Agriculture Reference
In-Depth Information
Table 2.2
Examples of differences in soil physical, biological and chemical characteristics of soil fertility in long-term field trials that include organic
farming treatments
Trial description (see Table 2.1
for details)
Physical fertility
Biological fertility
Chemical fertility
Roseworthy Farming Systems Trial,
South Australia
There was higher infiltration and
lower soil loss in the treatments
with stubble retained. In the
integrated treatment there was less
infiltration and greater soil loss
(after 4 years) due to lack of
disturbance of surface crust and
stock trampling. There was no
difference between treatments in
water-stable aggregation (Penfold
et al.
1995).
There was no significant difference
between treatments in microbial
biomass, cotton strip tensile
strength, or earthworms.
Compared to initial soil levels,
extractable P increased by 19% in
the conventional treatment and
declined by 9 and 12% in the
organic and biodynamic
treatments respectively, as a result
of lower inputs and less soluble
fertilisers. The P budget for
biodynamic treatment was
negative. There was no difference
between treatments in
exchangeable cations or DTPA
extractable ions (Penfold
et al.
1995).
DOK Trial, Switzerland
There was no difference between
treatments in bulk density, splash
erosion, volume of total or large
pores. Aggregate stability
(percolation method) was 10 to
60% higher in both organic
treatements than in either
conventional treatment, indicating
lower erodibility (Siegrist
et al.
1998).
Compared to the conventional
treatment, the organic treatment
showed higher microbial biomass
C and N, mycorrhizal colonisation,
enzyme activities (Fließbach and
Mäder 2000), earthworm biomass
and density (Siegrist
et al.
1998)
and microbial, faunal and plant
diversity (Mäder
et al.
2002). In the
laboratory, there was over 10%
greater organic matter
decomposition in the biodynamic
soil than in the conventional soils
(Fließbach
et al.
2000).
Available P was adequate but
decreased in all except the
synthetic fertiliser treatment. The
average P budgets (kg P ha
-1
y
-1
)
were 3.8 for synthetic fertilisers
only, -5.0 for synthetic fertilisers
and manure, -5.7 for organic and -
7.8 for biodynamic (Oehl
et al.
2002).
