Drought and water scarcity are putting more pressure on crop production. With this in mind, the way irrigation water is delivered to plants is becoming very important. Willem Botha, marketing manager at Netafim South Africa, says that the method of water delivery is what distinguishes drip irrigation from other methods of irrigation.
“The method used to deliver the water determines the way in which it is distributed through the soil. In the case of drip irrigation, the water is distributed by the soil rather than the irrigation system itself. This allows for water savings and numerous other benefits.”
This is made possible through the forces of adhesion and cohesion. “A drop of water exits the emitter and drops to the soil surface. It is distributed through the soil to where these forces take over.” In the case of micro sprinkler irrigation, for example, an emitter will spray the water through the air.
Drip or micro irrigation?
“If we compare the two irrigation methods, drip irrigation will wet a small area and micro sprinkler irrigation will wet a larger area, but both are have the same goal.” This in itself makes drip irrigation much more efficient.
Drip irrigation’s higher efficiency can be explained by evaporation. “The larger the wettened area, the more evaporation will occur. Futhermore, the wind cannot blow away the water if drip irrigation is used.” Although the exact percentage of water saved cannot be pinpointed, it is generally accepted that between 20% and 30% water is saved through drip.
“Just remember, though, that there is always a ‘but’. Savings on water and other inputs depend on proper planning, suitable installation, correct management and accurate scheduling. You can definitely waste water through drip irrigation if it is not properly managed.”
Factors that come into play when planning
When it comes to planning a drip irrigation system, there are quite a few factors to keep in mind. Most importantly, you have to start the planning process with your end goal in mind. “Are you installing the system to achieve better crop quality, greater yield or tofor better control fertiliser application and irrigation?”
The factors that should be considered are:
- Soil type
- Water availability
- Water quality
- Energy availibility
- Fertiliser needs
“Remember, nothing about this is simple. Every farm and situation differs and has different requirements. That is why it is very important to include experts in the planning process.” Willem encourages farmers to work only with certified system designers and soil spesialists, agriculturalists, crop specialists, nutrition specialists and any other trusted experts that could offer a significant contribution to the planning process. “The biggest mistake you can make is to go at it alone or with only a system designer. Everyone must to put their heads together.”
All soil types can be irrigated. The determining factor is which management inputs and decisions will be necessary to irrigate successfully. “One of the most important factors to remember, if you want to understand drip irrigation, is that water moves differently in different soil types,” says Willem. The soil type will affect everything – the flow rate, emitter spacing, irrigation times and so on.
“Clay soil and sandy soil, for example, have completely different irrigation patterns. Under drip irrigation water takes on the form of an onion with various layers. In sandy soil the distribution will be deeper but narrower and in clay soil the distribution will be wider but shallower.”
Benefits and risks
As we have already mentioned, the greatest benefit of drip irrigation comes from water saved by wetting a smaller area. “Further benefits include saving on the cost of energy, thanks to lower flow and pressure. One also saves on labour costs because of the lower maintenance requirements.”
There are, however, always risks involved. The greatest risk with drip irrigation is the risk of clogging. “That is why all decisions taken must be aimed at keeping the clogging risk as low as possible.”
Although drip irrigation has wonderful benefits, it is, as is the case with any other system, not foolproof. “Over- and under-irrigation is possible and will lead to stress in the plants due to certain physiological processes being put under pressure. This will lead to production losses,” Willem explains.
To prevent undue pressure, proper monitoring is important. This can be done through visual observations, observations with electric equipment and simply by digging a hole in the soil and having a look at what is going on.
The conclusion is simple but important: Plan thoroughly, make use of all the available expertise and monitor constantly. “If you do this, drip irrigation will yield numerous benefits.” – Marike Brits, AgriOrbit
For more information on Netafim South Africa’s products and services, phone 021 987 0477 or visit www.netafim.co.za.