Litter quality and decomposition of Vitis vinifera L. residues under organic and conventional farming systems

In viticulture, residue decomposition may be important in terms of fertilization, due to the low grapevine nutritional demands. Grapevine residue quality, mass loss and nutrient release rates were studied in an organic (Vorg) and a conventional vineyard (Vconv) for 19-months. Leaf and cane residues of the Vorg (Lorg, Corg) and of Vconv (Lconv, Cconv) were buried in litterbags in both vineyards. Lorg contained in mg g−1 526 C, 14.7 N, 1.2 P and 5.4 K; Lconv 509 C, 17.9 N, 1 P and 7.3 K; Corg 556 C, 5.7 N, 1.4 P and 6.9 K; Cconv 554 C, 7.6 N, 0.9 P and 7.7 K. Mean mass loss and N, P and K release rates (k′ = k × 105) were higher in leaf (k′ = 543, 541, 448, 725) than in cane residues (k′ = 146, 90, 136, 494). In Vorg, mass loss and N, P and K release rates were higher in Lconv (k′ = 904, 748, 630, 1287) than in Lorg (k′ = 293, 357, 336, 502). For Lorg, mass loss and N release rates and for Corg mass loss rate were lower in Vorg (k′ = 293, 357, 102) than in Vconv (k′ = 537, 541, 218). For Lconv, mass loss and N and K release rates were lower in Vconv (k′ = 440, 518, 557) than in Vorg (k′ = 904, 748, 1287). Incorporation of plant residues in Vconv allowed reductions of nutrient applications of 25, 2 and 21 kg ha−1 y−1 of N, P and K, respectively; in Vorg nutrient applications reduced by 7, 1, 5.5 kg ha−1 y−1.