Agriculture Reference
In-Depth Information
Grape yield map for precision viticulture (courtesy of R. G. V. Bramley; see color insert).
Figure 5.5
northwest sector be improved by installing under-drainage. If successful, this would
raise the overall productivity of the block substantially.
The essence of the precision approach to viticulture therefore involves three
steps: (1) acquisition of real-time or existing spatially referenced information (yield,
soil data, disease incidence, pruning weights, etc); (2) analysis and interpretation
of this information using a decision support system (DSS), usually incorporating
some modelling of soil-plant interactions; and (3) implementation of site-specific
management (relating to fertilizers, irrigation, spraying, fruit thinning, time of
harvesting, etc).
As more information is recorded in successive seasons, the vineyard and crop
response to environmental factors and management can be updated, the DSS re-
vised, and management actions modified through an iterative process. Precision
nutrient management is potentially a big improvement on the conventional prac-
tice of taking bulk soil or plant samples for diagnostic testing, where variation
within a site is averaged. Targeted nutrient management not only improves over-
all yields, but also reduces the waste of nutrients such as NO
3
through leaching
and/or denitrification.
Inputs and Outputs of the Major Nutrients
5.4
Nitrogen
The quantity of N per ha of vines depends on the planting density, as well as the
age and vigor of the vines. Data from California (Mullins et al. 1992) indicate N
contents (roots, shoots, and fruit) of 100-128 g N per vine for 10-year-old vines
at densities of 1120-1680 per ha. This suggests N contents from 112 kg N/ha at
5.4.1
