Agriculture Reference
In-Depth Information
(a)
(b)
(c)
0.25 %
Petiole P (%)
Interpretation
N
< 0.2
Deficient
Marginal (0.2 - 0.24)
Adequate (0.25 - 0.5)
High (> 0.5)
W
E
0.2 - 0.25
0.25 - 0.3
0.3 - 0.35
> 0.35
S
0 0 100 150 200
Metres
Fig. 3.10
(A-C)Mapsofpetiolephosphorus(P)concentrationinasmallCabernetSauvignon
vineyard in the Coonawarra region, South Australia, assessed by the “industry standard”
approach of analyzing a bulk sample (A) and intensive sampling of vines on a grid pattern
(B). Although the same criteria are used to interpret maps A and B, the map (C) that is based
on (B) presents a different conclusion with respect to P sufficiency from A. (Courtesy of
Dr. Robert Bramley, CSIRO Ecosystem Sciences, Adelaide, South Australia.)
and vines and because of analytical error. This uncertainty can be minimized with
the best sampling and laboratory procedures, but too much emphasis should not
beplacedonasinglesetofresults.Variationsinweatherfromseasontoseason
will affect leaf nutrient concentrations, so the best practice is to gather test results
over several seasons to show trends in nutrient status. As shown in figure 3.11, any
anomalous result will then become obvious.
Record the condition of the vines and soil (especially soil moisture) at sam-
pling time, as well as recent fertilizer or manure applications and cultural opera-
tions such as spraying with a fungicide. This information, together with the results
of plant analyses and any soil tests, provides a valuable record when compiled for
individual blocks over several seasons and should be part of any integrated produc-
tion system, as discussed in “Integrated Production Systems and Sustainability,”
chapter 6.
UsingCriticalValues
A critical value for each nutrient is ideally determined for an individual variety
when growth is not limited by any other nutrient or the water supply (critical val-
ues for plants under water stress tend to be lower than for well-watered plants).
However, varieties whether on own roots or rootstocks may differ in their nutrient
uptake and yield-nutrient relationships. This makes the task of calibrating plant
analyses for commercial combinations of variety and rootstock so large that only
a general set of values can be given, based on the much-studied Sultana variety
