Living Plough

CONSTELLATION BRANDS is using nature to drive better soil health, with the Living Plough project helping develop a “subterranean ecosystem” at its Fairhall vineyard. Grower viticulturist Mel Pierce has two 7 hectare trials on the 70ha block, with an array of deep rooted cover crops planted in either ripped or drilled soil, to ease soil compaction and increase vineyard health. “The Living Plough trial is to see if you can break up the soil with cover crops as well as you can by mechanical means,” she says, explaining how compacted soils can restrict vine roots to a small area, preventing the plant from fully developing. This also results in less drainage and deep water storage, and increased risk of drought stress between rain events. “So you have starved the vine of oxygen, you’ve starved it of water and nutrients, and you have prevented the flow of all of your organisms,” she says. “If you imagine a vine trying to grow through concrete, that’s what compaction is.”

It essentially means a vine lives like a pot plant, says Constellation Brands New Zealand national technical viticulturist Jeff Sinnott, who compares soil to a sponge that, while compressed, can no longer hold water or nutrients.

Jeff and Mel both joined the company a little over a year ago, and were excited by the prospect of using their technical skills and knowledge to enhance vines and yields at the Fairhall block, which has been through “20-odd years of a little too much taking and not enough giving”, Jeff says. The vineyard’s clay subsoils exacerbate the challenge, because they are particularly vulnerable to compaction, especially when tractor passes follow rainfall, evacuating soil aeration and solidifying the sponge. “When we got here, we saw a big opportunity to enhance soil health and in turn increase yield,” says Jeff. “A win-win.”

The duo both come from backgrounds of “precision viticulture” where the process is about give and take, “not take and take”, says Mel, who worked 12 years in the United States, where soil health was a key aspect of a vineyard manager’s role, because of the commercial consequences of its decline. “The vine gets weak, it has weaker shoot growth, it has lower yields. The root systems just can’t develop properly – especially in compacted soils,” says Mel, describing exacerbated issues of pest and disease in unhealthy soils, as well as lower production. “If we can find a way of breaking compaction without turning the soil, that is a huge win.”

The cover crops are not just about changing the physical state of the soil, and Constellation is working with Linnaeus Laboratory to analyse changes in various microbiome dynamics in the soil as the trial progresses. “It is basically creating a self-sustaining subterranean ecosystem,” says Mel. “We look at all the different interactions - how the physical, chemical and biological aspects interact, including parent material, organic matter and the soil microbiome.”

Living Plough includes one treatment where they undertook a mid-row rip to break the compaction zone, before planting deep rooted cover crops including radish, mustard, black oats, lupin, spinach and borage. “They are plants with huge biomass and also big root systems,” says Mel, explaining that for all the plants grow in height they will sink in depth as well, plunging as much as a metre down, and outwards as well, to break up the compaction.

In the second treatment, they sprayed out the native cover and drilled directly in, to see if they could get the same result without mechanical assistance. On the cultivated block, they plan to mow the cover crop and incorporate the organic matter back into the soil in spring and leave it to decompose, checking with Linnaeus on how that impacts the microbiome populations.

For the drill treatment, they will crimp-roll the crop down to create a matt, or mulch and disperse under the vines as a green manure, says Mel. “That is creating a habitat and food for our underground livestock,” she says. “This is an ecosystem we won’t disturb - we will keep adding to it year on year.”

The additional organic matter will help open up “big pores and little pores” in the soil, she says. Rainfall will fill those pores, with the large ones draining faster taking oxygen into the rootzone, while the small ones hold on to the water, and provide “amazing” storage.

Organic matter is a huge part of the equation says Jeff, explaining that an increase in 1% of organic matter in soils will increase their water holding capacity by 170,000 litres per hectare. “It’s all about surface area,” he says, “That’s how important those micropores are.”

Living Plough also includes “bug banks”, with an array of flowering species that will provide a food source for predator insects. “We are trying to create a slightly more diverse biology,” says Mel, who expects to see measurable differences this growing season.

The findings will help with management of all Constellation’s vineyards, although Jeff emphasises that each block has its own “peculiar sets of idiosyncrasies” and the holdings need to be categorised by individual soil signatures, not by vineyard. What might be true at Fairhall won’t be true everywhere, he says. “That is what is so exciting because every vineyard is so unique,” says Mel. “If you look at the soil structure you have the clay, the sand, the silt, the loams, and differences in organic matter, differences in parent material. There is no solution that can roll out everywhere.”

All wine companies are starting to look at their vineyards “through a slightly different lens”, says Jeff. “You can’t have healthy plants in an unhealthy soil.”