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Micro-irrigation, also called localized irrigation, low volume irrigation, low-flow irrigation, or trickle irrigation is an irrigation method with lower pressure and flow than a traditional sprinkler system. Low volume irrigation is used in agriculture for row crops, orchards, and vineyards. It is also used in horticulture in wholesale nurseries, in landscaping for civic, commercial, and private landscapes and gardens, and in the science and practice of restoration ecology and environmental remediation.
There are several types of micro-irrigation systems. Many of the components are the same for all of these types of systems. Most systems typically include filters, pipes, valves, and tubing. The main difference is in the type of emission device that is used to deliver the water to the plants. Drip irrigation utilizes drip emitters that deliver water at very low rates. The typical range is 0.2 to 4.0 gallons per hour. In some systems, the emitters are installed manually on the outside of the tubing and placed where needed. Other systems might use integral dripperline or drip tape with the emitters already installed at a predetermined spacing. Micro-sprinklers, which can include fixed stream sprays and rotating spinners typically deliver water at a higher rate, such as 10 to 25 gallons per hour and will cover a larger area than drip emitters. These are more typically used in tree orchards where the plants are larger. The goal is to distribute water slowly in small volumes and target it to plants' root zones with less runoff or overspray than landscape and garden conventional spray and rotary sprinklers. The low volume allows the water to penetrate and be absorbed into slow-percolation soils, such as clay, minimizing water runoff.
There are a wide variety of system components included in a micro-irrigation systems. Most systems include a filter. These may include pre-filters, sand separators, media filters, screen filters, and disc filters. The level of filtration required depends on the size of the emission device and the quality of the water source. A pressure regulator or regulating valve may be required to reduce the system pressure to the desired level. Automatic or manually operated valves will be required to switch from one irrigated section to another. An irrigation controller will be used with automatic systems and may also be needed for backflushing the filter or sand separator. Since water conservation is a frequent reason for choosing micro-irrigation systems, soil moisture sensors, rain shutoff sensors, and sometimes even weather stations may be installed.
Microtubing is one of the oldest types of drip irrigation devices and was used in greenhouses in the 1970s. It consists of a very small diameter tubing. Flow is regulated purely by the length and diameter of the tubing. Weights or stakes are sometimes attached to the end of the tubing to keep it in place.
Fixed flow drip emitters
Low-flow irrigation systems in gardens using drip apply water through two methods:
- pre installed small holes in small diameter tubes placed on or below the surface or
- self cleaning emitters, in different precipitation rates, pre installed or contractor installed for different rate emitters on same supply line (i.e. trees-higher, perennials-lower). The Flexible supply pipe can be buried either underground or pinned on the surface and buried under
Low volume irrigation systems often use the two delivery components of drip systems to apply water through small holes in small diameter tubes placed on or below the surface of the field. This is done instead of agricultural surface irrigation and furrow irrigation for vegetables, fruits and berries, and other high-value crops.
Adjustable drip emitters
Trickle emitters, also called 'spider sprays,' come in fixed or adjustable radius shapes and diameters, and are installed directly on the flexible supply pipe or on tubing connected to it, and mounted on small stakes. Trickle emitter-'Spider sprays' work well for plants with more fibrous root systems, tree and large shrub basins, and in pots and container gardens - allowing automated watering of plants on decks and patios. Mist emitters can also be used in pot, both on the ground and hanging, with humidity-fog watering for epiphytes and ferns replicating habitats.
In the Horticulture industry, wholesale growers and plant nurseries often use the trickle emitters for 5-US-gallon (19 L) and larger container stock, to automate watering. Attached to longer supply tubing on short stakes, they are easily movable to new containers when stock is moved or sold. Mist emitters are used for propagation, epiphytes, and other plants needing higher humidity.
Low volume micro-sprinklers may be attached to hard plastic risers or attached to standard sprinkler heads, but are more typically mounted on stakes and attached to small diameter micro-tubing connected to polyethylene tubing with a barbed connector. Some micro-sprinklers have a fixed spray or stream pattern, while others rotate. These are installed above ground and are often used for fruit and nut orchards and vineyards. These systems are expensive, even for large-scale agricultural use, and are predominantly used for high-value crops.
Ecological restoration and phytoremediation projects
Low-flow irrigation systems are used on some native plant habitat restoration and environmental remediation projects. The lower operating pressure can be the only choice for remote locations with wells or small storage tank water sources. It is used in temporary installations during initial establishment periods, and being on the soil surface easily removable with minimal damage to the recovering plant community. An example is its use in riparian zone restoration, and environmental remediation projects using Phytoremediation and Bioremediation techniques.
Water conservation and regulations
As municipal and agricultural water supplies become more limited; through increased population demands, droughts, and climate change; city, water district, and state-province level regulations and codes are beginning to encourage, offer rebates with use, or mandate significantly reduced water allowances, at higher costs, that are bringing many water conservation products and techniques both to the forefront and more competitively matched to traditional irrigation system costs.
Use of micro-irrigation systems on green building candidate projects can help them to accumulate points for LEED - (Leadership in Energy and Environmental Design) certification rating and awards.
- Deficit irrigation
- Drip irrigation
- Irrigation in viticulture
- Groundwater recharge
- Water conservation
- This article incorporates public domain material from the Congressional Research Service document "Report for Congress: Agriculture: A Glossary of Terms, Programs, and Laws, 2005 Edition" by Jasper Womach.