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2. (a) (i) Outline in reasonable detail why care should be taken in removing soil samples from a field before testing the soil fertility levels - Leaving Cert Agricultural Science - Question 2 - 2009
Question 2
2. (a) (i) Outline in reasonable detail why care should be taken in removing soil samples from a field before testing the soil fertility levels. (ii) What is meant ... show full transcript
Worked Solution & Example Answer:2. (a) (i) Outline in reasonable detail why care should be taken in removing soil samples from a field before testing the soil fertility levels - Leaving Cert Agricultural Science - Question 2 - 2009
Step 1
(i) Outline in reasonable detail why care should be taken in removing soil samples from a field before testing the soil fertility levels.
Answer
When removing soil samples from a field, it is essential to take precautions to ensure that the samples accurately reflect the soil's fertility. This involves avoiding contamination from external sources, as well as selecting sampling locations that are representative of the entire field. Sampling in different zones can yield varying nutrient levels, so care must be taken to collect samples uniformly. Additionally, factors such as wet spots, drain areas, or headlands should be avoided, as they may misrepresent the soil's overall condition.
Step 2
(ii) What is meant by the term lime requirement?
Answer
The term lime requirement refers to the amount of lime needed to be added to soil to adjust its pH to an optimal level for crop growth. This adjustment is crucial because soil pH affects nutrient availability and microbial activity. Lime is often applied to raise the pH, particularly in acidic soils, to enhance plant growth and soil health.
Step 3
(iii) List the elements found in ground limestone.
Answer
Ground limestone primarily consists of two elements: calcium and carbon. The chemical formula is typically represented as CaCO₃, which indicates the presence of calcium (Ca) and carbonate (CO₃). Limestone may also contain trace elements that contribute to soil fertility.
Step 4
(i) Explain cation exchange.
Answer
Cation exchange is a soil process where positively charged ions (cations) in soil solution are swapped with those held on the surface of soil particles. This process is essential because it regulates nutrient availability to plants. Soil particles attract cations, allowing them to replace other cations, thus facilitating the uptake of essential nutrients like potassium, calcium, and magnesium by plant roots.
Step 5
(ii) Explain the term cation exchange capacity (CEC).
Answer
Cation exchange capacity (CEC) is a measure of a soil's ability to hold and exchange cations. It is expressed in milliequivalents per 100 grams of soil. A higher CEC indicates a greater potential for nutrients to be retained and exchanged, which is vital for healthy plant growth. Soils with low CEC usually have limited nutrient-holding capacity, affecting their fertility.
Step 6
Step 7
(iv) Describe a method by which CEC may be increased in a soil.
Answer
One effective method to increase cation exchange capacity (CEC) is by adding organic matter to the soil, such as compost or well-rotted manure. This organic material improves soil structure and provides additional sites for cation retention. Additionally, using green manures or cover crops can enhance soil fertility by adding organic content, ultimately increasing CEC.
Step 8
Describe a laboratory experiment to test a soil for the presence of phosphates.
Answer
To test for the presence of phosphates in a soil sample, first, collect the soil using a suitable vessel and ensure the sample is free of debris. Next, add distilled water to the soil in a test tube and shake it to mix the components. Then, filter the mixture to obtain a clear solution. After this, add ammonium molybdate to the clear solution; a positive result will yield a yellow precipitate, indicating the presence of phosphates. If the solution turns blue after adding the reagent, it suggests the presence of soil test kits that confirm phosphate levels.