Tinwald Farm

When Amanda Currie looks at soil, she doesn’t see dirt - she sees a complex, living ecosystem alive with potential. When she and her husband Adrian bought their 750-hectare Central Otago farm a decade ago, they knew nothing about farming. Today, after years of trial and error, Tinwald Farm is beginning to reap what it’s sown. We visited Amanda and the team at Tinwald Farm, who showed us how paying attention to what’s beneath our feet might just change our footprints.

Set against a backdrop of snow-capped mountains, Tinwald Farm is based just north of Cromwell and has diversified its farming operations to cover several bases. The productive farming operation, under the management of Jason Sutherland, runs 2,000 sheep and 200 Angus and Speckle Park breeding cows. Alongside this, the farm has 20 hectares of Pinot Noir vines, which are looked after by vineyard manager Rob Andre, and is home to seven Clydesdale horses for pleasure, potential agritourism, and fertiliser - “at least that’s what I tell my husband,” Amanda joked.

She explained that the three pillars of Tinwald Farm are using ruminating animals like sheep and beef to remediate soil, studying microbial inoculants and soil microbial populations through field research, and diversification into Pinot Noir, plus exploring assets for an agritourism business.

The intrigue of Tinwald Farm is not based on what stock it has on its land, but rather the land itself. Amanda, who has a background as a chartered accountant has dedicated several years to soil biology after realising how input-heavy Tinwald Farm operations had been when they first took over.

“About six years ago, I looked at our farming method, and began to get concerned about the amount of inputs we were putting into the system. We’re fully conventional, but we’re reliant on commodity prices. If commodity pricing falls, nobody compensates us. We just have to bear the risk. I was also concerned about the environment and the amount of synthetic nitrogen and other insecticides and pesticides that were applied to the soil to get those crops to grow,” she explained. “I became interested in a different method of farming. One thing led to another, and I started looking into microbes and what role they might play in our journey.”

Since those fateful first thoughts, Amanda has gone “down a rabbit hole from which I’ve never emerged”. She explained that she sees soil microbes as a solution to many farming problems.

“Within a fully-functioning soil ecosystem, those microbes will be mining and producing all the nutrients that plants need, so there isn’t a need for us to put on so much of these conventional fertilisers that can suppress them. The soil systems are so much more resilient in terms of their water-holding capacity. And they’re also part of that carbon sink - so they’re helping or involved in the process by which we draw down carbon dioxide from the air, and bank it in the soil as either carbon deposits or deposits within the bodies of the microbes themselves. That just seemed to be such a worthwhile area of science to explore,” she said. “I can’t make much contribution to the farming here, because I don’t have an agricultural background. I don’t know much about vines. So, for me, it was fertile ground. Nobody stood in my way to start exploring what those soil microbes might be able to do for us.”

Amanda began experimenting. “I first left the soil a while to see whether, if you just left the system alone, these microbes would come back. And my observation was that they didn’t.” That realisation sparked a years-long process of learning how to breed microbes using compost, though compost itself wasn’t the goal. “I’m just interested in using that as a method of breeding the microbes,” she explained. It took three years and many failed attempts - “I could write a book about my failures. I could open a ski field on my discarded compost piles,” she laughed - before landing on the right formula. Now, the focus has shifted to extracting microbes from the compost, applying them at scale, and monitoring the soil’s response. “I’ve got to the point where I’m confident enough about my ability to breed the microbes, get them off into a water solution and apply them. Now I’m looking at how many applications I need to make to restore that system,” she said. “I’m halfway through a trial I began this autumn. In the coming spring, I’ll apply those microbes again, and I’d like to think that at that stage, I’ll be able to observe a much greater population, particularly of fungi.”

“Fungi, the slowest to return and most vulnerable to soil disturbance, have been the key focus. Fungi are critical to soil health because they help build soil structure, produce plant nutrients, and improve water retention. They can also naturally reduce pests and help store carbon when set up correctly.

A 2024 trial spanning five hectares with two microbial applications yielded promising results. Amanda said that they had started to notice very long fungal strands, an indication that they had been populating the soil in that space. The process is still evolving. “We need a lot of science to help us go from compost into something you can actually use at scale. Compost works in a garden, but not on 750 hectares.”

Jason, the farm manager, said they implement other stock management techniques that complement soil health on the farm. Dung beetles have become a vital part of the ecosystem. “They grab the poo and pull it under the soil. They do it faster than worms can. It speeds up fertilisation and helps with soil structure,” Jason said.

“We haven’t drenched any of our cattle in four years,” he added. “Our ewes, we don’t drench at all, and our lambs are down to just three times a year.” The introduction of dung beetles has meant rethinking drenches entirely. “Ivermectin kills the dung beetles,” he explained. “It can leave a residual in the poo for up to three months, and the beetles will die.”

Unlike most farms in the region which rely on fodder crops, Tinwald Farm is one hundred per cent grass-fed, year-round. “We used to run stock on crop, but it’s very detrimental to the soil. Since moving away from that, we’ve cut stock numbers but actually come out better off,” he said.

Managing pasture through extreme temperatures - 30°C summers to freezing winters - requires thorough planning. To avoid bare soil in the middle of summer, Jason said they run longer grazing rounds of up to 120 days, and their grazing ratio is 60% cattle to 40% sheep. Their hay usage is minimal, with just 250 bales annually, primarily for the health of their cows. “If we get the rumen balanced with hay, they need less feed. When the gut’s working well, intake can drop by nearly 50%. They get more from less.”

When Jason first arrived on the farm, it was all ryegrass and clover - and every summer, without fail, they’d hit what he called a “man-made drought.”

“Even though we had irrigation on, we would just hit the wall in the middle of summer and we’d have no feed. It’d be dry as. We thought this can’t be right. We keep doing everything everyone says, but our soil was compacted, we had no worms, we weren’t making a lot of money,” he said. That was the turning point when Amanda suggested trying regenerative practices.

A key early indicator was the presence of worms. “If we’re doing everything right, we’d have an abundance of worms. Worms are your first indicator. At the beginning, we had none. Now, worms are everywhere.”

They also ran a water infiltration test. “We got a cylinder, smacked it into the ground, and poured in 25ml of water. After 15 minutes we had to walk away because it didn’t even move. That meant any rain would just run off into the lake.” The goal was to build soil biology and improve water retention. “If our roots are only going down two centimetres, it’s like we’ve got a 20-litre bucket and we’re only using the top. But if we can get them down to 10 centimetres, suddenly our capacity doubles,” Jason said.

It’s taken six years to get real results. “Most of it is just rest. Your plant recovery drives everything. Our root depth used to be two centimetres. Now it’s 10 or 15. In autumn, our grass looked like we’d put fertiliser on - but we hadn’t.”

They’re also measuring Brix levels, an indicator of plant sugar and energy content. An increase in Brix levels means the cattle or sheep don’t need to eat as much to get the same energy. Jason hopes their mistakes and data can help others. “If someone turned up tomorrow and said, ‘I want to go regenerative, how can I do it without really impacting my production?’ We could say: here’s what we did, here’s what actually works. Drop 25% of your fertiliser the first year, that’s an instant win.”

Ultimately, it’s about hard data. “It’s not, ‘I think it looks better.’ We’ve got the infiltration rate, we’ve got the higher Brix levels, and we know at what point in our management they changed. That’s what people need, that actual data,” Jason said. “We’re still at the beginning, but we’re finally getting consistent results. We hope to build on it, increase our productivity, and share with others what we’ve learned.”

Though they are just getting started, the future looks bright for Amanda, Jason and the team at Tinwald Farm. It’ll be exciting to see where science, innovation and passion take them next.