Drip irrigation is the most efficient method of water supply, achieving over 90% efficiency. With drip irrigation, water is applied directly to the crop root zone, where soil soaks it immediately, thus reducing evaporation or runoff.
Despite its efficiency, prior to drip system installation, a farmer must be aware of the following limiting factors:
- Soil type (clay, loam or sand); important for determining dripline emitter and line spacing
- Planting scheme— dense, sparse or mixed plantings
- Topography (sloped or flat); used to determine inline tubing orientation and modify spacing or separate hydro-zones where needed
- Irrigation water type and characteristics
- Proposed planting, including relative water needs of all species, and sizes at planting and maturity
- Local conditions, including elevation differences, local climate data (ETo), and additional site specific information.
All of the aforementioned factors contribute to specific requirements regarding specific drip irrigation designs and components.
Drip Irrigation System Components and their Specific Function
The drip irrigation system is a set of various components which, combined together, provide water to plants in the most efficient way. This irrigation type suits any landscape and crop type, whether tree, vegetable, arable crop, or grass. It’s mostly used in farmland with runoff problems. Beneficial, it can be installed both above and below the soil surface.
Typical drip irrigation system consists of the following components:
1. Pump unit
The pump unit takes water from the source and provides the appropriate pressure for delivery into the pipe system.
2. Control head
The control head consists of valves and filters. Some control head units also contain a fertilizer or nutrient tank for the slow adding of measured fertilizer doses into the water during irrigation.
Valves control the discharge and pressure in the entire system. There are two different kinds of valves which can be installed to control the water flow:
- Isolation Valves –used for infrequent shut off of water supply, i.e. to shut off water for repairs or during non-irrigation season. Isolation valves are usually manually operated.
- Control Valves – used to irrigate individual areas that are separate from one another. There can be several control valves installed on drip irrigation.Control valves can be automatic or manual. Automatic are wired to a controller or solar powered.
A backflow preventer is a device which prevents the irrigation system water from being siphoned back into drinking water. To ensure a constant level of lower water pressure, the drip irrigation system needs to have a pressure regulator installed. It reduces water pressure up to 60 psi, in order to ensure regular operation of all drip components.
Filters are the head of the drip irrigation system. They clear the water and keep dirt and debris from clogging the drip emitters. Common types filters include screen filters and graded sand filters, which remove fine material suspended in the water.
3. Main, submain lines, and laterals
The main lines are the pipes which supply water from its source to valves. They are made of galvanized steel, copper, polyethylene (PEX), or PVC. Since PVC can be easily damaged by solar radiation, these main lines should be buried in the soil.
Submains and laterals supply water from the valve to the drip tube. They are usually made of PVC and polyethylene and therefore should be buried below the ground to prevent sun damage. Lateral pipes are usually installed on large drip systems, where multiple drip tubes are needed. Additionally, in small systems, the drip tube is connected directly to the valve.
Drip tubing is the special polyethylene or rigid PVC tube which transfers water to plants. It’s placed on the ground surface between the plants. Along its length, it has placed emitters which water the plants. Drip tubing systems are designed to last for 10 to 20 years or more. For this reason and the associated high initial cost, they are mostly used for permanent crop installations (fruit trees and vines).
Drip tape lasts for only a short time, from one season to a few years. Therefore, it’s most frequently used for row and field crops. Drip tape can be placed on the soil surface or with just below, enough so that the soil is protected against the wind and sun.
Both drip tubing (with in-line or built-in emitters) and drip tape can be installed for subsurface irrigation as well.
Micro, or spaghetti tubing, is an additional small tubing which delivers water directly to individual plants, from the drip tubing to the emitter.
All of these parts are connected to the main drip pipe with a swivel (tubing) adapter.
4. Emitters or drippers
Emitters are the main component of a drip system. These small devices control the water flow to the plants. They can be screwed or snapped onto the drip tube. Common practice is to apply 1 or 2 emitters per plant, depending on the crop size and row space. Hence, fruit crops usually have 1-2 emitters installed per plant, widely spaced, while in row crops, emitters are more closely spaced in order to wet a strip of soil.
Emitters can be installed on a drip tube by creating a hole in the drip tubing using a punch. Care should be taken to use a special punch designed for a certain emitter so as to avoid creation of big holes and water leaching. Some emitters are self-piercing, meaning they do not require the use of a punch. There are also drip tubes with already installed, uniformly spaced emitters inside the tube.
There are various emitter types which differ in flow rate, pressure, method of installation of drip tube, and design. The main benefit of every emitter is to provide a specified and constant water discharge that will not vary too much with pressure changes and won’t be blocked easily.
Additional Drip System Components
Tee Fitting - allows splitting drip line into separate lines flowing to different locations.
End cap – end of the main drip line in an irrigation system. The end cap is simply placed on the end of the line (tubing), then that line is bent and fed through the end cap, “pinching” off the main line.
Coupler Fitting – allows the connection of two pieces of tubing in order to continue a drip line to the desired location.
Air vent - prevents air from being sucked into the emitters when the system is turned off. It should be installed at the highest point on the drip tube to prevent it from being covered with dirt. The air vent is usually installed on large drip systems which are on a slope, as the elevation change creates a more powerful suction that will suck in more dirt.
Fertilizing system – used to add fertilizers and pesticides when watering the plants. This farm practice is called fertigation.
Due to the localized water application, drip irrigation system is a great solution for smart irrigation water management. It benefits both the farmer and a crop. Drip irrigation enables a farmer to achieve an easy and inexpensive installation, reduce weed growth, reduce insect pest and disease occurrence, and facilitate proper water management. Moreover, it can be used in all climates and on every soil and crop type.