Contents: • Definitions • Objective of irrigation methods • Choice of irrigation methods • Requirements of irrigation methods • Different methods of irrigation
IRRIGATION…? • Pouring water to the soil using proper methods and in proper times as required by the plant growth as a result of insufficient rain. IRRIGATION METHOD…? • The design, equipment and technique of replenishing the soil water deficit by applying irrigation water is referred to as irrigation method.
OBJECTIVES OF IRRIGATION METHODS • The primary objective of any irrigation method is to supply water to soil so that moisture will be readily available at any times for crop growth • To ensure maximum yield at optimum water utilization • To increase water use efficiency
REQUIREMENTS OF AN IRRIGATION SYSTEM • Application within desirable limits. • Afford a uniform water distribution in root zone of a crop with as small as 6 cm applications for light irrigation. • Allow heavy uniform application of 15 to 20 cm of water depth. • Suitable for use with economical conveyance structure.
Conti…. • Facilitate mechanized farming • Occupy minimum land under bunds etc • Inexpensive and economically justifiable • High efficiency of water application • Minimum wastage of water either through surface runoff or through deep percolation below the root zone of a crop.
FLOOD IRRIGATION Just flooding water. About 90% of the irrigated areas in the world are by this method. • Water is applied to the field in either the controlled or uncontrolled manner. • Controlled: Water is applied from the head ditch and guided by corrugations, furrows, borders, or ridges. • Uncontrolled: Wild flooding. • Surface irrigation is entirely practiced where water is abundant. The low initial cost of development is later offset by high labour cost of applying water. There are deep percolation, runoff and drainage problems
ADVANTAGES • The method is suitable for all medium to fine texture soils. • It has low cost and does not interfere with tillage. • Allows use of machinery for land preparation, cultivation and harvesting. • Helps to store the required amount of water in the capillary zone of the soil for supply to the root zone of plants.
DISADVANTAGES • Wasteful use of water • Non-uniform distribution of water • Excessive soil erosion on steeper slopes • Greater loss of water by surface runoff, infiltration and deep percolation • Low efficiency due to imperfect control over the water flow • Inferior quality crops with a low yield • Wasteful use of water compared to better irrigation methods
BASIN IRRIGATION SYSTEM In basin irrigation, water is flooded in wider areas. • It is ideal for irrigating rice. • The area is normally flat. • In basin irrigation, a very high stream size is introduced into the basin so that rapid movement of water is obtained. • Water does not infiltrate a lot initially. • At the end, a bond is put and water can pond the field. • The opportunity time difference between the upward and the downward ends are reduced.
BORDER IRRIGATION SYSTEM • In a border irrigation, controlled surface flooding is practiced whereby the field is divided up into strips by parallel ridges. • Each strip is irrigated separately by introducing water upstream and it progressively covers the entire strip. • Border irrigation is suited for crops that can withstand flooding for a short time e.g. wheat. • It can be used for all crops provided that the system is designated to provide the needed water control for irrigation of crops. • It is suited to soils between extremely high and very low infiltration rates.
FURROW IRRIGATION • In furrow irrigation, only a part of the land surface (the furrow) is wetted thus minimizing evaporation loss. • Furrow irrigation is adapted for row crops like corn, banana, tobacco, and cabbage. It is also good for grains. • Furrow irrigation is adapted for irrigating on various slopes except on steep ones because of erosion and bank overflow.
SUB-SURFACE IRRIGATION • Practice applied in places where natural soil and topographic condition favours water application to the soil under the surface. These conditions include: • Impervious layer at 15 cm depth or more • Pervious soil underlying the restricting layer • Uniform topographic condition • Moderate slopes
SUB-SURFACE IRRIGATION Contd. • The operation of the system involves a huge reservoir of water and level is controlled by inflow and outflow. • The inflow is water application and rainfall while the outflow is evapotranspiration and deep percolation. • It does not disturb normal farm operations.
MICROIRRIGATION • Delivery of water at low flow rates through various types of water applicators by a distribution system located on the soil surface, beneath the surface, or suspended above the ground. • Water is applied as drops, tiny streams, or spray, through emitters, sprayers, or porous tubing.
WATER APPLICATION CHARACTERISTICS • Low rates • Over long periods of time • At frequent intervals • Near or directly into the root zone • At low pressure • Usually maintain relatively high water content • Used on higher value agricultural/horticultural crops and in landscapes and nurseries
DRIP IRRIGATION • Water is applied directly to the crop i.e. entire field is not wetted. • Water is conserved • Weeds are controlled because only the places getting water can grow weeds. • There is a low pressure system. • There is reduced evaporation, only potential transpiration is considered. • There is no need for a drainage system.
DRIP IRRIGATION • In Drip Irrigation, the plant foliage remains dry . This prevents the diseases and leaf burns that are some times evident in sprinkler Irrigation. • Drip Irrigation is well suited to all soils and also for heavy soils with low infiltration rate or soils that from surface crusts when sprinkled. • In Drip Irrigation, the area between wetted strips is kept dry. This facilitates the movement of machinery and farm implements when irrigation is in progress. • Drip Irrigation requires no special land preparation.
DRIP IRRIGATION • Drip Irrigation can not be used for frost protection or for cooling during period of hot weather like sprinkler irrigation. • Like sprinkler irrigation, Drip Irrigation can not be used or suitable for supplemental irrigation of large areas. • In dry , windy regions, Drip Irrigation of young tree plants in “light” soils encourages soil erosion due to the very limited wetted area. Strong winds also presents problems of anchorage.
SPRINKLER IRRIGATION • Pressurized irrigation through devices called sprinklers. • Pakistan is fast heading towards a situation of water shortage with increasing population. • The surface water availability per capita was 5650 cubic meters in 1951, which reduced to 1400 in 2000. • The minimum water requirement to avoid being a "water short country" is 1000 cubic meters. • In the year 2012 Pakistan will have reached the stage of "acute water shortage". • Sprinklers are usually located on pipes called laterals. • Water is discharged into the air and hopefully infiltrates near where it lands.