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Worksheets26/12 AE Soil Moisture and Irrigation Quiz
Total questions: 10
Worksheet time: 5mins
A soil sample at saturation is analyzed. Which statement accurately describes the suction components present?
Both matric and osmotic suction are definitively zero.
Matric suction is zero, but osmotic suction may be non-zero depending on salinity.
Osmotic suction is zero, but matric suction is at its maximum value.
Both matric and osmotic suction are at their maximum values.
A tensiometer installed in a field stops providing readings when soil moisture tension approaches 0.82 atm. What is the primary physical phenomenon causing this limitation?
The water in the instrument reaches its permanent wilting point.
The ceramic cup of the tensiometer dissolves under high suction.
Cavitation occurs, breaking the continuous water column inside the instrument.
The soil's osmotic pressure exceeds the instrument's measurement capacity.
Which of the below statements is/are correct?:
Statement 1: FC represents a fixed, intrinsic moisture constant for a given soil texture.
Statement 2: At FC, soil moisture tension is higher in clayey soil compared to sandy soil.
Statement 3: FC marks the upper limit of readily available moisture for plants.
1 and 3 only
2 only
2 and 3 only
1, 2, and 3
When comparing a clay soil and a sandy loam soil at their respective Field Capacities, which statement accurately reflects their water retention characteristics?
The clay soil retains a greater volume of water, but this water is less accessible to plants due to its smaller pore size.
The sandy loam soil has a lower Field Capacity but retains moisture more effectively during dry periods.
The clay soil exhibits a higher Field Capacity and retains water more tightly, making it less available to plants.
The sandy loam soil allows for quicker drainage, resulting in less water retention compared to clay soil at Field Capacity.
An irrigation schedule is being designed for a crop. The total available moisture (AM) in the root zone is calculated to be 12 cm. For optimal plant growth without inducing stress, irrigation should be initiated when the moisture depletion reaches what approximate depth?
12 cm
3 cm
9 cm
6 cm
An increase in the pF value from 4.0 to 5.0 represents a far greater increase in soil moisture tension than an increase from 2.0 to 3.0. Why is this?
The pF scale is directly proportional to the moisture content percentage.
The pF scale is an arithmetic scale measuring the linear decrease in available water.
The pF scale is logarithmic, meaning each unit increase represents a tenfold increase in suction head.
The pF scale is only accurate in the lower suction ranges typical of field capacity.
A plant is growing in a soil with high moisture content, near Field Capacity. However, it shows signs of wilting and stress. What is the most likely cause from a soil-water perspective?
The soil is saturated, leading to a lack of oxygen for the roots.
The soil has a very high matric suction despite the high moisture content.
The soil's hygroscopic water content is excessively high.
The soil has a high osmotic suction due to high salt concentration.
Which of the following statements are correct, regarding the rsoil moisture constants relationship?
Statement 1: The best condition for most crops is Saturation Capacity, as it ensures maximum water is present.
Statement 2: Permanent Wilting Point (PWP) occurs at a soil moisture tension of approximately 15 atm.
Statement 3: Available Moisture (AM) is the theoretical quantity of water held between Field Capacity (FC) and the Hygroscopic Coefficient.
2 only
1 and 2 only
2 and 3 only
1, 2 and 3
A soil sample has a Moisture Equivalent (ME) of 28%. Based on established empirical relationships, what is the approximate Permanent Wilting Point (PWP) for this soil?
7%
14%
28%
56%
A clay soil has a Field Capacity (FC) moisture content of 40% and a PWP of 22%. A nearby sandy soil has an FC of 18% and a PWP of 8%. If both soils are at their respective PWP, and 10 cm of irrigation water is applied to a 50 cm deep root zone for both, which soil will retain more of this water as Available Moisture? Assume no losses and a soil dry density of 1.4 g/cm³.
The clay soil, because its total Available Moisture capacity is higher.
The sandy soil, because its initial moisture deficit is lower.
Both will retain the same amount as Available Moisture.
The clay soil, because its initial moisture deficit to reach FC is larger.
