A system has been developed in Thailand by a group known as ITAG (International Technical Assistance Group) which combines fish farming with the growing of vegetables and crops on raised beds. Long narrow fish ponds are dug in between long narrow raised beds. Both ponds and raised beds are about 2m x 15m. The ponds are about 1m deep. The top-soil (the top fertile layer of soil about 30–40cm deep) from digging the ponds is added to the raised beds.
The soil is double dug in the raised beds. First, the top layer of soil is dug well and mixed with compost. Then the top-soil (30–40cm deep) is removed at one end of the bed and placed to one side. The lower layer of the soil is then loosened. Top-soil is turned over onto the loosened subsoil and the process repeated right along the bed. This method allows water – both from the pond and from rain – to soak deep into the soil.
A mixture of crops and fruit trees are planted on the raised beds. Water from the pond will seep into the soil, allowing the roots to grow deeply, resulting in healthy plants. Because the beds are raised, they cannot be flooded. Mud from the pond bottom is added to the raised beds and is a valuable fertiliser. Plant wastes and weeds can be added to the pond for feeding the fish.
The fish species commonly used are tilapia, catfish and carp. The narrow pond allows for careful observation of fish for any signs of disease or parasite infections. Fish that show any sign of poor health are removed immediately.
There are many benefits from combining the two together. Both fish and vegetable husbandry benefit. Traditional methods produce 1–2.5 tons/ha/year. However, these methods produce 5 tons/ha in the first year, 10 tons/ha in the second and 20 tons/ha in the third year – a huge increase in production! The amount of labour is greatly reduced as there is no need to transport compost or water for irrigation. In addition, by using simple sand filters, water can be cleaned for household use.
This process was developed for ITAG in Thailand by Dr Richard Neve.
Know your fish!