In the low-lying coastal areas of Bangladesh, salinity affects approximately 2.9 million hectares of land. Until recently, this limited the farmers of the area to planting one rice crop a year and having to watch their fields lie fallow due to salinity for the other seven months. A pilot water management project of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture has identified salt-tolerant local crops varieties and, using neutron probes to measure soil moisture and set irrigation levels that will not affect soil salinity, made it possible for local farmers to plant a second crop after the rice harvest. The new crops, such as groundnuts, mungbean and chickpeas, add to local nutrition, but also fix nitrogen which improves the soil quality for subsequent seasons. Plus, the income from the second crop means farmers no longer must leave the area to seek employment in cities. From two pilot areas, the project is scaling up to cover about 1.8 million hectares, more than half of the coastal region.
Each spring, right after the monsoon rains finish in Bangladesh, farmers rush to their fields to plant their rice crops. It is the only time of year they can grow rice, because the heavy rains dilute or wash away the salinity that builds up in the delta’s low-lying soils. They use harvested monsoon rainwater to flood the rice during its growing season and then harvest in August. During the subsequent months of the dry season, the intrusion of tidal water from the coast increases the soil and water salinity eightfold. This natural salinization is a major threat to crop production, meaning a seven-month fallow season for some 90 percent of the arable land in the coastal areas.
As a result, many men move to the cities after harvesting their rice, looking for work to supplement their income, because their families cannot survive on income from one rice crop a year. The Bangladesh capital, Dhaka, already considered the world’s fastest growing megacity, has to absorb the seasonal migration of the men from the coastal areas along with the estimated 3-400000 migrants who arrive there each year, all of which adds up to untold
social problems. This seemingly insurmountable annual scenario held back development in the coastal region which is one of the most populated regions on earth, with a density of more than 200 people per km2.
In 2007, the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, in collaboration with the Bangladesh Institute of Nuclear Agriculture, launched a pilot effort to develop water management practices that could reclaim the coastal land from their saline soils and ensure year-round productivity. There were two parallel efforts: first, to identify salt-tolerant crop varieties to recommend to farmers and, second, to find ways to use brackish water to irrigate crops at a level that would not affect soil salinity.
