Influence of rootstock and vine spacing on root distribution, vine growth

Root profile mapping of Cabernet Sauvignon on AxR, 110R and St. George rootstocks grown at the Oakviiie Experimental Vineyard revealed that St. George had the greatest number of roots at most depths with AxR lowest and 110R intermediate. The general distribution of the roots of all three stocks were similar, even though the frequency of different size roots differed. There was a significant difference between rootstocks, in terms of both total root numbers and in the individual root classes of < 2 mm and > 2 and < 5 mm. Mean separation tests supported the observation that St. George is producing the most roots followed by 110R and then AxR. Liberal tests suggest a statistical difference between all three rootstocks. Root numbers always varied significantly with depth. There was a rootstock-depth interaction for all root sizes except for the largest class (> 12 mm). This indicates that certain rootstocks are more likely to be found at one particular depth. St. George was found more often at the deeper depths than the other two rootstocks. This agrees with our original hypothesis that rooting patterns are based in part on geotropic angles. Even in very homogeneous soils, slight changes in the gravel or clay fractions seem to alter root distributions, as do changes in water application. Neutron probe measurements of water utilization at different soil depths between 0 and 2 meters showed that AxR, 039-16, and 110R stocks utilized more water at deeper soil depths than 5C, 1616, 3309, and 420A 110R stock utilized more soil water between depths of 120 and 150 cm than 3309. 3309 made maximum utilization of water at depths between 90 and 120 cm. 3309 also appeared to effectively use water at depths down to 90 cm midway between vine rows, whereas 110R was more efficient at using water at deeper soil depths than 3309, i.e., depths greater than 120 cm. AxR#l appears to use the greatest amount of available soil water in defined active zones, while 039-16, 110R, 3309 and 420A display similar “active zones,” but at consecutively lower levels. Data from each of these five rootstocks suggest strong lateral root growth at a particular soil depth. The remaining rootstocks 5C and 1616 each demonstrate less of an affinity for a given depth, but rather a higher volume of water uptake throughout the entire soil profile. The multiple access tube sites of 110R and 3309 indicated the most active root zones for each of these two rootstocks. Distinct patterns existed with respect to common depths of activity. The rootstock 3309 showed greater root activity at shallow depths down to 120 cm, while 110R displayed greatest activity at 150 cm. 110R appeared to produce greater lateral root distribution than 3309. This was evident by the higher water use at greater distances from the vine. Each of the seven vines indicated root activity to depths of 150 to 180 cm, but 039-16 and 5C showed greater water use at 210 cm than the others, suggesting a deeper root distribution with these two varieties. AxR, 039-16, and 110R produced the most above ground vine growth, 420A the least, and 1616, 5C and 3309 were intermediate. The closer the row spacing, the greater amount of water utilized from soil at depths between 0 and 200 cm, however, spacing between vines within rows of 1 and 2 m did not differ in the amount of water that remained in the soil at various depths. The amount of vine growth did not differ between row spacings of 2, 3, and 4 m, but was significantly greater for vines spaced 2 m apart within rows than 1 m vine spacing. Crop yields of 039-16, AxR and 110R were highest, 420A lowest, and 1616, 5C and 3309 were intermediate. Per vine crop yield of 2 m in row spaced vines was greater than 1 m spaced vines, however, on a per acre basis, 1 m vine spacing was greater than 2 m spacing. Generally, fruits at harvest from the higher vigor rootstocks (AxR, 039-16, 110R) had higher titratable acidity and malic acid and lower pH than the lower vigor stocks (1616, 5C, 3309 and 420A).