Question 1
The diagram below illustrates the features observed after the evacuation of a site. Study it and answer the answer the questions that follow.
- Identify the diagram. (1 mark)
- Name the parts labelled A, B, C and D in the diagram. (4 marks)
- State the usual colour of each of the parts labelled A and B. (2 marks)
- A soil sample weighs 25g before being oven-dried. The soil weighs 15g after being oven-dried at 105 °C. Calculate the:
- Mention four ways of conserving soil water (4 marks)
(i) moisture content of the soil;
(ii) percentage moisture content (4 marks)
Observation
Majority of the candidates were able to correctly label the soil profile and also mention various ways of conserving soil water but could not calculate the moisture content and percentage moisture content in the given soil sample.
The expected answers include:
1. (a)Identification of the illustrated diagram
- Soil profile
(b) Names of labelled parts of the diagram
A – Topsoil
B – Subsoil
C – Parent material
D – Bedrock
(c ) Colour of the parts labelled A and B
A – Dark /Black
B -- Reddish brown, brown, orange
(d)(i) Calculation of moisture content of the soil
Weight of water in the soil = (weight of soil sample before oven-drying) – (weight of soil sample after oven drying)
Weight of water in the soil = 25g – 15g = 10g
(ii) Calculation of percentage moisture content
percentage moisture content = 10g x 100 25g 1
= 40 %
(e ) Ways of conserving soil water
- Mulching
- Cover cropping
- Organic manuring
- Fallowing
- Strip cropping
- Terracing
- Contour farming
- Afforestation
- Avoidance of overgrazing