Lp. Christensen et al., THE EFFECTS OF PRUNING LEVEL AND POST-BUDBREAK CANE ADJUSTMENT ON THOMPSON SEEDLESS RAISIN PRODUCTION AND QUALITY, American journal of enology and viticulture, 45(2), 1994, pp. 141-149
A three-year study was conducted in each of two Thompson Seedless vine
yards to determine pruning level effects on raisin yield and quality.
Cane severance after bud break was also evaluated as a possible means
to adjust year-to-year crop level differences for improved raisin qual
ity. The trial vineyards, of differing canopy size, utilized node leve
l treatments of 60, 90, 120, and 120-adjust and 60, 75, 90, and 90-adj
ust per vine. The node-adjust treatments were intended to reduce inflo
rescence numbers to near historic district averages. This was accompli
shed by counting inflorescences after bud break and then severing the
appropriate number of canes (1 to 3 canes of 15 nodes each per vine, d
epending on vine fruitfulness) for crop level adjustment. Increased no
de numbers resulted in increased shoots and inflorescences but at disp
roportionate levels due to reduced percent bud break. Other vine adjus
tments to increased node numbers were comparatively small and variable
among years and included smaller berries and clusters and lower fruit
soluble solids. Ultimately, there were no significant ANOVA year to y
ear treatment effects on raisin yield and only occasionally improved r
aisin grades when comparing the low- and mid-level pruning treatments
to the high level. However, regression analysis of overall means showe
d a 0.3 kg per vine raisin yield increase for each additional 15 nodes
(I cane) retained, accompanied by a decrease of 3% B and better raisi
n grade. Cane severance to adjust inflorescence numbers after bud brea
k was only effective in one of three years at each location in improvi
ng raisin quality. Yearly inflorescence numbers did not provide an acc
urate prediction of the response to or necessity of such a treatment.
Thus, higher pruning levels would appear to be of greatest economic be
nefit to growers, and cane severance after bud break is not a predicta
ble benefit for improved raisin quality.