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Mangrove soils

Mangrove soils are basically alluvial in nature and mainly consist of fine-grained sediment in which silt and clay predominate. The soils are often clayey or semifluid with abundant organic soil material in parts. Since the soils are almost permanently under submerged saline conditions, they are strongly reduced, have a low oxygen content, but high salt content. Hydrogen sulfide can often be smelled in areas where sediments are enriched with pyrites (FeS2). If the soils are high in pyrite, under natural conditions, the soil pH is higher than 7.0, but oxidation of the pyritic compounds occurs (if pyrites are present in appreciable amounts), as in the following equation:

Therefore, when mangrove soils are subject to strong acidification upon drying, they are generally called potential acid sulfate soils or saline acid sulfate soils. Regarding agricultural potential, the mangrove soils can be rated as ‘low’ in potential for crop production,
    due to:
- high salinity, derived directly from seawater intrusion or frequent flooding with
- adverse soil conditions both prior and after drainage, i.e. poor physical properties
    due to:
          unripe stage, and uneven land surface, and extreme acidification upon drying;
- high monetary input for major engineering measures needed, namely dike building,
          empoldering, proper drainage and flood control system; and 
- fragile ecosystem of the mangrove complex that is susceptible to rapid deterioration
          under improper use and management.

Reclamation of these soils faces three major problems:
flood protection
 2) leaching of salt
 3) proper water regulation to maintain water at a proper level to prevent oxidation
     (which produces extreme acidic conditions).The cost of reclamation is very expensive.
     Therefore, at present, it is imperative that these areas should remain as a nation’s
     resource. Although Thailand is likely to face a serious shortage of agricultural land, it is
     inadvisable to open new mangrove areas for crop production as long as the present
     utilization of this land remains inefficient. However, it is acceptable to utilize mangrove
     for the production of charcoal, timber and for fisheries. Nevertheless, proper
     management to maintain the highest possible production of the mangroves is required.
     Furthermore, management must ensure that the environment is not damaged.   

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