Soil and Water

SOILS Texture: % of sand, silt, and clay  Amount of water stored in soil

Texture

SOILS Structure: arrangement of particles  Amount of pore space

SOIL MOISTURE  Gravitational water: drains through soil by gravity

SOIL MOISTURE  Field capacity: soil moisture after gravitational water has been allowed to drain (24 hours)

SOIL MOISTURE  Permanent wilting point: plants can no longer extract moisture

INTAKE RATE  How quickly water enters the soil  Slows down as soil becomes wet  Cycle and Soak programs

AVAILABLE WATER HOLDING CAPACITY (AW)  Amount of soil moisture between field capacity and permanent wilting point

EVAPOTRANSPIRATION (ET)  Total water loss from evaporation and transpiration  Evaporation: loss of water from soil surface  Transpiration: loss of water through plant for cooling

EVAPOTRANSPIRATION (ET)  ET0 is a reference ET, locally or regionally

 facilities/ facilities/ facilities/  

PLANT REQUIREMENTS  Plant water needs vary  Root depth and physiology  Hydrozones: separating irrigation zones by plants  Turf, flowers, tree and shrub beds

IRRIGATION SCHEDULING 1. HOW MUCH WATER IS LOST PER DAY?  Loss of water through ET (inches per day) WATER LOSS = ET

IRRIGATION SCHEDULING 2. HOW MUCH WATER CAN BE LOST BEFORE REPLACING IT WITH IRRIGATION?  The READILY AVAILABLE WATER!

IRRIGATION SCHEDULING READILY AVAILABLE WATER  Don’t wait until all the water is gone from the soil! Readily Available Water = Root Water x Management Allowed Depletion

IRRIGATION SCHEDULING Root Water = Root Depth x Available Water Holding Capacity  Root depth of plants to be irrigated  Available water holding capacity of soil  Sand  Silt  Clay

IRRIGATION SCHEDULING Management Allowed Depletion  The amount of water allowed to deplete from soil before it’s replaced  Use table

IRRIGATION SCHEDULING 3. HOW OFTEN SHOULD YOU IRRIGATE? (Days)  Readily Available Water ÷ ET  Round the days up or down to a whole number

IRRIGATION SCHEDULING 4. HOW MUCH SHOULD YOU IRRIGATE?  = Days X ET

IRRIGATION SCHEDULING 5. HOW MANY MINUTES DO YOU RUN IRRIGATION?  (Irrigation Amount ÷ Precipitation Rate) X 60  Precipitation rate: how fast water is being applied  Inches / hour