The ecophysiological characterisation of terroirs in Stellenbosch : the contribution of soil surface colour

[摘要] Soil is a component of the environment and sustains growth of several plants and animals.It forms part of the biosphere and can be described as the interface between theatmosphere and the lithosphere. The interaction between soil, climate and topography andthe resulting agricultural aptitude forms the concept of terroir. This relationship is complexand it is difficult to quantify the contribution of each.Grapevines are exposed to an array of soil types. Soils have varying colours, which can beascribed to their origin from different parent materials and pedogenetic factors. Historicaland experimental evidence points to the key role that soil physical conditions play indetermining grape berry composition, but other soil related factors may also play a role.This study was conducted to investigate the effect of soil surface colour on the vegetativeand reproductive growth characteristics of Cabernet Sauvignon. The aim was to determinewhether a relationship exists between soil colour, reflective light quality below and insidethe grapevine canopy, vegetative growth of the grapevine and the berry and winecomposition.The reflected light from soils was measured in three positions of the canopy and acrossthe light spectrum (300–2500 nm) for three different soil surface treatments (black, red andgrey). The effect of soil colour on vegetative parameters, yield and berry composition andwine quality was investigated. Soil surface colour resulted in differences in the reflectedlight quality below and in the canopy. The differences in the light quality were associatedwith differences in vegetative parameters such as mean main leaf, with grey soils inducinghigher values. Potassium levels of the grapes and berry number per bunch appeared to beinfluenced by soil surface colour throughout berry development with red and black soilshaving higher levels of potassium and berry number per bunch than grey soils. Graperipening parameters were not influenced by soil surface colour, but the grey treatment hada significantly more intense grape colour measured at 520 nm (red pigments).It is assumed that the importance of soil colour is its association with the physical and thepedogenetic properties that contribute to the grapevine water balance. From these results it can be concluded that soil surface colour appeared to have a direct effect on someaspects of vegetative and reproductive growth, and berry composition, but the contributionof different wavebands and mechanism of their effect deserves further study.

[发布机构] Stellenbosch University