Conservation management practices reduce non-point source pollution from grazed pastures

Authors: Ashworth, Amanda; Moore, Philip; Pote, Daniel; Owens, Phillip; Martin, Jerry; ANDERSON, KELSEY - University Of Arkansas

Submitted to: Heliyon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2021
Publication Date: 2/10/2021
Publication URL: https://handle.nal.usda.gov/10113/7277409
Citation: Ashworth, A.J., Moore Jr, P.A., Pote, D.H., Owens, P.R., Martin, J.W., Anderson, K. 2021. Conservation management practices reduce non-point source pollution from grazed pastures. Heliyon. 7(2). Article e06238. https://doi.org/10.1016/j.heliyon.2021.e06238.
DOI: https://doi.org/10.1016/j.heliyon.2021.e06238

Interpretive Summary: Water quality impairment from poultry litter applications on pastures in Northwest Arkansas has resulted in several ongoing lawsuits between Oklahoma and Arkansas. Consequently, cow-calf and hay producers need new strategies for safely and sustainability applying poultry litter to pastures. Researchers evaluated two potential practices for reducing nutrient losses in water runoff compared to surface applications under grazing conditions. The first practice that was evaluated was sub-surface applying litter beneath the soil surface into bands, and the second or pasture aeration (also known as renovators) is a device that punches holes in the soil surface using mechanical-disturbance. Thereafter, surface water runoff was collected for 5 years and nutrients were quantified. Major nutrients (nitrogen and phosphorus) were reduced 34-51% by aerating pastures over the 5 year study period. While, sub-surface applying poultry litter decreased nutrients 58-81%, relative to surface poultry litter applications. Therefore, sub-surface applying poultry litter and pasture aeration are effective management options for producers interested in reducing nutrient losses from pastures while improving forage yields.

Technical Abstract: Producers in Northwest Arkansas need alternative management practices to ensure long-term sustainable and economical use of poultry litter, an abundant source of valuable nitrogen (N) and phosphorus (P). Project objectives were to identify the efficacy of best management practices (BMPs; i.e., pasture aeration and subsurface litter incorporation) to reduce nutrient runoff compared to poultry litter surface applications from small watersheds under rainfed conditions. Watersheds (0.23 ha each) were assigned a treatment [pasture aeration, litter incorporation, or surface application of litter (control)] on a Leadvale (fine-silty, siliceous, thermic Typic Fragiudult) silt loam under grazed conditions. Poultry litter was applied annually to all plots at variable rates (2.3-3.6 Mg ha-1) from 2007-2011. Over the 5-yr study period, runoff loads of NO3-N, total nitrogen (TN), soluble reactive phosphorus (SRP), and total phosphorus (TP) varied per conservation management treatment (P=0.05). Specifically, NO3-N, TN, SRP, and TP loads were reduced 51, 46, 28, and 34% following pasture aeration and by 81, 74, 58, and 61% from subsurface applying poultry litter, relative to surface poultry litter applications, respectively. However, conservation management practices did not reduce (P=0.05) runoff loads of ammonium (NH4+), total suspended solids (TSS), and total organic carbon (TOC) relative to surface poultry litter applications. Overall, subsurface banding poultry litter and pasture aeration are promising BMPs for improving forage yields and water quality while reducing non-point pollution in watersheds with nutrient imbalances.