4 Crop management
Since cropping on highly saline areas is a waste of resources, it was important to grow crops where tsunami impacts were minimal and soil fertility was relatively unaffected. Avoiding saline areas was relatively easy using EM38 surveys (see Section 3) to identify saline soils. Farmer knowledge and experience of tsunami flooding levels and the duration of inundation, soil and plant indicators of salinity, and soil tests also helped with salinity assessment.
The Aceh experience showed that salinity levels were related to the permeability of the soils, the duration of seawater inundation and the physical location. For instance, crop failures occurred in low-lying areas near tidal creeks after inundation during high-tide events. Crops grown in coastal soils, such as peanut, were more affected by seawater inundation than crops grown on better soils further inland, such as soybean. Sandier soils close to beach dunes appeared to be the most saline following the tsunami. Peanut crops on the dunes showed patchy growth or leaf yellowing. The patchiness was associated with salt that accumulated on the soil surface following evaporation of salty, shallow groundwater. The yellowing appeared to be a related nutritional problem, or possibly a disease problem.
Raised crop beds were useful in saline soils because the beds could be irrigated to leach salt before crops were planted. Raised beds were also useful in areas prone to waterlogging.