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1.         a) Differentiate soil  profile from soil catena                                                                          

            b) Name three types of soil types according to soil structure                                                 

c) i) Beside planting of trees state any other three measures that can be used to control


              ii) Explain how trees help in the conservation of the soil.                                       

2.         a) i) What is soil?                                                                                                       

                ii) Differentiate between soil catena and soil profile.                                          

            b)i) Explain how the following factors influence soil formation;

                                    – Climate                                                                                                        

                                    – Living organisms                                                                                         

                 ii) Give three factors that determine the colour of the soil.                                             

3.         a) Briefly explain the factors that influence the development of soil catena.           

          (b) (i) Define the term soil profile                                                                                           

                (ii) Draw a simple diagram of soil catena                                                                         

               (iii) Give any four soil forming processes                                                                         

             (iv) State four causes of soil degeneration                                                                           

4.         a)i) Define the term soil                                                                                                        

                ii) Name three components of soils                                                                                  

            b)i) Apart from living organisms state four other factors that influence soil formation      

                        ii) Explain how living organisms influence soil formation                                      

            c)         i) Distinguish between soil air and soil texture                                                        

                        ii) Describe the process of podzolisation                                                                  

                        iii) State the characteristics of soils in grassland areas                                            

5.         (a) Draw a diagrammatic representation of vegetation zones on a slope common in tropical          


 (b) (i) What is soil catena?                                                                                                    

           (ii) Draw a labeled diagram to show a well developed soil profile.                                       

(iii) State three characteristics of the soils found in the arid regions of Kenya.                  

    (b) Give three factors that determine the colour of soil.                                                               

    (c) Describe how laterization occurs.                                                                                            

    (d) Explain how the following farming practices cause soil erosion;

         (i) Burning.                                                                                                                               

         (ii) Continuous application of fertilizer on farm lands.                                                            

         (iii) Monoculture.                                                                                                                      

6.         (a) (i) Apart from latosols name any two other types of zonal soils                                     

                 (ii) Describe how lateritic soils are formed                                                                      

                   (iii) State any two characteristics of azonal soils                                                                       

            (b) (i) Explain any three ways in which rain water can lead to degeneration of soils.         

                 (ii) Apart from growth of plants, state any three other ways in which soils are beneficial

                       to people                                                                                                                      

7.         (a) (i) Differentiate between a soil profile and soil catena                                                    

      (ii) State two processes of soil formation                                                                        

(b) Explain how the following factors influence soil formation:

    (i) Climate                                                                                                                          

    (ii) Living organisms                                                                                                          

    (iii) Topography                                                                                                                 

(c) (i) What is soil degeneration                                                                                            

     (ii) Explain three ways through which vegetation naturally protects and prevent soil erosion

    (iii) Give two sound farming methods that help conserve soil erosion                             

8.         (a) (i) What is soil Catena?                                                                                                    

     (ii) State three factors  which influence the development of a soil catena                      

(b) Explain five negative effects of soil erosion                                                                    

(c) Describe how podzolization occurs in soils                                                                     

9.         (a) Name three components of soil                                                                                       

            (b) Explain how the following factors influence the formation of soil          :

                        (i) Climate                                                                                                                  

                        (ii) Parent material                                                                                                     

            (c) (i) Explain three ways in which human activities contribute to soil degeneration         

                  (ii) Draw a well labeled diagram to show a mature soil profile                                      

10.       a) What is a lake?                                                                                                                  

            b) State three ways through which lakes are formed                                                            

11.       a) Define the term “Soil”                                                                                           

b) Explain how the following factors influence the formation of soil                                               

                        i) Climate                                                                                                                   

                        ii) Topography                                                                                                           

            c)         i)State two ways in which humus improves the quality of soil                                 

                        ii) State four characteristics of desert soils                                                               

            d) Describe how the following types of erosion occur

                        i) Sheet erosion                                                                                                          

                        ii) Gulley erosion                                                                                                       

                        iii) State two economic uses of soils                                                                         

12.       (a) What is soil conservation?;                                                                                                            (b) State three methods that assist in soil conservation



1.         a)         – Soil profile is the vertical arrangement of various soils  in layer  showing  the

                        sequence of horizons from  the surface  to the parent  materials                            

– Soil catena is the sequence of different soils on a slope from the top of the

  hill to the valley Bottom                                                                                        


b)     –    platy/plate  soil structure                                                                                                  

  • crumb  soil structure
  • prismatic  soil structure
  • blocky/block soil  structure
  • granular  soil structure
  • columnar soil structure

 c i)                  – Controlling overgrazing                                                                                       

            – Avoiding bush fires

            – Controlling tree cutting

            – Practicing appropriate methods of cultivation e.g. planting cover crops, irrigation,

               mulching, terracing, contour farming

 c ii)                 – Leaves & branches reduce the force of rain drops which would otherwise loosen

                            and remove soil particles                                                                                           

  • Rate of infiltration of rain water into the soil is increased by vegetation cover thus reducing surface run off
  • Tree roots which penetrate the soil help to carry surface moisture into the ground. This allows the moisture to gradually percolate deeply
  • Tree roots bind the soil particles together and therefore the soil can not be easily carried away
  • Trees break the force of the wind at the ground and reduces the transportation of soil by wind

2.         a i) Soil is the top layer of loose or unconsolidated rock material overlying crustal rocks

                    and   on which the plants grow

            Or  – Is an accumulation of rock particles minerals, organic matter, water and air found on

                        the surface of the earth                                                                                       

   a ii) ) Soil catena : This is the arrangement of soil on a mountain slope from the top of the

                 valley bottom while soil profile is the vertical arrangement of various soils in layer

                 from surface to bed rock                                                                                                         

 .b i)  – – Climate

             -Seasonal variation of rainfall can cause accumulated concentration of salt in the soil

  • Rainfall provides water which make it possible for rocks to disintegrate to form soil
  • Rainfall also affect the rate at which some soil forming processes can occur (leaching)
  • High temperatures increase the rate of weathering by accelerating the raise of bacterial activities which generates some of the organic matter in the soil
  • Wind, ice, water erode, transport and deposit soil particles in other areas leading to the formation of new soils

                                    – Living organisms                                                                                      

– Living organisms add organic matter to the soil                                                                      

  • Areas with thick vegetation lead to the formation of fertile humus laden soils which is quite useful in aeration
  • Bacteria help to decompose organic matter
  • Bacteria fixes nitrogen into root nodules of plants thus enriching the soil
  • Human activities can change the nature of the soil through grazing cultivation, use of fertilizers e.t.c.

b ii) – Type of parent                                                                                                           

  • Amount of organic matter
  • Chemical composition i.e. minerals
  • Drainage of the soil or amount of water in the soil

3.         a) Relief                                                                                                                                

Slope influences the type of soil in that on steep slopes the soils that develop are thin, on gentle slopes the soils are deep and fertile. This is because the rates of erosion and weathering are quite rapid on steep slopes than gentle slopes


– The amount of moisture in the soil is determined by the slope. Steep slopes have

     well drained   but thin soils

  • Hill top has well drained and mature soils
  • Valley bottoms develop soils that are poorly drained

Mass wasting and surface run off

                        This leads to development of fertile soils at the valley bottom because the top soil

                        removed and deposited there


                        This is the movement or washing of soil minerals from one layer to another which will also affect the type of soil developing           

b i) the vertical arrangement  of  soil in layers from the top  the bedrock

b iii) elluviation                         calcification                                                                               

illuviation                          gleization

leaching                             ferrilisation



b iv)-  Excess irrigation                                                                                                      

– Over stocking                

4.         a i) Soil is a thin layer of natural material on the earth’s surface that supports plant

                   and  animal life

            ii)   – Inorganic matter                                                                                                        

  • Organic matter
  • Soil water
  • Soil air
  • Soil organisms   

. b i)  – Parent rock                                                                                                                         

  • Topography
  • Climate
  • Time

b ii)  –     Dense vegetation vital for fertile soils                                                                         

  • Micro-organisms like fungi fix nitrogen to the soil
  • Micro- organisms aerate the soil hence improve porosity
  • Activities of man i.e. grazing, use of fertilizers, construction

c i)           –  Soil air – gases that are available within spaces that separate soil grains    

                          –   Soil texture- size of individual soil grains    

c ii)       –    High amount of rainfall promote chemical weathering of acid parent rock materials

  • Long cold withers and short mild summers in temperate climates reduce bacterial activity
  • Weathering of parent rock materials releases iron, aluminum, silica and organic acids
  • Strong acid conditions enhance leaching of bases especially calcium along with iron and aluminum
  • Silica that is less soluble is left back with the top layers and staining the soil beneath
  • ash- grey                  

c iii)   – Develop mostly through calufication                                                                            

  • Have dark surface horizons
  • Rich in calcium
  • Have deep top layers of about I meter thick


b i) – Soil catena is the sequence of different soils on a slope


a iii) – The soils are light in colour                                                                                    

  • They are saline
  • They are sandy/ strong
  • They are loose in texture
  • They are thin
  • They have low moisture content        

b)    –  The type of parent rock                                                                                                      

– The amount of organic matter/ humus

– The chemical composition/ the degree of iron oxide/ minerals

– The amount of water in the soil/ drainage of soil        

c)    – During the wet season, mineral salts in the top layer of the soil dissolve rain water

– The dissolved minerals percolate seep downwards from the top soil to the sub soil

– The dissolved minerals are deposited further downwards to the lower layer

            – Insoluble minerals such as iron and aluminum are left on the up layers to form a crust

            of late rite soils       

d i)      – Burning destroys micro- organisms which are essential for formation of humus which

                            binds the oil particles together                                                                                   

– Burning destroys vegetable matter that protects the soil against erosion

– Burning destroys the nitrogen fixing bacteria making the soil less fertile

– Burning loosens the soil making it susceptible to erosion/ leaching which drains away   soluble mineral nutrients

d ii)    –  This increases the aridity of the soil/ changes the PH of the soil                 

          – The acidity destroys the micro- organisms in the soil/ bacteria/ fungi which could

  have helped in the formation of humus

d iii)    – Monoculture leas to exhaustion of certain minerals from the soil making it infertile

                      leading to its erosion                                                                                                         

                 – Monoculture leads to loosening of soils particulars there by encouraging soil erosion

6.         (a) i) – Tundra soils                                                                                                            

  • Podzols
  • Chernozens
  • Proure soils
  • Chestrut soils
  • Red Desert soils

a  ii)  – In warm to hot humid regions silica and other bases dissolve in water are   

            leached/percolate   when it rains seep downwards from the top soil           

  • This leaves iron and aluminium oxides which are insoluble on upper soil horizons.
  • This forms soils  on upper soils on the upper soil horizons rich in iron and alluminiumoxides called lateritic soils

a iii) – They are young/of recent origin                                                                            

– They are immature

– They are insufficiently affected by soil forming processes

– Characteristics depend on their origin

 b i) – High rainfall can lead to water logging and formation of acidic soils               

    – Heavy rainfall also results into surface run off that may lead to sol erosion run-off that may  lead to soil erosion

– Too much rain can alter the soil structure by causing crumb soil to form blocky or columnar  structure

– Heavy rainfall can led to leaching of nutrients from top soil to lower soil horizons depriving   the top soil of some nutrients

– Low rainfall leads to loose soils easily blown away by the wind

– Excessive drought leads to accumulation of salts in the top soil leading to salination

b    ii) – Soil is baked to make building and construction materials like bricks, tiles/whitewash

– Soils are used in making pottery/ceramics/sculptures and used by people

– Some soils contain minerals like apatite which is mined and used to make phosphatic


– Some soils are medicinal

– Some soils are food to animals and people

7          a i) soil catena is the  horizontal arrangement of soil  on a  mountain slope while a soil

                   profile  is the  vertical arrangement of soil particles in layers  or horizons                  

.           a ii)  -leaching                                                                                                                     



             -organic accumulation



           -organic sorting  

b i) – seasonal rainfall in temperature and rainfall  facilitating the rate of   weathering      

            -the rate at which organic matter decompose rise in to increase  in temperature  and rainfall   while dry areas are devoid of vegetation covers 

b ii) –  micro-organism cause both plants  and  animals to decay into humus .humus are

             added o the upper layers  of the  soil                                                                           

          -living organisms act on decaying organic matter through humification to form humus.

           This     humus consolidate forming  rich soils.

b iii)-  soils formed on steep  slopes  generally fails  to develop or mature  because most  of the

     rain    water runs of  along the surface ,this accelerate erosion which comes  away  the top layers of    soil                                                                                                                                             

          -on rolling and gentle slopes maximum soil development is likely to occur. This is because the rate of soil  erosion is   matched  by the rate of soil  formation due to good drainage

c i) soil degeneration  is  the  decline in the usefulness  of soil  resulting from either  soil

         mismanagement or environment causes                                                                         

c ii)    -plant roots  which penetrate the soil help  to carry surface moisture into  the soil  

   -vegetation helps to bind soil particles together                                                                                 

   -plant  cover breaks the  force of wind   and therefore reduces the  transportation  of soil particles

   -decayed  vegetation  matter provide humus which binds  the  soil  particles together

   -the  leaf cove  helps to  reduce  the force  of rain drops which would loosen  and remove soil


   -the rate of infiltration of rain water into the soil is increased by vegetation cover thus reducing 

     surface run offs

c iii) -crop rotation                                                                                                               

              -contour ploughing

            -strip cropping

              -inter cropping

             -bush fallowing

              -mixed cropping 

8. a i) -this is the sequence or arrangement of different soils down a slope                         

8. a ii)   -the relief/slope/steepness of the land                                                                          

-the drainage of the area

-the transportation of the soil debris

-the teaching process

8. b)      -the production topsoil is lost foe ever and his lowers the agricultural production of the land

-the soil left behind after erosion is thin and  cannot hold plants firmly in the ground.

-continued loss of soil  through erosion destroys vegetation cover  turning the area into

semi- arid/desert.

-soil erosion causes  water reservoirs to be filled up by silt adding extra cost of dredging.

-sediments which are carried into rivers/lakes/oceans may contain industrial effluents

which   kill aquatic life.

-gullies as a result of erosion expose water onto the surface leads to lowering of the

water   table

8. c)       -develop  best in areas which are cool and sufficiently wet                                     

-soluble soil constituents are moved downwards

-it leads to severe absence of bases throughout the soil profile resulting to low  PH and

 an   accumulation of hydrogen clays

-there is an accumulation of acid organic matter in horizon a leading to intense teaching

of  bases  and clays

-iron and humus are deposited in horizon B      

9.         a)  – Living organisms.                                                                                                        

            – Organic matter.

– Soil minerals.

– Soil matter.            

– Soil air.                   

  b i) – Climate influence type & rate of weathering.                                                                  

            – High rainfall influence leaching process runoffs resulting from high rainfall increases

             rate of erosion.

– It influence rate of decomposition

b ii) – Influence soil profile.                                                                                                

  – Parent material influence soil structure.

  – It influences soil colour.

  – It influences mineral composition.

  –  It influences soil texture.          

c i) – Over cultivation exhausts the soil fertility.                                                              

            – Monoculture exhausts soil minerals.

            – Clearance of land for agriculture interrupts nutrient cycling.

            – Application of fertilizer changes the P.H.

            – Construct of roads, mining, quarrying destroy soil structure.

             -Application of fertilizers change soil PH

c ii) A-TOP SOIL                                                                                                                             




10.       a)  – A lake is an accumulation of water in a wide hollow or depression                              

.           b)    –    By erosion                                                                                                             

  • By earth movements/ volcanic activity
  • By deposition
  • By human activity
  • By falling meteorites
  • By mass movements e.g. land slides
  • Weathering by solution

11.      a i) Soil is the upper most surface layer of unconsolidated material which lies on the                 

               surface  of the earth and in which plants grow/ soil is an accumulation of rock particles    

          or  minerals,   organic matter, water and air found on the surface of the earth        

. b i)  – Seasonal variation of rainfall can cause accumulation/ concentration of salts in soil  

– Rainfall provide water which make it possible for rocks to decay/ disintegrate to form soil

– Rainfall can affect the rate at which some soil forming processes can occur (leaching)

– High temperatures increase the rate of weathering/ accelerate the rate of bacterial activities

    which generates some of the organic matter in the soil

– Water, ice and winds erode, transport and deposit soil particles in other areas leading to the  formation of new soils (for example loess) 

b ii) – Valley bottoms/ gentle slope encourage the formation of deep and fertile soils due to

               deposition/ accumulation of minerals                                                                         

– Steep slopes encourage erosion of the top layer of soil thus slowing down formation of soil/    have thin soils

– Flat plains/ flood plains are saturated with water therefore slows down soil forming processes

– Slopes influence arrangement/ sequence of soil/ soil catena

– Some slopes are more exposed to the sun/ rain which influence weathering of parent rocks/   soil formation (aspect)

c i)     – Humus helps to improve soil porosity by aerating the soil                                         

– It improves the moisture – retention capacity of the soil

– Humus provides essential minerals to the soil

– It improves the soil texture

c ii)-  They are thin and shallow                                                                                                   

– They are sandy or stony

– They lack humus or have low organic matter content

– They are generally saline

– They are coarse- textured and quite porous

– They are alkaline because of high content

– They have low moisture content

. d i)   – This occurs on gentle slopes which are bare                                                               

– When heavy rain falls, water spreads over a large area

– As water moves, it removes the top layer of soil evenly over the area

. d ii) – It occurs on steep slopes                                                                                                  

– Rain water cuts deep grooves/ channels/ rills on the slopes

– The channels are widened and deepened to form gullies, through which soils are carried away

. d iii) – Soils are sources of valuable minerals                                                                          

– Soils are used raw materials for pottery/ ceramics/ tiles/ bricks

– Soils are used for agriculture

– Some soils are mixed with herbs and sold for medicinal purposes e.g. clay/ sold directly for


12.      a) – It is a careful management/protection of soil against erosion and exhaustion 

            . b) – Ploughing along the contour                                                                                   

– Controls grazing

– Stripping cropping

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