Nutrient Loss Research Around Lake Rotorua

The Lake Rotorua Primary Producers Collective was formed in 2011 to advance the interests of rural landowners facing major reductions in nutrient losses in proposed plan changes which would challenge the viability of their farm businesses.

Chris and husband Jamie Paterson started farming together as sharemilkers and bought their own 65 hectare farm at Reporoa in 1987. After 1996 they purchased a bare block at Kaharoa and set about converting it to a dairy farm called Hameldaeme (‘Home will do me’). They currently milk 285 cows on 120ha. They have recently been joined in the farm business by their son and daughter in law.

Chris is currently the chairperson of the Kaharoa Community Association, a member of Federated Farmers, Lions and Rural Women NZ but her busiest role at present is secretary for the Lake Rotorua Primary Producers Collective. Chris was awarded the Dairy Women’s Network Community Leadership Award in 2014.

Bay of Plenty Regional Council (BOPRC) has a stated aim to improve water quality in Lake Rotorua. The Lake Rotorua Nutrient Management Proposed Plan Change 10 is seen as a key part of the programme to reduce N from entering the lake thereby achieving water quality improvements.

The sustainable load to Lake Rotorua is currently assessed at 435t Nitrogen per year.

The target is to reduce N into the lake by 320 tonnes a year, down from 755 tonnes.

Under the proposed plan change from 1 July 2017, farming on properties of 40 ha or more will be considered a controlled activity. From July 1 2022, farming properties between 10 & 40ha and properties greater than 5Ha but less than 10Ha that are not ‘low intensity land use’ will all require a resource consent to farm. Land owners will be given a Nitrogen Discharge Allowance (NDA ) which they must meet by 2032. There are intermediate targets that farmers must also meet along the way. A requirement of the consent will be the development of a Nitrogen Management Plan that shows how a landowner will meet the NDA.

The Lake Rotorua Primary Producers Collective grew out of the local Federated Farmers branch as a group to work with BOPRC to advocate for farmers affected by the proposed plan changes. They have 46 members – 27 dairy farmers, 14 dry stock farmers and 5 rural professional associated members. The Collective has actively engaged in debate with other community stakeholders to represent the views of farmer members.

Members of the Collective believe that it is far from certain that dairy farmers in the area could stay viable under the proposed new rules.

Chris says farmers in the area want some certainty around their farming futures. If farming is to be a consented activity within a nutrient cap – they want to be confident that cap is based on robust science. They believe many of the targets being set under the current proposed rule changes are based on science that is by now quite old.

The Collective challenges some of the accepted benchmarks in terms of the loads on Lake Rotorua and wants those loads re-calculated and the terms of reference reopened for consultation. They also want the effects of the phosphorus/nitrogen ratio in the lake reviewed. They are pushing for a scientific review. They say science is still coming up with more information about the biology of the lake.

In particular they want the main regulatory tool – OVERSEER – to be tested and calibrated for their areas. Chris says for most of the last five years while Plan Change 10 was under development, they have relied on Overseer version 5.4 to estimate nitrogen loads both historic and recent, and at both farm-scale and catchment scale. Chris says these figures keep changing as new versions of Overseer are released. The current version is 6.2

Members of the Collective are participating in joint AgResearch, BOP Regional Council and DairyNZ funded research aimed at calibrating high rainfall nutrient loss. The trials have got underway with the placement of lysimiters over paddocks on the Paterson and Butterworth farms. For the next three years, samples from those paddocks will be recorded. This project is run by Stewart Ledgard and his team from AgResearch in Hamilton.

Each trial uses 100 samplers which are buried 60cm below the soil surface. These are used to sample for nutrient as it moves down the soil profile.