Irrigation is one of the oldest technologies and is the backbone of agriculture.
Irrigation vastly improves your yield and makes commercial farming a viable investment.
Drip irrigation is arguably the best option for watering your crops.
If you are wondering how does drip irrigation work, we cover this aspect and everything else you might ever need to know about this type of irrigation.
What Is Drip Irrigation & How Does Drip Irrigation Work?
Drip irrigation goes by several names including, localized irrigation, trickle irrigation, and micro-irrigation.
This irrigation system releases water in slow and steady amounts, usually between 2 and 20 liters per hour. A standard sprinkler may release 2 and 20 liters per minute.
Drip irrigation targets specific areas of the plant, usually the roots of the plant. This design ensures that the water is absorbed into the ground efficiently, preventing runoff and evaporating.
Drip irrigation is mostly used on row crops such as vine crops, trees, and row crops such as soft fruit and vegetables.
These systems can have a high initial cost, so many farmers prefer to use them on high-value crops.
There are smaller systems designed for domestic use, such as for a kitchen garden. Such an option is affordable, and a great alternative to a sprinkler system.
The system may be adapted to any slope and works on any soil.
The Two Main Types Of Drip Irrigation
1) Surface Drip Irrigation
Drip irrigation releases water on the surface of the soil at a controlled rate.
These systems typically use polyethylene pipes.
You can lay the pipes manually or using a machine if you need to cover a wide area.
Surface drip irrigation is popular in South Africa for its large range, diverse application, and relatively easy installation.
2) Sub-Surface Drip Irrigation
Sub-surface drip irrigation (SDI) works like surface drip irrigation except that the pipes are below ground. The piping is buried between 20 and 50 cm deep and is roughly 2 centimetres in diameter.
Some pipes release water throughout their length, while others only release water at specific points.
The piping is also buried deep enough that normal activities above ground won't affect the installation.
This type of irrigation is especially popular for perennial row crops such as fruit trees.
SDI installations can last up to 20 years or more.
What Are The Advantages And Disadvantages of Drip Irrigation?
1) Surface Drip Irrigation
- Low cost compared to subsurface drip irrigation systems.
- Requires minimal maintenance and energy to operate.
- Conveniently located above ground in case maintenance is required.
- Uses gravity rather than power.
- You can safely use recycled water straight from the source.
- Targeted irrigation means weeds are less likely to receive water needed to grow.
- Efficient use of water through a localized application.
- Irrigation does not wash off surface nutrients and fertilizer.
- Zero risks of soil erosion.
- Higher initial cost compared to other irrigation systems.
- Less efficient at applying water than subsurface drip irrigation.
- Exposed plastic piping may degrade under the sun and affect soil fertility and fertilizer quality.
- Prone to pest damage and vandalism.
2) Sub-surface Drip Irrigation
- Precise water application.
- A high degree of control over the irrigation system.
- Requires lower operating pressure than other options such as sprinklers.
- SDI systems have fewer parts than sprinklers and, therefore, fewer repairs and maintenance.
- Less chance of pest damage.
- Less water evaporation than other types of irrigation.
- Optimal soil moisture levels on the plant's roots.
- Reduced contact with plants, animals, and workers if you are using pre-treated, degraded, or wastewater.
- You can design the system to match the field size and shape and according to the available water supply.
- Potential for the emitter damage by root hairs.
- A limited wetting pattern in coarse soils.
- The drip line placement may affect tilling in certain areas.
- Drip lines may be destroyed under heavy machinery.
- Drip lines can be difficult or inconvenient to access for maintenance or repairs.
Equipment Required For A Drip Irrigation System
1) Water Delivery Systems
The preferred water delivery system for drip irrigation depends on the type of irrigation.
Subsurface drip irrigation uses PVC piping, while polyethylene is preferred for surface drip irrigation.
The water delivery system includes drip lines, pipelines, and mainlines, which are all interconnected.
2) System Controller
The system controller is the brains behind a drip irrigation system.
This equipment regulates the intervals between water application as well as the duration. System controllers are programmable, allowing you to set the preferred parameters for the type of crop, soil, season, and so on.
Manual system controllers only turn the water on and off based on the pre-set parameters.
More sophisticated computerized systems turn the water on and off based on the soil conditions and offer a hands-off approach to irrigation.
This is where the water leaves the pipe and goes to the plant's roots.
Most irrigation lines come with the emitters already installed.
These are usually spaced at least 450 mm apart along the piping. Emitter openings measure 0.2-2.0 mm in diameter.
You will need at least one or two emitters per plant.
4) Water Pressure Regulators
Water pressure regulators are tasked with ensuring that enough water is delivered to each part of the irrigation feed.
Pressure fluctuations can damage feed pipes or water the crops unevenly.
The pressure regulator solves both these problems.
Adjustable regulators allow you to set the ideal water pressure while fixed regulators release water at the factory-set pressure.
5) Water Filters
Water filters separate slit and other debris from your water to ensure that your plants receive clean water.
You can choose your filter depending on the type of water source you have.
Types of filters for drip irrigation include a screen, media, and disk filters.
Sand separators also help to prevent soil from clogging your fee lines.
6) Valves and Gauges
A drip irrigation system uses several valves to control water flow.
These include solenoid, ball, automatic gate, and anti-siphon valves.
Water meter gauges also indicate the level of water flowing through various parts of the line.
7) Control Head
This is usually where you will find the control valves and filters.
Some units also house the chemical injectors and a dedicated nutrient or fertilizer tank.
8) Chemical Injectors
Chemical injectors incorporate anti-clogging agents, pesticides, and fertilizers into the water.
The injectors mix the chemicals at pre-programmed ratios before it gets to the plants.
Tips For Installing Drip Irrigation
- Make sure you know the flow rate of the water source you will be using.
- Find the flow rate by taking a bucket of known capacity and filling it with water at full flow. Use a stopwatch to time how long it takes to fill the bucket. Use this formula to calculate (60 seconds/time it takes to fill the bucket) x the bucket's capacity = litres per hour or lph.
- Group plants with similar water needs together. This will help you to zone your irrigation system appropriately.
- Make sure that drip lines for surface irrigation are clearly visible. It will help you to locate and move them when you need to dig.
- Inspect and clean your filters regularly.
- Install a timer with your drip irrigation system to maximize efficiency.
Frequently Asked Questions
1) How Effective is Drip Irrigation?
In terms of water efficiency, drip irrigation is the most efficient irrigation method currently available.
You can hit efficiency ratings of between 90% and 95% when using these systems.
Flood and furrow irrigation systems have an efficiency rating of 60-70%. Sprinklers range between 80-85%.
2) Is Drip Irrigation Better Than Sprinklers?
If you have the budget for it, drip irrigation is better than sprinklers in most cases.
Drip irrigation applies water more frequently, more precisely, and promotes optimal moisture levels in the soil.
3) How Often Should You Water With A Drip System?
Watering frequency largely depends on the season.
Once a week or every other week is ideal during winter.
Water every other day in the summer and twice a week in spring and fall.
4) How Long Should I Water With Drip Irrigation?
How long to water with drip irrigation depends on the flow rate of your emitter.
High flow rate emitters (up to 20 lph) require about 12 minutes during each watering. Low flow-rate emitters ( between 1 and 4 lph) require 30-90 minutes per session.
Water is in short supply, and there is every indication that the problem will only get worse.
Drip irrigation conserves water by eliminating wasteful runoff.
The system also keeps your plant leaves dry and reduces the chances of diseases such as rust and blackspots.
The best part is you don't necessarily need a plumber to install the system.
Most systems come with easy-to-follow instructions to help with the installation.
Drip irrigation can be especially viable on small farms, gardens, or in a greenhouse.