Drip, or micro-irrigation, the technology uses a network of plastic pipes to carry a low flow of water under low pressure to plants. Water is applied much more slowly than with sprinkler irrigation.
Drip irrigation exceeds 90 percent efficiency whereas sprinkler systems are 50 to 70 percent efficient. It is so efficient that many water utilities exempt landscapes irrigated with drip from restrictions during drought. Note that any irrigation system is only as effective as the watering schedule used. If systems are set to water excessively, any system including drip can waste water.
Low volume application of water to plant roots maintains a desirable balance of air and water in the soil. Plants grow better with this favorable air-water balance and even soil moisture. Water is applied frequently at low flow rates with the goal of applying only the water plants need. Sprinkler irrigation results in a greater wet-to-dry fluctuation in the soil and may not produce optimal growth results.
Micro-irrigation systems are more widely available and better designed for use in home gardens than ever before. Traditionally used for growing commercial vegetables, orchards, windbreaks, greenhouse and nursery plants, micro-irrigation systems are well-adapted for home use. Use them in landscapes, vegetable and flower gardens and for small fruits. They are well-suited to irrigate container plants as well. When combined with a controller, drip irrigation systems can be managed with ease.
Micro-irrigation is ideal for berm plantings. Slopes are inefficient to irrigate because gravity pulls water downhill, causing runoff and water waste. The slow rate of water applied through drip irrigation is more likely to soak in before it runs off.
Advantages
Drip irrigation delivers water slowly immediately above, on or below the surface of the soil. This minimizes water loss due to runoff, wind, and evaporation. Drip irrigation can be operated during the windy periods frequently seen in Colorado.
The mold spots on house siding and the staining and deterioration of wood privacy fences experienced with overspray from sprinkler irrigation is eliminated with the use of drip. Because water doesn’t leave the landscape with drip irrigation, pavement deterioration associated with sprinkler irrigation runoff is eliminated.
Properties with old, galvanized steel water service lines where corrosion has resulted in a narrowed diameter may benefit from a retrofit to drip irrigation. The low volume requirements of drip irrigation are a good match with restricted supply lines.
Drip systems can be managed with an AC or battery powered controller. Automated landscape irrigation is an advantage to many people with busy lifestyles.
Adaptable and changeable over time, drip systems can be easily expanded to irrigate additional plants if water is available. Emitters can be simply exchanged or removed and emitter lines eliminated or repositioned. When plants are removed or die, drip lines should be plugged.
Disadvantages
If emitters are poorly placed, too far apart or too few in number, root development may be restricted by the limited soil area wetted. Water seeping at ground level is hard to see and makes it difficult to know if the system is working properly. An indicator device that raises and lowers a flag to show when water is flowing is available to overcome this issue.
Regular maintenance inspections are needed to maintain system effectiveness – the same as with high-pressure sprinkler systems. Clogs are much less likely with filtered water and proper pressure regulation used in combination with self-cleaning emitters.
Drip tubing can be a trip hazard especially for dogs and children but is less problematic if covered with mulch and fastened with wire anchor pins every 2 to 3 feet. Drip lines can also be easily cut while undertaking other landscape maintenance activities.
Where to Drip: Placing Emitters
Drip irrigation emitters must be placed so that water reaches the roots of plants. Roots will grow where conditions are favorable, primarily where there is the right balance of water and air in the soil.
Design the drip system around the irrigation needs of the plant. For new plantings, make sure emitters are placed over the root ball. Initial placement on perennials is often permanent, unlike trees and shrubs that require emitters to be moved away from the trunk and others added as plants grow. Generally, larger plants have larger and more extensive root systems. A greater number of emitters is needed with larger plants and higher water-using plants. Fewer emitters of lower flow are needed with lower water-using plants or plants that will receive only occasional water following establishment.
Drip emitter placement is also related to whether the soil is sand or clay. To compensate for variations in lateral movement of water in the soil, locate emitters 12 inches apart in the sand, 18 inches apart in loam, and 24 inches apart in clay. If one to two emitters are recommended for a plant in a clay soil, two or three may be required in a sandy soil to wet a sufficiently wide soil area.