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

Question 3

  1.   (i)   List two types of soil structure.            [ 2marks]

(ii)    Give two ways in which soil structure is important in
         crop production.    [ 2 marks]                                                                                             

  •    Explain the following types of soil water:
  •   gravitational water;
  •   capillary water;
  •   hygroscopic water.    [ 6 marks]

   (i)   Give four functions of nitrogen in crops;           [ 4 marks]

  (ii)   List two symptoms of nitrogen deficiency in crops.                [ 2 marks]


Many candidates attempted this question.  In 3a (i) and (ii), many candidates could not list types of soil structure and give ways in which soil structure is important in crop production.
However, in 3(b), majority of the candidates could explain the types of soil water (i.e  gravitational, capillary and hygroscopic water).  In 3c(i) and (ii), many candidates were able to  give functions of nitrogen in crops and list symptoms of nitrogen deficiency in crops.
The expected answers include:

              Types of Soil Structure

  • Platy/platelike
  • Prismlike/prismatic/columnar
  • Blocklike/Blocky
  • Spheroidal/Granular/crumb/single grained

Ways in which soil structure is important in crop production

  •  Affects aeration
  •  Affects drainage/infiltration
  • Affects water holding-capacity
  • Affects leaching
  • Affects erosion
  • Affects root penetration/penetration of groundnut pegs/gynophores
  • It determines the level of fertility of the soil/affects growth
  • It affects the activities of soil microorganisms.
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