested for hay to reduce the level of soil P that had accumulated in plots of Ruston soil (fine-loamy, siliceous, thermic Typic Paleudult) from six previous applications of poultry litter (0, 5, 10 and 20 Mg / ha; three replicates).  Plots were fertilized with nitrogen or potassium (as needed) without further addition of P.  Across three years after the last litter application and all previous litter rates, ryegrass hay contained a higher percentage of P (0.51 % ryegrass vs. 0.35 % bermudagrass) but ryegrass produced less dry matter (1.31 Mg / ha ryegrass vs. 1.56 Mg / ha bermudagrass).  Taken together, therefore, the data suggest that ryegrass may have equal or greater potential for P uptake / removal than bermudagrass.  While soil test P values (Bray 2) did decrease over all treatments, removal of residual P did not correlate well to soil test P level.   Assuming four harvests each per year, summer bermudagrass overseeded with winter annual ryegrass may lower soil total P by about 50 - 60 mg / ha annually.