Agricultural Practices and
Irrigation
NUMAN MIZYED
AN-NAJAH NATIONAL UNIVERSITY
Agricultural practices with significant
environmental impacts
y Irrigation
y Fertilization
y Pesticides, insecticides and herbicides application
Agricultural Activities
Agricultural activities:
Irrigation, fertilization,
agro-chemicals, ag. machinery
Impacts on crops,
Agricultural workers
Human health and
Consumers of products
Runoff to surface water
Soil root zone:
Root growth, biological activities,
Nitrification, de-nitrification ..etc
Impacts on groundwater: quality, quantity
Impacts on soil:
Compaction, hard pans
Increasing salinity
Degradation
Erosion
Irrigation
IRRIGATION IS THE APPLICATION OF WATER TO THE
SOIL FOR THE PURPOSE OF SUPPLYING THE MOISTURE
ESSENTIAL FOR PLANT GROWTH
Historical perspectives
y Ancient civilizations rose over irrigated areas
y Egypt claims having the world's oldest dam, 108m
long, 12m high, built 5,000 years ago
y 6,000 years ago, Mesopotamia supported as many
as 25 million people.
y The same land today with similar population
depends on imported wheat for food
Challenges for Irrigation
y Depletion of natural resources (soil and water)
y Salinization of soil
y Lower productivity of soil: tax records from
Mesopotamia barely yields were 2500L/ha, now only
¼ to ½ this value.
y Desertification
Irrigation & technology
y Hi-tech control: tensiometers, controls and
automation of irrigation and water application.
y Use of remote sensing for irrigation scheduling and
prediction of yield
y New job opportunities
Purposes of Irrigation
y Providing insurance against short duration droughts
y Reducing the hazard of frost (increase the
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temperature of the plant)
Reducing the temperature during hot spells
Washing or diluting salts in the soil
Softening tillage pans and clods.
Delaying bud formation by evaporative cooling
Promoting the function of some micro organisms
Sources of Moisture for Plant Growth
y Precipitation (includes rain, hail, snow):
{ Frequency
{ Intensity
{ Depth
•
•
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Atmospheric water
Flood water
Ground water
Crop processes requiring water
y Digestion
y Photosynthesis,
y Transport of minerals and photosynthesis,
y Structural support,
y Growth, and
y Transpiration.
Evapotranspiration (ET).
y More than 99% of water added to the plant is lost
through transpiration
y Water is lost from soil surfaces through direct
evaporation
y Evaporation and transpiration can't be separated
easily.
y Crop consumptive use versus evapotranspiration.
Factors affecting evapotranspiration
y Climatic factors: Such as temperature, solar
radiation, wind speed, humidity, precipitation.
y Crop type.
y Crop growth stage,
y Available water in the soil. More energy is required
to extract water from dry soil.
Measurements of Evapotranspiration
Rising Up Of Salts
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Salt Accumulation In
Furrow Irrigation
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Salt Accumulation In
Furrow Irrigation
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Drip Irrigation
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Salinity Accumulated On The Border Between The Wet To Dry 19
Zones In Drip Irrigation Saline Spots Created By Subsoil
Drip Irrigation
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Distribution Of Salts In Soil
As Influenced By Different
Irrigation System
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Soil Type And Water Movement.
The application Of Water Is By
Drippers
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Leaching
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y
Leaching consist of applying irrigation water
in excess of the soil moisture depletion level to
remove salts from the root zone. The excess
water flows down below the root zone,
carrying salts with it.
y
The leaching requirement is the leaching
fraction (the amount of excess water) needed
to keep the root zone salinity level within that
tolerated by the crop. This requirement is
determined by the crop`s tolerance to salinity
and by the salinity of the irrigation water.
y
This excess, water expressed as a percent of
the applied irrigation water, is the leaching
fraction.
Water Balance At The
Root Zone
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Salt and Water Balance
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y Water balance
Depth of irrigation water = ET + Depth of drainage water
|
Diw = ET + Ddw
y Salt balance
Diw * Eciw =Ddw * Ecdw
Ù
LF= Eciw/Ecdw = Ddw/Diw
Roots Distribution And Water Use
Affected
By
Depth
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Selection of irrigation systems
y Water source and value of water
y Cost of pumping and whether pumping is available
or not.
y Available cost of the system (the available capital).
y Type of soil and its topography.
y Type of crops.
Irrigation systems
y Gravitational methods: surface systems
y Pressurized systems:
{ Sprinklers
{ Trickle systems
Surface systems
y Advantages
{ High flow rates
{ Low cost
{ No pumping
y Disadvantages
{ Low efficiency
{ Erosion, leveling, operation, drainage
{ Not suitable for sandy soils and lands with high slopes
Types of surface irrigation
y Uncontrolled or wild flooding
y Border strip flooding
y Basin irrigation
y Furrow irrigation
Sprinkler irrigation
y Soil too porous for good distribution of water (sandy
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soils).
Topography as in hilly areas where the use of surface
irrigation will result in erosion and low efficiency.
Irrigation stream too small to use surface systems.
Labor is not experienced with surface irrigation.
Spacing between crops is too small which will
require a lot of drip lines
Classification of sprinkler systems:
y Solid set systems
y Move stop system
y Continuous move systems
{ Center pivot systems
{ Linear move systems
{ Big gun systems
Trickle Irrigation
Trickle Irrigation
y Advantages
{ Saving water
{ Saving energy – low pressure
{ Yield is higher than other systems when water with higher
salinity is used
•
{
{
Disadvantages
High cost
Salinization of soil between rows
Future perspectives and challenges
y Use of marginal water:
{ Brackish water
{ Treated wastewater
y Intensive agriculture
{ Increasing productivity per unit area
y Organic farming