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Agricultural Science Theory The diagram below illustrates an experimental set-up on soil. Study it and answer the questions…

The diagram below illustrates an experimental set-up on soil. Study it and answer the questions that follow.

 

a) (i) State the aim of the experiment. 

(ii)Name the parts labelled I and II in the diagram. 

 

b) Describe how the experiment is carried out. 

 

c) State four properties of sandy soils. 

 

 d) Describe a test for soil acidity using litmus paper. 

Explanation

(a)(i) Aim of the experiment

  • Separation of soil into its fractions/determination of soil texture by sedimentation                                                                                      

(ii)  Naming of the parts labelled I and II         I – Clay in suspension/Clay       II – Silt
                                                                          

(b)  Description of the experiment

  • Place a glass jar on a surface
  • Weigh about 70 – 100g of the soil
  • Add the weighed soil into an equivalent quantity of water in a glass jar
  • Add suitable dispersing agent e,g, NaOH, NaHCO3
  • Shake the glass jar vigorously to disperse any soil clods
  • Allow the glass jar to settle for an hour
  • Observe the result

(c)Properties of sandy soils

  • Low cation exchange capacity
  • Diameter is between 0.02 mm – 2m2
  • Well drained, loose and highly aerated
  • Low plant nutrients
  • Low buffering capacity
  • Leaching of nutrients is high/supports leaching
  • Easily gets hot and cold
  • Low water holding capacity
  • Particles are light and easy to till
  • Gritty/rough/coarse in nature
  • High percolation rate
  • Low capillary action
  • Cannot be moulded

(d)  Testing soil acidity using litmus paper

  • Mix the soil very well
  • Moisten with distilled water
  • Dip red and blue litmus paper into moistened soil
  • If blue litmus paper changes pink/red, the soil is acidic
  • If red litmus paper changes blue, the soil is basic/alkaline
  • If there is no colour change, the soil is neutral