The effects of organic and conventional management practices on feeding activity of soil organisms in vineyards

Abstract

This study investigated whether the activity of soil organisms in a vineyard soil in theWestern Cape, South Africa, was affected differently by different management practices. The influences of organic and conventional treatments were compared in two vineyard blocks, one previously organically and the other conventionally  managed. In each block, experimental plots received either full chemical weed control or ‘organic’ treatment, as recommended by the Organic Standards of the British Soil Association. Pest and disease control practices followed in the conventionally treated vineyard block included the use of various pesticides. The bait-lamina test was used to assess feeding activity of soil organisms. The feeding activity in the previously organically managed block, subsequently receiving conventional surface chemical treatment, decreased over time as the soil moisture content decreased. A comparison of feeding activity and moisture content on the previously organically managed block after both types of treatments, indicated that the activity was substantially higher in the organically treated plots compared to the conventionally treated ones, while the soil moisture contents were very similar. This indicated that the organic treatment favoured soil biological activity directly or indirectly. The treatment contributed to the preservation of more favourable  moisture conditions for soil biological activity. A microcosm study to determine feeding activity of fauna in soil from both vineyard blocks, each subjected to both a conventional and organic treatment under controlled conditions in the laboratory, showed a statistically significantly (P < 0.05) higher feeding activity in the soil that was organically treated and provided further indications that organic management practices, as used here, may result in higher soil faunal feeding activity over the short term compared to conventional practices.

Key words: soil organisms, bait-lamina technique, feeding activity, organic and conventional vineyard management.