Environment Canterbury (ECan) is currently trying to define GMP through its Land and Water Regional Plan which will likely incorporate the ECan’s Matrix of Good Management (MGM).
The MGM is an attempt to create a level of certainty around land use practices and environmental outcomes like nitrogen leaching and phosphorous losses expected under GMPs.
At Massey University’s Fertilizer and Lime Research Centre’s annual workshop in late February, Landcare Research scientist Dr Linda Lilburne, part of the MGM development team, explained some of the issues facing ECan.
“There is no consensus on the GMPs within, but particularly across, the different sectors,” she said.
“And then the impact of good management on nutrient losses is unknown.”
Lilburne said the purpose of the MGM was to determine expected nutrient losses under industry-agreed good management practices across the range of soils, climates and land uses around Canterbury.
“The two primary purposes – one, is for ECan to be able to assess cumulative nitrogen loads in any given catchment; and two, for farmers to be able to assess their environmental performance.”
Collaboration was very important in the development of the MGM.
“The GMPs will be agreed by consensus, and they will be agreed with the farmers,” she said.
“Farms must be environmentally and financially sustainable under the GMPs.”
The MGM will take the form of a lookup table with the first column having soil types, the next column rainfall bands and another column representing farm types.
Lilburne said a lot of work would go into characterising and differentiating the farm types. The various combinations of these factors will generate corresponding values for drainage below the root zone, nitrogen and phosphate losses.
“The important thing is that these numbers do not in themselves define policy,” she said.
“They are used to support the collaborative processes in each zone. There are zone committees who will be tasked with developing policy that is appropriate to their zone, depending on whether they are under-allocated or over-allocated.”
Development of ECan’s MGM is still in its early stages with Lilburne saying the team was in the process of collecting information about what farmers were currently doing onfarm, which would then be entered into Overseer to model nutrient losses for these real farms.
The next step was to apply the industry-agreed GMPs to those farms then model the nutrient losses again to see the difference between current practices and GMP. The MGM is scheduled to be completed by July next year.
