Agriculture Reference
In-Depth Information
Table 2.1
Examples of changes in soil organic matter with implementation of organic
management treatments in long-term field experiments
Trial description
Changes in organic matter
Roseworthy Farming Systems Trial, South
Australia
Conventional, organic, biodynamic and
transitional management of pasture-grain
production in 440 mm y
-1
rainfall area over
9 years. Different organic matter additions,
tillage, fertiliser and rotation.
The initial soil organic C content of 1.3%
increased to 1.54% in the conventional
treatment and remained unchanged in the
organic treatment after eight years. In the
organic treatment, the negative effects on soil
organic matter of tillage for weed control may
have offset the benefit of incorporating
4.3 t ha
-1
of green manure in the third year
(Penfold
et al
. 1995).
DOK Trial, Switzerland
Organic, biodynamic and two conventional
treatments over 18 years. Treatments had
identical rotation and tillage and all received
manure, except one of the conventional
treatments.
Compared to the beginning of the trial, soil
organic matter C:N and total N remained
unchanged. The initial soil organic C content of
1.7% decreased by 22% in the unmanured
conventional treatment and by 13% in the
manured treatments (Fließbach and Mäder
2000). The decreased light fraction C in both
organic treatments compared to both
conventional treatments (Fließbach and Mäder
2000) was attributed to increased organic matter
decomposition (Fließbach
et al
. 2000).
Sustainable Agriculture Farming Systems
Project (SAFS), California, USA
Organic, integrated and conventional
treatments with the same four-year rotation
and one conventional two-year rotation.
Compared to baseline levels, soil organic C and
N increased by 22% in the organic treatment and
<1% in the conventional treatment (Clarke
et al
.
1998). Carbon inputs to the organic treatment
(poultry and green manures) were 6.2 times
greater than to the conventional system
(Gunapala and Scow 1998).
Results after the first and second rotation. The
systems varied in fertiliser (synthetic or organic),
winter cover crop and irrigation frequency
(Gunapala and Scow 1998).
Rodale Institute Farming Systems Trial,
north-east USA
Conventional arable (synthetic fertiliser),
organic arable (green manures) and organic
mixed (green manure and manure) over 15
years.
The organic crop treatment had lower but more
diverse organic matter inputs than the
conventional treatment. In the organic crop
treatment soil organic C and total N increased,
whereas they decreased in the conventional
treatment (Drinkwater
et al
. 1998).
Apple production, Washington State, USA
Quantification of soil quality under
conventional, integrated and organic apple
production. Results 4 years after planting.
There was no difference between treatments in
soil organic C content after 4 years. However, in
the year following compost additions, soil
organic C in the integrated and organic
treatments was higher than the conventional
treatment (Glover
et al
. 2000). Lack of organic
matter additions was critical to the conventional
treatment receiving the lowest quality rating
(Reganold
et a
l. 2001).
Apple production during conversion,
California, USA
Conventional and organic irrigated apple
production. Results from the second and
third years of organic management.
There was no difference in soil organic C or total
N content despite 2.1 t ha
-1
of C inputs to the
organic treatment. Potentially mineralisable N
was larger in the organic treatment at some
sampling times (Werner 1997).
