Agriculture Reference
In-Depth Information
35
30
25
20
Very good
15
Good
10
Moderate
Bad
5
A classification of structural
quality for vineyard soils
Figure 7.3
Poor
0
5 0 5 025
30
35
(White 1997). Reproduced
AWC (%)
with permission of Blackwell
Increasing droughtiness
Science Ltd.
Values of
AWC
and air capacity have been used to create a classification of
structural quality
, in terms of the soil's susceptibility to waterlogging and droughti-
ness (fig. 7.3). Originally developed for topsoils in England and Wales (Hall et
al. 1977), this classification has proved valuable for vineyard soils (Cass et al. 1998)
and sets practical ranges for good aeration and water availability.
The Chemical Environment
7.2
A satisfactory chemical environment requires an adequate supply of macro- and
micronutrients, and an absence of any element toxicities and undesirable residues
from pesticides. Soil nutrients and their supply to vine roots are discussed in chap-
ters 4 and 5. Key management practices for achieving a satisfactory chemical en-
vironment are discussed in this chapter.
Soil and Plant Testing
For vineyards, the most important elements to monitor are N, P, K, and the mi-
cronutrients, usually by plant analysis (section 5.2.1). Appropriate decisions on
fertilizer application can then be made. Soil testing to a depth of 1 m, noting any
marked soil horizon changes, should be carried out when a vineyard is established,
as discussed in section 8.2.2.3.
Testing for soil pH is important because of its influence on the availability
of micronutrients (section 5.5.2) and also on the concentration of potentially toxic
Al
3
ions. Cass (1998) recommends a pH range (in water) of 5.5-8 for vines.
Vine root hairs, which facilitate the uptake of immobile nutrients such as P, are
most abundant at pH 5.7 (Richards 1983). Below pH 5.5, exchangeable Al
3
may exceed 1 mg/kg soil, and thus adversely affect root growth. However, because
grapevines grow successfully on low pH soils in many parts of the world, Winkler
et al. (1974) suggest that low pH itself is not critical. For example, in the delta
7.2.1
