Minimising Phosphorus in Waterways

Most farmers work hard to manage the water quality on their properties. They change grazing arrangements, manage their fertiliser applications, fence riverbanks and wetlands, plant trees and place sediment traps.

Dairy farm fertiliser effluent contains phosphorus that may enter freshwater from run off or leaching from paddocks. Although phosphorus is essential for plant growth and crucial for food security, it leaves a devastating footprint on the environment. A key ingredient in synthetic fertilisers, the damaging impacts are seen when phosphorus contaminates lakes, rivers and (ultimately) the ocean. Phosphorus can encourage the growth of algae in fresh water that pollute and degrade the health, mauri and wairau of our water. It means our waters may not be suitable for swimming, fishing and drinking, and affects its biodiversity.

The good news is, however, that in many areas the amount of phosphorus in our waterways is declining. All farmers should minimise the impact of phosphorous leaching by stock exclusion, creating riparian buffers, undertaking planting and preventing runoff from critical source areas.

The National Policy Statement for Freshwater Management (NPS-FM 2020) provides guidelines for monitoring and managing dissolved reactive phosphorus in rivers and how freshwater should be managed. Farmers are recommended to apply phosphorus to paddocks only if necessary. An increase in plant productivity could lead to a decrease in run off and less erosion. Using a phosphorus index ensures you can find paddocks that have high potential for phosphorus loss and therefore avoid using that fertiliser.

DISCLAIMER: All the information published is true and accurate to the best of the authors’ knowledge. It should not be a substitute for legal advice. No liability is assumed by the authors or publisher for losses suffered by any person or organisation relying directly or indirectly on this article. Views expressed are those of individual authors, and do not necessarily reflect the view of this firm. Articles appearing in this newsletter may be reproduced with prior approval from the editor and credit given to the source. Copyright, NZ LAW Limited, 2019. Editor: Adrienne Olsen. E-mail: adrienne@adroite.co.nz. Ph: 029 286 3650 or 04 496 5513.