Long-term vineyard sustainability index

The impact of viticulture on soil can be determined by comparing the biophysical properties that represent soil health at a particular site and depth with those same properties in soil considered to represent the ‘pre-vineyard’ state (the headland). Information gathered by this method shows the changes in soil properties following the change to viticulture depend on individual vineyard management and environment. Relative changes can be used for comparisons within regions. Our research took place over three years on soils of vineyards of different ages and under different management, in both the Awatere and the Wairau Valleys in Marlborough, New Zealand. Soil properties investigated were: pH (optimal value 5.5-7.0); organic carbon (OC, 3-5%); carbon/nitrogen ratio (C/N,10-20); bulk density (BD, 0.9-1.3 t/m3); macro-porosity (MP, 8-30%); microbial biomass (MB-C, g C/m2 in 15 cm of soil); basal respiration (BR-C, 1.5-4.5 g CO2-C/m2/day), respiration quotient (qCO2, 0.5-1.5 mg CO2-C/g MB-C) and kg carbon/m2 for 15 cm of soil (4.5-9.0 kg-C). Objective descriptions of vineyard soil quality would assist growers to apply and monitor sustainable vineyard management practices. This data set indicates changes in sustainability that can be expected after a change of land-use to grape growing.
Under average vineyard management, soil carbon declined rapidly during the first few years but reached a plateau after two or more years. Soil depth was shown to be influential, with soils below 15 cm much less affected by land use changes, but scoring lower for all soil carbon parameters (except for qCO2). Soils at this depth also scored lower for soil physical properties; they generally had a very high BD, low MP and low pH. These trends for the 15-30 cm layer are typical soil properties – they don’t imply that soil depth is a factor in sustainability indices per se.
The high variability and generally reduced levels of under-vine soil carbon compared with headland soil carbon, suggest the need to increase vineyard soil carbon content and thereby potentially sequestrate carbon.