Soil-Water-Plant Relationships
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What are the primary physical processes responsible for the movement of water within the hydrologic cycle?

  • Evaporation, Transpiration, Condensation, Precipitation
  • Evaporation, Condensation, Precipitation, Infiltration, Runoff, Subsurface Flow (correct)
  • Infiltration, Runoff, Subsurface Flow, Precipitation, Transpiration
  • Evaporation, Condensation, Precipitation, Infiltration, Runoff

The majority of annual global precipitation falls over landmasses.

False (B)

What is the primary driving force behind the movement of groundwater?

Gravity

The ______ is the boundary separating the zone of aeration and the zone of saturation.

<p>water table</p> Signup and view all the answers

Match the following terms with their corresponding definitions:

<p>Precipitation = The movement of water from the ground surface into the ground Infiltration = Condensed water vapor that falls to Earth's surface Percolation = The movement of water through soil layers by gravity and capillary forces Runoff = Water flowing over land surfaces towards rivers or streams</p> Signup and view all the answers

Which of the following factors directly influences the rate of infiltration?

<p>Soil moisture content (B)</p> Signup and view all the answers

Rainfall intensity is measured in millimeters per hour (mm/hr).

<p>True (A)</p> Signup and view all the answers

What is the name of the instrument used to measure infiltration rate?

<p>Infiltrometer</p> Signup and view all the answers

Run-off is the movement of water, frequently from ______, across the earth's surface.

<p>precipitation</p> Signup and view all the answers

Which of the following factors affect the run-off rate?

<p>All of the above (D)</p> Signup and view all the answers

The peak run-off rate is inversely proportional to the catchment area.

<p>False (B)</p> Signup and view all the answers

What is the formula for calculating the peak run-off rate, Qp?

<p>Qp (m^3/s) = [C I A] / 360</p> Signup and view all the answers

Match the following stream flow measurement methods with their descriptions:

<p>Continuity equation = Measuring the average velocity of flow and the cross-sectional area of the channel Float method = Estimating velocity by measuring the time taken for a floating object to travel a measured distance Use of weirs = Utilizing structures to create a predictable relationship between water level and flow rate Current meter = Directly measuring the velocity of water at different depths and positions in the stream</p> Signup and view all the answers

Which of these units is NOT used to express the Evapotranspiration rate?

<p>Liters per minute (B)</p> Signup and view all the answers

Evapotranspiration is the combination of evaporation and transpiration.

<p>True (A)</p> Signup and view all the answers

What is the metric unit for stream flow measured in m^3/s?

<p>Cumec</p> Signup and view all the answers

Which type of water is primarily used by plants for growth?

<p>Capillary water (D)</p> Signup and view all the answers

The permanent wilting point (θwp) is when the soil is completely dry and no water is available to plants.

<p>False (B)</p> Signup and view all the answers

What is the difference between field capacity and permanent wilting point?

<p>Field capacity is the state where the soil holds the maximum amount of water after gravitational water has drained, while the permanent wilting point is the point where the remaining water is too tightly held for plants to access.</p> Signup and view all the answers

The volume of water in the soil reservoir that can be used by plants is known as ______.

<p>total available water (TAW)</p> Signup and view all the answers

What is one consideration when applying methods for measuring soil moisture?

<p>Degree of dependence on laboratory availability (B)</p> Signup and view all the answers

Neutron probes require extensive calibration for each site.

<p>True (A)</p> Signup and view all the answers

Name one direct method of measuring soil moisture.

<p>Neutron Probe</p> Signup and view all the answers

The __________ method of measuring soil moisture involves assessing soil water potential.

<p>tensiometer</p> Signup and view all the answers

Match the following instruments with their primary function:

<p>Neutron Probe = Measuring soil moisture content Tensiometer = Measuring soil water potential Moisture Sensor = Continuous soil moisture monitoring Gypsum Block = Estimating soil moisture based on electrical resistance</p> Signup and view all the answers

What factor can impact the reliability of soil moisture measurement results?

<p>The complexity of the operation (D)</p> Signup and view all the answers

Bulk density is measured in grams per cubic centimeter (g/cm³).

<p>True (A)</p> Signup and view all the answers

What is the significance of comparing preliminary costs with subsequent costs in soil moisture measurement methods?

<p>To evaluate economic feasibility</p> Signup and view all the answers

What is the dry bulk density represented by?

<p>$M_s / V_t$ (A)</p> Signup and view all the answers

The major components of soil include air, water, and only organic matter.

<p>False (B)</p> Signup and view all the answers

What happens to water in the soil during heavy rainfall?

<p>The soil becomes saturated, and gravity pulls some of the water down through the soil.</p> Signup and view all the answers

The ratio of air to water stored in the soil pores is affected by _____.

<p>water addition or loss</p> Signup and view all the answers

Match the terms related to soil-water-plant relationships with their definitions:

<p>Saturated = All pores filled with water Transpiration = Loss of water from plant tissue Percolation = Seepage into lower soil layers Evaporation = Direct loss of water from soil to atmosphere</p> Signup and view all the answers

Which of the following factors can alter pore volume in soil?

<p>Tillage (D)</p> Signup and view all the answers

Water is lost from the soil only through evaporation and transpiration.

<p>False (B)</p> Signup and view all the answers

What are the three major parts of soil?

<p>Air, water, and solids.</p> Signup and view all the answers

What is the effective root depth primarily determined by?

<p>Crop and soil properties (A)</p> Signup and view all the answers

Evapotranspiration (ET) can only be determined by measuring rainfall and irrigation.

<p>False (B)</p> Signup and view all the answers

What does TAW stand for in the context of soil water?

<p>Total Available Water</p> Signup and view all the answers

In the formula ET = I + P - RO - DP + CR ± ΔSF ± ΔSW, the letter ET stands for __________.

<p>Evapotranspiration</p> Signup and view all the answers

Match the following terms related to soil water measurement with their descriptions:

<p>Water Content = Actual amount of water in the soil Water Potential = Tendency of water to move through soil Direct Methods = Involves taking soil samples for lab analysis Indirect Methods = Use instruments to infer soil moisture</p> Signup and view all the answers

If the soil moisture depletion (SMD) is 85 mm and the depth of rooting is 0.50 m, what is the approximate volumetric moisture content (Θ) at sampling?

<p>0.35 (C)</p> Signup and view all the answers

Capillary rise (CR) can transport water upward from a shallow water table towards the root zone.

<p>True (A)</p> Signup and view all the answers

What does the ratio MAD/TAW indicate in soil moisture management?

<p>It indicates the ratio of moisture deficit to total available water.</p> Signup and view all the answers

Flashcards

Hydrologic Cycle

The continuous movement of water on, above, and below Earth's surface.

Precipitation

Condensed water vapor that falls to the Earth's surface, often as rain.

Rainfall Intensity

The quantity of rain falling for a given time, measured in mm/hr.

Infiltration

The flow of water from the surface into the ground, becoming soil moisture.

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Infiltrometer

A device used to measure the rate of infiltration in soil.

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Percolation

The movement of water through soil layers due to gravity and capillary forces.

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Vadose Water

Water in the zone of aeration where air exists, above the water table.

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Water Table

The boundary between the vadose zone and the zone of saturation.

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Run-off

The movement of water across the earth's surface towards channels, lakes, or oceans.

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Factors Affecting Run-off

Includes rainfall intensity, catchment size, slope, soil type, and ground cover.

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Peak Run-off Rate (Qp)

The maximum rate at which water flows from a catchment area, calculated as Qp = C I A / 360.

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Continuity Equation

A method to calculate stream flow using average velocity and cross-sectional area: Q = A x V.

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Float Method

Estimating velocity by measuring how long a float takes to travel a distance.

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Evapotranspiration (ET)

The combined loss of water from soil by evaporation and from plants by transpiration.

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Evapotranspiration Rate

Amount of water lost from a surface, expressed in mm per time unit.

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Measurement Units for ET

Evapotranspiration can be measured in mm per hour, day, or year.

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Hydrologic Cycle Impact

Ways humans affect the natural hydrologic cycle.

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Soil Composition

Soil consists of air, water, and solids (minerals and organic matter).

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Pore Volume

The space in soil occupied by air and water, changing with moisture levels.

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Dry Bulk Density (γb)

Mass of solids divided by total volume of soil, indicating compactness.

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Mass Wetness (W)

The ratio of water mass to the mass of soil solids in a sample.

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Volume Wetness (θ)

Water volume compared to total soil volume, indicating saturation.

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Soil Saturation

Condition when all pore spaces in soil are filled with water.

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Water Loss Mechanisms

Processes of losing water from soil: evaporation, transpiration, drainage.

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Gravitational Water

Water that moves from the root zone due to gravity.

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Field Capacity

The maximum water soil can hold after drainage.

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Capillary Water

Water held in soil pores after gravitational water drains.

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Permanent Wilting Point

Water level where plants can no longer extract water.

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Total Available Water (TAW)

The volume of water in soil usable by plants.

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Management Allowed Deficit (MAD)

Water volume depletion allowed before irrigation.

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Soil Moisture Deficit (SMD)

The depletion of soil moisture below field capacity.

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Effective Root Depth (RD)

The soil depth accessible to plant roots for water.

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Effective Root Depth

The depth of soil from which a crop extracts most of its water.

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Soil Water Balance

A method assessing water flow into and out of the crop root zone.

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Soil Moisture Depletion (SMD)

The reduction of soil moisture in the root zone after usage by plants.

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Capillary Rise (CR)

The upward movement of water from the water table to the root zone by capillary action.

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Direct Method of Soil Moisture Measurement

Requires large samples from the field to determine moisture content chemically.

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Indirect Method of Soil Moisture Measurement

Uses instruments to gauge soil properties related to moisture without taking samples.

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Operational Applicability

The relevance of a method based on its practical use and requirements.

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Method Complexity

The degree of difficulty involved in performing a method of measurement.

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Laboratory Dependence

Reliance on laboratory facilities to conduct measurements or experiments.

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Direct Methods

Measuring soil moisture by directly observing and obtaining data from the field.

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Indirect Methods

Approaches to estimate soil moisture without direct observation, often using calculations or models.

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Neutron Probe

A tool used to measure soil moisture content based on neutron scattering principles.

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Tensiometers

Instruments that measure soil water potential by assessing tension in soil moisture.

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Soil Water Potential

A measure of the energy status of soil water, indicating how tightly water is held in soil.

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Study Notes

Soil-Water-Plant Relationships

  • Soil composition involves three main components: air, water, and solids.
  • The solid component forms the soil framework, comprising minerals and organic matter.
  • Mineral components include sand, silt, and clay particles.
  • The pore volume reflects the proportion of soil occupied by water and air.

Schematic Diagram of Soil

  • A diagram illustrates the soil as a three-phase system, showing the components (air, water, solid) and their respective volumes (Va, Vw, Vt).

  • Variables like Ma (mass of air), Ms (mass of solid), and Mw (mass of water) are also presented.

  • Vt represents total volume.

  • Y is calculated as Ms/Vt (dry bulk density)

  • W (mass wetness) is represented as Mw/Ms

  • Θ (volume wetness) is Vw/Vt or W*Yb

Pore Volume

  • Pore volume is generally constant for a given soil layer.
  • Air and water proportions in pores change with added or lost water.
  • Water loss occurs due to factors like run-off, evaporation, transpiration, percolation (seepage), or drainage.

Soil Moisture States

  • Soil pores act as reservoirs for water.
  • Not all water in the reservoir is directly available to plants.

Effective Root Depth (RD)

  • Effective root depth (RD) represents the depth to which plants can access water.
  • Crop roots extract water unequally from the root zone, so effective root depth is crucial in determining water availability.

Soil Water Balance

  • Evapotranspiration (ET) is calculated using components of the soil water balance: incoming water (rainfall, irrigation), outgoing water (runoff, deep percolation, surface runoff), and changes in soil water content(ASW/SWC).
  • This approach assesses water fluxes within the root zone over time.
  • Soil water balance assists in determining ET.

Worked Problems

  • Examples show calculations related to total available water (TAW) and soil moisture deficit (SMD).
  • These problems demonstrate practical interpretations and applications of soil and water balance calculations.

Measurement of Soil Moisture

  • Methods for measuring soil moisture status are categorized into three types: determining water content, water potential, and instrument-based measurements.
  • These are further broken down into direct and indirect methods.

Gravimetric Method

  • A direct method for determining mass wetness.
  • Involves weighing soil samples in both wet and dry states.
  • The difference represents the "weight loss in drying."
  • Dry weight is obtained by drying at 105°C for 24 hours.

Dielectric Constant (TDR & FDR)

  • Probes measure the dielectric properties of soil, which are affected by soil moisture content.
  • TDR (Time Domain Reflectometry) and FDR (Frequency Domain Reflectometry) are crucial instruments used to measure soil moisture content.

Tensiometers

  • Used to measure soil moisture tension.
  • Hollow tubes filled with water, a porous cup, and a vacuum gauge.
  • Tensiometers measure soil moisture tension, providing an index of how tightly water is held in the soil.

Neutron Probe

  • A method for measuring total soil water content.
  • Measures neutron slowdown rates, which are linked to hydrogen content in water within soil pores.

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AGE 3116: Irrigation & Drainage Lecture Notes PDF

Description

This quiz focuses on the fundamental concepts of soil composition, including the roles of air, water, and solids. It also explores the three-phase system of soil, along with key variables that describe soil properties such as dry bulk density and wetness. Test your understanding of these essential concepts in soil science.

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