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SULPHUR AND ITS COMPOUND SULPHUR AND ITS COMPOUND:A.SULPHUR (S) Sulphur is an element in Group VI(Group 16)of the Periodic table . It has atomic number 16...







The hydrological cycle.

The circulation of water from the earth’s surface to the atmosphere and back.

Sources of water.


  • Surfaces water sources.
  • Ground water sources.
  • Rain
  • Surface water sources.


Rivers, streams, lakes and dams.

  1. Rivers, streams and dams.

Rivers and streams originate from water catchment areas such as mountains, hills and forests.

To facilitate collecting of this water, weirs and dams are constructed to raise the water levels.


Barrier constructed across the river to raise the water level and still allow the water to flow over it.


Barrier constructed across a river or a dry valley to hold water and raise its level to form a reservoir or a lake. However a dam has a spillway provision to allow excess water to flow away.

  • lakes

These are huge collections of water on land depressions. Some lakes are salty and cannot be used for farming.


Underground water sources.


Springs, wells and boreholes.


Water comes out of the ground as a result of an impervious layer meeting the ground surface.

Later it collects into a stream. It should be fenced around to prevent contamination by animals. Spring water is less contaminated than rivers or lake water.


These are holes dug in the ground until the water table is reached. Wells should be dug during the dry season when the water table is very low. A reinforced concrete slab with a lockable lid should be constructed to prevent accidents, contamination and wearing of the topsides of the well.


These are deep holes drilled or sunk into the ground by the use of drilling machine sunk up to the parent rock. Special pumps are used to lift water out of the hole.

                                 Rain water.

Rain water is collected from rooftops and stored in tanks during the rainy season.  Ponds can be dug to collect the runoff. Rainwater is the purest water compared to water from other sources.



  • They are constructed to collect and store water. The bottom part of the area behind the dam should have an impervious layer such as clay or rock to prevent water seepage.
  • The embankment should be free from trees and bushes to prevent the roots from damaging it.
  • Grass should be planted on the embankment to prevent soil erosion.


They are used to raise the water level in a river to facilitate pumping or flow by gravity.

Water tanks.

Made of concrete, stone, metal sheets, plastic or rubber.

They store water from rain or that which has been pumped. Tanks should be covered to prevent contamination from dust. Stone and concrete tanks should be reinforced with wire mesh or barbed wire during construction so as to resist water pressure. 

Drums may be sued to store water but care should be taken to establish what these drums contained initially to avoid possible poisoning.

Pumps and pumping of water.

Pumping is the lifting of water from one point to another by use of mechanical force.

Water pumps.

  1. Centrifugal/rotardynamic pumps.

These have metal discs with blades that rotate at high speed. Water is driven out by a centrifugal force to the outlet. They can pump large quantities of water. They are driven by petrol or diesel engine.

  1. Piston/reciprocating pumps.

Have pistons that move back and forth, thus pushing water through the pipes.

They do not pump a lot of water. Most are petrol/diesel driven or hand operated.

  • Semi-rotary pumps.

Are used to pump water from wells by hands. They are manually operated and pump little amount of water mostly for domestic purposes.

  1. Hydram

They are operated by the force of flowing water. The higher the speed of water, the greater the pressure created in the pump.

The limitation is that they cannot pump stationary water.

However, they pump water to considerable heights.


Conveyance of water.

This is the process of moving water from one point, mostly the source or point of storage, to where it will be used or stored.

 Methods of conveying water.

  • Piping
  • Use of containers. S Use of canals.

Type and choice of pipes.

  • Metal pipes.

There are two types of metal pipes.

  1. Galvanized iron pipes.

Are heavy and suitable for permanent installations.  ii.   Aluminum pipes.

Are light and are used in irrigation systems. Metal pipes are expensive but durable.

  • Plastic pipes.

They are inexpensive and easy to install compared to metal pipes.

They are durable when properly installed.

Limitations of plastic pipes.

  • They can burst under high pressure.
  • They become brittle when exposed to the sun.
  • They can be gnawed by rodents such as moles.


  • Hose pipes.

They are two types of hose pipes. Plastic and rubber hose pipes.

Rubber hose pipes are more expensive but are more durable.

  • Use of containers.

Water is drawn and put in containers such as drums, jerry cans, pots, gourds and buckets which are carried by animals, bicycles and human.

  • Use of canals.

Water is conveyed from a high point to a lower along a gradual slope to avoid soil erosion. Such water is used for livestock and irrigation.

Water treatment.

Process of making it safe for use in the farm.

 Importance of treating water.

  1. To kill diseases causing micro-organisms such as cholera and typhoid bacteria that thrive in dirty water. ii. To remove chemical impurities such as excess fluoride which may be harmful to human beings. iii. To remove smells and bad taste. Smells and bad taste in water make it unfit for human consumption.
  2. To remove sediments of solid particles such as soil, sand and sticks. This makes water clear.

 Process of water treatment.

  • Stage one: filtration at water intake.

v Water leaves the source and pass through a series of sieves before entering intake pipe. Sieves have different size meshes. As raw water enters the pipe, large particles of particles of impurities are trapped by these sieves.

  • Stage two: softening of water.

v Water flows into mixing chamber. This is a small tank where water circulates and is mixed with soda ash. And alum. Soda ash softens the water, while alum helps to coagulate solid particles which settle down to the bottom of sedimentation tank in stage three.

  • Stage three: coagulation and sedimentation.

v The softened water moves to coagulation tank which is circular and large. Solid particles such as silt and sand settle down. The tank is also open to allow in fresh air into the water removing bad smells.  Water should stay for at least 36 hours to kill bilharzia worms which cannot survive in stored for that long.

  • Stage 4: filtration.

v Water with few impurities pass into filtration tank where all the reaming solid particles such silt are removed. Filtration tank has layers of different sizes of gravel and a top layer of sand. The layers allow water to seep through very slowly leaving all the solid particles behind.

  • Stage five: chlorination.

v Filtered water enters chlorination tank. Small amount of chlorine solution is added. Flow of chlorine solution is controlled by a doser .the chlorine is used to kill micro-organisms in water.

  • Stage six: storage.

v Water is stored before distribution. Should be out of bounds to unauthorized persons. It should be covered and the area around it well fenced.


Treatment of water by boiling.

In small-scale domestic, water is boiled to kill organisms that cause diseases such as bilharzia, cholera and typhoid. Boiling is expensive and can be done with small amounts especially for drinking.

General uses of water on the farm.

  1. For domestic purposes such as washing utensils, cooking, drinking, washing clothes and cleaning the house.
  2. For watering livestock, washing animals for example, pigs, washing and cleaning livestock buildings and cleaning farm equipment.
  • For diluting chemicals which are used in the control of pests and diseases in both crops and livestock.
  1. During the processing of farm produce such as coffee, carrots, beets, hide and skin.
  2. In the construction of buildings, for example concrete mixing and curing. vi. For irrigating crops especially during the dry season.


It is the artificial application of water to soil for the purpose of supplying sufficient moisture to the crops. It is a method of land reclamation.

Conditions under which irrigation is applicable.

  1. In dry areas.

These are areas that receive low amounts, insufficient for crop production. It is used as a method of land reclamation. ii. During dry periods.

Some crops such as coffee, citrus, pineapples and other horticultural crops requires irrigation during the dry spell to meet their moisture requirements for high production.

iii.      In the growing of paddy rice.

Paddy rice requires flooded conditions throughout the growing period.

 Types of irrigation.

They include.

  • Surface
  • Overhead
  • Sub-surface.
  • Drip/trickle.

Factors determining the choice of irrigation method to use.

  • Capital availability.
  • Water availability.
  • Types of soil.
  • Type of crop to be irrigated.

 Surface irrigation.

Water is brought to crop fields from its source through canals or furrows.

Include: flood, furrow and basin irrigation.

Factors to consider in choosing surface irrigation.


The land must be fairly level.

ii. Amount of water.

There must be a lot of water available for this type of irrigation

iii.Soil type.

Soil must be able to hold a lot of water and allow it to stand for long period as it seeps into the soil by the roots.

Flood irrigation.

Water is allowed to flow into the field from a source such as a river through furrows or canals.

They are fitted with sluice gates to control the flow of water. The land to be irrigated must be level and there must be plenty of water.

It is relatively cheap to establish and maintain.

However there is uneven distribution of water to crops and plenty of water is wasted.

Furrow irrigation.

Water flows from irrigation canals into furrows. Furrows should be dug along the contours to reduce soil erosion. Crops are planted on the ridges of the furrows.

Furrows should be maintained by repairing when eroded or worn out, removing weeds and accumulated silt.

  • It reduce fungal diseases such as blight as it does not wet the leaves. S It is cheap to establish and requires little skills.

However the limitations are:

  • A lot of water is lost through evaporation and ground seepage.
  • Soil erosion may occur where furrows are not properly planned or maintained. 


Basin irrigation.

  • Involves flooding the whole are enclosed by earth embarkments called dykes or levees.
  • The depth of water is controlled by the dykes or levees. Soil should be made level and dykes constructed around the leveled ground.
  • The levelled ground surrounded by dykes is called the level basin.
  • Soils should be able to hold water for a long time with little infiltration. Requires soil such as clayey. Common in rice fields which are flooded throughout the growing period.
  • For land that is not level, it becomes very expensive to construct level basins.
  • It may results in accumulation of a lot of salts I n the soil.
  • Maintenance involves rebuilding the levees if broken and removal of weeds from canals, basin inlets and outlets.
  • Sub-surface irrigation.

Involves laying perforated pipes underground to allow water to pass through tiny holes and wet the soil around the root zones of the crop.

Requires soils of high capillarity and water holding capacity.

Advantages of sub-surface irrigation.

  1. Minimizes labour requirements, especially in changing water pipes. ii. No need of constructing dykes, levelling or making level basins. iii. It can be practiced on both sloppy and flat land. iv. Water does not cause erosion because it comes out in small amounts.
  1. Fungal diseases such as blight are reduced, because water does not accumulate on leaves.
  2. Economises on the use of water. vii. Minimizes possible theft of pipes.


  1. It is an expensive undertaking for example in buying pipes and laying them especially in large areas.
  2. Pipes can be broken during weeding or land preparation. iii. Nozzles can be blocked and this makes irrigation inefficient.

 Drip or trickle irrigation.

Plastic pipes with tiny perforations are mainly used. They are laid on the ground wetting the soil around the base of the crop.

Advantages of drip irrigation.

  1. Little amount of water is required as compared to other types of irrigation. ii. Water under low pressure can be used as long as it can flow along the pipe.
  • It discourages fungal diseases such as blight, CBD and others, as it does not wet the leaves of the crop.
  1. It does not encourage the growth of weeds between the rows.


  1. The pipes are expensive to buy and thus it is practiced on limited scale.
  2. Requires clean water only as dirty water blocks the perforations.

Overhead irrigation.

Application of water above the crops by means of sprinklers or watering cans. Water must be under high pressure. Wind may misdirect the water and thus a windbreak may be established.


  • Lubricating the rotating parts.
  • Repairing broken parts.
  • Cleaning to unblock nozzles.

Advantages of overhead irrigation.

  1. Water is evenly distributed over the required area. ii. Water is evenly distributed over the required area. iii. There is less water distributed over the required area. It can be practiced even in sloppy areas. iv. Foliar fertilizers can be applied together with irrigation water thus reducing the labor costs.
  2. Sprinkler systems can easily be moved from one place to another.


  1. Expensive installations are required e.g. buying pipes sprinklers and a water pump. ii. Encourages fungal diseases such as blight due to water accumulating on leaves. iii.   Causes soil erosion if it is not properly controlled especially in sloppy ground. iv.       It may require the establishment of windbreak.
  2. Maintenance of the system requires a lot of skill and it is also expensive.



It is a method of removing excess water or lowering the water table from marshy waterlogged land. It is a method of land reclamation.

Importance of drainage as a land reclamation method.

  • It increases soil aeration: excess water around the root zone retards plant growth because it fills the air spaces restricting air movement.
  • To increases soil volume: amount of soil around the root zone from which roots can easily get nutrients easily is increased.
  • To raise soil temperature: improves the rate at which soil warms up for better plant growth.
  • To increase microbial activities: micro-organisms in the soil increase in number due to proper aeration. Help to improve soil structure and make plant food more readily available.
  • To reduce soil erosion: well drained soils have high water holding capacity which helps to reduce run-off and increase infiltration rate.
  • To remove toxic substances: due to waterlogging, soluble salts increases in concentration to levels that are toxic to plants. Drainage removes such salts from the soil.

Methods of drainage.

  • Open ditches.

Ditches are dug for water to flow in by gravity thus lowering water table. Ditches may be U-shaped, V-shaped or trapezoidal.

  • Underground drain pipes.

Perforated pipes are laid underground where water seeps from the surrounding area into the pipes. Such drains do not interfere with field operations. Drain pipes could be made of steel, clay or plastic materials.

  • French drains.

Ditches are dug, filled with stones and gravel and then covered with soil.  Water from the surrounding area seeps into these drains and is carried into a waterway.

  • Cambered beds.

Raised beds are constructed and are use with combination with ditches. Used on poorly drained soils such as black cotton soil.

In low lying areas where other methods are not suitable water is pumped out of the soil.

  • Planting trees.

Trees such as eucalyptus that consume a lot of water are used to drain excess water from soils. 


Any process which leads to harmful increase in the amount of chemical substance or forms of energy released into the environment by human activities.

Agricultural practices that pollute water.

  1. Use of inorganic fertilizers.

These get leached through the soil, they are carried into water bodies thus polluting the water. ii. Use of pesticides.

Excess pesticides used in agricultural production seep into the soil and finally join the water bodies causing pollution. iii. Poor cultivation practices.


  • Over cultivation. This encourage soil erosion which eventually causes siltation in water sources.
  • Leads to soil erosion which causes siltation thus pollution.
  • Cultivation along river banks. This encourages soil erosion and subsequent pollution of the rivers.


 Methods of preventing water pollution.

  1. Soil conservation measures should be taken to minimize soil losses through erosion. Terraces should be constructed in steep areas.
  2. Fencing of water sources to minimize possible pollution by livestock or humans.
  • There is a need to enforce by laws the use of integrated methods of controlling pests and weeds as opposed to using chemicals.
  1. River banks should be vegetated by planting grass to minimize siltation in rivers.
  2. Employing adequate storm water control methods and disposal systems especially in areas with heavy rains.