Ag Research sheep are fitted with a measuring device to detect the amounts of nitrous oxide emitted from their urine. Photo / Bruce Mercer

Ag Research sheep are fitted with a measuring device to detect the amounts of nitrous oxide emitted from their urine. Photo / Bruce Mercer

Images of carefree cows roaming free, chewing grass or silage year round (well, almost), used to be the green selling point of New Zealand's dairy industry.

Not for us those "factory farms" of the Northern Hemisphere where the poor cows are consigned to sheds and fed grain for long periods.

But Federated Farmers' president Don Nicholson says greenies should be careful what they wish for. Their agitation about dirty dairying has led New Zealand farmers to import foreign concepts such as feed sheds to keep cows, and their effluent, off paddocks in winter.

Increased use of feed pads and stand-off pads is touted as improving productivity while reducing the problem of nitrate from urinating cows leaching into waterways when soils are wettest. Nitrous oxide from urine patches also contributes to our greenhouse gas emissions when plants aren't growing and absorb less nitrogen.

"The greenies love the free range grazing regime but their influence has made farmers more industrialised," says Nicholson.

"In Southland especially, farmers are actually building big feed sheds for 600 to 700 cows and taking them to milking without crossing a paddock. The greenies have made industrialised farming start to happen here."

The Green Party this week further raised farmers' hackles when it unveiled its recipe for reducing our greenhouse gas emissions excess ahead of next week's Government announcement of a target figure. The Green Party reckons we could shave 36 million tonnes off our emissions and thereby hugely reduce our obligation to buy carbon credits at enormous cost. It found potential savings in agriculture of 2.7 million tonnes by 2020 if dairy farmers reduce the number of stock they run from an average 2.8 cows per hectare to 2.3. On sheep, beef and deer farms, management tools such as diet changes and better soil drainage could reduce nitrous oxide and save another half a million tonnes, said the Greens.

The party tried to sweeten the deal for dairying by suggesting that the current high stocking levels, with requisite high use of fertilisers and supplementary feed, were unprofitable once milk payouts were below a certain level - $5.50 a kilo of milk solids - as they are now.

The hard sell: farming less intensively by lowering stocking rates and reducing fertiliser inputs could actually increase profitability.

DairyNZ, which represents dairy farmers, was quick to brand the Green Party study "incorrect and misleading".

"DairyNZ has proven that profit is very closely linked to the efficient harvest of pasture by cows, which in turn, is strongly influenced by stocking rate," said CEO Tim Mackie.