Tunnel irrigation must be designed, managed, and maintained to provide the right amount of water at the right time for the crop to grow optimally.
In most cases micro-irrigation (drippers or micro-sprayers) is used, and modern micro-irrigation has developed from a simple water source management system to a complex, knowledge-intensive management system that manipulates the chemical, physical, and biological environment in which the plant functions.
Type of tunnels
When we talk about tunnels or greenhouses, two types are used in South African agriculture:
A multi-span tunnel that is large (1 000 m² to 10 000 m² or 0.1 ha to 1.0 ha)
A small tunnel (300 m² or 0.03 ha).
As far as the soil medium is concerned, several are used successfully:
Soil- Most tunnels use the natural soil on which they are located.
Soilless- Most tunnels use a soilless medium such as coconut fibre, wood chips, gravel, polystyrene, or mixtures.
When it comes to micro-irrigation systems, farmers today can buy various systems that are technologically advanced and reliable. In addition to technologically advanced products (filters, control equipment, drippers, and micro sprayers), this technology includes, among other things, automation systems that integrate with focused farming principles to do precise fertilizer application with the water placement as and when the plant needs it.
Three types of irrigation systems can be distinguished:
– For crops grown in the soil.
– For crops grown in soilless media:
– Trough, where integral drip lines are used.
– Bags, where separate button drippers are used.
- Overhead sprayers.
- Commonly used for cutting cultivation.
- Overhead micro-sprinklers.
- Commonly used for the germination of seedlings in seedlings
- Sometimes used for dense plantings grown in the ground.
This article is mainly about drip irrigation used in soil or soilless conditions. A crop requires water that is delivered accurately and evenly through the tunnel for each plant through irrigation and it must be consistent in the amount of water with the right concentrate of nutrients.
The basic properties of drip irrigation are given in Table 1.
|Application||Row crops (both permanent and annual crops),|
|Method of application
|Point application by means of drip action, lateral distribution by soil or grow medium|
|Potential system efficiency||95% +|
|Mounting of emitter in relation to lateral||On wall inside lateral, or in-line as integral part of tubing, or directly/ indirectly on outer wall of tubing|
|Emitter interval||Externally mounted: At random.
All other: At fixed intervals varying between 0,3 m and 1,25 m
|Emitter discharge||0,5 – 8 ℓ/h|
|Operating pressure||5 to 40 m (50 – 400 kPa)
(also, pressure compensating)