SUBJECT: Agricultural Science
LEVEL: Forms 4 & 5
CSEC Agricultural Science Syllabus
SECTION A: Introduction to Agriculture
- Agricultural Science and Agriculture
1.3 Describe conventional and non-conventional crops and livestock farming systems (aquaponics, hydroponics, grow box, trough culture, urban and peri-urban farming)
This a system that combines both aquaculture (rearing on fish inland) and hydroponics (growing of plants in water).
Aquaponics = Aquaculture + Hydroponics
A farmer can get two products from an aquaponics system:
- Primary or main products are crops/ plants
- Secondary product is the fish
Parts of an Aquaponics System
The main parts (components) of an aquaponics system are:
- Rearing Tank – where the fishes grow
- Growing Bed – where the plants are located
- Water Pump and tubing – Pump is located at the lowest point of the system and used to push water back to the upper level.
- Aeration system (air pump, air stone, filter, tubing) – to provide oxygen
- Solid Removal/ sedimentation tank – to remove solid particles which the plant cannot absorb and may block the tubing etc.
- Bio-filter – the location at which the nitrification bacteria can grow and convert ammonia to nitrates.
- Sump – lowest point in the system to catch water. The pump can be placed here.
Lifeforms in an Aquaponics system
These three living entities each rely on the other to live.
Fishes are used in an aquaponics system to provide nutrients for the plants. These nutrients come from their fecal matter and urine (which contains ammonia) and other waste from their bodies. It is critical to control the amount of ammonia in the system; therefore, the pH, oxygen and temperature must be properly managed.
Conversion of Ammonia by Bacteria
Beneficial bacteria convert ammonia to nitrate. The fecal matter and urine of fish contain ammonia. However, the plants are unable to use the nitrogen in ammonia in this form because it is toxic to the plants. Therefore, the ammonia must be converted to a non-toxic form which is the nitrate form. This conversion is done by bacteria. The bacterial is called nitrifying bacteria and they live in the tank walls, underside of the growing medium, rafts which old the plants etc. These bacteria are natural and will start living in a system when ammonia is present. Nitrifying bacteria naturally live in the soil, water or air. These bacteria convert ammonia first to nitrite and then to nitrate which plants consume.