IRRIGATION DEFINITION. irrigation is defined as the artificial or man-made application of water to soil or land for farming purposes. In other words, irrigation is the artificial application of water to the soil to supplement insufficient rainfall. Irrigation is mainly practiced in areas where there is in insufficient rainfall. read about biotic and abiotic factors here
Water is the most important determinant in the growth of crops. The choice of irrigating system depend on:
(1) Availability of water: For irrigation to operate, water must be available insufficient quantity. Water should therefore come through rivers, streams and boreholes.

(2) Slope of the land: The choice of irrigation-al system depends on the shape and slope of the land. While surface type requires sloping land, sprinkler method requires a flat land.
(3) Soil type: The choice of any irrigating system depends on the type of soil in the area. Surface irrigation may be effective in a clayey type of soil to aid water run-off
(4) Types of crops: The choice of which farm to irrigate also depends on the type of crops to be grown. While cereals and leguminous crops will require sprinkler irrigation, tree crops may require surface irrigating.
(5) Size of farmland:any watering system depends on the size of farmland. Irrigation becomes effective and efficient if the farm land is large.


(i) To add water to the soil in order to supply moisture for plant growth.
(ii) To ensure the survival of crops during droughts
(iii) To cool the soil and the atmosphere, thereby making the environment more favourable for plant growth
(iv) To make early planting possible


(1) It softens the soil for easy tillage operations
(2) It provides moisture in the soil for root absorption

(3) It reduces the amount of salts accumulated in the top soil, which could be harmful to crop plants
(4) It also cools the soil by reducing the soil temperature during the dry season when the soil temperature is very high. Plant growth is thus improved.
(5) Irrigation enables the crop to be well established even when rain is erratic.
(6) It increases crop productivity or crop yield.
(7) Irrigation provides humid environment for the breeding of pest and pathogens of crops
(8) It helps in the improvement of microbial decomposition of organic manure to release nutrients for crop plant
(9) Irrigation dissolves nutrients for root absorption
(10) It assists in facilitating crop production all year round
(11) Irrigation encourages the spread of weed seeds


Irrigation system or types can be grouped into three main classes: Surface irrigation, sub-surface irrigation and overhead irrigation

irrigation and drainage

In this system, water from rivers, dams or streams flows along the surface of the land to farmland. This can be in form of channels, flooding, contour ditch, furrow, basin, border dyke, border and ditch. The most important condition for surface irrigation to be efficient is for the land to have a gentle slope towards the direction of the farmland.


(i) It removes excess water caused by heavy rainfall especially in heavy soils.
(ii) It is easier to construct.
(iii) It is cheap to establish and maintain
(iv) It prevents accumulation of alkalis.
(v) It increases the activities of microbes in top soil
(vi) It helps in the collection and disposal of surface run-off


(i) It cannot be practiced where the land is hilly.
(ii) It cannot be successful in sandy soil
(iii) The volume of water, especially in flooding, may be difficult to control
(iv) Some crops may not tolerate heavy flooding


(i) The topography or sloppy and
(ii) The soil type
(iii) The type of crop to be grown
(iv) The size of the farmland

what is Sub-surface Irrigation? :

In this system, water is applied below the soil surface by maintaining an artificial water level at certain depth. This, however, depends on the type of crop and the nature of the soil. In all cases, perforated pipes are used to deliver water within the soil, and this water gets to the roots of crops through capillary action.


(i) By irrigation, it is possible to maintain water at optimum depth for need.
(ii) in addition, water use efficiency is high
(iii) It also ensures low evaporation losses from soils.
(iv) It does not create obstruction or obstruction or obstacles when carrying out cultural practices

Disadvantages Sub-surface Irrigation

(i) Water which has a high salt content cannot be used
(ii) It requires some level of expertise or technical know-how
(iii) It is a bit expensive
Factors to be considered in choosing sub-surface irrigation method
(i) The permeability of substratum
(ii) The level of water table
(iii) Soil texture or capillarity
(iv) Soil structure

Overhead irrigation :

In overhead irrigation system, water is supplied to the farmland above the surface of the soil

Problems associated with overhead irrigation

(i) Wind distorts sprinkler patterns and causes uneven distribution of water.
(ii) The spray force can damage ripening soft fruits
(iii) A stable water supply is required for economic use of the equipment
(iv) The water must be clean and free of sand, debris and large amounts of dissolved salts.
(v) The initial investment is usually high.
(vi) Power requirements for pumping water is high
(vii) Requires technical know – how
(viii) Can spread diseases
(ix) Lateral pipes hinder movement of farm machines
(x) High cost of maintenance/repairs/ spare parts not ready available.
Over head irrigation exists in two forms: sprinkler irrigation and drip irrigation

Sprinkler type of irrigation

in this system, water is sprayed from the air and allowed to fall on the ground surface somehow as rainfall, through nozzles under high pressure
Pumping machine which operates under high pressure is needed to pump water into irrigation pipes which are spaced to ensure even distribution of water


(i) The amount of water supplied is regulated
(ii) It economizes the use of water
(iii) It is suitable for high arid lands with high evapo-transpiration rate
(iv) Soluble fertilizers and herbicides can be applied through the irrigation water
(v) It can be used for all crops except trees like cocoa.
Disadvantages of Sprinkler irrigation
(i) Sprinkler irrigation is costly to operate
(ii) High wind velocity may prevent distribution of water
(iii) A stable water supply is required
(iv) It requires high power to produce the high pressure needed to pump water into pipes
(v) There is lack of sufficient technical know-how on sprinkler irrigation operation

Drip irrigation:

Drip or tickle type of watering the farm is a new method of irrigation where water is discharged through nozzles called emitters or drippers at selected spacing to deliver water to the soil surface near the base of the plant. With this system, loss of water through deep percolation, run-off and evaporation is greatly reduced.

Advantages of Drip Irrigation

(i) It is economical in the use of water
(ii) It reduces alt concentration in the root zone
(iii) Fertilizers can be applied through this system
(iv) It operates with slower line pressure
(v) It is the most appropriate system needed in arid semi-arid areas.

Disadvantages of Drip irrigation

(i) It is very expensive to set up and maintain
(ii) Water cannot be distributed in a sloppy farmland evenly
(iii) Water with high salt content cannot be used


There are many problems associated with irrigation and these are:
(i) Inadequate water supply for irrigation
(ii)  equipment is expensive
(iii) Pests from dry surroundings may invade and damage crops in irrigated land
(iv) Disease-causing organisms increased with increasing humidity.
(v) Vectors of diseases like snails and tsetse flies breed freely in irrigated areas
(vi) mechanical Irrigating equipment are expensive to maintain
(vii) Lack of adequate technical know-how on  the establishment and operations of irrigation scheme.
(viii) Excessive dissolution of salt in irrigated water prevents proper growth of crops
(ix) It may lead to pollution, if it contains dangerous chemicals.
(x) It disturbs the free movement of farm machinery
How to reduce disease build-up in irrigated farm
Reduction of disease build-up in an irrigated farm may be achieved through:
(i) Use of disease-resistant varieties
(ii) Crop rotation
(iii) Use of appropriate chemicals
(iv) Use of clean tools
(v) Use for clean or healthy planting materials
(vi) Destruction of diseased crops to prevent its spread
(vii) Avoidance of excessive irrigation
(viii) Weed control


Small nursery can be irrigated through
(i) Manual sprinkling e.g hand, brooms and brush

(ii) Use of watering can
(iii) Drip irrigation
(iv) Channel irrigation
(v) Sprinkler irrigating system
(vi) Sources of water for irrigation include rivers, lakes, streams, ponds, dams, boreholes, wells and reservoirs.


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The growing use of artificial subsurface or tile drainage in the world has sparked much debate about its impact on local hydrology and water quantity and quality. On this so here, are a few facts

  • Explain how subsurface drainage affects soil water and the water balance.

  • Describe how water balance relates to the crop-soil system and drainage.

  • Address several commonly asked questions about drainage, soil water and hydrology

When a soil is sufficiently wet, its capillary forces can hold no more water and the soil is at field capacity. The actual soil moisture content at field capacity varies with soil texture, typically ranging from 15 to 45 percent by volume. Plants can easily extract water from a soil when its moisture is at or near field capacity.

However, as a soil begins to dry out, increasingly stronger forces hold the pore water until plants can no longer extract any water from the soil. This state of soil moisture is the wilting point of a soil.

Soil moisture content at wilting point typically ranges from 5 to 25 percent by volume. Water in the soil between field capacity and wilting point is the plant-available water

Improving drainage of agricultural farm can be achieved by three primary means: 1. installing subsurface, artificial “tile” perforated pipe drains at some depth below the soil surface;  2. surface ditching, (3) land shaping (usually used with either ditching or subsurface drainage which also helps to reduce land degradation. Both the subsurface tile drainage and ditch-type systems function to lower the water table in the soil below the crop’s root reach, while land shaping prevents water lodge on soils with very low infiltration capacity by building a loamy soil surface to direct surface flow from the field. These practices are usually used in combination. surface-shaped fields need to drain to a ditch. Selection of a drainage system depends in part on the drainage problem that exists and the particular soil characteristics causing the issues

  1. Cross breeding–=== Cross breeding is the act of mating of animals from two breed of same species. Normally, breeds are chosen that have complementary traits that will enhance the offspring for economic purposes and business
  2. selective breeding== an animal selection practice to encourage chosen qualities. a process where some animals were chosen because of their special qualities. these qualities can be because of pure strength for the sole purpose of farm work like tillage practices
  3. selective smart breeding—=== plant selection practice to encourage chosen qualities. this type breeding takes place amongst plants only mostly if the plant species that is intended for use a special resistance capability for resisting diseases
  4. inter-breeding===the act of mixing different species or varieties of animals or plants and thus to produce hybrids. this requires high scientific foundation

Reasons for breeding of animals

The following reasons are some the triggers for breeding purposes. Breeding can be carried out in order to improve the inherited potential of the animal.
To improve production by introducing new genes.
This process overcome production problems created by the environment.
in order to satisfy consumers taste.
a farmer may decide to carry out specific purposes just For economic reasons e.g fast growth rate to reach the market early.

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