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.

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

• Two 25cm3 conical flasks
• 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.