Production and Processing Waters in Watercress Farming – Environmental Impacts, Mitigation and Water Resource Management

Producing and processing watercress could not take place without reliable and plentiful supplies of high quality water. In the case of the Vitacress Salads’ site at St Mary Bourne, a renowned chalk stream is maintained wholly by water used in watercress production and processing. However, the aquatic macroinvertebrate community in this stream differs from others in southern English chalk rivers. Although freshwater shrimp are present, until recently their numbers were relatively low.

Low concentrations of substances in the water appear to impact the fauna in the stream. This effect may be due to the release of phenylethylisothiocyanate (PEITC) by harvested watercress. Many crop plants produce this natural pesticide as a defence against herbivores.

Melanie Dixon, a student at the University of Southampton, supervised by Dr Pete Shaw, has embarked on a three year study, sponsored by The Vitacress Conservation Trust, which will address three main themes:

How and why water used in watercress production and processing affects ecosystems in receiving streams.

The potential for on-site mitigation of ecological impacts of PEITC.

How the artificially maintained discharges from the St Mary Bourne site can be used to benefit local habitats and biodiversity.

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