There's an old saying about soil: they're not making any more of it.

But some farmers are.

In just five years, Niels Olsen used his own invention to build more soil on his property in Gippsland, Victoria.

It delivered him the title of 2019 Carbon Farmer of the Year and it's vastly improved the health of his land — but it requires an unconventional approach.

A smorgasbord of crops

Mr Olsen aimed to unlock the hidden potential of soil through his invention, a seed planter called the SoilKee Renovator.

It mulches narrow strips of pasture and sows a mind-boggling seasonal mix of seeds.

The Olsens plant an array of seeds to promote fertility in the pasture. ( Supplied: Niels Olsen )

This winter, the Olsens used it to sow peas, oats, barley, rye, corn vetch, chickory, plantain, brassicas and the tillage radish.

When summer comes, the machine will be run through again, sowing crops like maize, sorghum, oats, peas and barley.

This smorgasbord can be grazed several times, but food for livestock isn't its only purpose.

The mass of plant roots stores carbon, improving fertility, aeration and water-holding capacity, and allowing the soil to support multiple plants.

"We have converted that 50 to 60 millimetres of topsoil into 200 millimetres of topsoil in the last five years, which has greatly increased the ability to push out some pasture on top," Mr Olsen said.

His soils have gone from holding 3 per cent of carbon to more than 10 per cent.

This high carbon content also helps retain valuable water in the soil.

"For every tonne of carbon, it can hold 30 tonne of water, so if you are storing that in your soil profile, you're a long way in front," Mr Olsen said.

He said carbon has also brought some much-wanted visitors to the pastures.

The SoilKee Renovator mulches narrow strips and sows multiple seeds to encourage carbon storing. ( Supplied: Niels Olsen )

"When we first started with the SoilKee, we might have had one or maybe two worms in a large shovelful of soil," he said.

"We now have 40 to 50 worms at times.

"That's why we have been able to increase our productivity in our pasture from around six to seven tonnes of dry matter per hectare to 20 tonne, without any synthetic fertiliser."

The quest for carbon credits

In March, Mr Olsen made history as the first Australian farmer to earn carbon credits through the federal government's Emissions Reduction Fund.

"It's not going to make us rich in a hurry at today's prices," he said.

"It's probably around $15,000 for 100 hectares for the year, but there's talk it could go to four times that.

Soil with a higher carbon content is more likely to store water and increase fertility. ( ABC Landline: Prue Adams )

"The main benefit is the yield increase and being able to grow fodder in the tougher times when it's too cold and wet and when it's too hot and dry."

Matthew Werneke, managing director of carbon development company Agriprove, facilitated the Olsens' carbon credit payments.

"Most farmers when they hear carbon credits think about trees, whereas what we're doing with soils is we're not taking land out of production, we're actually enhancing the productivity of the land and getting a level of carbon credits creation similar to what you would get with trees," he said.

The Olsens are also experiencing an unforeseen upside.

Cattle enjoy grazing the crops planted in the Olsens' pastures. ( Supplied: Niels Olsen )

They're building SoilKee machines and have a backlog of domestic and overseas orders.

"We are in the stage now where we are getting that many machines ordered that we're going to have to expand and speed up production very quickly," Mr Olsen said.

Watch this story on ABC TV's Landline this Sunday at 12:30pm or on iView.