The edaphic and climatic effects on production and wine quality of Cabernet Sauvignon in the Lower Olifants River region

[摘要] ENGLISH ABSTRACT: Cabernet Sauvignon is the most planted red cultivar in South Africa and the secondmost planted red cultivar in the Olifants River region. The cultivar is prone to vigorousgrowth with low yields. Excessive irrigation could accentuate these cultivarcharacteristics. Considering the foregoing, the aim of the study was to describe howCabernet Sauvignon will react to climate, soil type (texture) and irrigation within theLower Olifants River wine region to enable growers to make the right decisionsregarding long term as well as short term cultivation practices. This study is part of aproject carried out by the ARC Infruitec-Nietvoorbij at Stellenbosch to determine theeffects of soil type and atmospheric conditions on yield and wine quality of CabernetSauvignon in different grape growing regions of South Africa. Similar studies are beingcarried out in the Orange River, Stellenbosch and Swartland regions of South Africa.The Lower Olifants River region could be divided into three climatic regions.Furthermore, two climatic regions is evident regarding the formation of grape winecolour and aromas. Proximity to the Atlantic Ocean would play an important role in acultivar establishment policy.The variation in stem water potential (ΨS) could be related to soil water statusexpressed in terms of matric potential (ΨM). In the case of sandy soils, ΨS decreasedsubstantially more as the ΨM decreased compared to the sandy loam soils. The reasoncould be that the unsaturated hydraulic conductivity in sandy soils decreased morerapidly as the ΨM decreased compared to the heavier soils. Thus could explain why thegrapevines in the sandy soils experienced more water stress than the ones in the sandyloam soils at a given ΨM.Climate had a strong influence on grapevine water status with grapevines nearer tothe ocean experiencing less water stress compared to the ones further inland. This wasespecially true for grapevines in the sandy soils.Vegetative growth and yield of grapevines in the sandy soils were more sensitive towater deficits compared to the ones in the sandy loam soils. For deficit irrigatedgrapevines in the sandy soils, vegetative growth and yield decreased by ca. 30% whenca. 55% less water was applied from flowering to harvest. Yield reduction were ca. 15%with no or very little influence on vegetative growth with ca. 80% reduction in waterapplied from flowering to harvest for grapevines in the sandy loam soils.The influence of soil texture on wine quality and style were evident under intensiveirrigation as well as over different climatic regions. Overall sensorial potential winequality of grapevines in sandy soils tended to be higher compared to the ones in thesandy loam soils. Deficit irrigation tended to increase wine colour intensity, irrespectiveof soil texture. Furthermore, deficit irrigation in sandy loam soils tended to increase winefullness and the berry characteristics of the wine. Berry characteristics of wines from thesandy soils tended to be higher compared to the ones from the sandy loam soils. Toosevere water deficits in sandy soils could be detrimental to wine quality. Climate tended to have an influence on wine style of grapevines in the sandy soils with wines producedfurther away from the ocean tended to have higher berry characteristics.Irrigation management could be a powerful tool to manipulate the grapevine insandy soils. For grapevines the sandy loam soils in addition to regulated deficitirrigation, additional canopy management practices could be needed to improve winequality.

[发布机构] Stellenbosch University