Soil is a non-renewable resource that growers must make every effort to conserve. Huge soil losses have occurred on the hillside vineyards of France and olive groves in southern Spain, which threatens the viability of farms. A new project, involving cover crop management, is looking to provide potential solutions.

The fragile soils on some of the most prestigious vineyards in France are, quite literally, washing away. An erosion process that's been going on for centuries, it has been exacerbated in recent years by tempestuous storms and flash flooding associated with Global Warming.

In the worst instances, whole hillside vineyards and olive groves in southern Spain have perished, a fate that could be repeated on many others if growers don't take action, believes Syngenta Environmental Soil Specialist, Mike Lane. "It's a real problem on the thin soils overlying limestone bedrock. Whilst the low fertility and steep south facing slopes are perfect for growing grapes and olives with the most concentrated flavour, in some areas the plants can no longer survive; the whole culture is unsustainable," he said.

Mr Lane says the major problem results from the tradition of constantly cultivating land between the crop rows, to keep it free of weeds that compete for essential moisture. The repeatedly broken soil structure - involving up to five cultivations a year - is extremely vulnerable to heavy rainbursts washing away the soil. Once the soil starts moving from the hilltop, it's incredibly difficult to stop. The problem is compounded by particles eroding more soil as it gathers pace moving down the hill.

One simple solution would be to control any weed growth with chemical herbicides instead of cultivating. "There are certainly cost and time saving advantages to this route," he advises, "but you are still leaving bare soil with little structure dangerously exposed to the elements."

The Soil Conservation Project involves sowing a specific cover crop between the rows, a process that has a number of advantages. It serves to improve infiltration rates, which reduces the risk of flash flooding and could also increase the water holding capacity of the soil and, equally importantly, the crop's root structure stabilises the surface and holds the soil in place during the winter rains.

The project will enable the researchers to study precisely the effects on yield, crop quality and the level of soil erosion from a number of cover crop options and management practices.

The management options include the complete burn-off of the cover crop with Gramoxone when the rains cease in early summer, or just burning off the edges of strips that might compete with crops; the cover can then be re-established in the autumn with direct drilling. Other regimes may simply involve cutting or leaving the cover crop untouched.

On the 140 hectare Pierre Amadieu vineyard estate, producing famous Rhone wines in the heart of Provence, a series of giant tanks have been built below the ground to capture the entire water run off from individual rows of vines. Remote sensing equipment can measure the rate of water flow following rain, as well as capturing any soil movement. Water quality will also be closely monitored.

The Estate's Domains Manager, Claude Amadieu, says the production of exceptional quality wines has always been the family-owned company's objective, since its inception in 1929 and now including the largest vineyard in the Gigondas Appellation. "It is an area with a long-history for the production of unique wines, combining the best of traditional techniques with the modern scale of production and marketing to create a viable business for the many families that live and work on the estate.

"We need to ensure that the essential cultivation of high quality is sustainable for generations to come. If we can develop a system that will minimise the effects of soil erosion, without compromising the quality and yield of the vines or the economic viability of the estate, it will help to secure the long-term future."

Mr Amadieu added: "It is important that we can learn how to manage the cover crops dynamically, according to the season and the state of the crop and that it can create a practical solution within the existing farming system."

The Gigondas project is being mirrored on an olive estate in southern Spain. The results of both will, however, be equally applicable on vulnerable soils across southern Europe. The benefits of reducing soil erosion on the hills will also be felt downstream, where the eroded soil deposited in drainage ditches, rivers and water treatment works requires expensive remedial action.

Mike Lane says the establishment of cover crops also creates the opportunity to significantly increase biodiversity in the intense monoculture of vineyards and olive groves. The project will be assessing both soil flora, especially earthworm populations, and insect numbers. It may be possibly to create cover crops that specifically encourage beneficial insects that could help with pest control.

It is acknowledged that this technique will require investment in new equipment for direct drilling cover crop seed. But Mr Lane believes it is the sort of specialist tool that could be operated by a contractor or growers would get together to buy. "Many of the vineyards and olive growers already work in close co-operation for harvesting, processing and selling their crop, so this should not be a problem." The co-operative nature of the farms also makes it easier to communicate technology transfer messages, he believes.

The project working closely with the Pan-European Soil Erosion Risk Assessment (PESERA) project. It will provide valuable data to calibrate the model being developed and GIS tools to plot areas of highest soil erosion risk. It also has applications to minimise soil erosion in Italy, Belgium and the UK, which are currently being studied by a number of research agencies, Government bodies and the EU Soil Bureaux.