WINETECH Technical Yearbook 2021

inside established vineyard blocks, and this is done in conjunction with unique fertilisation programmes formulated on block level. Precision farming essentially has four defined steps: 1. Collection of information at ground level. 2. Analysis of the information. 3. Decision-making at ground level based on analysis information. 4. Implementation of these decisions. Within a soil-scientific context, these steps are practically applied especially when it comes to creating unique maintenance applications and fertilisation programmes. The type of information that is collected for these purposes, includes: taking soil samples according to a distribution pattern, cultivar and rootstock information, block size, leafroll status, yield history, historical fertilisation programmes and applications, and vigour evaluations of existing vineyards. Soil samples are sent to an accredited laboratory for analysis, and the soil scientist then considers all the aforementioned data holistically to make recommendations and propose management decisions. The final step – implementation – depends on the producer

of the soil types and accompanying factors that influence block layouts, include: structure, texture, increase in clay content, stone percentage, depth at which signs of wetness occur (which influences effective depth), drainage requirements, soil preparation actions and accompanying implement choices. The more physical limitations occur in the soil, the lower the vegetative growth potential of the specific soil form will be, and more additional actions will have to be taken to manage the soil ef- fectively. • Chemical/ameliorant additions (full control): The producer has full control over choices of fertiliser, pes t i c ides , herbi c ides , t ime of application and efficacy of applications, but these actions must preferably be performed in consultation with an independent soil scientist (or similar expert) to ensure that correct, data- driven decisions and actions are executed. • Planting (full control): The choice of crops, cultivar/rootstock choices (more or less suited to the environment), and plant population (row spacing, intra- row spacing, etc.) must be done in consultation with viticulturists who can interpret the physical soil information.

Physical properties of soil (Limited control)

Climate (No control)

Quality & Yield

Crop/Plant (Full control)

Chemical/ ameliorant additions (Full control)

FIGURE 1. Factors that influence quality and yield.

and fulfilment of the precision farming cycle is therefore outside of consultants’ power. Several factors influence crop production and quality, as set out and summarised in figure 1 (Rüsch, 2001). Note also how the factors mutually influence each other. In the management of vineyard blocks, all of these factors must be considered. • Climate (no control): The influence of changing weather conditions on plants, yield and quality, especially in

climatic conditions like South Africa, is obvious. The recent and persistent drought in certain wine producing areas, is probably the best example of this. • Physical soil properties (limited control): Enormous variation occur- ring within short distances is charac- teristic of South African soils, and this property is often neglected when it comes to the layout and management of vineyard blocks. Physical limitations

WINETECH TECHNICAL YEARBOOK 2021 | 140