Irrigation, defined as a system used for watering crops and plants, requires proper design and operation along with experience, science and even some art. A basic irrigation system must begin with a landscape design that specifies plants suitable for the topography, soil, climate and water. After creating the basic irrigation system design, the type of irrigation system must be determined. Three basic irrigation types are used in horticulture applications. These are sprinkler, drip and surface. Each of these irrigation systems have variations adaptations that work with certain conditions. Other factors to consider are plant water requirements, condition of water and its supply, soil type, condition and topography, microclimate concerns and irrigation scheduling constraints.
Sprinkler systems, commonly used for turf applications, depend on the size and shape of the area irrigated as well as the flow rate and pressure of the water supply. Variations of this system include rotating sprinklers, fixed spray sprinklers and drip and micro sprinklers.
Rotating sprinklers, either full or part circle rotating sprinklers, are used on large areas, such as golf courses, parks, commercial or large residential landscapes. This type of sprinkler system can have single or multiple nozzles, gears, cam or impact driven, spacing from 35 to 115 feet, operating pressure from 40 to 100 psi, and flow rates from 6 to 65 gpm. Rotating sprinklers can even have built-in valves, which is a valve located in the sprinkler head and/or pressure regulators.
Fixed Spray Sprinklers, often referred to as pop-up sprinklers, have a pattern that can be full, part circle or rectangular with radiuses from 4 to 22 feet. This type sprinkler system offers several angles of spray trajectory with application rates ranging from less than 1 to over 2 inches per hour. When planning irrigation scheduling for this type of sprinkler system, consider the high application rates of the spray nozzles to prevent runoff.
Drip and Micro-Sprinklers, a cross between spray nozzles and drip irrigation, are well suitable for ornamental plantings and as well as a single tree or shrubs. This type of sprinkler system has a low flow rate, low application rate, small radius that range from 4 to 12 feet and operate with low pressures. Micro sprinklers require filtered and pressure regulated water.
Drip irrigation, also known as micro irrigation, applies water to the soil at point locations using low controlled flow rates and drip emitters that discharge at a rate of .5 to 2 gallons per hour. These emitters can be pressure compensating and apply a nearly constant application rate over a wide range of pressures. Drip irrigation, used on individual plants or groupings of plants, should include a filter and pressure regulator. Drip tubing and bubblers are two types of drip irrigation.
Drip tubing applies water using equally spaced emitters, 6 to 60 inches, along a semi-rigid tube. Depending on the drip irrigation tubing type, operating pressures range from 5 to 20 psi. Drip irrigation, installed on top of the soil or buried in the soil, is used to irrigate turf.
Bubble irrigation does not have drip emitters, but works very similarly; the difference is that bubble irrigation uses a higher flow rate that ranges from 2 to 6 gpm. The flow rate of bubble is higher than the soil intake rate, resulting in a flooding situation. When this situation occurs, the infiltration of the soil continues after the bubbler has been shutoff. Only use bubble irrigation where small basins are capable of being constructed to contain the water and the ground is level.
Surface irrigation, also known as flood irrigation, is the least commonly used system. This system applies deeper irrigation and requires higher flow rates for shorter periods. Use surface irrigation on leveled and diked turf areas only if the soil infiltration is slow enough for the water to flow over the entire area. In a surface irrigated system, soil is used as the distributing and infiltration system and the system requires careful design for it to be efficient. Occasionally, surface irrigation is used for furrow or diked irrigation for landscapes and gardens.
Irrigation systems are designed to supply an adequate amount of water in a timely manner to plants. Keeping this in mind is important when designing an irrigation system. Irrigation zones and irrigation system layout help achieve this goal. Select irrigation zones by determining the plants’ water requirements with the availability of the water supply. For instance, sprinkler systems are better for turf areas and landscape plants do better with low-flow drip or micro-spray irrigation. Controllers of irrigation systems vary as much as the systems themselves. The more expensive the controller, the more options they have to offer such as being capable of separating irrigation frequency for different zones. These more expensive controllers also require more effort to program and understand. Often times the simpler controllers are the more practical, less expensive and will have the capability to accomplish the task. Sometimes using two or more simpler separate controllers instead of one more expensive one is cost effective.
Irrigation system layout is also very important when installing an irrigation system. Controllers, which are the time clock, along with valve boxes should be accessible and be protected from rain and direct sunlight. Before laying out any irrigation hardwater, draw a scale that shows the irrigated property along with the location of the plants. Base the selection of the sprinklers on the size of the irrigated property. Sprinkler location should begin in the corners where a sprinkler will be located, and place the next sprinkler by using head-to-head sprinkler spacing. Drip systems, laid out a little differently, begin by locating the emitters and positioning them next to the individual plants or plant groupings that they will irrigate. The spacing of these emitters is determined on the spreading of the root system and the soil type. After the initial placement of the emitters, install the remaining water supply lines.
Successful irrigation depends on all the factors being present. These factors are the water source, the water meter, backflow prevention and vacuum breaker device, valves and wire, pressure regulator, filtration system, controller and related hardware, pipe and fittings, sprinklers, drip emitters, bubblers or tubing. Every one of these factors is important.
