Agriculture Reference
In-Depth Information
TABLE 1: Comparison of soil carbon sequestration between organic and conventional rice
fields in the top 10 cm soil depth.
Soil Bulk Density g mL -1
Carbon Content %
Soil Carbon Storage Mg ha -1
Organic
0.88
2.89
25.0
Conventional
0.80
2.22
17.6
Significance
NS
*
**
**,* and NS indicate significance at 1% and 5% level and not significant, respectively.
Using Table 1 data, we can estimate the soil carbon sequestration abili-
ty. Organic farming can increase 1.85 ton C per hectare per year compared
with the conventional farming system. This value also agrees with the data
that Shirato et al. [12] obtained from paddy fi elds in Thailand. The rate of
increase in SOC stock resulting from changes in land-use and adoption of
recommended farming practices, follows a sigmoid curve that attains the
maximum 5-20 years after adoption of recommended farming practices
[8]. In addition, the amount of organic carbon stored in paddy soils is
greater than in dry fi eld soils, due to different biochemical processes and
mechanisms specifi cally caused by the presence of fl oodwater in paddy
soils [13]. These results show organic rice farming has a lot of potential to
improve soil carbon sequestration and it may also mitigate global warming
in Indonesia.
The humid tropic condition covers a large area in west Java with very
high annual rainfall (>200 cm). Tropical evergreen forests are the climax
vegetation, and crop production is limited by low fertility and soil acidity
due to leaching and rapid invasion by weeds. On suitable soils, notably on
rice paddies, intensive food cropping systems exist [14]. In general, if crop
residues are returned and supplemented with nutrient inputs, these systems
maintain adequate soil organic matter and production levels in the humid
tropic regions [15]. However, burning crop residue is common practice
in the conventional rice production system in west Java. When stubble is
removed or burned, only the root systems are recycled. The SOC contents
of these managed paddy soils were very low, for example, Kyuma [16]
 
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