Soil management in relation to training system in a steep vineyard

In the North-West Italy, close spaced and low trunk vines are vertically trellised and Guyot pruned. In these conditions the permanent grass cover may compete with grapevine leaves and clusters for air and light, and with grapevine roots for water and nitrogen. In a « White Muscat » vineyard, grafted onto « 420A », the following soil management techniques were compared: a) permanent grass cover controlled by mowing; b) permanent grass cover controlled by foliar herbicides; c) no tillage using residual + foliar herbicides. The maximum soil cover was found on the grass cutting treatment. A good but reduced cover was obtained by the foliar herbicide used alone, stimulating the vine vigor, and giving more yields with higher total soluble solids concentration. The soil nitrifying microflora was less reduced by glufosinate-ammonium than by glyphosate. The grass cover was minimum using residual herbicides; as a consequence the erosion risk was enhanced, the soil total N and organic matter were reduced, yield and gray mold damages were increased.