File(s) not publicly available

The potential for phosphorus loss to groundwater from soils irrigated with dairy factory wastewater

journal contribution
posted on 2024-06-21, 03:50 authored by Carolina Lizarralde, Rich McDowellRich McDowell, Leo Condron, Jeffrey Brown
Soils irrigated with phosphorus (P)-rich wastewater can increase the risk of P losses from land to water. We investigated if wastewater-irrigated soils can leach P through the soil profile and enrich groundwater. Soils were sampled annually for 20 years to 7.5 cm depth and for one year to 2.2 and 15 m. A mass balance showed that topsoils >200 mg L‚àí1 Olsen P (and <50% anion storage capacity, ASC) were no longer accumulating P and had very high concentrations of water and CaCl2-extractable P (designed to indicate loss to runoff and leaching, respectively). Samples in five paddocks showed substantial P leaching to 2.2 m, while sampling to 15 m showed leaching to 4.5 m depth. Deeper layers, especially in the 15 m deep cores, had a coarse texture and low capacity to sorb P, which caused high P concentrations (1.9 mg L‚àí1) at one groundwater site. Based on these data preventing soils from reaching the thresholds of 200 mg L‚àí1 Olsen P and 50% ASC is necessary to prevent excessive P losses.


Funded by the New Zealand Ministry for Business, Innovation and Employment's Our Land and Water National Science Challenge (Toitū te Whenua, Toiora te Wai) as part of project Phosphorus Best Practice


Publication date



  • English

Does this contain Māori information or data?

  • No

Journal title

New Zealand Journal of Agricultural Research

Usage metrics


    Ref. manager