Irrigation scheduling is the process used by

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

system managers to determine the correct frequency and duration of watering. The following factors may be taken into consideration: * Precipitation rate of the irrigation equipment – how quickly the water is applied, often expressed in inches or mm per hour. * Distribution uniformity of the irrigation system – how uniformly the water is applied, expressed as a percentage, the higher the number, the more uniform. * Soil infiltration rate – how quickly the water is absorbed by the soil, the rate of which also decreases as the soil becomes wetter, also often expressed in inches or mm per hour. * Slope (

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

) of the land being irrigated as this affects how quickly runoff occurs, often expressed as a percentage, i.e. distance of fall divided by 100 units of horizontal distance (1 ft of fall per {{convert, 100, ft, m, abbr=on would be 1%). * Soil

available water capacity Available water capacity is the amount of water that can be stored in a soil profile and be available for growing crops. It is also known as available water content (AWC), profile available water (PAW) or total available water (TAW). The concept, p ...

, expressed in units of water per unit of soil, i.e. inches of water per foot of soil. * Effective

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

ing depth of the plants to be watered, which affects how much water can be stored in the soil and made available to the plants. * Current watering requirements of the plant (which may be estimated by calculating

evapotranspiration Evapotranspiration (ET) refers to the combined processes which move water from the Earth's surface (open water and ice surfaces, bare soil and vegetation) into the Atmosphere of Earth, atmosphere. It covers both water evaporation (movement of w ...

, or ET), often expressed in inches per day. * Amount of time in which water or labor may be available for irrigation. * Amount of allowable moisture stress which may be placed on the plant. For high value

vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...

crops, this may mean no allowable stress, while for a

lawn A lawn () is an area of soil-covered land planted with Poaceae, grasses and other durable plants such as clover lawn, clover which are maintained at a short height with a lawn mower (or sometimes grazing animals) and used for aesthetic an ...

some stress would be allowable, since the goal would not be to maximize production, but merely to keep the lawn green and healthy. * Timing to take advantage of projected

rainfall Rain is a form of precipitation where water droplets that have condensed from atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. ...

* Timing to take advantage of favorable utility rates * Timing to avoid interfering with other activities such as sporting events, holidays, lawn maintenance, or crop harvesting. The goal in irrigation scheduling is to apply enough water to fully wet the plant's root zone while minimizing overwatering and then allow the soil to dry out in between waterings, to allow air to enter the soil and encourage root development, but not so much that the plant is stressed beyond what is allowable. In recent years, more sophisticated irrigation controllers have been developed that receive ET input from either a single on-site weather station or from a network of stations and automatically adjust the irrigation schedule accordingly. Other devices helpful in irrigation scheduling are rain sensors, which automatically shut off or may turn off manually an irrigation system when it rains, and soil moisture sensing devices such as capacitance sensors,

tensiometer Tensiometer may refer to one of a number of devices. The two most common are: * Tensiometer (surface tension) an instrument used to measure the surface tension of liquids * Tensiometer (soil science) an instrument to determine matric water p ...

s and gypsum blocks.

References

Irrigation Association Smart Water Application Technology
– site with generic information on smart controllers Irrigation Land management Agricultural soil science

See also

References