Agriculture Reference
In-Depth Information
Table 3.7
Micronutrient Concentrations in Petioles for Assessing the Nutrient Status of
Grapevines
Low to
marginal
(mg/kg)
Micronutrient
element
Deficient (mg/
kg)
Adequate
(mg/kg)
High to excessive
(mg/kg)
Fe
25-30
>30
Cu
<3
3-5
6-11
>40
a
Zn
<15
15-25
26-150
>450
a
Mn
<20
20-29
30-60
>500
a
B
<25
25-34
35-70
>100
Mo
<0.05
0.05-0.19
0.20-99
>100
a
Mayindicatespraycontamination.
Compiled from Robinson et al. (1997), Goldspink and Howes (2001), and Robinson (2005).
Assessment of a vine's N status is improved when NO
3
-N concentration is
used together with a total N analysis, but general leaf color and vine vigor should
also be considered. There is an interaction between N and K in vines that results in
petiole K concentrations being lower when vines are well supplied with N. For this
reason, K analyses should always be interpreted in conjunction with N. Ideally,
the K-to-N ratio should be between 1 and 2.
Soil Testing
Because it is a perennial, the grapevine is best suited to plant analysis, when
repeated samples can be collected from the same plant from year to year.
Notwithstanding that soil testing is more widely used for annual crops, soil analy-
sis still has value for grapevines, especially at vineyard establishment when it is the
only tool available (see “Describing a Soil Profile,” chapter 2). A soil test is essen-
tial for pH, from which a decision is made to apply lime if the soil pH is too low
(see box 3.6) or whether a micronutrient deficiency might occur if it is too high.
In France, a soil test is used to estimate “active” calcium carbonate, which if too
high can reduce Fe availability; soil tests are also valuable for indicating salinity
and sodicity (see “Soil Testing for Salinity”).
Varioustestshavebeendevelopedtomeasurekeychemical,physical,and
biological properties of soil. Here I deal briefly with the chemical tests; relevant
physical tests are discussed in chapter 4 and biological tests in chapter 5. The
prime purpose of a chemical test is to assess the soil's ability to supply an essential
nutrient or to determine whether there is a potential toxicity, as in the case of
salinity for example. Although analytical methods have been developed to extract
the “available” part of the total element in a soil, this is but a snapshot in time.
Moreover,thisconceptofavailabilityisincomplete,becauseavine'sdemandfora
