Geoscience Reference
In-Depth Information
Table 25.3
Methods utilised to minimise variability in controlled arable agricultural eco-
systems, including broad aims and unintended effects
Method
Aim
Unintended effects
Biotic variability
1) Planting of a single
species (often a
single genotype)
2) Addition of
herbicides and
pesticides
1) Reduce species interactions
such as competition and
herbivory, which may
reduce yield
2) Species/genotype chosen to
ensure high yield and for
other desirable
characteristics (e.g. taste,
appearance) to make a
marketable product
1) Reduction of genetic
variation within the
planted species
2) Loss of ecosystem
functioning and
stability due to
decreased interactions
3) Loss of biodiversity at
a range of scales and
taxa
Climate/hydrological variability
1) Irrigation
2) Polytunnels
1) Provision of a constant or
regular water supply to
enable consistent growth
and high yields
2) Mitigation of variations in
climate and weather which
may lead to e.g. dry periods,
frost etc.
1) Degradation of water
supplies outside the
ecosystem
2) Increased soil erosion
3) Interruption of
ecosystem functions
which require such
variability (e.g. life
cycles of invertebrate
species)
Soil variability
1) Ploughing of fi elds
2) Addition of
fertilisers
1) Break-up soil structure to
reduce compaction, prevent
distinct horizons forming in
the upper layers, and allow
surface organic matter to
mix with lower layers where
plant roots are common
2) To reduce spatial and
temporal differences in the
structure, texture and
nutrient content of soils to
ensure consistent yields
1) Reduction in soil
biodiversity
2) Increased soil erosion
nitrogen, root depth, drainage and hydrological connectivity between measurement
points were not made, and may help explain this residual variability. Furthermore,
the model was unable to account for low plant populations and non-uniform plant
spacings (Batchelor et al., 2002). Similarly, high-resolution measurements of spatial
variability in environmental and management factors (including herbivory by
soybean cyst nematodes and weed competition) were incorporated into the
CROPGRO soybean model in the same fashion, explaining 80 percent of the vari-
