Publication history: Accepted - 26 May 2021; Published online - 12 August 2021.Minimizing slurry phosphorus (P) losses in runoff requires careful management in the context of both soil P surpluses and changing patterns in rainfall.
Increasing the time interval between slurry application and the first rainstorm
event is known to reduce P loss in runoff although the risk period for elevated
P concentrations in runoff can extend for weeks. This study investigated the impact of increasing the time interval between slurry application and first rainstorm
event on P concentrations in runoff. Simulated rainfall (40 mm h−1) was applied
at 2, 4, 10, 18, 30 and 49 days after dairy slurry was surface-applied to a grassland
sward in Ireland. Increasing time to runoff resulted in a decrease in dissolved
reactive P concentrations from 5.0 to 1.0 mg P L−1 and a P signal in runoff for
18 days. Beyond 18 days, elevated P concentrations were observed in runoff collected from natural rainfall that preceded the day 49 rainstorm event. A published surface phosphorus and runoff model (SurPhos) was used to understand
the slurry P dynamics controlling P interactions with runoff. Dissolved reactive P
in runoff was predicted with accuracy by SurPhos, R2
= .89. The SurPhos model
implied thatslurry P mineralization occurred during the experimental period that
resulted in a small spike in P concentrations beyond the defined risk period. This
study shows that the experimental data have the potential to be extrapolated to
different weather scenarios using SurPhos and could test when and where slurry
P could be most safely spread.Open access funding provided by IReL.
WOA Institution: University College
Dublin Blended DEAL: IReL
