(a) With the aid of the litmus paper and water provided, classify specimens G, H and I. (b) Outline the steps taken in classifying specimen G (NEUTRAL SOIL)...

Answer Details

(a) Classification of the specimens using litmus paper and water

• G (Neutral soil): Neither red nor blue litmus paper changes colour.
• H (Acidic soil): Turns blue litmus paper red.
• I (Alkaline / basic soil): Turns red litmus paper blue.

(b) Steps in classifying the specimens

1. Place a small portion of each soil sample (G, H and I) into separate clean containers.
2. Add distilled water to each and stir to make a soil suspension or paste.
3. Allow the mixture to settle for a few minutes.
4. Dip a strip of red litmus paper and a strip of blue litmus paper into each suspension.
5. Observe and record the colour change: no change means neutral (G); blue turning red means acidic (H); red turning blue means alkaline (I).

(c)

(i) A pH value of 4.5 indicates that the soil is acidic (strongly acidic).

(ii) Three effects of acidity on crop production

• It reduces the availability of essential nutrients such as nitrogen, phosphorus and potassium.
• It causes toxicity of aluminium, iron and manganese to plant roots.
• It lowers the activity of soil micro-organisms and poor nodulation in legumes, leading to stunted growth and low yield.

(iii) Three factors that could cause acidity

• Leaching of basic cations by heavy rainfall.
• Use of acid-forming fertilizers such as ammonium sulphate.
• Decomposition of organic matter releasing organic acids.