Organic conversion – starting at the roots
Davenport Vineyards has 10 acres of productive vines, the oldest planted in 1991. The winery in East Sussex has a 60 tonne capacity, excess space being filled by contract winemaking. Use of herbicides was stopped in 1996 and mildew has been controlled by copper and sulphur sprays since 1998. Botrytis sprays (Elvaron, Rovral and Scala) have been applied until 1999, using 3 applications per year.
In 2000 we decided to take the plunge and register all our vineyards with the Soil Association as organically managed, and now we are starting into our first full season of organic grape growing. I hope to use this article to tell you about the process we have been through in converting our vines to full organic management.
The essential starting point of any organic venture is a healthy soil. Soil imbalances are the main cause of problems in the first few years of conversion. It takes time to make improvements and the vines suddenly find themselves without the crutches that help them to grow in chemically managed conditions. There are three components to a healthy soil – physical, chemical and biological. The eventual aim is to have all three in a healthy balanced condition.
The first step in our conversion was to get a soil analysis from the Elm Farm Research Centre, who specialise in organic advice. The results were a bit of a shock. We knew that our clay-based soils were poorly drained and slightly compacted, but the potash, phosphorus and organic matter were all shown as extremely low. Looking at the data, you may think that our vines had been in an extremely poor state, but they always survived and produced reasonable crops. Fortunately the pH balance was acceptable. It was clear that a lot needed to be done if we wanted our vineyard to be organically viable in a year or two.
Getting our soil into an organically healthy state has been a priority ever since. The vines grow better in a balanced soil, and this gives them better disease resistance, better cropping levels, and riper grapes (because the vines do not become stressed towards the end of the season). Repairing the soil balance is a long-term project and it may take several years before we can rely on routine annual manure applications. It will require continual monitoring and adjustments.
We planned to use four main methods to restore the soil to a balanced condition:
- Sub-soiling is required to reduce compaction, but wet ground prevented this from being done last autumn. This is now on my list of priority jobs to do after harvest. We will sub-soil alternate rows, doing the rest in the following year. This way the vine roots get pruned on one side only in each year.
- Cover crops - We bought a disc harrow last summer and cultivated alternate rows (we have always had permanent grass in the vineyard before). These rows were sown with a mixture of vetch and radish last autumn. The seeds germinated and covered the bare earth over winter, preventing winter soil erosion. In the spring the seedlings took off, growing a large amount of leaf. Vetch is a legume, which fixes nitrogen, while the radish grows a long tap root, breaking up the soil further down. In May the plants are mown and disc harrowed into the soil. This composts down and increases the organic matter of the topsoil. This year we are repeating the green manure treatment on the rows that weren’t done last winter. Green manure seed mixtures can be adjusted over the years to deal with a wide range of soil conditions.
- Fertilisers - The Soil Association permits the use of some fertilisers. 250kgs/acre each of rock phosphate and rock potash was applied this year and will probably have to be repeated next year. We had to apply for special permission from the Soil Association to use the potash, although after seeing our soil analysis, they didn’t argue. A foliar feed, home-made from comfrey leaves, is included in the spray program. This liquid stinks, so it must be good for the vines, and it is diluted before use, so 100 litres covers 5 acres for a season. Comfrey is rich in potassium and nitrogen; it is easy to grow and is an excellent free source of nutrients for fruit growers.
As a result of the organic soil maintenance I have had to re-assess our vineyard machinery. We have always used a fairly old collection of implements, including a 1968 Massey Ferguson 135 (since sold). We didn’t have any soil cultivation equipment and over the last year we have purchased a 5 year old Fiat 70HP tractor, which can cope with cultivating up our steep slopes (4 wheel drive), a 4 foot wide disc harrow, a sub-soiler, and a tined cultivator. Finding this sort of equipment to fit down our vineyard rows has been difficult (I am averse to buying new machinery), and I am still looking for a 5ft-power harrow. We have also bought a new Pellenc under-vine cultivator, which will help us to keep a clean soil strip under the vines.
So far (August 2000) the vine health is definitely looking better this year than previous years. We have seen some powdery mildew (never seen before in our vineyard), but leaves seem to be greener, and possibly fruit bunches are larger. The organic conversion so far has appeared to give an improvement in vine health, and it looks good for future years when the soil is in an even better state. My motivation for wanting to go organic is primarily that I believe the vines will produce better fruit with more intensity of flavour. I have to admit that it is really experimental, but the theory makes sense to me. Of course it would be wrong to draw conclusions from a single year.
Our vines have always been low yielding, and so the argument that organic management leads to a reduced crop doesn’t apply to us. I hope that by improving the soil we may actually see an increase in yield over the years. By increasing the quality of our wine, and maybe the yield, we will be able to sell our wine for higher margins. This is not allowing for any organic premium. I believe that organic wine does not in fact gain much of a premium over conventional wines because most wines are priced according to their quality, not their status as organic. It is therefore essential to improve the wine’s quality as part of the organic conversion, rather than to simply rely on the public to pay extra for the same product (with an organic label).
My main worry, and the one that deterred me from an earlier conversion, is botrytis. There is no organic spray to prevent this infection, and we will soon see if it is going to be a problem on our vines this autumn.
Will Davenport