This question was fairly popular among the candidates.  In 4(a), Majority of the candidates could not use the appropriate conjunctions/table to differentiate between macro nutrients and micro nutrients as used in crop production.  Although in 4(b), most of the candidates could mention four ways by which plant nutrients are lost from the soil but in 4(c), majority of them could not discuss the effects of clean clearing and crop rotation on the soil.  However, most of the candidates could state two ways in which soil organisms improve soils for crop growth as required in 4(d).
The expected answers include:
4(a)        Difference between macro-nutrients and micro-nutrients in crop production
Macro-nutrients are mineral salts required in large quantities by plants
whereas/but/on the other hand/while
Micro-nutrients are mineral salts required in small quantities by plants.                                
       (c)            Effects of farming practices on the soil
                    (i)                Effects of clean clearing on the soil:
                                        -     Exposes the soil to agents of erosion such as wind and water.

• Direct exposure to sunlight increases the rate of evaporation.
• Increases the soil temperature.
• Oxidation and loss of soil nutrients.
• Destruction of soil structure.
• Soil compaction as a result of the heavy farm machinery used in clearing.
• Soil microbes are reduced.                                                                                                                   

(ii)                           Effects of crop rotation on the soil

• Allows for optimum utilization of soil nutrients at all levels.
• Maintains the soil fertility.
• Controls soil erosion.
•  Increases the nitrogen content of the soil through the inclusion of a leguminous crop in the crop rotation pattern.
• Controls soil-borne pathogenic organisms such as nematodes.
• Controls the build up of pests of crops as crops that are hosts to the same pest are  not allowed to follow each other.
• Improves soil moisture.
• improve soil aeration.