Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/28/2011
Publication Date: 10/16/2011
Citation: Zhu, Q., Schmidt, J.P., Bryant, R.B. 2011. Hot moments and hot spots of nutrient losses from a mixed land use watershed[abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. Paper No. 138-10. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: Non-point nitrogen (N) and phosphorus (P) pollution from agriculture has increasingly received more public attention. However, when, where and how N and P export occurs from a watershed is not completely understood. In this study, nitrate-N, dissolved P (DP) and particulate P (PP) concentrations and loads were investigated for four sub-basins (labeled 1 to 4 going up the watershed) within a mixed land use watershed (39.5 ha) in the Appalachian Valley and Ridge Physiographic Province. Greater nitrate-N concentration and load were observed in base flow and during the non-growing season than in storm flow and during the growing season. The nitrate-N concentrations in base flow and during the non-growing season were about 1.1-1.7 and 1.2-1.9 times of those in the storm flow and during the growing season, respectively. Dissolved P and PP concentrations (about 0.03 mg per L for both DP and PP) and loads (0-0.3 kg per month for both DP and PP) were low and temporally consistent in base flow at all flumes, but high and temporally variable in storm flow. The DP concentration and load were great from May to Dec. (greater than 0.08 mg per L in storm flow) and from Sept. to Nov. (generally greater than 0.25 kg per month in storm flow), respectively, while the PP concentration and load were great from Jan. to June (greater than 0.30 mg per L and greater than 0.4 kg per month in storm flow). The nitrate-N, DP, and PP loads were compared for all four sub-basins on a loss per length of stream reach basis). The greatest nitrate-N loads were observed in Sub-basins 1 and 4 during the non-growing season base flow period and in Sub-basin 2 during post-growing season base flow period (greater than 110 g per meter per month). The greatest DP loads were also observed in Sub-basins 1 and 4, but during the growing and post-growing season storm flow period (greater than 1.4 g per meter per month). In contrast, the PP load was the greatest in Sub-basin 3 during the pre-growing and growing season storm flow, as much as 13.4 and 14.1 g per meter per month, respectively. Controlling factors of nutrient export were discussed in this study, including season, hydrology (base flow, storm flow, surface and subsurface runoff) and land use. Although different hot moments and hot spots within the watershed were identified for nitrate-N, DP, and PP losses, the implementation of a couple of management practices (cover crops and no-till) might still be efficient to reduce nutrient losses from this and similar Valley and Ridge watersheds.