Drip irrigation is a form of micro-irrigation and is undoubtedly one of the most significant innovations for growing more food and plant bio-mass with less water.
Drippers provide a carefully controlled flow of water – common flow rates being 2, 4, 6 or 8 litres per hour. Pulsed drip irrigation systems utilize ultra-low flow rates of 1 or less litres per hour.
In contrast to traditional irrigation methods of flooding rows or using impact sprinklers to soak a large area, drip irrigation equipment allow for distributing water to the only place it is needed – the root zone of plants. Constant dripping on a single patch of soil over many hours causes the water to soak deeply into the soil, eliminating surface run-off and evaporation. Plants on drip irrigation need less fertilizer inputs, also allowing for liquid fertilizers to be applied through the irrigation system.
Most drip irrigation components require a pressurised water source of at least 1 Bar (15psi) to achieve target flow rates. Usually a pump with a pressure switch is connected to the water source and irrigation system to provide a constant preset pressure. Gravity fed drip systems are possible on a smaller scale if the water source is sufficiently raised above the area requiring irrigation.
Setting up a drip irrigation system is more expensive and time consuming than traditional sprinkler systems as more pipes are needed to distribute water to each plant. Additionally, each plant requires an individual dripper. It is a good idea to add a particle filter to the water source to ensure sand and other dirt doesn’t block the small dripper holes – this will require regular cleaning to keep the system free flowing.
The simplest dripper design includes a plastic barb on one side and the dripper head on the other. Using an irrigation tool or other sharp implement (such as a drawing pin) a hole is punched into the pipe where the dripper is to be located. The dripper barb is then pushed into the hole – usually an audible click indicates a flush fit. Some dripper designs have a screw thread and are screwed into position.
Often it is not practical to lay the irrigation pipe directly in the beds or directly next to the stem of the plants – in these instances, a thin flexible pipe is fitted over the dripper head – the other end positioned precisely where water is required.
Ready made dripper pipes are available in some places, which come from the factory with drippers installed at regular intervals. This allows for much faster installation, but less flexibility with regards to spacing and location of the drippers.
To maximize efficiency of the system, it is advisable to add a timer so that irrigation can take place at the coolest time of the day – usually early morning. Annual vegetables and other plants with compact root systems will need irrigation more frequently – possibly daily or every 2 or 3 days. Larger perennials and trees should be watered less frequently but for longer durations to soak the soil completely and encourage deeper, more extensive root growth. Innovative devices like the Tree Tray are excellent companions for drip irrigation systems as they provide a guide slot to keep pipes in position and allow for less precise positioning of drippers, as water is channeled from a wide area to the base of the plant or tree.