Long-Term effects of grazing management and buffer strips on phosphorus runoff from pastures fertilized with poultry litter

Authors: KELSEY, ANDERSON - University Of Arkansas; Moore, Philip; PILON, CRIS - University Of Georgia; Owens, Phillip; Ashworth, Amanda; MILLER, DAVID - University Of Arkansas; DELAUNE, PAUL - Texas A&M Agrilife

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2019
Publication Date: 2/27/2020
Publication URL: https://handle.nal.usda.gov/10113/6937386
Citation: Kelsey, A.R., Moore Jr, P.A., Pilon, C., Owens, P.R., Ashworth, A.J., Miller, D., Delaune, P. 2020. Long-Term effects of grazing management and buffer strips on phosphorus runoff from pastures fertilized with poultry litter. Journal of Environmental Quality. 49:85-96. https://doi.org/10.1002/jeq2.20010.
DOI: https://doi.org/10.1002/jeq2.20010

Interpretive Summary: Phosphorus runoff from pastures can cause pollution of surface waters that leads to algal blooms. However, few long-term studies have been conducted on the effects of best management practices, such as rotational grazing and/or buffer strips on P losses from pastures. The objective of this study was to evaluate long-term effects of grazing management and buffer strips on P runoff from pastures receiving annual poultry litter applications. A 15-yr study was conducted on 15 watersheds with five treatments: hayed, continuously grazed, rotationally grazed, rotationally grazed with an unfertilized buffer strip, and rotationally grazed with an unfertilized fenced riparian buffer. The average annual runoff volumes from hayfields and riparian buffer strips were lower than continuously grazed and rotationally grazed pastures. Runoff volumes, phosphorus runoff concentrations and loads were higher in years with more rainfall. Rotational grazing alone did not reduce phosphorus compared to continuous grazing. However, phosphorus runoff was reduced by 36% with unfertilized buffer strips, 60% with unfertilized fenced riparian buffer strips, and 49% by converting pastures to hayfields. Hence, the use of unfertilized buffer strips, unfertilized fenced riparian buffer strips, or converting pastures to hayfields are effective BMPs for reducing P runoff in Southeastern U.S. pasture systems.

Technical Abstract: Phosphorus (P) runoff from pastures can cause accelerated eutrophication of surface waters. However, few long-term studies have been conducted on the effects of best management practices (BMPs), such as rotational grazing and/or buffer strips on P losses from pastures. The objective of this study was to evaluate long-term effects of grazing management and buffer strips on P runoff from pastures receiving annual (5.6 Mg ha-1) poultry litter applications. A 15-yr study was conducted on 15 watersheds with five treatments: hayed (H), continuously grazed (CG), rotationally grazed (R), rotationally grazed with an unfertilized buffer strip (RB), and rotationally grazed with an unfertilized fenced riparian buffer (RBR). Average annual runoff volumes from H (40 mm yr-1) and RBR (48 mm yr-1) were lower than CG and RB, which were both 65 mm yr-1, and from R (67 mm yr-1). Runoff volumes, P runoff concentrations and loads varied annually concurrent with trends in precipitation. Rotational grazing alone did not reduce P loads compared to continuous grazing (1.88 and 1.71 kg P ha-1 for R and CG, respectively). However, total P losses from RB pastures were reduced 36% with unfertilized buffer strips (1.21 kg P ha-1), 60% in RBR watersheds with unfertilized fenced riparian buffer strips (0.74 kg P ha-1), and 49% by converting pastures to hayfields (0.97 kg P ha-1). Hence, the use of unfertilized buffer strips, unfertilized fenced riparian buffer strips, or converting pastures to hayfields are effective BMPs for reducing P runoff in Southeastern U.S. pasture systems.