The efficacy of good practice to prevent long-term leaching losses of phosphorus from an irrigated dairy farm

We measured P fractions in leachate at 70cm depth from two soils of low-P sorption capacity in an intensively grazed dairy farm. In response to best-practice annual applications of P as either fertiliser or a lower rate of fertiliser plus FDE, dissolved and particulate P concentrations increased annually 4% to 7%. Mean total P load over 14 years (2001–2015) from the FDE-treated, free-draining shallow soil was 1.46 kg ha‚àí1 yr‚àí1, much greater than the same soil without FDE (0.25 kg ha‚àí1 yr‚àí1) or the moderately well-drained soil with or without FDE applied (0.12 kg ha‚àí1 yr‚àí1, for both treatments).