Cropping Systems Intensification in the Coastal Zone of the Ganges Delta: Opportunities and Risks

Abstract

The coastal zone of the Ganges delta has many constraints and threats that have hampered development. However, recent research indicates that there are numerous viable options for cropping systems intensification that have yet to be fully exploited. The main opportunity involves changing the cropping season to use stored water with a low solute potential in the rabi season and to harvest crops early to avoid crop stress from waterlogging, salinity/drought, heat and or storms. Early planting of rabi season crops requires harvest of kharif rice 15 to 30 days earlier. Several earlier maturing cultivars have been identified with yield gains of 0.5 to 1 t ha^-1. The early harvest of kharif rice opens up opportunities for promising new crops for the rabi season such as zero tillage potatoes. Moreover, for a range of other rabi crops (e.g. wheat) early sowing results in higher yield potential. Realising the higher yield potential depends on early drainage of excess floodwater, and a drainage system to mitigate the risk of heavy rainfall events in the rabi season. Canal and pond water remains mostly below 4 dS m^-1 and hence is suitable for irrigation during the rabi season but the volume available is limited. Low cost drip irrigation was shown to be highly profitable and is a potential technology for value addition of the scarce water supplies. In the coastal zone, current kharif season rice supplies are not sufficient to meet food security needs. Aus rice was successfully grown at a number of locations and produced good yields (4.0-4.5 t ha^-1). A diverse range of new crops were successfully grown especially vegetables for which local markets exist. However, dry season cropping in the coastal zone involves risks, particularly from heavy rainfall either at the end of the monsoon season or from February onwards and climate analysis suggests the frequency of these heavy rainfall events has increased in the last 40 years. The technologies developed and the risk management strategies required will need to be adapted to the variation in rainfall and river water salinity across the coastal zone of the Ganges delta.