The science-based organic advocate

Former climate change scientist turned organic vegetable grower, Dom Ferretti, says
farmers can use pasture to remove carbon from the air. Anne Hardie reports.

A typical mix of seeds used for Dom’s cover crops. Dom is an advocate of regenerative agricultural practices and encourages pasture farmers to give it a try.

You don’t expect an organic vegetable grower to say there’s nothing better for the soil than pasture and cows, but that’s exactly what Dom Ferretti advocates.

Climate change scientist turned organic vegetable grower, Dom Ferretti, in his organic garden.

As a former climate change scientist with a PhD who worked for NIWA on greenhouse gases (GHG) including carbon dioxide, methane and nitrous oxide, he’s qualified to make that statement. He says farmers can use pasture to remove carbon from the air and store it in the soil, reduce methane emissions from their animals and also reduce nitrogen leaching.

After 12 years working on climate change issues, he now puts science into practice, using regenerative agriculture methods on an organic market garden in Nelson with his partner, Jeanette Ida. Ferretti Growers is a small business near Brightwater where they grow half a hectare of vegetables outside, plus 600m2 under plastic, with most packed into weekly boxes for their regular customers.

For years they made copious amounts of compost for their soils and it cost them thousands of dollars each year, plus time to mix, load and spread it onto their gardens. Any imbalance in the compost caused an imbalance in the soil. It got them thinking about alternatives and when they learnt they could get enough nitrogen for their vegetables from cover crops, they decided to try that route. Dom says their first trial with cover crops was a “lightbulb moment” for him that showed they could grow their vegetables with a lot less work and spend just a couple of hundred dollars a year on a mix of seeds.

Within the mix are plants with roots to open up the soil, add nitrogen and other nutrients, or produce flowers to attract beneficial insects. The positives don’t stop there. There’s less risk of nitrate leaching, the plants provide a stable form of nitrogen and improve the soil health, while providing the invisible benefit of sequestering carbon from the air and storing it in the soil. He says it’s not just about the nitrogen and carbon though. In the soil there’s the increased microbial activity and fungi networks that connect individual plants together and transfer not just nitrogen and carbon, but also water, other nutrients, minerals and trace elements.


It works well for an organic market garden and Dom says the potential is even greater for pastoral farmers who can make a difference in the battle against climate change. He says regenerative agriculture has the ability of increasing the soil carbon by 1% per hectare per year by sequestering

it from the atmosphere and storing it in the soil.

“Grasses are so good at absorbing carbon because of their extensive root systems. That enables them to draw carbon out of the atmosphere quickly and in big quantities.

“It’s the fastest way to sequester it out of the atmosphere and store it in the soil.”

He says the best way of drawing that carbon from the air is to let the grass grow as long as possible – the longer round the better on dairy farms – which increases the root system in the soil. Stalky grasses are high carbon crops that are particularly good to store in the soil.

Cows enter a paddock as a herd, eat it down and trample stalks and stems into the soil which stores that carbon and feeds the soil biology below the surface.

Farmers need to keep the soil covered in pasture or crop though.

If the surface is bare, the microbes head deeper to avoid the sun, the soil surface dries out and carbon will oxidise back into the atmosphere, depleting the soil.

If just 10% of farmers across the world adopted regenerative agriculture practices, Dom says they could absorb all the carbon that needs to be stored. New Zealand farmers, with their pasture-based agriculture, only need to tweak their systems to do their part.

“We’re in a pretty unique position as a country to make major changes.”

But he acknowledges it is a mind shift for farming and help is needed from the Government to fund New Zealand, research, workshops and seminars to show farmers how it can be done and the results. He says there is plenty of research with proven results in North America and Europe.

Storing carbon in the soil has benefits that go beyond climate change. For every percent of carbon stored in the soil, Dom says the topsoil will store another couple of hundred litres of water.

“You’ve got a longer stand of grass and root system which stops water running off. If you’ve got a drought, you’ve got that extra water held in the topsoil so pastures keep going longer.”

Storing extra water reduces leaching and runoff, which for dairy pasture means more nitrogen is held in the soil profile rather than leaching into the water table.

In the market garden, they are replanting with cover crops as soon as vegetables are harvested to stop the soil drying out and also stop weeds taking over. Next, they plan to work out ways of interplanting rows of vegetables with green cover crops to keep down weeds and actively feed the soil biology while simultaneously cropping. Basically a path of living mulch.

Pastoral farming gets the same benefits. As well as storing carbon and reducing leaching, Dom says growing a diverse mix of grasses and legumes to a decent length and time is simply good for the soil.

The longer the grass the better as that increases activity below ground and more decaying plant matter becomes food for the microbes, worms and everything from beetles to slaters and centipedes.

Grazing itself is one of the best practices for the soil as manure and urine add beneficial microbes and the process of trampling forces biomass into the soil to feed its living food web.

“In a forest, the leaf litter layer between the soil and mulch teems with life. Properly managed pasture can achieve similar results.”

A broad mix of plants also reduces the fertiliser bill as he has discovered for their organic vegetables.

“The first thing for me was you can get enough nitrogen into the soil through legumes, so I don’t need to make mountains of compost. For farmers, you can get that nitrogen into the soil through clovers and other legumes. There are so many different types of clovers. The second realisation for myself, which is just as applicable to pasture farmers, is that you don’t need as many inputs when the microbial activity is more diverse and is functioning in a better way. They’re accessing a wider web of nutrients in the soil that plant roots can’t get on their own and they are making it available to the plants. They’re working in a symbiotic relationship and partnering up, they can bring in more water, more nutrients and minerals so the resulting growth is better.”

Spraying a paddock out to plant a crop destroys much of that activity in the soil. He says it kills microbial activity, especially when it’s a systemic spray that travels down the roots of the plant where microbes and bugs feed.

“After spraying with glyphosate, the little guys come in to feed on the dead material and get a big hit on their populations.”

With fodder crops, he says those crops would benefit from other plants planted with them because of the benefits to the soil and also to reduce pests.

“Whenever you have a monoculture you have a great magnet for whatever pest likes that crop to come and have a massive party and invite all its friends.”

When it comes to methane belched into the atmosphere from cows, Dom says regenerative agriculture can reduce the amount of methane produced. In his time with NIWA, he worked on the development of instruments to measure methane from animals. Though he now thinks that was tackling the wrong end of the stick because we should be researching what goes into the cow’s diet.

Methane, he says, is a waste product of ruminant digestion and if the gut bio doesn’t have the right microbes or doesn’t have big healthy populations of them, the gut won’t be able to digest that food well.

Ruminants were designed to eat a varied diet in the wild, he points out. A varied diet leads to a healthy population of bacteria in the gut and therefore better digestion to absorb more minerals and goodies out of the food that bodies need.

“We just need to put more grasses that already exist into their diet – a little tweak and a tune -and we won’t have so much of a problem. We could still have cows roaming around emitting lots of methane and it actually wouldn’t matter that much if we had healthy soils absorbing carbon through regenerative agriculture practices because the large farmed areas would soak up so much carbon into the soils.”

A mix of plants in the diet is the equivalent of ‘five a day’ of fruit and vegetables, he says, that provide different compounds, minerals and oils that are nature’s medicines.

“Animals respond well, you don’t need as many chemicals or fertilisers and farmers and stock lead happier lives.”

The reason methane is such a big deal in New Zealand is because of high stocking numbers, the use of herbicides, monoculture crops and tillage which he says results in a net carbon source to the atmosphere. Those practices also mean the soils aren’t thriving, he says.

If more farmers could switch to regenerative agriculture, soils wouldn’t lose as much carbon and it would start going back into the soil.

Again, he says it’s a mind shift for farmers to move toward regenerative agriculture though. Which is why he suggests farmers try regenerative planting methods on just one paddock of their farm. He says all they need is a good mix of pasture species with different root systems to direct drill into existing pasture.

“We all need to be aware of the important role plants and soil have in affecting climate change. We can capture carbon in the soil and keep it there. The soil can literally save us. This is our chance to stop major climate change and clean up our waterways. Rather than being blamed for the problem, farmers can actually be our heros.”

He says there are now groups being set up to support farmers wanting to know more about regenerative agriculture. He also suggests interested farmers look online for podcasts, documentaries and short films to get them started.