Effect of Different Environmental Factors on the Performance of Sauvignon blanc Grapevines in the Stellenbosch/Durbanville Districts of South Africa. I. Geology, Soil, Climate, Phenology and Grape Composition W.J. Conradie1, V.A. Carey1*, V. Bonnardot2, D. Saayman3 and L. H. van Schoor1 1) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, South Africa 2) ARC Institute for Soil, Climate and Water, Private Bag X5026, 7599 Stellenbosch, South Africa 3) Distell, Box 184, 7599 Stellenbosch, South Africa Submitted for publication: June 2002 Accepted for publication: August 2002 Key words: Geology, soil, climate, terroir, grapevine, phenology, growth, yield, must analysis A study in five commercial Sauvignon blanc vineyards, grown at different localities in the Western Cape of South Africa, was carried out over a period of seven years. These localities (four within the district of Stellenbosch and one in Durbanville) were within a radius of 15 km and underlain by different geological formations. Two experimental plots, representing different soil forms, were identified at each locality. In some cases soils could be related to the s Grapevine . materials l geologica f o s mixture m fro d develope s soil e th s case r othe n i t bu , materials t paren g underlyin were not irrigated and root distribution was mostly affected by factors such as soil moisture, compacted layers and percentage stone, and not necessarily by geological parent material. Relatively good root distribution was obtained for at least one soil from each parent material (granite, hornfels, shale). Management practices, such as liming and fertilisation, changed the chemical properties of the soil. However, the lowest levels of potassium were found in soils originating from phyllitic shales. Despite their geographic proximity, meso-climates differed between the five locali- ties, especially during summer. This was mainly due to their various landscape positions and distance from the ocean. Maximum temperatures for February differed by 3.1°C between the warmest and coolest locality. The lowest tem- perature variability index was experienced at the localities closest to the sea, due to moderate maximum and mini- mum temperatures. Time of budburst was not necessarily earliest at the warmest localities, but at the warmer sites grapes were generally harvested one to three weeks earlier than at the cooler localities. Ripening was also affected by soil type, resulting in differences of up to 12 days for time of harvest for grapes from different soil types, at the same locality. Acidity was lowest, and pH highest, for grapes from the warmest locality, but low acidity and moder- ately high pH values were also found for grapes from the coolest locality, probably on account of differences between clones. Within a specific locality, however, acidity tended to be lowest, and/or pH highest where water stress was the highest. Investigation of the effect of soil and climate on wine quality is part of an ongoing study. In accordance with the Wine of Origin legislation, vineyards in terroir concept has been done in South Africa. The current state South Africa are currently demarcated by technical experts of knowledge, especially as far as the South-Western Cape is con- (Saayman, 1998). Such demarcation is theoretically based, due to cerned, is summarised below. insufficient historical information on grapevine performance/ Climate wine quality being available in South Africa, which is a relative- ly young wine-producing country. Areas are allowed to express The Western Cape Province is situated between approximately their specific wine style and character after demarcation, instead 33°S and 34°S, and experiences a warm, temperate climate of proving originality beforehand. Demarcation is not necessari- (Kendrew, 1961; Schulze, 1972). In an earlier study (Le Roux, ly specific enough to meet the demands of consumers (Van Zyl, 1974) temperature was identified as the single most important cli- 2000). Further delimitation must therefore be applied. The terroir matic factor whichthat affects grape quality and character in the concept provides a rational basis for such delimitation. A terroir Western Cape. Using data from the few weather stations available can be defined in different ways, but Carey (2001) described it as at that stage, the Western Cape was divided into five climatic "a complex of natural environmental factors, which cannot easily classes according to the growing degree day model of Amerine & be modified by the producer. This complex will be expressed in Winkler (1944). In a later study (De Villiers et al, 1996) the the final product, with the aid of various management decisions, South-Western Cape was subdivided into different climatic resulting in distinctive wines with an identifiable origin. regions, largely according to the index of Smart and Dry (1980), Therefore the terroir cannot be viewed in isolation from manage- which is based on mean January temperatures, because January is ment and cultivation practices, although such practices do not the warmest month for regions with the same continentality. form part of the intrinsic definition". In view of the complexity of However, De Villiers et al. (1996) used mean February tempera- soil/climate/cultivar relationships, little experimental work on the tures for their classification, because February was the warmest Africa South Matieland XI,7602 Bag (Stellenbosch), Private University, Oenology,and Stellenbosch Viticulture of Department *Presentaddress: Acknowledgements: Technical assistance by the project team at Nietvoorbij, as well as financial support by Winetech, is appreciated. S. Afr. J. Enol. Vitic., Vol. 23, No. 2, 2002 78 EnvironmentalDifferent of Factors Effect 79 month at 80 percenand/oy rqualit t oe f thwin e , weathegrowth r e stations grapevin an o t d becausy directl e l most materia t en n I . March d an y Februar g durin n ripe e Cap n Wester e th n i s grape n o y geolog f o t effec e th n o s studie r othe o N . character e win - differ h wit s region n i n grow blann s cwa Sauvigno e wher l tria a grapevine performance have been reported from South Africa. ent macro-climates (Stellenbosch, Elgin, Robertson), a "cool cli- Soil type mate" and a "warm climate" wine style could be identified f o l shortfal l principa e Th . 1999) , Haasbroek & (Marais r - Hunte , vine d classifie t tha d showe ) 1983 , (Seguin x Bordeau n i h Researc ) al,el 1996 s Villier e D ; 1974 , Roux e (L s map c climati y earl e th e th e regulat o t l soi f o y abilit e th o t y superiorit r thei e ow s yard was that t thbu r e distancewate e s betweeexcessiv g n weathedrainin y r stationrapidl , s wervines e eth too t o r greawate t fof o r y suppl t pas e th r Ove . them n betwee d interpolate y reliabl e b o t a dat , that e rat a h suc t a t i g deliverin d an , water t sufficien g retainin - pro n bee s ha stations r weathe f o k networ e th , however , decade although the vines experience some stress towards ripening, this gressivelo t ye expandedguid r poo . a Intensiv e b o t d e recordinfoun s wa ge oftyp climati l Soi . c data, sucexcessive t h no a s i s stres that which is now available for the Bottelary-Simonsberg- vine performance and wine quality, unless considered in con- s area n withi n eve , that n show s ha , area g wine-growin g Helderber junction with climate, cultural practices and the specific require- with a e uniforclimat m d macroan s -soil climatef o t , certaiaccoun n O n . aspects cultivars o fl climate maindividua f o y s ment vary considerably (Carey, 2001). In order to gain further infor- being vastly different, models developed in Europe cannot be mation on genotype/climat o Rankint g eal. interactionset e Accordin . , anAfrica d thh e effectSout o t sy of sucdirectl h d applie y proximit e clos n i s plot e referenc , character e win n o s interaction s it f o s term n i e climat o t e rol subordinate a s play l soi , (1971) to the - weathehowev r , stationsAfrica h werSout e n monitoreI . regions d (Carem war yn i et y al., 2001)qualit e .win Thn o e s effect effect of season and site climates on the aroma profile of the er, soil may have a pronounced effect, as was shown by Saayman wines - wavar s s cleawine r t for alCinsau lf o thre s e cultivarcharacteristic s e (Sauvignoth t tha d n foun blanco wh ,, (1977) Chardonnay and Cabernet Sauvignon). However, the effect of soil ied according to the soil type on which the vines were grown, water status on aroma profile was not taken into account in this even when meso-climatic conditions were the same. Since 1977 . al.,et 2001) y (Care y stud e grapevin n o e typ l soi f o t effec e th n o s studie c scientifi r furthe o n . Africa h Sout n i d reporte n bee e hav e performanc Geology l soi f o s statu t Nutrien Apart from the indisputable effect of climate on wine character, n o t effec g predeterminin l potentia a e hav o t d considere s i y geolog e hav y ma h whic s element o tw e th s soil d vineyar n Africa h Sout n I - pri e th s wa y Geolog . 1998) , (Wilson y qualit d an r characte e win a definite effect on wine quality are nitrogen and potassium, assum- mary ke- yele tl o identifessentia r y thothe e e "Uniteth f o s s Terroir deficiencie d es Baseseriou " o in e thar e e Midther -t tha g in Loire Valle, y inripening Franc s e delay (Morlat n , 1996)nitroge e .