The Proterra project in France was based in two vineyards in the departments of Vaucluse (la Romane, near Gigondas) and Aude (Villarzel-Cabardes, near Carcassone) in the South of France.

For more information about the sites go to

In common with all other ProTerra sites, these vineyards compared conventional soil management where the soil between the vines is cultivated 4-5 times per year to a Conservation Agriculture system where a grass cover crop was planted between the rows to protect the soil. The growth of this cover crop was suppressed using the herbicide, paraquat, in the spring to prevent competition with the vines during the summer months, when the supply of water can be limited. On occasions, spraying with paraquat was combined with mowing the cover for an integrated management system. More information about the choice of cover crops can be found at cover crop rationale , or double click below to see the photos on the web site.

The cover crop at La Romane was a commercially available seed mix (Agro Plan 20) consisting of 30% English rye grass, 50% creeping red fescue and 20% chewing red fescue, which combine to provide a good ground cover that does not place great moisture demands on the soil.  At Villarzel-Cabardes, Viver PP60, another commercially available mixture of 60% smooth meadow grass, 30% creeping red fescue and 10% English rye grass was planted.

The extent of the problem and a practical solution

In the Vaucluse at La Romane

In the first years of the trial while the grass cover crop was establishing itself, Conservation Agriculture was not as efficient in preventing soil erosion as the project had hoped. From October 2001 to April 2003, 137 t/ha of soil were lost from the conventional plots and 114 t/ha from the conservation plots.

However after this establishment phase, the effectiveness of the cover crops was clear. Between April 2003 and November 2004, 28 t/ha of soil was eroded from the conventional plots, but only 8 t/ha from the conservation plots. (see Figures 1 and 2 below). On these cultivated plots losing 28 t/ha of soil with an average soil density of 1.5 kg/L is equivalent to losing 1.9mm of soil across the whole field every 18 months – or 127mm every one hundred years.

Figure 1 – Soil Erosion, La Romane 2003 and 2004

Over the same period the loss of soil organic matter was 309 kg/ha from the conventional plots and only 85 kg/ha from the plots where the cover was well established and being managed using paraquat in the spring (see Figure 3 below). Such a loss of organic matter from the conventional plots is unsustainable leading to poor soil health and potentially negative impacts on biodiversity.

Figure 3 – Soil Organic Matter Loss, La Romane 2003 and 2004

“On the 3rd of September 2002 , a period of dramatic storm activity hit the region. This lasted for several weeks, with event intensities as high as 22.6 mm/hour ( 9 Sept 2002 ). Considerable quantities of soil were washed from the conventionally managed slopes causing rivers, field ditches and the main estate road to become inundated with sediment [see Plates 1 and 2]. A large scale clean-up operation using bulldozers and diggers was necessary. The situation was compounded by the ground remaining heavy and difficult to work for several weeks after the rains stopped. The harvest had to be delayed and the farmer was faced with substantial accommodation costs for his migrant labour force. Subsequent storms in October rendered the land impassable by machinery until March 2003, thus preventing other practices from taking place.

Throughout this storm period, the grassed inter-rows of the conservation-oriented treatment stayed intact and they could easily sustain pedestrian traffic immediately after rainfall [see Plate 3]. This simple demonstration under extreme conditions was enough for the farmer to consider employing the use of cover crops on other vulnerable parts of the estate”   

Ceri Llewellyn , soil erosion researcher

In the Aude region at Villarzel-Cabardes

A similar trend during the establishment phase of the cover crop was observed at the second ProTerra site in France . From November 2001 to April 2003 the soil losses totalled 19 t/ha from the conventional plots and 12 t/ha from the conservation plots. These erosion rates are much lower than those seen at La Romane because of the Aude site's lower rainfall and a more gentle slope

Between April 2003 and November 2004 soil losses from the conventional plot totalled 24 t/ha but only 1.3 t/ha from the cover cropped area. Over the same period the loss of soil organic matter was 246 kg/ha from the conventional plots and only 22 kg/ha from the conservation treatment (see Figures 3 and 4).

Figure 3 – Soil Erosion, Villarzel-Cabardes 2003 and 2004

Impact on Soil Health

A visual soil assessment made at Villarzel-Cabardes demonstrated that the quality of the soil in the conservation treatment was ‘good', with a quality index score of 29. While the soil in the conventional plot was only ‘moderate' with a quality index score of 22.5 (Table 1). According to Shepherd (2000), good soils score >25 and poor soils <10. This suggests that the health of the soil in the conservation treatment had improved even over the short duration of the ProTerra project.

This has benefits on and off the farm both now and in the future as a healthy soil is less likely to be susceptible to erosion and that the change already seen is likely to further improve with time.

COVER CROPS HAVE BENEFITS BOTH FOR THE FARMER AND SOCIETY

Once the cover crop had properly established, soil and organic matter losses from the conservation treatment at both vineyards were less than that from the conventionally managed area. This was due to improvements in soil structure from greater plant root activity, the addition of organic matter, the protection of the soil surface from raindrops by plant cover, and improved sediment-trapping efficiency provided by the cover crop.    

The results demonstrate that the use of conservation-oriented agriculture (using managed vegetative cover cropping) is an effective and importantly, a practical alternative to conventional cultivation in Mediterranean vineyards. On the farm, the farmer benefits from a healthy soil which is kept in his fields and enables him to get on to his land to prune and harvest his crops in difficult weather conditions.

The practice also benefits the local community by ensuring that eroded soil does not block streams and rivers exacerbating the risk of flooding or end up on roads.  

This work proved invaluable at demonstrating to farmers the benefits and practicality of cover crops in protecting their soil.

SUMMARY

Conservation Agriculture worked efficiently to reduce soil erosion and organic matter losses compared to the conventional practice of repeated cultivations. The reductions were attributed to improvements in soil structure (due to plant root activity and the incorporation of organic matter), protection of the soil surface from rain splash, and improved sediment-trapping efficiency by the cover crops. The results indicate that the use of cover cropping is a robust alternative to conventional soil management in Mediterranean vineyards.