Introduction of Irrigation & it's Methods Water Quality for irrigation Soil Water Relationship

1. RAMANUJ JALDHARIV Sem

2. INTRODUCTON

3. DRIP IRRIGATION
• This is latest method of irrigation.
• Water is applied to the land surface near the base of the plants
by a
• network of plastic pipes (PVC pipes) and drip nozzles called
drippers.
• Require a pumping unit, pipe lines and drippers.
• Highest water application efficiency (as high as 90 % ).
• Suitable for areas where there is water scarcity and salt
problems
• (saline lands).
• Evaporation loss is reduced.
• Quite suitable for small trees and widely spaced plants, for fruit
plants.
• Can be used for any topography. Land need not be level.
• Not suitable for closely planted crops such as wheat, rice etc.

4. DRIP IRRIGATION

5. SPRINKLER IRRIGATION
• Water is applied in the form of spray by pipes and
nozzle system.
• Erosion of soil is eliminated.
• More land available.
• Uniform application of water is possible.
• No land preparation is required.
• Wind may distort the application of water.
• Power requirement is more for constant pumping
of water.

6. SPRINKLER IRRIGATION

7. STANDARDS OF QUALITY FOR
IRRIGATION WATER
1. Based on Concentration of Total Dissolved
Salts:
Based on value of electrical conductivity,
irrigation
water is classified as four types.

8. STANDARDS OF QUALITY FOR
IRRIGATION WATER
2. Sodium Adsorption Ratio
Sodium Adsorption ratio (SAR) is a measure of the amount of
sodium (Na+) relative to calcium (Ca2+) and magnesium (Mg2+)
in the water extracted from a saturated soil paste.
SAR is calculated from the equation:

9. STANDARDS OF QUALITY FOR
IRRIGATION WATER

10. STANDARDS OF QUALITY FOR
IRRIGATION WATER
3. Based on Boron & Selenium Concentration
Boron, selenium are highly toxic element for plants
• Boron concentration > 0.5 ppm
• Selenium concentration > 0.01 ppm

11. Question 4 U………
A water have electrical conductivity 500mho/cm and
SAR 22.Which type of water from following?
A) C2-S2 B) C3-S2 C) C2-S3 D) C4-S1

12. CLASSIFICATION OF SOIL
WATER
Soil water may be classified into the following
three categories.
(i) Gravitational water
(ii) Capillary water
(iii) Hygroscopic water

13. CLASSIFICATION OF SOIL
WATER
Gravitational Water
• It is the water not held by soil.
• It can get drained out from the soil freely by
action of gravity.
• It is the water stored between saturation
capacity and field capacity.

14. CLASSIFICATION OF SOIL
WATER
Capillary Water
• It is the water retained by the soil after the draining off of the
gravitational water.
• It is held by surface tension force in the soil, as a continuous film
around the soil particles and in the capillary pores between the soil
particles.
• It is the water held in the soil against the force of gravity.
• This water is most useful water, the major source for plant growth.
• Also called available water.
• Permanent wilting point (PWP) is the lower most limit of capillary
water.

15. CLASSIFICATION OF SOIL
WATER
Hygroscopic Water
• It is the unavailable water.
• It is the water adsorbed by particles of dry soil from the
atmosphere and is held as a thin film on the surface of
soil particles.
• Water contained by the soil below PWP is the
hygroscopic water.
• This water cannot be taken out from a soil even by a
force.
• Only oven-heating will make this water thrown out of
the soil.
• Also called “inextractable water”

16. CLASSIFICATION OF SOIL
WATER
Remember:
Gravitational water = undesirable water
Capillary water = useful water
Hygroscopic water = inextractable water

17. DIFFERENT MOISTURE CONTENTS
OF THE SOIL
1. Saturation capacity (SC)
• It is the maximum water holding capacity of the
soil.
• It is the water content of a soil when both
capillary and non-capillary pores are
completely filled with water.
• At this moisture content, SMT value is almost
zero.

18. DIFFERENT MOISTURE CONTENTS
OF THE SOIL
2. Field Capacity (FC)
• When after gravitational water is drained off a soil,
the moisture content of the soil is called field
capacity.
• At FC, 100% capillary pores are filled with water
100% Non-capillary pores are filled with air.
• It is the upper limit of the capillary water.
• Time taken to achieve FC by a soil after the soil has
been thoroughly wetted by irrigation:
1-3 days - coarse grained soils
4-8 days - medium grained soils
10-15 days - fine grained soils

19. DIFFERENT MOISTURE CONTENTS
OF THE SOIL
3. Optimum Moisture Content (OMC)
• It is the water content of the soil at which irrigation
water must be supplied to field.
• A good quality irrigation engineer should release
the water to the field, once Moisture Content of
the soil has reached OMC.
• OMC is the optimum level upto which the soil
moisture may be allowed to be depleted in the
root zone without fall in the crop yield.

20. DIFFERENT MOISTURE CONTENTS
OF THE SOIL
4. Temporary Wilting Point (TWP):
• At this WC, the plant starts undergoing wilting.
• Development of white patches bending and shrinking
of leaves indicates that the moisture content is TWP.
5. Permanent Wilting Point (PWP):
• PWP is the moisture content at which the films of water
around the soil particles are held so tightly that the plant
roots cannot extract enough moisture at sufficiently rapid
rate to satisfy the transpiration requirements thus
resulting in the wilting of the plants.

21. DIFFERENT MOISTURE CONTENTS
OF THE SOIL
6. Ultimate Wilting Point
• It is the moisture content of the soil when it is not having even hygroscopic
water.
• Dry most status of soil
7. Available Moisture (AM)
• AM = FC - PWP
• It is the water stored in the soil in the form of capillary water for being
used subsequently by the plants.
8. Readily Available Moisture (RAM)
• RAM = FC - OMC
• It is that portion of the available moisture which is most easily extracted by plant
roots
• Only about 75-80% of the available moisture will be readily available moisture.

22. CONSUMPTIVE USE OF WATER
• Also Known as Evapo-Transpiration.
• It means depth of water consumed by evaporation
&
transpiration during crop growth.
• Measured by Lysimeter.

23. Any Query……???