Picadilly Park

Monoculture to Diverse Polyculture – Regenerative Agriculture on a Macadamia Farm

In the 1980s, Rex Harris and family purchased a 60-hectare farm on the outskirts of Bangalow. The property was degraded due to erosion from high rainfall, over cultivation and heavy grazing. They invested significantly in fertiliser while planting an orchard of 16,000 macadamia trees. Rex experimented with a range of conventional practices to address erosion and declining soil quality. Picadilly are now half way through a radical seven-year program to transition from conventional monoculture to polyculture using regenerative agricultural practices.

Watch 'Picadilly Park – Monoculture to diverse polyculture' (13:44)

Monoculture to diverse polyculture

(Duration: 13 minutes 44 seconds)


[Screen reads, Monoculture to Diverse Polyculture, Regenerative Agriculture on a Macadamia Farm.]

Rex Harris:

Diversity is a very important thing, in agriculture in general. Farmers would grow a crop, it might be corn, it might be soybeans, it might be wheat and then they were leaving their farms fallow, until the next season.

[Screen shows, various crops.]

So, they were discovering that by having nothing there, they weren't growing anything.

So, there's no exudating of sugars or starches. There's nothing going in to feed the biology.

So, all of a sudden, we're waking up to the fact that you need to grow the plants and a diversity of plants to feed the diversity of soil life, the biology in the soil, that drives everything.

Rex Harris: [Picadilly Park, Bangalow NSW]

Well, hi, I'm Rex Harris, my family and myself own Picadilly Park, which is a 200-acre, or 80-hectare macadamia plantation, 2 kilometers South of Bangalow, on the far North Coast of New South Wales.

[Screen reads, Rex Harris, Picadilly Park, Bangalow NSW.]

We purchased the land in September 1998. And at that time, it had been used for grazing cattle. But we did discover that during the early 80s, the owners of the property at that time ploughed the land, and grew corn and potatoes for approximately 7 years, but gave up because of the heavy rainfall and the loss of topsoil from the heavy rains.

[Screen shows, a topographic map of the property.]

The land was fairly well degraded from ploughing the fields on hillsides, and we were aware that it had some problems, and it needed a lot of restoration work.

[Screen shows, topsoil being washed away and an image of the degraded land.]

Our initial soil test revealed really high aluminium toxicity, and it was obvious to my observation, that the cattle weren't eating grass and had been eating lantana in preference to the grass.

We took to a long program of planting approximately 40,000 rainforest species, over about a 5-year period and that's been an absolute joy.

Because we have provided a really nice habitat, wallabies started to move in hinthars, tadpoles along the creek system, and it's all basically because there was a nice, nice habitat of rainforest trees.

[Screen shows, various wildlife in a rainforest habitat.]

And we noted like it was prolific amount of fungi everywhere within the rainforest, and the macadamia tree is a rainforest species.

So, we got to get the knowledge of whatever we're providing in compost to feed our macadamia trees we were using a lot of carbon, which will provide a habitat for fungal dominance, to make our trees in a paddock feel like they were in a rainforest.

[Screen shows, a tractor and composter, composting.]

Our initial program after clearing the land of weeds and planting our rainforest and so forth was the plant our macadamia orchard, which was a total of 16,000 odd trees. And it took us 3 to 4 years, to plant those trees.

We were following conventional practices, which is basically herbiciding from the trunk line out to the drip line of the trees and then mowing grass with grass between the tree rows.

And that left a lot of bare soil which left the ground open to erosion by water from sometimes we get very large rainfall events if there's an East Coast low, we can get two to 300 mils of rain in a very short time period.

[Screen shows, bare soil between macadamia trees, in an orchard.]

And we were noticing a lot of the rows which are running down the slopes were starting to erode.

[Screen shows, heavy water running down the slopes, causing erosion.]

And it's at that time that we realized that by herbiciding in our tree lines, we were killing off our ground cover.

So, we changed course, and we started on a long-term program of planting species from South Africa, which is sweet smother grass, and it's 80% or 85% shade tolerant so it can grow in and under the trees and it meant that we had to change our harvesting equipment to harvesters that could pick up, nuts off from grass rather than collected picking nuts off bare soil.

Another thing that we noticed with our conventional practices of herbiciding was that we had a lot of root exposure.

So, macadamia trees being a rainforest species have surface roots and that's how they're fed by in a rainforest by fungi breaking down the leaf litter and water view, where today we apply 100 kilos of compost per tree per annum.

[Screen shows, a tractor spreading compost under macadamia trees.]

And that's the main feed source, at which then the fungi breaks that down for the trees to provide a natural food source, rather than chemical fertilizers.

[Screen shows fungi growing.]

As the trees become mature, we started discovering a new problem as the trees are canopied over.

And so, the trees are actually blocking the sunlight onto the surf ground onto the soil.

So, we started to lose our ground cover and that was terrible. We'd be all these years, we've been trying to improve the soil from previous practices. We were at risk again of having a soil erosion.

So that's when we started on a 7-year program of removing every second row of trees through the orchard.

[Screen shows, a macadamia tree being removed.]

So, each year we're removing 1000 trees, that presented a new problem where now we've got large swathes of soil unprotected and sort of studying looking around and trying to find out what to do to protect that soil, we came across cover crops.

[Screen shows, cover crops between macadamia tree rows, in an orchard.]

Our cover crops that we plant, we grow 2 summer crops, and one winter crop and the mix in a summer crop could be sunflowers, cowpea, mung bean, lablab several grasses, butterfly pea, a mixture of legumes which are naturally fixing nitrogen to the soil.

[Screen shows, sunflowers, cowpea, mung bean, lablab several grasses, butterfly pea, a mixture of legumes.]

Sunflowers are a great attractive, for pollinators and all sorts of beneficial insects.

The cover crops that we grow are not harvested, they're not cash crops, they're purely there to improve the soil.

And we when we replace them, we roll them down and flatten them with a roller crimper and the roller crimper has flat blades that don't cut the stalks, but they put a crimp in the stalk about every 100 mil and it makes the plant limp, and it can't stand up.

[Screen shows, summer crops being rolled down and flattened and crimped with a crimper.]

So that gives us a nice, thick mulch bed on the surface of the soil. And then we come along with a no-till drill, and it cuts through the stalk and the soil about 2 inches deep and places the new seed there.

[Screen shows, a no-drill cutting through the stalk and soil, adding liquid application and mulching.]

And now our drill also liquid application of all the goodies like mycorrhizal fungi, the rhizobium inoculants, for example, that go in that slot with the seed and then it's got this nice layer of mulch over the top, which the plants come through, they grow through and then we've got an incredible ground cover keeping the soil cool, insulated.

[Screen shows, lavish ground cover between rows, of macadamia trees.]

In conventional farming, people will get out with a bulldozer and have a deep ripper in and rip through or to open the soil up. And in regenerative farming, the it's a no, no to plough on the soil and you can use plants to fix this problems.

So, you can use plants for example compaction, you can plant daikon radishes, which will bust through their compaction layer with their 2- to 3-meter-deep tap roots.

[Screen shows, various plants used for compaction. Screen reads, smart radish and shows, their long tap root.]

Or you can use ryegrass, that over a period of years we'll do breakthrough rock.

So, there's lots of things you can use plants for, another example is planting legumes, which if the seeds been coated with the right rhizobium bacteria, that plant will take nitrogen from the atmosphere and fix nitrogen nodules to the roots of the plant, thus feeding adjoining plants naturally without having to use chemical fertilizers, which tends to kill all the soil off.

[Screen shows, the roots of a legume plant.]

Plants can also attracting insects and pollinators.

[Screen shows, various insects.]

Plants can, using exudates from their roots can bind sand particles and soil particles into aggregates.

[Screen shows, different soils, and sand particles.]

And therefore, instead of having a tight soil, you can have a crumbling soil like cottage cheese, which allows water and air, importantly air into the soil.

[Screen shows crumbling soil.]

All life needs water and air to survive.

Plants are providing all these natural, system services there's lots and lots of them.

These plants providing these natural services and sequestering carbon, which is really important and with climate change, the farmers using these practices can sequester so much carbon, from the atmosphere into the soil using plants and you can't do without plants.

Plants photosynthesize an extra day, starches and sugars into the soil and carbon. Once you've got a carbon rich soil, it holds a lot more water for example, if you increase your carbon by 1%, the soil that extra 1% can hold an additional 140,000 litres of water per hectare.

So that in a dry continent like Australia, is an amazing thing so farmers can sequester carbon, they can hold moisture, instead of having hard soils where the water runs off.

Using plants and regenerative agriculture, you can open the soil up where it'll allow water penetration and hold it in the soil, it's a marvellous natural system.

The conventional monoculture is to apply chemical fertilizers and to spray chemicals to control insect infestations.

On the extremities of our property, and in a central area we're developing permanent insectarys.

So, what we'd love to be able to have, is something like a meadow we have got self-generating flowers, and plants have a great diversity that self-generate and attract all of the beneficial insects.

[Screen shows, a meadow with varying flowering plants and insects.]

One problem that we have with a macadamia kernel weevil, the assassin bugs or soldier flies are starting to control that.

[Screen shows, a weevil, an assassin bug and a soldier fly.]

We don't know the extent yet it's only early days but could well be that we have good control of this new weevil that has emerged into our district, the beneficial insects or controller nicely.

Besides the fact when the trees canopied over and we've lost light onto the orchard floor, and we've lost started to lose our ground cover, which then we have our precious soils unprotected.

We also had a problem where the trees weren't getting sufficient light into the whole of the tree, it was just on the on the top of the trees because they were totally canopied across.

[Screen shows, various images of the macadamia, orchard canopies.]

And so, the production of macadamias was declining, because the lack of sunlight.

And since we've removed the trees, we now have sufficient sunlight penetrating the trees and where they were sort of forced to grow vertical growing for light, now that because there's so much sunlight, the trees are able to relax their branch and the innards of the tree is starting to branch up in what we call fruiting wood and leaf and it's looking a whole lot healthier.

So, the production is increased. So, we're getting production up and then we've also getting ground cover back protecting our precious soil because we've got sunlight.

[Screen shows, macadamia nuts on a branch.]

So, sunlight it's so important, so important it's the driving force of everything happening on a farm.

So, all plants photosynthesizing, for example, exudating starches and sugar and carbon into the soil.

So, without sunlight, none of that would happen.

When you look at those tree rows now where we've taken every row out, they'll canopied over again, so what do we do?

It's better for us to replant back into the entire row and take the older ones out.

So, you're always renewing your orchard basically, that's a 20-year cycling.

[Screen shows, a macadamia tree being removed.]

So that gets the grandkids busy.

[Screen reads, piecetogther productions, Piece Together Productions acknowledges that Aboriginal and Torres Strait Islander people, the traditional custodians of the land on which we live and work, have applied sustainable knowledge and practice to caring for country and community for millennia. We pay our respects to elders past, present and emerging.]

[End of transcript]

Return to top of page Back to top