In rural villages of Bangladesh, which are dependent on local agriculture for both income and food, excess water can be devastating. Melting snow caps in the Himalayas are causing rapid increases of water levels in tributary rivers, encroaching on already limited agricultural land space. Bangladesh is covered by over 230 of the world’s most unstable rivers, and flooding is becoming more common. Traditionally, flooding was predicted in the monsoon season for around 2 months, allowing crops to be grown for the remainder of the year. Recently, however, flooding has intensified and soils remain waterlogged for most of the year. This makes common agricultural practices nearly impossible.
The case study of rural villages in Bangladesh (such as Charbhangura) shows the importance of adjusting agricultural practices to changing climatic conditions, and adopting innovative solutions in response. So what’s the solution here – floating farms!
Floating farms (or ‘dhap’, meaning soilless farming) provide a platform for crops to be grown that adjusts to changing water levels. They are usually made from organic matter such as bamboo, hyacinth, soil and cow dung, or can be floated with empty oil drums. It is essentially similar to hydroponics, but uses locally available materials. The plant bed size varies, but is usually 15-50m in length, 1.5-2m wide, and 0.6-0.9m thick.
Many varieties of vegetables and spices are already being grown on floating farms, including beans, tomatoes, cauliflower, eggplant, carrots, ginger and radishes. Floating farms are also used for poultry, such as ducks. Plant beds from the previous harvest can also be re-used as fertiliser in the following season.
How to make a floating farm
1) A raft is made by overlaying hyacinth (this is a weed in many parts of the world that clogs waterways) with bamboo poles. This process is repeated, and weaved together, until the raft is thick and buoyant. The bamboo rods are then removed.
2) A week later as the initial hyacinth has begun decomposing, more hyacinth is added to reinforce the structure.
3) Mulch, soil, compost and dung are added on top for the plants to be grown in. Azola is a good nitrogen fixing plant used at this stage.
4) Seeds are sown. The recommended technique involves rolling a couple of seeds into a ball of compost (commonly the organic fertiliser Tema – or decomposed water hyacinth), and leaving them to germinate in a shaded area. They are then planted as seedlings onto the raft.
Floating farms have been incredibly successful! Papon Deb, Project Manager for the Wetland Resource Development Society, states “the productivity of this farming system is 10 times higher than traditional land-based agricultural production in the southeast of Bangladesh”.
For more information, and to see floating farms in action, watch this video from the United Nations Environment Program.