title: Incidental nutrient transfers: Assessing critical times in agricultural catchments using high-resolution data.
abstract: Managing incidental losses associated with liquid slurry applications during closed periods has significant cost and policy implications and the environmental data required to review such a measure are difficult to capture due to storm dependencies. Over four years (2010-2014) in five intensive agricultural catchments, this study used high-resolution total and total reactive phosphorus (TP and TRP), total oxidised nitrogen (TON) and suspended sediment (SS) concentrations with river discharge data to investigate the magnitude and timing of nutrient losses. A large dataset of storm events (defined as 90th percentile discharges), and associated flow-weighted mean (FWM) nutrient concentrations and TP/SS ratios, was used to indicate when losses were indicative of residual or incidental nutrient transfers. The beginning of the slurry closed period was reflective of incidental and residual transfers with high storm FWM P (TP and TRP) concentrations, with some catchments also showing elevated storm TP:SS ratios. This pattern diminished at the end of the closed period in all catchments. Total oxidised N behaved similarly to P during storms in the poorly drained catchments and revealed a long lag time in other catchments. Low storm FWM P concentrations and TP:SS ratios during the weeks following the closed period suggests that nutrients either weren't applied during this time (best times chosen) or that they were applied to less risky areas (best places chosen). For other periods such as late autumn and during wet summers, where storm FWM P concentrations and TP:SS ratios were high, it is recommended that an augmentation of farmer knowledge of soil drainage characteristics with local and detailed current and forecast soil moisture conditions will help to strengthen existing regulatory frameworks to avoid storm driven incidental nutrient transfers.
authors.affiliation: Agricultural Catchments Programme, Teagasc, Johnstown Castle Environment Research Centre, Wexford, Co. Wexford, Ireland.
authors.forename: Mairead
authors.initials: M
authors.lastname: Shore
authors.affiliation: School of Geography and Environmental Sciences, Ulster University, Coleraine, N. Ireland, United Kingdom.
authors.forename: Phil
authors.initials: P
authors.lastname: Jordan
authors.affiliation: National Centre for Engineering in Agriculture, University of Southern Queensland, Toowoomba, Australia.
authors.forename: Alice R
authors.initials: AR
authors.lastname: Melland
authors.affiliation: Agricultural Catchments Programme, Teagasc, Johnstown Castle Environment Research Centre, Wexford, Co. Wexford, Ireland.
authors.forename: Per-Erik
authors.initials: PE
authors.lastname: Mellander
authors.affiliation: Agricultural Catchments Programme, Teagasc, Johnstown Castle Environment Research Centre, Wexford, Co. Wexford, Ireland.
authors.forename: Noeleen
authors.initials: N
authors.lastname: McDonald
authors.affiliation: Agricultural Catchments Programme, Teagasc, Johnstown Castle Environment Research Centre, Wexford, Co. Wexford, Ireland.
authors.forename: Ger
authors.initials: G
authors.lastname: Shortle
keywords: Catchments; Closed-period; Incidental; Nutrients; Slurry; Water-quality