Agriculture Reference
In-Depth Information
7
Soil Quality in Vineyards
The Physical Environment
7.1
The soil must provide a favorable physical environment for the growth of vines—
their roots and beneficial soil organisms. Some of the important properties con-
tributing to this condition are infiltration rate, soil strength, available water ca-
pacity, drainage, and aeration.
Infiltration Rate
Ideally, the
infiltration rate IR
should be
50 mm/hr, allowing water to enter the
soil without ponding on the surface, which is predisposed to runoff and erosion.
The range of infiltration rates for soils of different texture and structural condi-
tion is shown in table 7.1. Typically, the soil aggregates should have a high de-
gree of water stability so that when the soil is subjected to pressure from wheeled
traffic or heavy rain, the aggregates do not collapse, nor do the clays deflocculate.
Some of the problems associated with the collapse of wet aggregates and clay de-
flocculation, and the formation of hard surface crusts when dry, are discussed in
section 3.2.3. Pans that develop at depth in the soil profile, as a result of remolding
of wet aggregates under wheel or cultivation pressure, can be barriers to root
growth.
7.1.1
Soil Strength
Soil strength is synonymous with
consistence
, which is the resistance by the soil to
deformation when subjected to a compressive shear force (box 2.2). Soil strength
depends on the soil matrix potential
7.1.2
m
and bulk density
BD
, as illustrated in fig-
ure 7.1. In situ soil strength is best measured using a
penetrometer
, as discussed
in box 7.1. The soil strength at a
m
of
10 kPa (
FC
) should be
2 MPa for
easy root penetration and should not exceed 3 MPa at
1500 kPa (
PWP
). As
shown in figure 7.1, when
m
is between
10 and
100 kPa, the soil strength
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