Using Saline Water in Salt Affected Soils to Enhance Food Productivity and Farmer Incomes in Bangladesh

Bangladesh is a deltaic country with a total area of 147,570 km2, agriculture accounting for a major sector of the national economy. The coastal regions that occupy about 20% of the country's land area are very fertile and are used primarily to grow rice. During the rice season from April to the harvest in August river water as well as monsoon rainwater, harvested in large ponds and natural depressions, is used to flood the rice. During the subsequent months of dry season the intrusion of tidal water from the coast causes the soil and water salinity to increase from around 1 ppt (parts of salt per thousand grams of soil or water) in August to 8 ppt or more in April. This natural salinization is a major threat to crop production, so that about 90% of these potentially arable lands remain unused during the dry season. Key challenges to increasing the cropping intensity of these fertile lands are to use the collected pond water, consisting during the dry season of a mixture of rainwater and saline ground- and tidal waters, for crop irrigation without aggravating the natural soil and groundwater salinity, and to identify crops that will thrive in these saline conditions. In order to meet these challenges, irrigation must be applied at the right time and in the optimal amount for each type of crop so as to minimise the use of groundwater that would otherwise cause a further ingress of saline seawater and a resultant increase in soil salinity. Through an IAEA technical cooperation project, the Bangladesh Institute of Nuclear Agriculture identified and assessed crop varieties for their tolerance to salinity and evaluated the use of water from ponds and natural depressions for drip irrigation during the fallow period from August to April at pilot sites in the Noakhali and Satkhira coastal regions. Saline-tolerant varieties of wheat, mung bean, mustard, sesame, chickpea, tomato and groundnuts were identified using the carbon isotope discrimination methodology and made available to participating farmers. Yields obtained by farmers with these varieties at both Noakhali and Satkhira ranged from 1 to 3 tons per hectare. Such a harvested yield, compared with nothing if land were left fallow, would provide a substantial increase in food crop production and a significant economic benefit to resource-poor farmers. The soil moisture neutron probe (SMNP) was used to measure the soil content in order to ensure optimal irrigation scheduling. The soil salinity observed after the harvest of the crops in March/April averaged 1.5 ppt with drip irrigation, compared to 6.9 ppt on fallow land, hence showing that there is no adverse effect on soil salinity associated with the sustainable and productive use of these fallow lands for additional food production and income generation.