Proceedings - Balai Penelitian Tanah

INTRODUCTION
154
Sammut et al.
Brackishwater aquaculture is a major industry in the coastal lowlands
of Aceh (Nanggroe Aceh Darussalam Province), Indonesia. Before
the December 2004 earthquake and resultant tsunami, there were
over 200,000 individuals involved in the production of fish and shrimp
(Phillips and Budhiman, 2006). In Aceh most farms are based on
‘extensive’ culture systems which feature low stocking densities, tidal
delivery of water and minimal farm inputs. The tsunami destroyed
primary, secondary and tertiary dykes and canals, and also deposited
debris in ponds. Almost all (271) of the 297 coastal hatcheries were
also destroyed (Mangalagiri, personal communication, 2006), and
technical support and extension services were impacted through the
loss of life and facilities. The major facility responsible for providing
technical support to the aquaculture industry in Aceh, the Centre for
Brackishwater Aquaculture Development (CBAD) Ujung Batee, was
badly damaged in the tsunami. Laboratories, hatchery facilities and
staff housing were destroyed.
In March of 2005, the Australian Centre for International Agricultural
Research (ACIAR) conducted a development visit to Aceh to identify
opportunities to assist in the redevelopment of the aquaculture
industry and other forms of agriculture. Acid sulfate soils (ASS) and
other problematic sediments were identified as a significant constraint
on reconstruction. The destruction of dykes led to daily exposure of
pyrite (FeS2) in ASS-affected pond bottoms during low tide which
generated more soil acidity than before the tsunami (Sammut and
Tarunamulia, 2006). The reconstruction of ponds would also involve
the excavation of ‘raw’ soils, that is, ASS containing sufficient pyrite to
generate large amounts of acid once exposed to oxygen. New or
repaired dykes have a high acid generating capacity because fresh
sediments, excavated from pond bottoms, have a larger concentration
of pyrite than soils in older dykes (Sammut and Tarunamulia, 2006).
Reconstruction of dykes, ponds and canals using raw ASS without
proper assessment and remediation would lead to production losses,
as occurs throughout Indonesia (Sammut and Hanafi, 2000). Before
the tsunami many ponds were also built in sandy soils and
experienced recurrent production problems. Sandy sediments are not
suitable for ponds because they are highly erodible and prone to
leakage. Maintenance of ponds in sandy soils is often prohibitively
expensive due to the need to regularly rebuild slumped or eroded
dykes. Without proper assessment, the re-use of sandy sediments or
the development of new ponds in affected areas, would ultimately lead
to unmanageable dyke erosion and slumping, and high levels of water
loss. Disease risks are also considerably higher because of the
transfer of pathogens or infected stock between ponds when dykes
fail (Sammut and Tarunamulia, 2006). These environmental and
International Workshop on Post Tsunami Soil Management, 1-2 July 2008 in Bogor, Indonesia