Down on the farm a change is in the air

Standoff pads allow farmers to keep cows off pasture in winter, when ground is waterlogged and prone to leaching more nitrates into waterways. Photo / Supplied

A suite of measures is being worked on to tackle agricultural emissions - with no single tool likely to suit all farmers in all climatic and soil conditions.

Some are available now, some are still in the laboratory. The spectrum ranges from greener on-farm practices (such as reduced fertiliser use, low methane forage crops, nutrient budgeting and no-till crop production) to high science including ... drumroll please ... the methane vaccine.

THE METHANE VACCINE

It is early days and, naturally, there is no silver bullet, but a lot of store is being placed in efforts to develop a vaccine which limits the amount of methane produced in the rumen (the fore-stomach) of cows, deer and sheep during digestion.

It would work by inhibiting microbes known as methanogens which produce methane as a by-product of that digestion. The Pastoral Greenhous Gas Research Consortium last year achieved a world first by mapping the genetic sequence of the microbe.

"There's still some way to go before we can say we have a vaccine," says consortium manager Mark Aspin, "but the idea we could vaccinate our animals maybe once a year, or once a lifetime, and that would result in lower emissions is a pretty appealing approach.

"We may not be able to induce host antibodies against the methanogen but perhaps still target specific aspects of the methanogen to inhibit them.

A major challenge is to successfully inhibit methanogens without affecting digestion and productivity.

"It's technically challenging but we think its feasible. Vaccines are already used quite widely across the industry."

Aspin says a solution could be in farmers' hands within seven years.

BREEDING LOW-METHANE STOCK

Researchers have identified high emitting and low emitting cows and sheep after screening 700 dairy cows and 105 ewe lambs.

The challenge, says Aspin, is to develop a cost-effective way of identifying productive animals with low emissions. "Farmers have to understand the trait is advantageous to productivity."

NITRIFICATION INHIBITORS

Bearing no resemblance to the methane-collecting masks placed on sheep in trials, nitrification inhibitors are applied to pasture to target urine patches - the main source of nitrous oxide and nitrate leaching on pasture.

They slow or stop the conversion of soil ammonium to nitrate. They can be added ahead of the winter wet season and in early spring to minimise nitrate leaching into waterways and reduce nitrous oxide emissions. Reducing the loss of nitrogen can mean less fertiliser is required, reducing costs and improving pasture growth.

DIET MODIFICATION

Crops high in oils and tannins have shown a reduction in methane production in the rumen but cost effectiveness is an issue, says Aspin.

"We've found you can add up to 7 per cent oil to a ruminant's diet and that will result in lower methane but after that it starts to play with its digestion.

"We've yet to find forages that will give us lots of feed and result in lower emissions - crops that seem to have some influence on methane are pretty challenging to farm 365 days a year."

There are also carbon costs associated with the production of forage crops.

WINTERING BARNS, FEED PADS AND STANDOFF PADS

These investments allow farmers to keep cows off pasture in winter, when ground is waterlogged and prone to leaching more nitrates into waterways and plants are unable to absorb nitrous oxide.

BIOFILTERS

Landcare Research is working on developing organisms with the ability to break down methane which could be used to reduce emissions from effluent ponds, responsible for between 9 and 17 per cent of total methane emissions.

A pilot is about to start at Massey University.

SOIL CARBON SEQUESTRATION

Some farmers claim success in retaining soil carbon by the use of different root crops and techniques including no-tillage, crop rotation and fallow periods. Farmers who can boost carbon content could potentially claim carbon credits.

A technique called Biochar, where high charcoal organic matter is added to soil, is also gaining popularity. Biochar is said to prevent nutrient leaching, reduce the need for fertilisers and reduce nitrous oxide and methane emissions from soil.

Landcare Research global change research leader Surinder Saggar says the jury is still out on whether these techniques retain more carbon in soils long term.

MEASURING AND MONITORING

Landcare Research is developing a DNDC (denitrification/decomposition) model for measuring nitrous oxide emissions from dung and urine, which vary considerably.

The tool will identify exactly where, and to what degree, emissions are a problem.

Another model being worked on measures nutrient transfers in high country sheep grazing.