Agriculture Reference
In-Depth Information
density (BD). Soil samples were dried at 50
o
C, ground to pass a 2 mm
sieve and stored until analysis. Organic carbon content was analyzed by
the Walkley-Black Procedure [11] and soil organic carbon storage (SCS)
was calculated as following.
SCS (Mg ha
-1
) = BD × SOC ×DP × 100
where, BD: bulk density (g mL
-1
); SOC: soil organic carbon content (%);
DP: soil depth (m).
To obtain the soil carbon distribution between conventional and or-
ganic rice fi elds, soil samples were collected from different fi elds managed
by the fi elds mentioned above (where topsoil samples were taken), using
a post hole auger at depth of 0-2.5, 2.5-7.5, 7.5-15, and 15-30 cm at har-
vest of rice in September 2009. These soil samples were also analyzed for
organic carbon content by the above mentioned methods.
Rice yields were estimated by air dried subsamples taken using a 1 m
row section after manually harvesting whole fi elds in September 2008.
5.3 RESULTS AND DISCUSSION
The soil in the organic farming system showed higher soil carbon content
than conventional soils after four years of continuous organic farming,
however, there were no significant differences in soil bulk density between
the two farming systems (Table 1). Soil carbon storage in organic farming
was significantly increased compared with conventional farming. These
differences were also obvious in soil carbon content profile, which was
significantly higher in the organic field than the conventional field, espe-
cially in the top 10 cm soil layer (Figure 3). However, soil carbon contents
are somewhat lower in Figure 3 compare with Table 1. This difference
suggests that there was diversification of soil carbon content depending on
the site specific location, however, organic fields showed higher carbon
content than the conventional fields in both 2008 and 2009.
