2. 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

3. 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 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

4. Typical Drip Irrigation Set-up

5. Drum Kit - Vegetable Typical IDE Drip Irrigation Set-up

6. The Soil as Water Reservoir Total Soil Volume V T = Vs + Va + Vw Vs = volume of solids Va = volume of air Vw = volume of water

7. Forces Acting on Soil Water

8. 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)

9. 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)

10. Typical Soil Moisture Constants

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

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

13. 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

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

15. Evapotranspiration E T ET = E + T

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

17. Typical Variation of Crop Coefficient

18. Reference crop (potential) evapotranspiration

19. 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)

20. When to irrigate? Use of tensiometer or soil moisture meter Use of tensiometer or soil moisture meter

21. When to irrigate? Use of tensiometer or soil moisture meter Use of tensiometer or soil moisture meter

22. When to irrigate? Use of Use of Full Stop Wetting Front Detector

23. When to irrigate? Use of Use of Full Stop Wetting Front Detector

24. 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