Agriculture Reference
In-Depth Information
TABLE 1.6
Key Parameters Important to Soil Quality and Sustainability
Soil Parameters
Physical
Chemical
Biological
1.
Structure
: aggregation,
penetration resistance, bulk
density, texture, mineralogy,
SOC concentrations,
sesquioxides consistency,
shrinkage characteristics
1.
Reaction
: pH, electrical
conductivity, total acidity
and exchangeable Al,
soluble salt concentration,
sodium absorption ratio
1.
SOC
: total and different
fractions (e.g., labile,
passive, heavy, light),
MBC
2.
Water retention
: field
capacity, wilting point, clay
content, SOC concentration,
pore size distribution
2.
Charge properties
: total
charge cation and anion
exchange capacity, point of
zero charge, effective
cation exchange capacity,
relative abundance of
different cations
2.
Soil macrofauna
:
earthworms, termites,
centipedes, millipedes,
nematodes
3.
Water transmission
:
aggregation, total and
drainage on macroporosity,
bulk density, crusting,
horizonation, hydraulic
conductivity, infiltration
capacity
3.
Plant nutrients
:
concentration of total and
available macronutrients
and micronutrients
3.
Rhizospheric
: disease
suppressive properties, soil
enzymes
4.
Erodibility
: texture,
aggregation, clay minerals,
SOC concentration,
infiltration rate
4.
Elemental imbalances
:
toxicity (Al, Fe) and
deficiency (macron and
micro nutrients) heavy
metal concentration (Pb,
Hg, As, Cd)
1.4.1 t
echnological
o
ptionS
for
S
oil
S
uStainability
The basic strategy is to (1) replace what is harvested; (2) respond prudently and ratio-
nally to what is transformed naturally or anthropogenically; (3) predict, anticipate
plan for, and adapt to potential perturbations; and (4) use technology wisely. The
SOC concentration [including total stock, depth distribution to 1 m, different frac-
tions, and the mean residence time (MRT)] is a key determinant of soil chemical,
physical, and biological quality and biogeochemical cycles (Manlay et al. 2007).
Thaer's “humus theory” proposed in 1809 is indicative of the recognition of the
importance of SOC to agronomic productivity.
Soil degradation by accelerated erosion leads to rapid depletion of the SOC pool
and thus to adverse changes in soil properties. Land use, and specifically uncon-
trolled and intensive grazing, can also affect the SOC pool and its variability across
the landscape (du Preez et al. 2011a,b). Land use and soil management influence the
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