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2. (a) Cementation and separation are two processes that affect the development of a soil structure - Leaving Cert Agricultural Science - Question 2 - 2020
Question 2
2. (a) Cementation and separation are two processes that affect the development of a soil structure. (i) What is meant by each of the terms cementation and separat... show full transcript
Worked Solution & Example Answer:2. (a) Cementation and separation are two processes that affect the development of a soil structure - Leaving Cert Agricultural Science - Question 2 - 2020
Step 1
What is meant by each of the terms cementation and separation?
Answer
Cementation refers to the process where soil particles are bonded together by minerals that precipitate from water, resulting in a more solid structure. Separation, on the other hand, describes the breakup of aggregated or large soil particles into smaller particles, which can occur due to various factors like erosion or mechanical disturbance.
Step 2
Outline any two factors that contribute to cementation.
Answer
- Biological activity: The presence of soil microbes can lead to the formation of organic binders that promote the adhesion of soil particles.
- Mineral precipitation: The dissolution and subsequent precipitation of minerals from water can fill voids between soil particles, thereby binding them together.
Step 3
Outline any two factors that contribute to separation.
Answer
- Freeze-thaw action: This cyclical process causes expansion and contraction of soil, leading to the breaking apart of aggregated particles.
- Root activity: The growth of plant roots can exert pressure on soil aggregates, causing them to separate as the roots expand.
Step 4
What is meant by the term cation exchange capacity?
Answer
Cation exchange capacity (CEC) is a measure of the ability of a soil to hold onto and exchange positively charged ions (cations) like calcium, magnesium, and potassium. This property reflects the soil's fertility and its capacity to retain essential nutrients.
Step 5
Give two reasons why CEC is lower in sandy soils than in clay soils.
Answer
- Sandy soils consist of larger particles, which provide less surface area for cation adhesion compared to the finer particles in clay.
- Sandy soils are often less chemically reactive; they have fewer negative charges, meaning they hold fewer cations compared to clay soils which have higher retention capacity.
Step 6
Describe a method by which cation exchange capacity may be increased in a soil.
Answer
To increase cation exchange capacity, one can add organic matter, such as farmyard manure or compost, to the soil. This organic material not only provides nutrients but also enhances the soil's structure and increases the overall negative charge, thus allowing it to hold more cations.
Step 7
Describe an experiment to test for the presence of a named soil mineral.
Answer
To test for the presence of calcite as the named soil mineral, one can take a soil sample and add a few drops of dilute hydrochloric acid. If calcite is present, noticeable fizzing or effervescence will occur due to the release of carbon dioxide gas as the acid reacts with the mineral.