Introduction

Pruning is one of the most important aspects of vineyard management, where selecting the optimum cane can be time consuming and difficult. Although the influence of pruning techniques and training systems on vine growth and yield is well documented 4,5, little is known regarding the influence of cane diameter on yield and gross profit. Understanding the influence of cane selection on yield allows for a more informed decision regarding harvest logistics, potential financial gains, storage space, equipment usage and matching market demands.

Our study investigates the influence of cane diameter on inflorescence architecture, yield and the subsequent gain or loss in gross profit.

Methods

Vitis vinifera L. Sauvignon blanc vines grafted on SO4 rootstock, in a commercial vineyard in Marlborough, New Zealand (41.53° latitude, 173.88° longitude), were used for the study. Vine rows are planted in a north-south orientation with 1.8 meters between the vines and 2.4 meters between vine rows. The training systems were established on whole vine rows (approximately 120 meters long), randomly distributed within four replicate blocks. Four vine rows per training system were used for this study.

Vines were pruned during the winter as follows:

  1. A bilateral-trained cordon spur-pruned to retain two nodes per spur and 10 spurs per vine;
  2. Head-trained four-cane, 10 nodes per cane (40 nodes per vine); and
  3. Head-trained two-cane (20 nodes per vine).

Gross profit per vine was calculated according to equation 1. Average bunch number per cane was calculated from the relationship of cane diameter compared to bunch number per cane.

Equation 1

Gross profit per vine = (number of canes per vine) x (average bunch number per cane) x (average berry number per bunch) x (average berry weight) x (grape price).

(Photo: New Zealand Institute of Plant & Food Research Ltd.)

 

FIGURE 1. Effect of grapevine diameter on: a) the average number of inflorescences per shoot along a cane, 2011/12 growing season (──, y = -2.29x10-5x² + 0.0098x + 1.22, R² = 0.92, P<0.05), 2012/13 growing season (‒ ‒ ‒, y= -2.29x10-5x² + 0.0098x + 0.77, R²= 0.95, P<0.05); and b) the average proportion of basal inflorescences along a cane that had an outer arm with flowers, 2011/12 growing season (──, y = -9.4x10-6x² + 0.0036x + 0.63, R² = 0.86, P<0.05), 2012/13 growing season (‒ ‒ ‒, y = -9.6x10-6x² + 0.0079x - 0.17, R² = 0.94, P<0.05). Cane cross-sectional area was grouped into 10 mm2 increments. Frequency = number of measurements in each diameter grouping. FIGURE 2. The effect of cane diameter and the value of grapes (dollars per ton) on the increase or decrease in gross profit per vine relative to the three-year average cane diameter left after pruning (10.92 mm). Gross profit and dollar per ton values were calculated from the relationship of cane diameter compared to inflorescence number along a cane (2011/12 data). [Reprinted with permission of Practical Winery & Vineyard (Eltom et al. 2015).] TABLE 1. Influence of cane diameter on gross profit * Change in gross profits were compared to the three-year average cane diameter left after pruning (10.92 mm). FIGURE 2. The effect of cane diameter and the value of grapes (dollars per ton) on the increase or decrease in gross profit per vine relative to the three-year average cane diameter left after pruning (10.92 mm). Gross profit and dollar per ton values were calculated from the relationship of cane diameter compared to inflorescence number along a cane (2011/12 data). [Reprinted with permission of Practical Winery & Vineyard (Eltom et al. 2015).]

 

Results

The average inflorescence number per shoot and the proportion of inflorescences that had an outer arm with flowers along a cane increased with cane diameter (P<0.01 between growing seasons, Figure 1). The pruning system had no influence on the number or structure of inflorescences (P>0.05). Subsequently, an increase or decrease in inflorescence number per shoot due to the diameter of the cane will influence gross profits (Table 1).

There is greater variation in the change in gross profit per vine as the price of grapes increases. As the price of grapes increases (dollar per ton), an increase or decrease in yield due to cane diameter is more detrimental to the gain or loss in gross profit per vine (Figure 2).

Summary

The influence of cane diameter on yield was examined during two growing seasons. Inflorescence number per shoot along a cane increased as the diameter of the cane increased, resulting in a change in gross profit in the range of approximately +/- 15%.

Conclusions

The influence of cane diameter on inflorescence number and architecture per shoot along a cane was investigated. Cane diameter is an indication of the average inflorescence number and structure along a cane, thereby influencing gross returns. The results indicate that viticulturists can manipulate yield, and subsequent gross profits, as early as pruning through cane selection. Temperatures during inflorescence primordia initiation, however, have a major influence on the inflorescence number per bud6, and thus the subsequent shoot, highlighting the importance of yield prediction tools. Therefore, temperature will in part, determine the extent that cane selection is able to manipulate yield.

The decision to manipulate yield via cane selection will depend on production requirements. Selecting larger diameter canes may result in an increase in gross profit. This may, however, result in an undesirable crop load. Additionally, selecting thicker canes will result in a greater proportion of bunches with an outer arm. While the presence of an outer arm will increase yield, it may cause an increase in the variability of berry composition at harvest1, which is desirable in some, but not all wine styles.

An increase or decrease in gross profit per vine is further compounded by the number of vines being pruned. The accuracy and attention to detail of the pruning team will ultimately determine what canes are being selected. It may be of significant benefit to provide additional education, instruction or even financial incentives to assure appropriate diameter canes are being selected.

References

Eltom, M., Trought, M.C.T. & Winefield, C.S., 2014. The effect of pre-bud break cane girdling on the physical and phenological development of the inner and outer arm in Vitis vinifera L. ‘Sauvignon blanc’ inflorescence structures. Vitis 53, 21 – 28.

Eltom, M., Trought, M.C.T. & Winefield, C.S., 2015a. Effect of pruning system, cane size and season on inflorescence primordia initiation and inflorescence architecture of Vitis vinifera L. Sauvignon blanc. Australian Journal of Grape and Wine Research 20, 459 – 464.

Eltom, M., Trought, M.C.T. & Winefield, C.S., 2015b. Cane selection and gross profit. Practical Winery and Vineyard, February edition.

McLoughlin, S.J., Petrie, P.R. & Dry, P.R., 2011. Impact of node position and bearer length on the yield components in mechanically pruned Cabernet Sauvignon (Vitis vinifera L.). Australian Journal of Grape and Wine Research 17, 129 – 135.

Reynolds, A.G. & Vanden Heuvel, J.E., 2009. Influence of grapevine training systems on vine growth and fruit composition: A review. American Journal of Enology and Viticulture 60, 251 – 268.

Trought, M.C.T., 2005. Fruitset – possible implications on wine quality. Midura, Australia (ASVO: 32 – 36).

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