The dirt on Our Mates’ Farm

This article originally appeared in the Spring 2021 edition of AFG magazine, available online here.

Matthew Tack’s orchards at Our Mates’ Farm in the Huon Valley have been certified organic for seven years. He is one of the Tasmanian growers taking part in the Soil Your Undies Challenge – but he’s already started experimenting with methods to boost soil health sustainably.

“This challenge is a great way to get growers testing their soil and really thinking about how ‘alive’ it is,”
Matthew said. “We find the soil in our orchard is full of worms whenever we have a poke around, which
is a good sign, so I’m hoping the test will show we’ve already got healthy soil.”

Matthew’s farm is mixed-use, with both apple orchards and livestock. When he came to select cover crop species for planting in the inter-rows and under the trees, he approached it from a grazing management perspective.

“Last year we decided to trial cover cropping different species,” Matthew said. “Our test area was in 14–15 alternating 80m rows of the orchard and we sowed a mix including wheat, oats, barley, vetch and tillage radish. We wanted the ground cover to help the soil in a few different ways. We have grazing
animals in our orchards over winter that could benefit from the feed, and we were also dealing with
soil compaction from vehicle movement that we wanted to address.”

Grass is greener

Matthew has already seen benefits from grassy ground cover after seven years of organic management: improved soil carbon, lower irrigation costs and lower costs for fertiliser.

“Our soil is 100 per cent covered,” Matthew said. “It makes a difference in summer; we don’t get the evaporation under the dripline. By letting grass get longer when it’s dry, we tend to keep moisture in
the soil. We’ve found we’re turning irrigation on later and later each year.

Matthew Tack is seeing a range of soil health benefits from inter-row cover cropping

“We have now compared area under grass with area under mixed species cover – the ground under the mixed species is fantastic. The growth on them is about 60cm high, while the grass hasn’t changed much over winter. It’ll be interesting to see what happens over the summer. We’re going to trial a spring sowing in the cider apple orchard next – possibly include some other species in the mix like sunflowers.”

In spite of the benefits of grassy ground cover, Matthew feels grass gets a bad rap among orchardists.

“Growers are concerned about competition, but when you’ve got established trees, I don’t think grass is a bad thing at all,” Matthew said. “There’s also this assumption that grass causes blackspot, and that it has to be sprayed to maintain a healthy orchard. But growers who spray grass still find they have to worry about blackspot even with bare soil.

The soil life isn’t there to break down the fallen fruit and leaves that host the blackspot spores.

“Ground cover protects and drives good soil health. When it’s bare, it dries out, you don’t get the earthworms and living things. And the more diversity above the ground the more diversity below it.”

Carbon credit

Carbon is a key measure of soil health, and offers some indication as to how Matthew’s planting and
grazing activities are impacting the soil.

“I’m intrigued by the increases in soil carbon we’ve seen in areas where we graze and areas where we mulch our prunings and mowed grass,” Matthew said. “By using rotational grazing in other parts of our farm we’ve improved our soil carbon from 2.8 per cent to 4.8 per cent since we bought it.

“When it came to choosing our ground cover mix, we had good nitrogen from clover, so I was looking more at building up that carbon by planting cereal species like oats, based on what I wanted my carbon ratio to look like.

“We’re a small farm, so we can afford to experiment and be quirky, but we’ve also followed the lead and learned from the bigger Tassie organic growers who are driving large-scale soil improvement with compost and biochar.”

For Matthew, the ‘perfect’ soil is still a work in progress.

“I think all growers are learning and evolving in soil health,” Matthew said. “An orchard is a living
environment. At the end of the day, we’re managing forestry.”