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Contributions of Systematic Tile Drainage to Watershed‐Scale Phosphorus Transport
Author(s) -
King Kevin W.,
Williams Mark R.,
Fausey Norman R.
Publication year - 2015
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.04.0149
Subject(s) - tile drainage , watershed , hydrology (agriculture) , environmental science , tile , drainage , phosphorus , soil water , geology , ecology , geography , soil science , biology , materials science , geotechnical engineering , archaeology , machine learning , computer science , metallurgy
Phosphorus (P) transport from agricultural fields continues to be a focal point for addressing harmful algal blooms and nuisance algae in freshwater systems throughout the world. In humid, poorly drained regions, attention has turned to P delivery through subsurface tile drainage. However, research on the contributions of tile drainage to watershed‐scale P losses is limited. The objective of this study was to evaluate long‐term P movement through tile drainage and its manifestation at the watershed outlet. Discharge data and associated P concentrations were collected for 8 yr (2005–2012) from six tile drains and from the watershed outlet of a headwater watershed within the Upper Big Walnut Creek watershed in central Ohio. Results showed that tile drainage accounted for 47% of the discharge, 48% of the dissolved P, and 40% of the total P exported from the watershed. Average annual total P loss from the watershed was 0.98 kg ha −1 , and annual total P loss from the six tile drains was 0.48 kg ha −1 . Phosphorus loads in tile and watershed discharge tended to be greater in the winter, spring, and fall, whereas P concentrations were greatest in the summer. Over the 8‐yr study, P transported in tile drains represented <2% of typical application rates in this watershed, but >90% of all measured concentrations exceeded recommended levels (0.03 mg L −1 ) for minimizing harmful algal blooms and nuisance algae. Thus, the results of this study show that in systematically tile‐drained headwater watersheds, the amount of P delivered to surface waters via tile drains cannot be dismissed. Given the amount of P loss relative to typical application rates, development and implementation of best management practices (BMPs) must jointly consider economic and environmental benefits. Specifically, implementation of BMPs should focus on late fall, winter, and early spring seasons when most P loading occurs.