Valuing mitigations
A Waikato demonstration farm has discovered the value of its environmental loss mitigations, thanks to MitAgator.After investing in mitigations to better manage its losses to the environment, Owl Farm, a 160 ha demonstration dairy farm beside the Waikato River near Cambridge, wanted to find out the value of these mitigations.
“For the last 4 years, we’ve had quite a dedicated approach to reducing our environmental footprint, and at the same time we’ve looked closely at our business costs, which were about 15 to 20 per cent higher than our business as usual model. So we wanted to find out what we’d generated for our business – the value of our investment,” explains Owl Farm Demonstration Manager Jo Sheridan.
The mitigations that had been implemented on the farm include constructed wetlands and fenced grass buffer strips along streams. Figure 1 provides a map of the already completed mitigations.
Ballance, an industry partner of Owl Farm, is involved in guiding and improving its farm management policies. To this end, Ballance Farm Sustainability Specialist George Hyauiason used MitAgator (see sidebar) to help Owl Farm identify the value of its existing mitigations.
As well as identifying critical source areas and the most effective mitigations to reduce losses, MitAgator can capture the value of completed mitigations. It does this by calculating the reduction in losses for nitrogen (N), phosphorus (P) and sediment, and the reduction in risk for E. coli losses.
On Owl Farm, sediment and E. coli losses pose a low risk overall, due to the primarily flat terrain and fenced waterways. Losses of N and P, however, are greater risks, especially due to the farm’s free draining soils and connectivity to streams flowing directly into the nearby Waikato River.
Loss reductions achieved
MitAgator calculated existing mitigations on Owl Farm have resulted in an 8.5 per cent reduction in N losses (from 41.5 to 38.0 kg/ha/year). This reduction was achieved by fencing waterways, increased effluent pond storage and constructed and natural wetlands.
The areas of highest risk of N loss on Owl Farm are shown in purple on the MitAgator N loss risk map (Figure 2). These are effluent sprayed crop paddocks and an area next to the river on free draining pumice soil, prone to N leaching.
MitAgator calculated Owl Farm’s mitigations have resulted in a 38 per cent reduction in P losses (dropping from 0.44 to 0.27 kg/ha/year). This reduction was achieved by using SurePhos, a slow release P fertiliser which can reduce phosphate loss
by up to 75 per cent relative to superphosphate1, increased effluent pond storage and fenced grass buffer strips along streams.
The MitAgator P loss risk map (Figure 3) shows the areas of greatest P loss risk (pink and purple) are steeper slopes. Moderate P loss risk areas (green) are on pumice soil or planted with summer brassica crops. This is due to the pumice soil’s propensity to P loss, and the summer brassica crop area being vulnerable to soil compaction and soil and associated P loss.
A decision making tool
“We had been using Overseer as a model in the past, but it just gives you numbers. When you see your farm in an almost three dimensional model, it actually relates what you see to how you tangibly manage the land – it brings Overseer alive,” says Jo.
“As a demonstration farm, MitAgator provides really nice visuals to help us talk about our strategies when we’re talking to our farm team or others.
“MitAgator has helped us explain our investment to date, but we’re looking forward to using it to understand future investment. MitAgator gives you a point in time historically but it’s also a future planning tool. It’s something we’ll revisit when we’re at a decision point. If we were to have a change in how we do things on farm, MitAgator would be one of those key tools we’d use alongside our other tools, like financial budgets and FARMAX feed modelling.”
Interested in finding out more?
Our dedicated team is here to support you on your journey, get in touch with our Farm Sustainability team today. Find out more about our full range of services here.
Email: farm.sustainability@ballance.co.nz
Phone: 0800 222 090
1 McDowell RW, Smith C, Balvert S 2011. The environmental impact and agronomic effectiveness of four phosphorus fertilisers: Report for Ballance Agri-Nutrients, October 2011
