Methane, nitrous oxide levels can be reduced

Methane and nitrous oxide levels can be reduced on-farm and mitigation options are already available for farmers.

AgResearch science impact leader Robyn Dynes spoke to a group of rural professionals in Invercargill recently about what mitigation options were available to reduce greenhouse gases.

Methane is produced by cows when feed is digested by rumen microbes and 87%-92% of it is produced in the rumen.

Four options either available to farmers at present or being worked on would help reduce methane levels, Dr Dynes said.

These were low methane feeds, low methane animals, methane inhibitors and a methane vaccine.

Low methane feeds could reduce methane levels by about 25%, Dr Dyne said.

''With forage rape we got a significant reduction.''

Forage rape reduced emissions by 20%-30% in sheep, while studies with fodder beet were ongoing, Dr Dynes said.

There was also testing done on high cereal diets, which meant more than 80% of the diet, which showed a reduction.

Maize silage provided inconsistent results, she said.

When selecting cows with a lower methane level, the heritability was about 11%, Dr Dynes said.

Studies were done in sheep between high emitters and low emitters, which found the low emitters had a smaller rumen, which did have implications.

''DairyNZ has just started the same exercise for dairy.''

The methane inhibitor work is being carried out by AgResearch and aims to find new types of inhibitors of methane production that slow down or kill the methanogens, Dr Dynes said.

Another option was the methane vaccine, where research was ongoing.

''The size of the prize is so big, we need it.''

The other gas was nitrous oxide, which had two real mitigation options, through managing soil and soil processes and managing feeds.

''Avoid having urine being deposited at risky times of the year,'' Dr Syne said.

This could be done through such ways as stand-off pads or animal shelters. Testing in the Waikato and in Southland showed a decrease in both nitrate leaching and nitrous oxide emissions when using a stand-off pad or housing, she said.

Farmers could also use inhibitor urea hydrolysis or feed low greenhouse gas feed.

Final options to reduce overall emissions was looking at the farming operation as a whole, she said.

Farmers could do this in many ways which included increasing genetic merit/breeding worth, lower stocking rates, reduce replacement rates, improve animal health, improve reproduction, improve pasture quality or better use supplements, Dr Dynes said.

-By Nicole Sharp

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