DETAILED COMMENTS ON EACH QUESTION
Question 1
The diagram below illustrates an experimental set-up on soil. Study it and answer the questions that follow.
-
- State the aim of the experiment.
(1 mark)
- Name the parts labelled I and II in the diagram.
(2 mark)
- State the aim of the experiment.
- Describe how the experiment is carried out.
- State four properties of sandy soils.
- Describe a test for soil acidity using litmus paper
(4 mark)
(4 mark)
(4 mark)
Observation
- Most candidates were unable to state the aim of the experiment as many erroneously
described it as a soil profile; thus mislabelling its parts. - Candidates were however able to state the properties of sandy soil as well as describe a
test for soil acidity using litmus paper.
The expected answers include:
-
- Aim of the experiment
- Naming of the parts labelled I and II
-Separation of soil into its fractions/determination of soil texture by sedimentation
I Clay in suspension/Clay
II Silt
- Description of the experiment
- Properties of sandy soils
- Testing soil acidity using litmus paper
- 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
-Low cation exchange capacity
-Gritty/rough/coarse in nature
-Diameter is between 0.02mm – 2m2
-High percolation rate
-Well drained, loose and highly aerated
-Low capillary action
-Low plant nutrients
-Cannot be moulded
- 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
- 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