A long-term field experiment (28 years) was begun in 1976 in a Chinon vineyard, in the Loire Valley, France. Different types and application rates of organic amendments were compared in six treatments: crushed pruned vine-wood at 2 t/ha every year, cattle manure at two rates, corresponding to 10 and 20 t/ha every year, spent mushroom compost at two rates, corresponding to 7 and 14 t/ha, and a control without any addition of organic matter. Treatments were evaluated for their effects on root system, pruning weight, grape yield and its components, and on the leaf nutrient status of the vines. Significant effects were recorded only 14 years after the beginning of the experiment. With high application rates of organic amendments, such as 20 t/ha/yr of cattle manure, the vine root system was reduced in size, compared with the control, but the single rate of the pruned vine-wood (2 t/ha/yr) stimulated vine rooting. High rates of organic amendments decreased pruning weight and yield because of a possible water supply reduction or an eventual depressive effect of a higher salinity of soil, but more probably a toxic effect of high nitrogen levels. This undesirable influence did not appear in plots fertilized with the lower rates of organic manures of 10 t/ha/yr. Results showed a trend toward a favorable influence of crushed pruned wood treatment on vine behavior. Application of high annual organic amendments that provide the greatest soil nitrogen supply was an unprofitable exercise since it provided no further benefits in terms of vine durability, vine growth, and vine productivity. In contrast, moderate rates, applied particularly as pruned vine-wood, seemed well adapted to a sustainable viticulture.
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