As the demand for sustainable gardening practices grows, more gardeners are looking for ways to conserve water in their vegetable gardens and landscapes. One such method is drip or trickle irrigation, a precise watering system that delivers moisture directly to the plant roots. Drip irrigation systems use flexible polyethylene tubing with devices for dripping water (emitters) and low volume sprays. These systems are quite easy to install. They require no trenching and just a few simple tools.
Advantages | Planning a System | Using the System | Soaker Hoses | More Information
Advantages of Drip Irrigation
Drip irrigation has several advantages over hand-watering, sprinklers, and other traditional watering methods. It conserves water by putting water exactly where it is needed and keeps paths and areas between plants dry. They can use 30 to 50% less water than sprinklers or other watering methods.
Drip irrigation delivers water slowly and evenly over a large area. Hand-watering and sprinklers often deliver water faster than some soils can absorb leading to run-off. Additionally, very little water is lost to evaporation in these systems.
Drip irrigation saves time. Most systems can simply be turned on and allowed to operate while you work on other projects. That reduces a lot of time standing at the end of a hose! The system can be controlled by hand or even by an automatic timer. They can also be used to apply fertilizers.
Drip irrigation can help greatly with disease management. Many diseases occur when foliage is wet. Drip irrigation systems apply water directly to the soil beneath the plants. The plant's foliage stays dry and reduces the occurrence of diseases, especially on leaves and fruit.
While there are many advantages, there are some potential drawbacks. The small openings of the emitters can easily clog without proper care. These systems also have a higher cost of installation which can be prohibitive for some home gardeners.
Planning
Drip irrigation is effective for vegetable gardens, landscape plants, and containers. A drip system can be any size or shape. For a small garden, a homeowner may purchase a kit from garden centers or online retailers.
To plan your system, sketch your yard, noting areas that need watering and barriers like driveways, sidewalks, and retaining walls. Consider slopes, shaded areas, and dry spots.
Zones
Drip systems are divided into watering zones. Each zone contains plants or containers with similar water requirements. For many homeowners, the zones may simply be a division of those plants requiring frequent and infrequent watering. Smaller gardens may require only one zone utilizing additional or faster emitters to take care of thirsty plants. Large landscapes may need zones for hedges, trees, shade gardens, full sun gardens, etc.
Calculating Pressure & Flow Rate
The typical household faucet will provide water at a higher pressure and rate than what is needed for a drip irrigation system. Most homes provide water at 25-35 pounds per square inch (psi) and most drip or trickle irrigation systems operate at around 10 psi. A gate valve or regulating disc is used to reduce the water pressure. To measure pressure, utilize a pressure gauge available at hardware stores or irrigation equipment suppliers.
To determine the faucet's flow rate, run the water at full force into a measured bucket and time how long it takes to fill. For example, if a five gallon bucket takes 30 seconds to fill, the flow is 10 gallons per minute (gpm), or 600 gallons per hour (gph). The maximum usable flow is 75 percent of the flow rate. In this example, 450 gph. This is the largest amount of water the source can supply at one time. Emitters are typically available in flow rates of 1/2, 1, or 2 gallons per hour.
Supply Line Set-up
The main line consists of a 1/2-inch or 1-inch and runs from the water source (faucet) to the garden. This could be a regular garden hose or black polyethylene pipe commonly used for irrigation systems. The main line can be buried to make walking and mowing easier. In most cases the sod can be just lifted and replaced over top.
Several other pieces of equipment are needed at beginning of the main line. A filter with a 100-mesh screen is a must. If not filtered, the emitters are easily clogged which will allow some plants to dry out. Clogs like this often go unnoticed until plants wilt or die.
A gate valve is needed to control the pressure of the system and a pressure gauge is installed after the gate vale to check for constant pressure of 10 psi. In many home drip irrigation kits a regulating disc takes the place of a gate valve and a pressure gauge.
The system can be operated manually by turning the system on and off when needed. Connect the supply line to the faucet or use a y-valve to keep the main line connected while still being able to use the faucet for other types of watering around the home. For convenience, the system can be automated by installing a water timer or solenoid valve connected to a time clock between the filter and the gate valve. This is a useful feature especially if you go on vacation. This automated system will regulate the amount of water applied to the garden by controlling the number of hours the system in on. Set the system to run early in the morning so it doesn't interfere with morning showers or other regular water use in the home.
Lateral lines connect to the main line and distribute water throughout the garden, typically running down each row and ending with a cap. Supply tubes that connect to the emitters are hooked up to the lateral lines. Many drip irrigation kits provide a punch or tool to connect the emitters to the lateral lines. In larger gardens a 1/2-inch or 1-inch header line connects to the main and runs the width of the garden with lateral lines coming off of the header to run the length of each row.
Headers and lateral lines can be placed on the soil surface or beneath the mulch. Orient tubing to prevent accidental crushing or cutting when doing work in the garden like digging, weeding, or harvesting.
Emitter Placement
When deciding where to place emitters, consider the size of root zone and the soil type. Water moves downwards in soil due to gravity and from particle to particle in all directions due to capillary action. In sandy soil, gravity affects water movement more than capillary action. In clay soils, capillary action will tend to spread the water before penetrating very deep.
In vegetable gardens and annual flower beds, space emitters every 12 inches or for widely spaced plants 1 emitter for every plant. Perennial flowers should have an emitter at every plant. Small shrubs 5 feet tall and under should have an emitter placed at either side. Large shrubs should have an emitter placed every 3 or 4 feet around the shrub. Place the emitters about 2 feet from the base of the shrub. Trees should have emitters placed approximately every 4 feet within the dripline of the tree.
Using the System
The object of drip irrigation is to maintain plant moisture levels at near optimum levels. Factors like soil type, root depth, air temperature, humidity, and plant age influence watering schedules.
Typically, a vegetable garden needs about one inch of water per week, which can come from rainfall or irrigation. Install a rain gauge to monitor rainfall; if Mother Nature provides at least one inch in a week's time, supplemental watering isn't necessary. In most situations, perennials, annuals, and woody trees and shrubs also benefit from approximately one inch of water per week.
When using drip irrigation, initially soak the garden to a depth of 10 to 12 inches. After this, water only to replace what is lost to evaporation or transpiration, usually every one to two days for a few hours. To check the wetting depth, simply dig a hole. Once you know the time it takes to wet the soil to 12 inches you know how long to run these systems in the future. Most drip irrigation kits offer specific guidelines for frequency and duration based on soil type, number of emitters, and emitter flow rates.
Dealing with Clogs
Care with installing the system avoids many clogging problems. Flush out main, header, and lateral lines before connecting emitters. Clogging can be corrected by cleaning the filter, then removing the cap from the end of the later line and flushing the system at full pressure.
Soaker Hoses
An excellent tool to water perennial beds and the vegetable garden is a soaker hose. Soaker hoses are some of the easiest "drip irrigation systems" to set up. They are inexpensive and a great way to start with water-conscious irrigation.
A popular soaker hose is made from recycled tires. Water oozes out along its entire length and into the soil. When watering the vegetable garden, the soaker hose can be laid along the rose. A distinct advantage is that vegetables can be watered without wetting the foliage. This will reduce disease problems in the garden. One challenge with soaker hoses is that they can wet the areas in-between plants potentially encouraging the growth of weeds.
Soaker hoses should be operated in the same manner as drip or trickle irrigation systems. After the initial soaking run the system every one to two days for a few hours. Check the soil to be sure you are wetting the soil down to 10-12 inches.
More Information
- Watering Tips for the Garden, Lawn, and Landscape
- Using Sprinklers in the Landscape and Garden
- Watering the Home Vegetable Garden
- Watering Home Lawns
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