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Contributions of systematic tile drainage to watershed scale phophorus transport
- King, Kevin W., Williams, Mark R., Fausey, Norman R.
- Journal of environmental quality 2015 v.44 no.2 pp. 486-494
- Algae, algal blooms, application rate, best management practices, ecosystem services, fields, freshwater, losses from soil, phosphorus, spring, streams, summer, surface water, tile drainage, water pollution, watersheds, winter, Ohio
- Phosphorus (P) transport from agricultural fields continues be a focal point for addressing harmful algal blooms (HABs) and nuisance algae in freshwater systems throughout the world. In humid, poorly drained regions, attention has turned to P delivery through subsurface tile drainage. Research on the contributions of tile drainage to watershed scale P losses, however, is limited. The objective of this study was to evaluate P movement through tile drainage and its manifestation at the watershed outlet. Hydrology, along with associated P concentrations were collected for 8 years (2005-2012) from 6 tile drains and the watershed outlet of a headwater watershed within the Upper Big Walnut Creek watershed in central Ohio, USA. Results showed that tile drainage accounted for 51% of the discharge, 47% of the dissolved P, and 43% of the total P exported from the watershed. Average annual total P loss from the watershed was 0.98 kg/ha and annual total P loss from the 6 tile drains equaled 0.48 kg/ha. Phosphorus loads in tile and watershed discharge tended to be greater in the winter and spring, while P concentrations were greatest in the summer. Over the 8 year study, P transported in tile drains represented less than 2% of application rates and greater than 90% of all measured concentrations exceeded recommended levels (0.03 mg/L) for minimizing HABs 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 application rates, development and implementation of best management practices must jointly consider both economic and environmental benefits.