|MARTIN, JAY - The Ohio State University
|BROWN, LARRY - The Ohio State University
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2017
Publication Date: 2/1/2018
Citation: Pease, L.A., Fausey, N.R., Martin, J.F., Brown, L.C. 2018. Weather, landscape, and management effects on nitrate and soluble phosphorus concentrations in subsurface drainage discharge in the western Lake Erie basin. Transactions of the ASABE. 61 (1): 223-232.
Interpretive Summary: Harmful algal blooms such as those seen in Lake Erie and the Gulf of Mexico have drawn attention to the need to reduce nutrient loss from agricultural land. In the Western Lake Erie Basin, subsurface drainage is used to make land productive for growing crops. However, it is also a major contributor of agricultural nutrient loss. Nutrient loss varies greatly due to variations in weather, soil properties, and farm management. Water quality data from multiple drainage outlet sites in northwest Ohio showed that fertilizer application rate and timing have the strongest impact on agricultural nutrient loss to subsurface drains. Farmers must follow fertilizer recommendations and practice nutrient stewardship principles such as the '4R' management strategy to reduce risk of off-site nutrient loss. Results also showed that different nutrients move differently through the soil to reach underground drains. Strategies that work to reduce loss of one nutrient may not work for others, so farmers should stack conservation management practices for maximum water quality protection.
Technical Abstract: Subsurface drainage, while an important and necessary agricultural production practice in the Midwest, contributes nitrate (NO3) and soluble phosphorus (P) to surface waters. Eutrophication (i.e., excessive enrichment of waters by NO3 and soluble P) supports harmful algal blooms (HABs) in receiving waters. The magnitude of NO3 and soluble P loss in subsurface drainage varies greatly by landscape, weather, and field management factors. This study evaluated both the relative and combined impact of these factors on observed NO3 and soluble P concentrations in subsurface drainage water in the Western Lake Erie Basin watershed. Water quality data from multiple drainage outlet sites in northwest Ohio provided evidence that the primary management factors affecting NO3 and soluble P loss were the amount and time of fertilizer application. Results strongly support following Tri-State fertilizer recommendations and ‘4R’ nutrient stewardship principles to reduce risk of NO3 and soluble P loss. Results also provided evidence of NO3 and soluble P transport to subsurface drains via different pathways. Due to differences in NO3 and soluble P transport through the soil profile (via baseflow or via preferential flow, respectively), management approaches taken to reduce one nutrient may exacerbate losses of the other. Further research is needed to address potential changes in field hydrology (and consequently the in-field transport of soluble nutrients) from different types of Best Management Practices (BMPs), and to evaluate optimal stacking of BMPs to achieve reductions in both NO3 and soluble P loss. Controlled drainage has a high potential for stacking with other BMPs because it is primarily a physical discharge and load reduction practice.