Dictionary of Terms

Sprinkler Types

Sprinkler type is important because it determines two things:

Application Rate: The rate at which the sprinklers release water. This coupled with information pertaining to soil type helps determine how long to water before runoff occurs, and ultimately wastes water. 

Uniformity: Used to measure how evenly water penetrates the soil. Different sprinkler types have different uniformity. For instance, spray sprinklers have about a 65% uniformity rate while rotor sprinklers have about a 75% uniformity rate, if well maintained. Uniformity is really an expression of efficiency. I.e., watering longer must be done to cover areas of the lawn that the sprinklers don't reach as well.


  • Spray-type sprinklers are the types of sprinkler that spray a fixed water pattern similar to how a old-fashioned shower head works
  • They are typically used for smaller sized areas
  • Typical application rate: 1.4 in/hr
  • Typical uniformity: 65%


  • Rotor sprinklers use a rotating stream (or multiple streams) of water to apply the water to the ground
  • Rotor sprinklers are used for larger areas (generally more than 18' in width)
  • Typical application rate: 0.7 in/hr
  • Typical uniformity: 75%


  • Drip irrigation is an efficient irrigation method, in which slow and precise delivery of water goes directly to the root and/or base of one’s plants, trees, shrubs, etc
  • By delivering water directly to the roots / base of the plants, optimum moisture level in the soil is retained
  • Application rate varies quite a bit from drip system to drip system
  • Uniformity is assumed to be close to 100% since drip systems are targeted to the plants roots

Plant Types

Plant type impacts watering based on several factors including root depth, root zone (i.e., how much of the soil's water reserve can the plants can use), amount of water needed (e.g., trees and shrubs require about half the water that grass needs) and the best time of day to water.

Grass / Garden

  • The rule of thumb with grass is to only water it when it needs it
  • Overwatering is bad for a lawn’s health and can contribute to the development of fungus and disease
  • Some types of grass require more watering than others - environmental factors such as temperature, humidity and wind can dramatically affect how frequently one needs to water their lawn
  • When grass needs water, it will begin to take on a blue-gray tint, and the older leaf blades on the plant will begin to curl up or wilt
  • A lawn needs to be watered when grass won’t “bounce back” - e.g. if footprints remain on the grass for longer than usually, that’s a sign it’s not “bouncing back”
  • Typical root depth zone is 6”-12”

  • The morning is the best time to water the lawn because the air is cooler and there’s usually not much wind to blow the droplets
  • In the middle of the day, water evaporates too quickly
  • In the evening, water clings to the blades of grass overnight, which can cause fungus to grow and cause lawn diseases
  • The best time is early in the morning: 4 a.m. to 10 a.m.

Shrubs / Perennials

  • The same principles that apply to trees apply to shrubs / perennials, but with a lesser scale
  • Shrubs come in a variety of sizes and root balls
  • The goal is to get the whole root ball moist by watering slowly so that the water does not run off
  • Typical root depth zone is 12”-24”

  • The morning is the best time to water the lawn because the air is cooler and there’s usually not much wind to blow the droplets
  • Additionally, by watering in the morning as the sun hits the plants and they start their photosynthesis, their roots are wet and the nutrients in the soil (from the watering) are in liquid form; therefore, the plants can eat, digest and take care of their processing before they shut off in the heat of the day



  • Effectively watering trees requires slowly watering the soil and/or mulch over the root ball so that water does not run-off, and slowly percolate down into the soil, soaking the entire root zone
  • Typically, the easiest and cheapest way to water a tree is to lay a hose at the base of the trunk, a few inches away. Turn the hose on a slow trickle and keep an eye on it.
  • Typical root depth zone is 12”-24”


  • Often referred to as zero-scaping is landscaping and gardening that reduces or eliminates the need for supplemental water
  • It is often promoted in regions that do not have easily accessible, plentiful, or reliable supplies of fresh water
  • Xeriscapes are often primarily comprised of water-conserving plants that hold onto the water they receive longer
  • Xeriscapes usually use drip irrigation to water as drip delivers water to the base of the plants, slowly, and uses 30-50 percent less water than spray and rotor sprinkler heads

  • The morning is the best time to water Xeriscape because the air is cooler and there’s usually not much wind to blow the droplets

Annuals / Bedding Plants

  • Root depth typically  in the 3”-8” range
  • Require consistent moisture in the soil to grow and bloom
  • Requires shorter watering periods unless it is hot and dry and the first few inches of soil and mulch dry out
  • Should not water within 3-4 hours of dusk, so the plant leaves don’t remain wet all night and promote fungal diseases
  • Water needs vary with the weather and seasons
  • When annuals / bedding plants start to dry out, they get droopy and wilt
  • Most annuals require water when the top two to three inches of soil are dry


Soil Types

The soil type input helps determine how fast water can be absorbed into the soil (i.e., soil intake rate) and how much water the soil can hold.


  • Clay is primarily fine-grained soil that combines one or more clay minerals
  • Clay soil is typically composed of many tiny plate-like soil particles that can compact with time to form hard, solid mass
  • Clay particles are packed with places to hold on to water and fertilizer
  • Clay can hold a lot of nutrients whereas sandy soil cannot
  • Many perennials and annuals thrive in clay soils because their roots are able to get a firm grip on the soil
  • Clay soils hold on to bad things too, like salt, and good things, like minerals
  • For irrigation purposes, it is important to remember water is absorbed and moves slowly through clay soils, but once wet, they retain significant amounts of moisture
  • Therefore, when irrigating clay soils, water should be applied slowly over longer periods of time but then the site may not need irrigation for several days
  • Clay does not allow water or air to circulate easily


  • Silt is a granular material ranging in size between sand and clay
  • Silt has a moderate specific area with a typically non-sticky, plastic feel
  • Silt usually has a floury feel when dry, and a slippery feel when wet
  • Like sand, naturally occurring silt is typically composed of irregularly shaped and sized particles, predominantly of quartz.
  • Because of its small size, silt is able to sustain an adhering film of clay to its surface, giving it many clay-like attributes, including plasticity, stickiness, and adsorption
  • When dry, silt has a texture similar to flour
  • Silt holds moisture and nutrients better than sand, and can become compacted when wet
  • Silt soil feels slick and smooth when wet
  • Silty soil feels soft and soapy, it holds moisture, and is usually very rich in nutrients.
  • Silt is easily cultivated and can be compacted with little effort

Sandy Clay

  • It's advised that water applied to sandy clay be done so quickly, but for short periods of time
  • Irrigation times on sandy clay should be shorter, otherwise water moves beyond the root zone, becoming unavailable to the plant and contributing to soil leaching

Clay Loam

  • Clay loam is a soil mixture that contains more clay than other types of rock or minerals
  • Because clay has very small, compact particles, clay loam can be heavy and dense.
  • Water does not infiltrate as easily - requires extended watering
  • Clay loam is comprised of nearly equal parts clay, loam, silt and sand
  • Typically, clay loam is more reddish in color

Silty Clay Loam

  • Silty clay loam contains 50-80% silt
  • It has very high runoff potential
  • Low infiltration rates when thoroughly wetted
  • Moderately fine texture
  • Soil material that contains 27-40% clay and less than 20% sand

Sandy Clay Loam

  • Sandy clay loam material contains 20-35% clay, less than 28% silt and 45% or more sand

Silty Loam

  • Silty loam is common in valley floors where erosion has deposited large quantities of loose, fertile soil
  • Silty loam retains water very well and offers fertile conditions
  • Typically a loose soil


  • Loam material contains 7-27% clay and 28-50% silt and less than 52% sand.
  • By definition loam is somewhat gritty but less so than sandy loam
  • Loam soils generally contain more nutrients and moisture than sandy soils, have better drainage and infiltration of water and air than silty soils, and are easier to till than clay soils
  • Loam is the best type of soil for growing plants because it retains moisture and nutrients and also has good drainage

 Sandy Loam

  • Sandy loam is a soil material that contains 20% or less clay, sand grains can be seen and felt between the fingers when rubbed together after being lightly dampened and will feel gritty
  • Sandy loam retains water easily

Loamy Sand

  • Sand that has more clay, and retains more water than sand and fine sand

Fine Sand

  • Very small water storage capacity and a very high infiltration rate
  • Find sand requires frequent, but small irrigation applications, in particular when the sandy soil is also shallow.


  • Sandy soils have a low water storage capacity and a high infiltration rate.
  • They require frequent but small irrigation applications, in particular when the sandy soil is also shallow.
  • Typically, under these circumstances, sprinkler or drip irrigation is often suitable 
  • Sandy soils are made up of particles of disintegrated rock such as granite, limestone, quartz and shale
  • Large particle sizes, coarse and loose
  • Because sandy soils drain quickly, they do not hold nutrients well
  • Sandy soil feels gritty and falls apart easily


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