How are farmers keeping rivers clean?

PETER KEMP
Last updated 05:01 25/08/2014
Peter Kemp
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UNDER COVER: Peter Kemp, head of Massey University's Institute of Agriculture and Environment, stands in front of a cow shelter on No. 4 Dairy Farm on the university's agricultural experiment station in Palmerston North.

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OPINION: Too many environmental advocates are ignoring the impressive effort and big money being put into effluent management research and infrastructure in the wake of the Fish and Game New Zealand's ''Dirty Dairying'' campaign.

The campaign made water quality the top priority environmental issue in New Zealand. It was a wake-up call for the farming industry, but let's be honest, changes in attitude always take time, especially when they require spending your own money.

If you consider farmers slow to change, reflect on how long it has taken ratepayers in many towns to accept paying higher rates for sewerage systems that don't pollute the local rivers.

So what have farmers, with strong support from regional councils and the wider industry, done to help clean up waterways? They have fenced off waterways, implemented sustainable nutrient management plans, upgraded their effluent systems, established wetlands, planted trees and supported research through the levy they pay.

The Garrett family, who dairy farm 1200 cows on a 440ha block near Lake Ellesmere in Canterbury, provide a great example of the big money being pumped into environmental sustainability. They were recently awarded the Diana Isaac Cup for their native tree plantings along Boggy Creek that improved the health and clarity of the waterway. They have seen production increase 40 per cent and nitrogen leaching drop from 16-18 kilograms loss to groundwater per hectare to 6-8 kilograms since constructing a free stall barn two years ago to house 900 cows during winter and applying effleuent over the farm, instead of bought-in fertiliser.

In most areas, nitrate leaching into waterways is the most difficult water quality problem to solve. The impact of urine from livestock is the main issue. The nitrogren concentration in cow urine is too high for pasture to use. Each urination applies approximately 800 kilograms of nitrogen per hectare to the pasture patch it creates.

Some of that nitrogen moves through the soil as nitrate. In soils with artificial drainage systems, this nitrate is conducted directly to streams and rivers. In free draining soils, the nitrate moves downwards and enters the water table and then into the waterways. These processes are called leaching and can take place over a few hours or decades. So how might research help with this long term and important problem?

We are seeing rapid technological innovation in hyperspectral soil mapping, filters, pumps and robotics that will provide farmers with even better tools for preventing nutrients leaving the farm in the future. The the continued funding of this research is critical in order to develop future farm systems that further decrease nutrient loss and faecal microbe pollution.

There are currently four large scale farm system experiments being conducted across Waikato, Manawatu, Canterbury and South Otago, funded by the Pastoral 21 consortium of farming and research organisations. The key objective is to decrease nitrate leaching while improving profitability.

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Dairy NZ's Scott Farm in Hamilton is focused on milk production, Canterbury's Lincoln University, farming systems and stocking rates, South Otago's Telford Farms Dairy Unit, winter crop feeding and indoor wintering, while Massey University is researching free stall cow barns, grazing and effluent management systems.

Cows at Massey’s agricultural experiment station are being grazed for the minimum time required to obtain their daily feed intake and are then moved to a cow shelter.

Dung and urine is captured in the cow shelter, stored in a pond and then applied to the pasture at a rate low enough for pasture to use the nitrogen. Early results have shown the system decreases nitrate leaching by as much as 50 per cent and provides an extra 130 kilograms per hectare of nitrogen for pasture growth that otherwise would have been lost from the farm.

The problem is, this infrastructure doesn’t come cheap. A cow shelter costs about $5000 per cow and a modern effluent system costs around $1000 per cow.

However, research is also being conducted into whether the cost is covered by the increased pasture and milk production.

Farmers are now spending large sums of money managing nutrient losses from their farms and also supporting research on environmentally sustainable farm systems.

So yes, farmers were too slow to recognise it was time to change their farming systems but they are changing.

* Peter Kemp is head of Massey University's Institute of Agriculture and Environment.

- Stuff

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