|The main areas in the viticultural industry where mechanisation is possible, are:
The size of the trellis system (height of poles) will be influenced by the cultivar and soil potential, but mechanisation is also possible where the trellis system stands at a height of 1,0 m. Full mechanisation, including harvesting and foliage management, is only impossible in areas where vines are grown as bush vines due to poor soil potential.
This discussion will therefore focus on the decision whether or not to establish or adjust vineyards for mechanised pruning.
Especially where mechanised pruning is considered on medium potential soil, an adjustment is required in the normal approach to average vigour and cultivation practices which enhance vigour should be implemented. Various smaller areas in the Paarl area will be discussed briefly with regard to possibilities and dangers.
Decisions which will influence mechanised pruning practices:
- Soil potential
- Available irrigation water
1. Soil potential
Medium to high potential soil is important when vineyards are developed for mechanised pruning. Sufficient vigour is an important prerequisite during the transformation of vineyards to mechanised pruning or when vineyards are planted for mechanised pruning.
Medium potential soil must also be managed to ensure strong vigour.
2. Irrigation water
Availability of water during January and February is very important. Total requirements will range between 2 500 – 4 000 m for a trellis system with large leaf surfaces. Considering the climatic conditions of the Paarl area, it will be quite impossible to use mechanised pruning techniques without irrigation.
Water requirements will be as much as 50% higher than at present with smaller vines and smaller leaf surface.
As a result of higher fertilisation levels, the harvest may be delayed and more water will be required.
Strong growing cultivars which may be considered:
a) Ruby Cabernet
c) Cabernet Sauvignon/Cabernet Franc
d) Chenin blanc
Rootstocks are important for the Paarl area. Strong growers are required, seeing that few soils actually induce profuse vigour.
Rug140, Ramsey, R99, SO4, P1103, US8-7 are stronger growing rootstocks. Cultivars such as Chardonnay, Merlot, Pinotage are risky because they do not grow profusely. A cultivar such as Sauvignon blanc grows well in Paarl, but shadow is required on the grapes to capture any flavours. Due to the fact that bunches are far more exposed to the sun with pruning systems for fully mechanised pruning, Sauvignon blanc is not recommended – only due to quality disadvantages.
The trellis systems used for mechanised harvesting are more vulnerable where strong winds occur, seeing that the foliage and crop are carried very high. However, mild wind may have advantages with regard to diseases.
5. Areas in Paarl
- Sufficient irrigation water available until February.
- A few blocks of deep, fertile alluvial soils for more profuse vigour.
- With the right cultivar choice, quality will not be sacrificed.
- Sufficient wind for disease control with the correct row direction.
- Small areas are suitable for full mechanisation.
- Sufficient irrigation water until February (Berg River).
- Deciduous fruit also requires a lot of irrigation water and will compete with wine grapes for the same source.
- A few smaller areas with fertile alluvial soils do occur.
- Many soils will have to be properly managed to obtain sufficient vigour while retaining quality.
Simonsberg + South Agter Paarl:
- Limited water from dams, but in certain instances Berg River scheme water will ensure sufficient irrigation until the harvest.
- Areas where Shiraz and Cabernet Sauvignon can be planted, but not always on the best soil suitable for mechanised pruning.
- Areas for mechanised pruning with the right cultivar choice, but sometimes practically impossible because the high potential soil is allocated to cultivars with weaker growth such as Pinotage and Chardonnay.
- Very sandy soils with insufficient vigour.
- Farms with high potential soil have limited irrigation water.
- No or extremely limited possibilities for mechanised pruning.
- Possible on a few non-irrigated farms with cultivars such as Shiraz or Cabernet Sauvignon on the right soil types. The possibility of insufficient soil moisture during ripening remains a risk.
- There is sufficient irrigation water available on the farms which participate in an irrigation scheme.
- Soil ranges from high to low potential over a very short distance and blocks therefore have to be planned very carefully.
Northern Paarl and Paarl Valley:
- High potential soils available with irrigation.
- Table grape and fruit cultivation compete for space.
- On fertile soil which will ensure sufficient vitality, cultivar choice is limited.
- Limited irrigation water.
- Sufficient medium to high potential soil for strong growth.
- Strong south-easterly wind threatens the big trellis systems.
- Fruit is cultivated in windless areas which limits the blocks for the establishment of wine grapes intended for mechanised pruning.
- The Paarl area as a whole has limited potential for adaptation of vineyards to mechanised pruning.
- Mechanisation of harvest and foliage management (tip/top) is easy to implement.
- Only a few blocks per farm will be suitable for transformation to mechanised pruning and it will not be able to replace manual labour altogether. This makes the capital investment in apparatus very expensive.
- It is important to realise that vineyards identified for high quality wine according to the choice of the terrain should not be fully mechanised.