Photo AI
Summer 2018 saw drought conditions across many parts of Ireland, which greatly affected both crop and grass growth - Leaving Cert Agricultural Science - Question 2 - 2019
Question 2
Summer 2018 saw drought conditions across many parts of Ireland, which greatly affected both crop and grass growth. (i) Explain the following terms: 1. Moisture str... show full transcript
Worked Solution & Example Answer:Summer 2018 saw drought conditions across many parts of Ireland, which greatly affected both crop and grass growth - Leaving Cert Agricultural Science - Question 2 - 2019
Step 1
Explain the following terms: 1. Moisture stress
Answer
Moisture stress refers to a condition in plants where the water available in the soil is insufficient for normal biological functions. When moisture levels are lower than normal, plants may experience wilting, reduced growth, and increased susceptibility to diseases. This stress occurs when water is held tightly by soil particles, making it unavailable for uptake, or when water loss through transpiration exceeds the water replenishment rate.
Step 2
2. Permanent wilting point.
Answer
The permanent wilting point is the minimum soil moisture level at which plants can no longer extract water and begin to wilt irreversibly. At this point, the water is held too tightly within the soil matrix for plant roots to extract, leading to cell turgor loss and eventual plant death if conditions do not improve.
Step 3
ii) Available water capacity is an important term in the context of soils. 1. What is meant by the term available water capacity?
Answer
Available water capacity is the range of moisture that can be readily absorbed by plant roots from the soil. It is defined as the difference between field capacity, the amount of water held after excess water has drained, and the permanent wilting point, the moisture level where plants can no longer extract water.
Step 4
2. Which soil type has the highest available water capacity? Give two reasons for your answer.
Answer
The soil type that generally has the highest available water capacity is clay soil.
-
Clay particles have a small size and a large surface area, allowing them to hold more water compared to larger soil particles found in sandy soils.
-
Clay soil can retain water due to its ability to form aggregates, which create tiny pore spaces that store moisture effectively, enabling higher water retention even under drought conditions.
Step 5
b) Agricultural land usually becomes more acidic over time. (i) List any four causes of increasing soil acidity over time.
Answer
- Rainfall and acid rain producing aluminum ions in the soil.
- Crop production and nutrient removal without adequate replenishment.
- Use of certain fertilizers that acidify the soil (e.g., ammonium-based fertilizers).
- Decomposition of organic matter which leads to the release of organic acids.
Step 6
ii) Explain in detail how any one of the above causes increases soil acidity.
Answer
Using ammonium-based fertilizers contributes to increasing soil acidity because when these fertilizers are applied, the ammonium ions undergo nitrification. During this process, ammonium (NH4+) is converted to nitrate (NO3-) by soil bacteria, which leads to the release of hydrogen ions (H+) into the soil. The accumulation of these hydrogen ions lowers the pH of the soil, making it more acidic. This change affects nutrient availability and can harm plant growth.
Step 7
c) Describe an experiment to show flocculation in a soil sample.
Answer
To demonstrate flocculation, take equal volumes of soil in suitable containers and add deionised water to one, while adding a named flocculating agent (such as clay or alum) to another. Stir both samples for an equal amount of time and allow them to stand undisturbed. Observe the differences in flocculation where the sample with the flocculating agent should show clumps of soil particles aggregating, indicating effective flocculation.