Jonathan Grieve, viticulturist and owner of Avondale Wine Estate
near Paarl, Western Cape, is pioneering an ecosystem management strategy called Bio-LOGIC, which transformed his run down old vines through a combination of organic and biological methods and a strong focus on soil health. Wouter Kriel reports.
When the Grieve family bought the farm Avondale in 1996 it was run down with only old vines and citrus trees. No wine was being produced on the farm at the time. “We started with a complete overhaul,” says Jonathan Grieve, who took over the management of the farm in 1999. “The historic buildings were restored, old vines removed, drainage of waterlogged land improved, dams built and restored and the irrigation system upgraded.”
Until then production techniques were traditional and chemically based. “Maybe it was my complete lack of agricultural training that allowed me to look at our production practices without being hampered by convention,” says Jonathan.
“We used to have a mealybug and scale problem and the chemical programme wasn’t working. We were in a spiral of using more and more chemicals.” Jonathan decided to experiment by introducing a predator-control method and released wasps into the system. The success rate was 100% and he realised alternatives to traditional chemical production do exist. Initially the wasps were as expensive as chemical control, but as the environment adjusted to their presence, less needed to be spent to maintain the balance.
The root of the problem Jonathan says everything starts with the soil and after extensive research he took several soil-management philosophies and fused them into what he calls Bio-LOGIC.
“Simply being organic or biological – or any of those labels – doesn’t satisfy me,” says Jonathan. “Each approach has strengths and weaknesses and one has to be careful not to get caught up in the dogma of a certain philosophy.”
South African soils are mineral-depleted. The soil on the farm was in a bad condition after more than 60 years of extensive chemical use. Using basic Albrecht principles, Jonathan started working towards balancing soil microorganisms and micronutrients into balance. According to the Albrecht method of soil management, the important thing is not the exact amount of specific elements in the soil, but rather the ratio of elements to one another. It’s a complex soil-management system and Jonathan is still working on it after seven years.
When he started working with the soil on the farm, it had low phosphate levels of between 2ppm and 6ppm in Bray 2.
For the soil to produce optimally, it should have phosphate levels of between 50ppm and 100ppm. Normal synthetically produced phosphate is very soluble for short periods, binding with other elements and becoming unavailable to plants.
“Chemical fertilisers also kill soil organisms, so we opted for a softer approach with soft-rock phosphate applied at 500kg/ha,” says Jonathan.
Since Avondale also improved soil microorganism levels, the level of accessible phosphate has improved to between 50ppm and 70ppm.
“We only expected to see result after two to three years, but after the first season we had luxury levels,” says Jonathan. “We expect this to last for four to five years before we review it. Low magnesium levels were corrected by applying dolomitic lime.”
Potassium chloride (KCI), also called potash, is a relatively cheap fertiliser, but chloride (Cl) is used in swimming pools for sterilisation. It kills fungi and many other forms of soil life essential to a healthy productive system. “Why would you want to do this to your soil,” asks Jonathan? “We use potassium sulphate if soil and leaf analysis shows a need for it.”
The reintroduction and management of micronutrients impacts directly on the quality and taste of fruit.
“Modern agricultural practices tend to neglect micronutrients,” he says. Important work is being done on how to balance the soil naturally, which includes the study of the impact of applying volcanic rock dust and concentrated sea solids.
Avondale farm has 11 different soil types. The farm’s layout has been changed so the soil types coincide with different blocks of vineyard. This way the unique characters of the soil, or terroir, become pronounced in the wine.
Commercial agriculture is often accused of having monoculture characteristics. “I avoid this by using cover crops in the vine rows,” explains Jonathan. “We use 10 different cover crops, including grains and legumes. This increases biodiversity in the vineyards. By using legumes, which are natural nitrogen binders, I’ve been able to stop using chemical nitrogen. Natural nitrogen is available to plants and it isn’t leached from the soil as easily as chemical nitrogen. There are also no negative effects on the soil.”
“We encourage natural growth of indigenous fynbos as part of our practice of re-populating vineyards to enhance diversity,” says Jonathan.
The cover crops also help with weed control. Black oats, for instance, has an allopathic affect, inhibiting other seeds from germinating in its proximity. Bitter lupins and vetch have strong root systems preventing weeds and breaking up compaction. “We inoculate legume cover crops with rhizobium bacteria, stimulating nitrogen binding,” explains Jonathan.
In spring, cover crops are mown into banks and rolled. A compact, textured mulch layer is formed from different plant species. The mulch creates a habitat for microorganisms and fungi to flourish and almost no weeds can penetrate it.
On rocky soil, where planting is impossible, a mix of medics and balansa clover is sown. It becomes self-sustaining after a few years.
“Organic material provides a habitat for soil life,” explains Jonathan. “A self-sustaining ecosystem develops with organisms and plants living together to provide food for each other. It was interesting to see how the weed profile in the vineyards started changing as the soil balance was restored. I actually don’t see why vineyards should be weed-free because some are beneficial to grape production and every plant tells a story.”
Natural weed control
Jonathan says nutsedge (uintjies) is a difficult weed to control. “Instead of trying to eradicate it with chemicals, we investigated why it occurred,” explains Jonathan.
It flourishes in soils low in calcium, phosphate and zinc and prefers wet, anaerobic and compacted soils with a low carbon content.
“We had a tract of marshy soil with this problem,” says Jonathan. “To correct the problem we aerated the soil, planted cover crops and corrected the pH, calcium, phosphate and zinc levels.
“There used to be an uncontrollable nutsedge problem, but that has virtually disappeared. The cover crops don’t compete with the vines and we don’t have to use herbicides.”
Compost played a central role in kick-starting the farm’s recovery programme. “But the future ideal for Bio-LOGIC is to use no additional inputs and have a huge, completely self-sustaining living system.
Other pest control methods
The snail population on Avondale is controlled with ducks. Traditionally snail bait was placed evenly throughout the vineyard, but snails occur in colonies, feeding in dense pockets. This makes bait ineffective, as some spots will always have too much and others too little.
The ducks are merciless and their patrol speed is regulated by the number of snails in any given spot.
“We buy day-old ducks, and they are ready to work in the vineyards from one-and-a-half months,” explains Jonathan. Other pests are also controlled naturally.
“We’ve erected specially designed owl houses, encouraging barn owls to nest on the farm. They help with rodent control and contribute to our biodiversity. It’s amazing to see the life that has come back to the farm.”
Labelling and marketing
Although a section of the farm is certified organic, Jonathan doesn’t believe in using organic-certified herbicides or pesticides.
“This is where our concept of Bio-LOGIC goes further,” explains Jonathan. “Our focus is purely on creating a natural balance without killing. Organic herbicides and pesticides also kill beneficial organisms which then disrupts the natural balance.”
Bio-LOGIC is about combining all natural disciplines with modern science and research. “I can’t say we’re there yet, but we are well on our way and it’s exciting.”
Contact Jonathan Grieve on (021) 863 1976 or e-mail [email protected]. |fw