Explanation

(a) Classification of specimens G, H and I according to their pH

• Specimen G- neutral soil  
• H- acidic soil
• I- alkaline/ basic soil

(b) Steps taken in classifying specimens G, H and I

• Add some quantity of water to each of specimens G, H and I.
• Stir thoroughly.
• Test each of the specimens with litmus papers
• Specimen G- no change in colour of litmus paper neutral
• Specimen H- blue litmus paper turned red- acidic
• Specimen I-red litmus paper turned blue - alkaline/ basic

(c)(i) Condition indicated by pH value of 4.5; Soil acidity

(ii) Effects of soil acidity on crop production

• Could damage the roots of plants
• Hinders the absorption of mineral ions
• Lowers the rate of decomposition of organic matter due to its adverse effects on soil micro-organisms
• Humus could easily be leached out of the soil.
• Causes nutrient deficiency especially calcium - and phosphorus
• Causes certain nutrients to be present in the soil in toxic levels, e.g. manganese and iron
• Depresses nitrification because of its adverse effect on soil microbes/ low pH reduces the activities of soil micro-organisms
• Reduces microbial population
• Low pH reduces the formation of pods in legumes.
• It causes reduced growth and yield of crops.

(iii) Factors that could cause soil acidity

• Absorption of basic cations / Nutrient uptake by plants
• Use of nitrogen/ sulphur-based fertilizers
• Leaching
• Erosion
• Acidic parent material
• Acid rains in industrial areas
• Presence of sulphur in the soil leads to the formation of weak acid.

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