Definition of Irrigation application of the right quantity

Definition of Irrigation -application of the right quantity of water at the right time to satisfy the evapotranspiration requirements of crops in a given area

1. Methods of Irrigation A. Surface or Gravity Irrigation methods 1. Basin irrigation 2. Border irrigation 3. Furrow irrigation 4. Corrugation 5. Wild flooding B. Overhead or Pressurized Irrigation methods 1. Sprinkler irrigation 2. Drip or trickle irrigation C. Subsurface Methods

Typical Drip Irrigation Set-up

Typical IDE Drip Irrigation Set-up Drum Kit - Vegetable

The Soil as Water Reservoir Total Soil Volume VT = Vs + Va + Vw Vs = volume of solids Va = volume of air Vw = volume of water

Forces Acting on Soil Water

How much water to apply? Net depth of application: dn = MAD*(AWHC)*Drz dn = net application depth (mm) MAD = management allowable deficit AWHC = available water holding capacity (mm/m) Drz = rootzone depth (m)

How much water to apply? Net depth of application: dn = MAD*(FC-PWP)As*Drz dn = net application depth (mm) MAD = management allowable deficit FC = field capacity (dry mass basis) PWP = permanent wilting point (dry mass basis) As = apparent specific gravity Drz = rootzone depth (m)

Typical Soil Moisture Constants

How much water to apply? Gross depth of application: dg = dn/Ea Ea = application efficiency

How much water to apply? Gross Volume of application: V = dg*A*Pw/100 A = total area irrigated Pw = % area wetted

Application Rate i = dg/t i = application rate (mm/day) dg = gross application depth (mm) t = irrigation period (hr) Note: Application rate i should not exceed the soil infiltration capacity

Application Rate q = V/t V= gross volume of application (L) t = irrigation period (hr)

Evapotranspiration T E ET = E + T

Crop Evapotranspiration ETcrop = kc*ETo ETcrop = actual crop evapotranspiration (mm/day) Kc = crop coefficient ETo = reference crop (potential) evapotranspiration (mm/day)

Typical Variation of Crop Coefficient

Reference crop (potential) evapotranspiration

When to irrigate? Irrigation interval or frequency: f = dn/ETcrop f = irrigation interval (days) dn = net application depth (mm) ETcrop = actual crop evapotranspiration (mm/day)

When to irrigate? Use of tensiometer or soil moisture meter

When to irrigate? Use of tensiometer or soil moisture meter

When to irrigate? Use of Full Stop Wetting Front Detector

When to irrigate? Use of Full Stop Wetting Front Detector

Contact Information Dr. Victor B. Ella Dean and Associate Professor College of Engineering and Agro-industrial Technology (CEAT) UPLB, College, Laguna Tel/fax: 536 -2873 E-mail: vbe@laguna. net or vbella@up. edu. ph