Article taken from the Soil Foodweb Australia 2009 September Newsletter.
The photo on the left shows weed dominated soil, photo on the right shows grass dominated soil. Read out below to find out what made the difference.
Stuart Proud is a Vineyard and Biological Farming Consultant working in the Yarra Valley region of Australia. Stuart has worked in the viticulture and wine industries for over 15 years, and has experience covering a wide range of locations throughout Australia. For the past 8 years, Stuart has focussed on an organic and biological approach. He has achieved some great results in improving soil biology, diversity and structure which has lead to healthier vines and in turn wines with more depth, structure and balance have been made.
Documenting trials and recording results has enabled a better understanding of what is happening in the soil. Applying Dr Elaine Ingham’s and the Soil Foodweb principles has meant positive results are obtained more quickly. The scientific data collected and reports produced back up these results instead of just relying on anecdotal evidence.
As Stuart says, “Having worked in various vineyards and managed large properties myself, I never used to think twice about applying hi-analysis NPK fertilisers. The vines responded quickly and plant sap tests indicated the vines were taking up the nutrients. Using synthetic chemicals to control pests, diseases and weeds was standard practice and having a neat, tidy and weed free vineyard was a sign that you were a good manager.
However several years ago I began to wonder why pests and diseases would come back every year, no matter how many chemical applications were applied. And why did the weeds persist even when pre-emergent and systemic herbicides were sprayed multiple times through the year?
As I have learnt over the last few years, it’s all about getting the biology right at the ground level. Once the soil is improved the plants become healthier – ‘Build it and they will come’”
Stuart believes that a key factor lies in the soils. Most vineyards under conventional management practices tend to have soils that are high in bacterial numbers, low in active and total beneficial fungus (therefore unable to suppress disease causing fungus) , low in flagellates, amoebae and nematodes (this means low nutrient cycling) and slightly high in ciliates (this means soils are on the anaerobic side of the scale). This is shown by testing in many regions. Vineyards which have been managed using natural inputs and lowered pesticide and herbicide use tend to have a better fungal to bacterial ratio and more diverse protozoa and beneficial nematode numbers.
Ideally good vineyard soils will have between a 2:1 and 5:1 fungus to bacterial ratio but this is rarely the case when vineyards are managed with pesticides, herbicides and hi analysis NPK fertilisers. These all contribute to decreasing biological diversity, lowering natural disease suppression, increasing soil compaction and salinity levels. A healthy soil should contain 23% water, 25% Oxygen, 7% organic matter and 45% minerals. Compacted, unhealthy soil will have about 12% water, 15% Oxygen, 3% organic matter and 70% minerals.
A simple on farm test that anyone can do is to count earthworms in the soil. Digging a hole 30cm x 30cm and 15cm deep and counting the worms will give a quick indication of soil health. If numbers are greater than 15 then soil biology and diversity is alive and kicking, if there is only 1 or 2 then it’s time to change as something is wrong in the management practices. Stuart reports that he has had soils where herbicide use was eliminated, only natural fertilisers were used and 40 worms were found in a single soil sample. The results in earthworm numbers under different management practices have been supported from studies done by Dr Linda Thompson from Melbourne University.
Nutrient cycling should also happen when the full soil foodweb is present. Testing sap at flowering is a standard industry practice, and Stuart has had results that showed vineyard blocks under organic/biological management practices where the vines had all nutrients in the ideal range when compared to other conventional blocks which were low in several micro and macronutrients. Having a biologically healthy soil means nutrients can be unlocked and are in a plant available form which allows the vines to grow and function with right amount of nutrient at the right time. As Dr Ingham’s studies reveal the plant is able to control pH around the rhizosphere of the root zone which means it can decide what nutrients are needed and when they are needed to best support plant function.
In following editions of the Newsletter we will be continuing Stuart’s story – especially the important details of how he has improved the soil and through that, the performance of the vines. In the photos above (both taken in June 2009), the left-hand photo shows weed-dominated soil that has not been aerated, and has had a single application of compost tea as a soil drench over a 9 month period. The right-hand photo shows grass-dominated soil that has been twice aerated, and has had six applications of compost tea as a soil drench and foliar spray, over the same period.