Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2016
Publication Date: 3/17/2017
Publication URL: https://handle.nal.usda.gov/10113/5661752
Citation: Lizotte Jr, R.E., Yasarer, L.M., Locke, M.A., Bingner, R.L., Knight, S.S. 2017. Lake nutrient responses to integrated conservation practices in an agricultural watershed. Journal of Environmental Quality. 46:330-338. https://doi.org/10.2134/jeq2016.08.0324.
Interpretive Summary: As we continue to work to reduce nutrient loads and improve water quality through the use of agricultural best management practices (BMPs), we need to better understand how effective these BMPs are within an entire watershed. To address this, we collected lake nutrient measurements of total phosphorus, soluble reactive phosphorus, ammonium, and nitrate in Beasley Lake, a Conservation Evaluation Assessment Program watershed in the Mississippi Delta from 1996 to 2009. We observed how a variety of BMPs in the watershed changed lake nutrient concentrations. BMPs put in place from 1997-2006 included within-field, edge-of-field, and Conservation Reserve Program (CRP) practices. Over the 14 years we studied lake nutrient concentrations, the lake had lower total phosphorus, ammonium, and nitrate concentrations coinciding with the amount of BMPs put in place and these changes were seen most strongly during spring. Our study showed that BMPs put in place reduced nutrient loads, improved lake water quality, and will help make a healthier, more sustainable lake. These results are of interest to regulatory and other agencies and farming stakeholders by providing additional information to improve and sustain lake and flood plain water quality and overall environmental quality using conservation practices.
Technical Abstract: Watershed-scale management efforts to reduce nutrient loads and improve conservation of lakes in agricultural watersheds require effective integration of a variety of agricultural conservation best management practices (BMPs). Such efforts require watershed-scale long-term studies assessing nutrients. This study assessed the influence of multiple integrated BMPs on oxbow lake nutrient concentrations in a 915 ha watershed of intensive row-crop agricultural activity during a 14-y monitoring period (1996-2009). A suite of BMPs within fields, at field edges throughout the watershed, and enrollment of 112 ha into Conservation Reserve Program (CRP) were implemented from 1997-2006. Total phosphorus (TP), soluble reactive phosphorus (SRP), ammonium, and nitrate were measured approximately bi-weekly from 1996-2009. Decreases in lake nutrient concentrations occurred after BMP implementation, and clear seasonal trends were observed. Reductions in TP concentrations were greatest during spring and were associated with increased BMPs north of the lake, as well as changes in cotton production. No clear patterns of changes in SRP concentrations were observed. Reductions in ammonium concentrations were greatest during spring in association with conservation tillage and CRP. Reductions in nitrate concentrations were greatest during spring in association with BMPs implemented to the north of the lake. These results present direct evidence of how watershed-wide BMPs assist reducing nutrient loading in aquatic ecosystems and promote a more viable and sustainable lake ecosystem.