Agriculture Reference
In-Depth Information
Color and mottling: in the B horizon, orange and red colors indicate good
drainage, whereas grey colors indicate poor drainage. Mottles of red in a
grey matrix indicate periodic waterlogging.
Aggregate consistence: a strong to rigid consistence, especially when the soil
is moist, is likely to indicate impedance of root growth; this may need
confirmation by penetrometer tests.
Aggregate stability and dispersion: slaking in water indicates a weak structure;
dispersion, as described in box 3.2, indicates varying degrees of sodicity and
the likelihood of permeability problems (section 7.2.3).
Salinity: grapevines, especially those on “own roots,” are moderately
sensitive to salinity. Soils with EC e values 2 dS/m should be avoided,
although vines on Ramsey rootstock can tolerate EC e up to 4 dS/m (table
7.3).
The SOILpak-PLM (Precision Land Monitoring) system has been adapted
for vines from a system developed for cotton growers (McKenzie 1998). It is based
on Wetherby's system, with some modifications, for example, sampling at fixed
depths of 0-30, 30-60, and 60-90 cm down the profile. This approach gives
three layers of data, amenable to GIS entry, which can be mapped consistently
across any range of soil variation in the field. Individual Soil Factor Maps (e.g.,
soil pH) can be produced for each layer and linked to Soil Improvement Maps,
as shown in table 8.2. The Soil Improvement Map quantifies the treatment that
may be necessary, for example, the amount of lime per ha needed to raise the pH
of an acid soil to the desired level and the method of application (section 5.5.3).
The information in the Soil Improvement Map can also be converted into a Cost
of Repair Map and summed across the GIS map units to give a single cost of de-
velopment for the site. Additionally, Soil Factor Maps can be used to create a map
of on-site and off-site environmental risks, such as erosion, nitrate leaching, soil
compaction, and subsoil acidification. This information can be the basis for an
Environmental Management System.
Soil Factor Maps and Related Soil Improvement Maps
Derived from the SOILpak-PLM System
Table 8.2
Soil Factor Map
Soil Improvement Map
pH
Rates of liming material (kg/ha) to raise the
soil pH to a desired level
Deep tillage or ripping recommendations
Severity of compaction (based on aggregate
consistence or penetrometer test of soil
strength)
Dispersion in water (visual assessment)
Depth to mottled or gleyed subsoil
Gypsum recommendations
Recommendations for subsoil drainage or for
“ridging” to increase topsoil depth
Guidelines for the design of an irrigation
system
Type and rate of fertilizer to be applied
RAW (based on texture and soil depth)
Nutrients
Source: Adapted from McKenzie (2000)
 
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