Environment Canterbury (Ecan) has commissioned the large-scale project, aiming to use leaching numbers as regulatory triggers across the region by 2017.
Nine other councils from around the country are also looking at the matrix and are putting up funding to resource it.
ECan director of investigations and monitoring, Ken Taylor, said all up it’s costing about $3 million over two years with some of that cost also being met with in-kind support from industry organisations such as DairyNZ through the use of scientists’ time. While the data included in the matrix might not be relevant to the soils and climates of other regions, other councils are interested in the process behind it and being able to use it for their own situations without having to start from scratch.
The MGM project first had to determine the leaching loads under current farming practices and then what’s possible under good management practice. Importantly that’s meant defining exactly what good management practice includes.
Taylor said about 200 dairy farmers’ data has been used in the project to give robustness to the outcomes.
A range of companies and organisations now collect nutrient information on farms but privacy issues in using it were a factor taken seriously by the project’s governors and managers.
A strict anonymity protocol was used to protect farmers’ identity, Taylor said.
A reference group including farmers as well as industry and non-industry experts has been established to “tyre kick” the definitions in terms of good management practice and outputs of the matrix and a scientific peer review-type process will also take place, he said.
The MGM will essentially be a table including farm type, soils and climate associated with nitrate and phosphorus losses.
DairyNZ senior scientist, Ina Pinxterhuis, is leading much of the project for dairying with other farming sectors such as arable and sheep and beef running parallel processes. She said the categories are likely to be broken down further for dairying to accommodate the array of farm systems used in the sector.
For instance, a high-input farm operating at good management practice level could have a different leaching profile to that of a low-input farm also operating using good management even though they are on the same soil type with the same climate.
A lot of work was currently going on to establishing how farms could best be categorised. Researchers were also putting effort in to determining how to group soils and climate information given the range in rainfall, elevation, soil types and soil moisture holding capacities across Canterbury.
“We could literally have thousands of different combinations but that makes it too unwieldy so we have to work out what we can put together and still get outputs that are fair and realistic under good management practice.”
Taylor said farmers unhappy with their MGM number do have a means of redress when they’re released, likely to be later next year.
“If you don’t believe your number, absolutely we want to hear from you. We want to know your views.”
The inclusion of farmers in the reference group and significant involvement of industry groups such as DairyNZ and Federated Farmers on the governance group should minimise any major disagreement though.
Taylor applauded the primary sector’s efforts and willingness to be involved in the project.
“Their attitude is one of – well, if limits are going to be set we want to be involved in that process.”
But farmers have been concerned at the reliance on the Overseer model in determining good management practice leaching levels because of variability in outputs and some shortcomings in recognising benefits of some practices.
Taylor said the council was continuing to work with Overseer developers and over the next two years a significant amount of work was expected on the model. Model updates would be taken into account.
Overseer will not be the only model involved, with the MGM project using an Australian modelling tool, APSIM, to help calibrate and corroborate Overseer information along with the Farmax model.
ECan commissioner Tom Lambie reiterated the role industry groups and farmers have to play in setting the MGM numbers along with scientists and other experts. He accepted farmers were concerned about Overseer but believed the consensus-type approach being taken would ensure the right outcomes from the project.
“That’s why we have industry involved and at the table,” he said.
“We know we have to take into account farms could have a range of soil types and activities. We’ve recognised that and over the next 14-15 months we’ll have a robust table that takes account of those variables.”
