Understanding nutrient management on Waikato peat soils

The first step of a new farmer-led programme to better quantify nutrient loss from Waikato peat soils is underway with a long term goal to improve sustainable nutrient management in the region.

AgResearch’s Dr Gina Lucci says peat soils are notoriously difficult to manage because they have high organic matter content, low nutrient levels and water table fluctuations. As a result they behave differently from mineral soils in nutrient transformations and cycling.

Many dairy farmers in the Waikato are facing strict new rules around dairy effluent storage because the peat soils have been classified as having a high risk for effluent irrigation. Furthermore, their management is under the spotlight with the implementation of the National Freshwater Policy Statement.

Dr Lucci, heads the research project and says until now there’s been little research on peat soils in their natural state, and even less on those soils that have been farmed for 50 years or more and which could have changed in composition.

The three-year, $490,000 project is a collaboration with local farmers, the Ministry for Primary Industries through the Sustainable Farming Fund, DairyNZ, Ballance Agri-Nutrients, the Waikato Regional Council and Landcare Research. The goal is to gather significant data from farmed peat soils to quantify the nutrients lost from peat.

“The knowledge gap of how nutrients move through peat soils into waterways has meant that regulators are treating peat in the default position of high risk and that can have significant effect on a farms effluent management requirements,” says dairy farmer and project Chairman Ian Taylor.

“For example the required size of a lagoon in an area of high risk is three to four times the size required in an area of low risk. In this case lack of good science was having a direct effect on farm costs, so we got the project together to get questions answered rather than relying on assumptions.”

“It has been estimated that there are 70 to 90,000 ha of peat soils being farmed in the region,” says project team member and DairyNZ North Waikato Regional Leader Phil Irvine.

“Better knowledge equals better decisions, so understanding how nutrients react in a peat soil environment is key to good soil management. This leads to more efficient fertiliser use and effluent application for these farmers.”

Some of the six farmers will be undertaking field trials during the three-year project.