Long-Term Additions of Organic Amendments in a Loire Valley Vineyard on a Calcareous Sandy Soil. III. Effects on Fruit Composition and Chemical and Sensory Characteristics of Cabernet franc Wine

Abstract

A long-term experiment (28 years) conducted in a vineyard in the Chinon region (Loire Valley, France) compared a control (no addition of organic matter) and three types of organic amendments: dry crushed pruned vine-wood (VPW), cattle manure (CM), and spent mushroom compost (SMC). Each year, VPW was applied at the rate of 2 t/ha (VPW2), CM and SMC were added at two rates (medium and high) of 10 t/ha (CM10) and 20 t/ha (CM20) for cattle manure, and 8 t/ha (SMC8) and 16 t/ha (SMC16) for spent mushroom compost. Treatments were studied for their effects on berry and wine composition (soluble solids, titratable acidity, pH, anthocyanins, total polyphenol index, and minerals) and on the sensory characteristics of wine. High rates of organic amendments, particularly CM20, delayed berry maturation. Total soluble solids, anthocyanin, and tannin content in the juice were lowered, whereas pH, nitrogen, phosphorus, and potassium were significantly increased, compared with the control. Many of these effects were also found in the wine. As a consequence, the wine corresponding to the high rate of cattle manure had the lowest color intensity and aromatic persistency, with the highest herbaceous and animal odors, compared with other treatments. Heavy nitrogen supply to vines as a result of high rates of organic amendments could be the most important factor to explain these effects. If the goal of winegrowers is to produce top-quality grapes for top-quality wines, the application of high rates of organic amendments should be avoided and vine nitrogen nutrition should be managed with a flexible and adaptive approach in relation to environmental conditions.