(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), H (ACIDIC SOIL) and I (ALKALINE / BASIC SOIL)
(c)(i) If the pH value of one of the soil samples provided is 4.5, what condition does this pH value indicate in the soil sample?
(ii) State three effects of the condition indicated in (c)(i) on crop production.
(iii) List Three factors that could cause the condition indicated in (c)(i).
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.