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 Agricultural Science Paper 2, Nov/Dec 2009
 Questions: 1 2 3 4 5 6 7 8 9 10 Main
Weakness/Remedies
Strength

Question 4

1.   (i)   What is an inorganic fertilizer?                                                       [ 2 marks]

(ii)     List two methods of fertilizer application.                                     [ 2 marks]

•   Describe an experiment to show the presence of living micro-organisms in a sample of fresh garden soil, under the following headings:

•   apparatus and materials;                                                              [ 2 marks]
•   procedure;                                                                                    [ 3 marks]
•   observation;                                                                                 [ 2 marks]
•   conclusion.                                                                                   [3 marks]
•    State two ways in which the carbon cycle is important in agriculture.   [ 2 marks]
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OBSERVATION

Few candidates attempted this question.  In 4 a(i) and (ii), majority of the candidates  were able  to define inorganic fertilizer and list methods of fertilizer application.

However, in 4 b(i-iv), majority of the candidates could not describe an experiment to show the presence of living micro-organism in a sample of fresh garden soil.  In 4(c), many candidates  were able to state ways in which the carbon cycle is important in agriculture.

Description of experiment to show the presence of living micro-organisms in a sample of fresh garden soil:
Apparatus and materials

• Rubber corks
• Lime water
• Garden soil(fresh)
• Heated garden soil
• Muslin bag
• String
• Source of heat (Heater).

Procedure

• Put a handful of fresh garden soil in muslin bag and suspend it with the string in a flask labeled A, containing lime water and cork it.
• In another muslin bag, put another sample of garden soil which has been strongly heated to kill any living organisms in it; and suspend it with the string in a flask labeled B, containing lime water and cork it.
• Leave the set-up for about 4 hours.

Observation
The lime water in flask labeled A containing the fresh soil will turn milky, whilst that in flask B  containing the heated soil B will remain clear.

Conclusion
When carbon dioxide dissolves in lime water, it turns milky-Carbon dioxide which turned  the lime  water milky in the flask A containing fresh soil is from respiration by living  organisms present in the fresh soil.

There is no respiration to produce any carbon dioxide in the soil in flask B because the  organisms are dead, as a result of the heating.  This is why the lime water in flask B remains clear.