Implications of grapevine row orientation in South Africa

Row orientation is a critical long-term viticulture practice, which may have a determining effect on grape and wine quality as well as cost efficiency on a specific terroir selected for cultivation. In the Southern Hemisphere in particular, little information is available upon which recommendations on the orientation of rows within a particular terroir, can be based. Shiraz(clone SH 9C)/101-14 Mgt was planted during 2003 to four orientations, i.e. North-South, East-West, North-East-South-West, and North-West-South-East, in the Breede River Region at the Robertson experiment farm of ARC Infruitec-Nietvoorbij, Robertson, South Africa. Vines are spaced 1.8 x 2.7 m. Photosynthetic active radiation patterns showed highest values in January. Largest differences occurred during grape ripening with the EW orientation maintaining stable, low interior canopy interception, the NS orientation displaying two clear peaks each in the morning and in the afternoon, and the NE-SW and NW-SE orientations showing peaks in the afternoon and morning, respectively. The EW orientation induced higher water retention in the canopy. Naturally higher water deficits were induced by the other row orientations, NE-SW and NW-SE orientations resulting in lowest overall leaf water potential. In line with the movement of the sun, W, SW, S, and SE canopy sides displayed lower average photosynthetic activity. Primary shoot lengths of the treatments were similar, reaching approximately 120 cm. Similar leaf area and leaf mass were found. Longer secondary shoots with higher total leaf area were found for the EW row orientation, resulting in highest secondary leaf area as percentage of primary leaf area.
Berry temperatures increased during the day, generally being 3.5 – 6 ⁰C higher in the afternoon than in the morning. Lowest average berry temperatures for the day were found for EW orientated rows, followed by NS, NW-SE, and NE-SW orientated rows. The latter three treatments had similar berry temperatures that were approximately 1 ⁰C higher than those of the EW row orientation. No large differences in berry temperature between canopy sides were found for any of the row orientations.
Reproductive growth parameters seem to indicate highest fertility for the NS rows and lowest for the EW rows. The lowest number of berries, but largest berries, per bunch was found for EW rows and highest number of berries, but smallest berries, for NS rows. The NE-SW and NW-SE orientations had similar berry number and size. Rot and sunburn differences were small.
The EW row orientation resulted in must soluble solid contents being higher than those of the other treatments. The pH of the treatments was similar. Highest titratable acidity was found for EW and NW-SE row orientations. Slight differences in grape skin colour occurred. Best ⁰B:TA ratio was found for NS rows and worst ratios for EW and NW-SE rows. Wines of the different row orientations had similar anthocyanin and phenolic concentrations, although slightly lower phenolic contents seemed to occur for the EW row orientation. Preliminary wine evaluation showed good, medium intensity colour with lively fruit for all wines, but particularly for wines made from NS and NE-SW orientations. Vegetative character was perceived for the EW orientation. Data point to different styles of wine, not only in terms of taste and aroma profiles, but also in terms of alcohol content, that may be expected when a particular row orientation is selected. Results are preliminary