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RBSE SS Voc Micro-Irrigation Tec study materials
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RBSE SS Voc Micro-Irrigation Tec practice questions

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Question 1Fundamentals of Irrigation and Soil-Water-Plant Relationships

In irrigation scheduling, soil moisture tension is best described as which of the following?

  1. The total volume of water held in the soil profile after drainage has stopped
  2. The negative pressure (suction) that plant roots must overcome to extract water from soil pores Correct answer.
  3. The mass of dry soil per unit volume including pore space
  4. The rate at which water moves downward through the vadose zone under gravity

Explanation

Soil moisture tension is the suction or negative pressure holding water in soil pores; as soil dries, tension rises and roots must exert more effort to extract water. It is expressed in units such as kPa or bars and is the basis for tensiometer-based scheduling. It is distinct from water content, flux, or bulk density.

Question 2Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which soil texture class typically holds the greatest volume of plant-available water per unit depth of soil?

  1. Coarse sand
  2. Gravelly loam
  3. Silt loam Correct answer.
  4. Coarse sandy loam

Explanation

Available water capacity is greatest in medium-textured soils such as silt loam because they combine substantial porosity with strong capillarity. Sands drain too freely to store much available water, and gravels store very little. This is why texture guides irrigation interval and emitter spacing decisions.

Question 3Fundamentals of Irrigation and Soil-Water-Plant Relationships

Field capacity is conventionally defined as the water content of a soil after which condition has occurred?

  1. After oven drying at 105 degrees Celsius to constant mass
  2. After gravity drainage has largely ceased, typically about two to three days after saturation Correct answer.
  3. After plants have permanently wilted and cannot recover
  4. After the soil has been saturated and standing water remains on the surface

Explanation

Field capacity is the water retained after excess gravitational water has drained from a saturated soil, usually reached within two to three days in many soils. It represents the upper limit of readily available water used in irrigation scheduling. Oven-dry and permanent wilting point describe much drier states.

Question 4Fundamentals of Irrigation and Soil-Water-Plant Relationships

A tensiometer installed at 30 cm depth reads 55 kPa two days after irrigation. What does this reading most directly indicate?

  1. The tensiometer is reading the osmotic potential of the soil solution
  2. The soil at that depth has reached permanent wilting point and the crop is dead
  3. The soil at that depth is close to saturation and drainage is still occurring
  4. The soil at that depth has dried and matric suction has increased, suggesting water may soon be needed Correct answer.

Explanation

A tensiometer measures matric suction, so a rising reading from a low post-irrigation value shows the soil is drying and suction is increasing. Growers compare such readings to a crop-specific threshold to decide when to irrigate. Tensiometers do not measure osmotic potential, and 55 kPa is not saturation.

Question 5Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which statement correctly distinguishes adhesion from cohesion in soil-water relations?

  1. Adhesion is attraction between water molecules; cohesion is attraction of water to soil particles
  2. Adhesion moves water upward in the xylem; cohesion moves water downward by gravity
  3. Adhesion is attraction of water to soil particle surfaces; cohesion is attraction between water molecules Correct answer.
  4. Adhesion applies only to saturated soil; cohesion applies only to dry soil

Explanation

Adhesion is the attraction of water molecules to solid surfaces such as soil particles and pore walls, while cohesion is the attraction of water molecules to one another. Together they generate capillarity, which holds water in small pores and drives matric suction. Reversing the two terms is a common error.

Question 6Fundamentals of Irrigation and Soil-Water-Plant Relationships

A soil has a volumetric water content of 0.22 in the top 60 cm. What depth of water is stored in that layer?

  1. 220 mm
  2. 36 mm
  3. 132 mm Correct answer.
  4. 13.2 mm

Explanation

Stored water depth equals volumetric water content multiplied by soil layer thickness: 0.22 times 600 mm equals 132 mm. This conversion lets managers compare soil storage against crop water use in millimetres per day. Failing to convert centimetres to millimetres is the usual source of error.

Question 7Fundamentals of Irrigation and Soil-Water-Plant Relationships

Reference evapotranspiration (ET0) represents which of the following?

  1. Total irrigation water delivered to a field including losses
  2. Evapotranspiration from a standardized reference surface such as a well-watered grass or alfalfa crop Correct answer.
  3. Water lost only through evaporation from bare soil
  4. Water use of the actual crop under field conditions including stress

Explanation

ET0 is the evapotranspiration rate of a defined reference surface, commonly a well-watered grass or alfalfa crop with specified height and canopy resistance. Actual crop ET is obtained by multiplying ET0 by a crop coefficient. ET0 is therefore an atmospheric demand index, not a field delivery figure.

Question 8Fundamentals of Irrigation and Soil-Water-Plant Relationships

If ET0 is 6 mm per day and the crop coefficient at mid-season is 1.15, what is the estimated crop evapotranspiration?

  1. 5.2 mm per day
  2. 1.15 mm per day
  3. 6.9 mm per day Correct answer.
  4. 7.15 mm per day

Explanation

Crop ET is calculated as ET0 multiplied by the crop coefficient, so 6 mm times 1.15 equals 6.9 mm per day. This value estimates the depth of water the crop removes daily and sets the irrigation replacement target. Adding or dividing the values instead of multiplying gives incorrect results.

Question 9Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which practice best reduces non-beneficial soil evaporation while keeping transpiration supplied in a micro-irrigation system?

  1. Applying water frequently at low volume through emitters that wet only part of the root zone Correct answer.
  2. Wetting the entire soil surface with high-volume sprinklers at midday
  3. Increasing emitter discharge so that water ponds on the surface
  4. Flooding the field between crop rows to raise the water table

Explanation

Micro-irrigation wets only a portion of the soil surface, so a smaller evaporating area is exposed to the atmosphere, and frequent low-volume applications keep the wetted bulb supplied. This raises the proportion of applied water used in transpiration. Surface ponding and whole-field wetting increase evaporation and losses.

Question 10Fundamentals of Irrigation and Soil-Water-Plant Relationships

A soil probe shows the root zone at 40 percent of available water depletion. For a crop that tolerates 50 percent depletion before stress, what is the appropriate management conclusion?

  1. Irrigate immediately because the crop is already stressed
  2. No irrigation is yet required, but the next application should be scheduled before 50 percent depletion Correct answer.
  3. Permanently reduce the irrigation interval to daily regardless of ET
  4. The soil is at permanent wilting point and the crop cannot recover

Explanation

With a 50 percent allowable depletion threshold, the crop can still extract water without stress at 40 percent depletion. Irrigation should be planned so the next event occurs before the threshold is crossed, accounting for daily ET. Immediate irrigation is unnecessary, and the soil is far from wilting point.

Question 11Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which of the following best explains why clay soils generally have lower infiltration rates than sandy soils?

  1. Clay soils have higher total porosity but no capillary forces
  2. Clay soils contain more organic matter that repels water
  3. Clay soils have smaller pores and stronger adsorptive forces that resist water entry Correct answer.
  4. Clay particles are larger and pack more loosely than sand grains

Explanation

Infiltration is governed by pore size rather than total porosity; clay soils have fine pores and strong adhesion, so water enters slowly. Sandy soils have large pores and conduct water rapidly. This difference is why emitter discharge must match soil intake to avoid runoff.

Question 12Fundamentals of Irrigation and Soil-Water-Plant Relationships

In a drip-irrigated field, the wetted soil volume beneath an emitter is often called which of the following?

  1. The leaching fraction
  2. The capillary fringe
  3. The wetted bulb or wetted zone Correct answer.
  4. The saturation deficit

Explanation

Water from a point source such as a drip emitter moves outward and downward, forming a wetted bulb whose size depends on soil texture, emitter discharge, and application duration. Root distribution and emitter spacing are planned around this wetted zone. The other terms refer to salinity management, groundwater effects, or water balance concepts.

Question 13Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which condition most directly causes salt accumulation at the edge of a wetted bulb under drip irrigation?

  1. Water moving upward from a shallow water table
  2. Continuous saturation of the whole root zone
  3. Uniform leaching of the entire soil surface by rainfall
  4. Salts being carried outward by water and left behind as the wetting front advances and soil dries Correct answer.

Explanation

As water moves outward from an emitter, dissolved salts are carried with it and concentrate near the wetting front where the soil dries. This creates a saline ring at the edge of the wetted zone, which is why emitters and wetting patterns must be placed to keep salts away from germinating seed and active roots. Whole-profile leaching removes salts rather than concentrating them.

Question 14Fundamentals of Irrigation and Soil-Water-Plant Relationships

A grower wants to apply a 15 percent leaching fraction. If the crop ET is 34 mm over a period, what total applied depth is required?

  1. 5.1 mm
  2. 39.1 mm
  3. 34 mm
  4. 40 mm Correct answer.

Explanation

The applied depth equals crop ET divided by one minus the leaching fraction: 34 divided by 0.85 equals 40 mm. The extra 6 mm moves salts below the root zone. Adding 15 percent of ET to ET gives a slightly different and less precise figure, while treating the fraction as the added depth is a common mistake.

Question 15Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which soil water potential component is most affected by dissolved salts in the soil solution?

  1. Gravitational potential
  2. Osmotic potential Correct answer.
  3. Pressure potential
  4. Matric potential

Explanation

Osmotic potential arises from dissolved solutes and lowers the free energy of soil water, making it harder for roots to extract water. Matric potential comes from adsorption and capillarity, gravitational potential from elevation, and pressure potential from hydrostatic pressure. Salinity therefore acts mainly through the osmotic component.

Question 16Fundamentals of Irrigation and Soil-Water-Plant Relationships

Why does a plant temporarily wilt at midday even when soil water is adequate?

  1. The soil has reached permanent wilting point by mid-morning
  2. Transpiration demand exceeds the rate at which roots can supply water, causing a transient loss of turgor Correct answer.
  3. Stomata open wider at midday, increasing water uptake
  4. Roots stop absorbing water entirely once soil temperature exceeds 20 degrees Celsius

Explanation

At peak evaporative demand, transpiration can outpace root water uptake, so leaf water potential falls and turgor is temporarily lost. The plant usually recovers in the evening as demand drops. This transient wilting differs from permanent wilting caused by depleted soil water.

Question 17Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which pair correctly matches the lower and upper limits of plant-available water in soil?

  1. Lower limit saturation, upper limit permanent wilting point
  2. Lower limit field capacity, upper limit saturation
  3. Lower limit permanent wilting point, upper limit field capacity Correct answer.
  4. Lower limit hygroscopic water, upper limit permanent wilting point

Explanation

Plant-available water is held between the permanent wilting point, below which roots cannot extract water, and field capacity, above which water drains as gravitational flow. Water beyond field capacity is transient, and water below wilting point is unavailable. This range defines the irrigation management window.

Question 18Fundamentals of Irrigation and Soil-Water-Plant Relationships

A field has 120 mm of available water at field capacity and an allowable depletion of 45 percent. How much water can the crop use before irrigation is required?

  1. 54 mm Correct answer.
  2. 75 mm
  3. 120 mm
  4. 45 mm

Explanation

Manageable depletion equals available water multiplied by the allowable depletion fraction: 120 mm times 0.45 equals 54 mm. This is the net irrigation depth that should be replaced when the threshold is reached. Using the fraction as a depth or ignoring the fraction gives the other values.

Question 19Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which statement best explains why micro-irrigation can maintain crop yield at lower total applied water than furrow irrigation in many fields?

  1. Micro-irrigation reduces deep percolation and wetted-surface evaporation by applying water near the root zone in small, frequent doses Correct answer.
  2. Micro-irrigation eliminates all evaporation from the soil surface
  3. Micro-irrigation raises the permanent wilting point so plants extract more water
  4. Micro-irrigation changes the crop coefficient to a value below zero

Explanation

Because water is delivered near the root zone in small amounts, less is lost to deep percolation below the roots and less soil surface is wetted and exposed to evaporation. This raises application efficiency relative to surface methods. No system eliminates evaporation entirely, and the wilting point is a soil property that irrigation does not change.

Question 20Fundamentals of Irrigation and Soil-Water-Plant Relationships

A soil sample weighs 150 g wet and 125 g after oven drying. What is the gravimetric water content on a dry-mass basis?

  1. 20 percent Correct answer.
  2. 83.3 percent
  3. 16.7 percent
  4. 25 percent

Explanation

Gravimetric water content equals the mass of water divided by the oven-dry soil mass, multiplied by 100. Here 25 g of water divided by 125 g of dry soil gives 0.20, or 20 percent. Dividing by the wet mass instead of the dry mass produces a different and incorrect figure.

Question 21Micro-Irrigation Systems: Types, Components and Layout

In a drip irrigation system, what is the primary function of the filter (screen, sand, or disc) installed at the head?

  1. To remove suspended particles that would otherwise clog emitters Correct answer.
  2. To inject fertilizer into the water at a controlled rate
  3. To measure the volume of water delivered to each block
  4. To increase the pressure of water before it enters the mainline

Explanation

Micro-irrigation emitters have very small flow passages, so any sand, silt, or organic debris carried in the water can block them. The filter at the head removes these suspended particles before the water reaches the laterals. Fertilizer injection and flow measurement are handled by separate components such as the venturi/fertilizer tank and water meter.

Question 22Micro-Irrigation Systems: Types, Components and Layout

Which micro-irrigation method delivers water as a continuous fine spray or mist over the soil surface around the plant?

  1. Surface furrow irrigation
  2. Subsurface drip irrigation
  3. Micro-sprinkler irrigation Correct answer.
  4. Bubbler irrigation

Explanation

Micro-sprinklers throw water through the air as fine droplets or a small spray pattern, wetting a localized area around each plant. Subsurface drip discharges below the soil through buried emitters, and bubblers release a low-volume stream at a single point. Furrow irrigation is a surface method that is not classified as micro-irrigation.

Question 23Micro-Irrigation Systems: Types, Components and Layout

In a drip irrigation layout, what is the component that connects the sub-main to the lateral and usually contains the emitter or dripper?

  1. The sand separator
  2. The lateral line itself (with in-line or on-line emitters) Correct answer.
  3. The non-return valve at the source
  4. The pump unit

Explanation

The lateral line is the small-diameter pipe laid along the crop row, and it carries the emitters either built into the pipe (in-line) or attached to it (on-line). Emitters dissipate pressure and deliver the designed low flow at each plant. The pump, separator, and non-return valve belong to the head control unit.

Question 24Micro-Irrigation Systems: Types, Components and Layout

Why is a pressure regulator commonly installed downstream of the filter in a micro-irrigation head?

  1. To mix fertilizer evenly with the irrigation water
  2. To prevent soil particles from entering the lateral pipes
  3. To keep the operating pressure within the range the emitters were designed for Correct answer.
  4. To automatically flush the laterals at the end of each irrigation cycle

Explanation

Emitter discharge varies with pressure, so a pressure regulator holds the downstream pressure at a set value to keep emission uniform and prevent pipe or emitter damage. Flushing is done manually or with flush valves, and fertilizer mixing is the role of the injection unit. Keeping soil out is the job of filtration and proper installation.

Question 25Micro-Irrigation Systems: Types, Components and Layout

What distinguishes a bubbler irrigation system from a drip system?

  1. Bubblers operate only below the soil surface
  2. Bubblers apply water at a higher, localized flow rate at each plant rather than through many small emitters Correct answer.
  3. Bubblers require no filtration at all
  4. Bubblers distribute water only through overhead sprinklers

Explanation

Bubblers deliver a relatively higher flow at a single point, forming a wetted basin around the plant, whereas drip systems use many low-flow emitters along a lateral. Both are micro-irrigation methods and both need filtration. Bubblers can be at or above the surface and do not use overhead sprinklers.

Question 26Micro-Irrigation Systems: Types, Components and Layout

What is the main purpose of a flush valve at the far end of a drip lateral?

  1. To allow accumulated sediment and debris to be discharged from the line Correct answer.
  2. To increase the emitter flow rate during irrigation
  3. To inject air into the lateral to clear it
  4. To measure the pressure at the end of the line

Explanation

Even with good filtration, fine particles and precipitates can settle in laterals, so end-of-line flush valves are opened periodically to purge them. Flushing protects emitters from gradual clogging and extends system life. Flush valves do not boost emitter flow, inject air, or measure pressure.

Question 27Micro-Irrigation Systems: Types, Components and Layout

Which water source characteristic most directly increases the risk of emitter clogging in a drip system?

  1. Cool water temperature at the intake
  2. High suspended sediment and dissolved iron content Correct answer.
  3. Slightly acidic pH with low hardness
  4. Low total dissolved solids

Explanation

Suspended sediment physically blocks emitters, and dissolved iron can oxidize and precipitate as a sticky deposit inside laterals and emitters. Together these are major clogging hazards requiring filtration and, for iron, treatment. Low dissolved solids and cool temperature are not clogging risks, and slight acidity with low hardness does not promote scaling.

Question 28Micro-Irrigation Systems: Types, Components and Layout

In a micro-irrigation system, what does the term 'emission uniformity' describe?

  1. How much fertilizer is mixed into the water
  2. How evenly emitters along the system discharge water Correct answer.
  3. How often the filter must be backwashed
  4. How quickly water infiltrates the soil after application

Explanation

Emission uniformity expresses how similar the discharges of individual emitters are across a block, which depends on pressure variation, manufacturing variation, and clogging. Poor uniformity causes over- and under-irrigated zones and uneven crop growth. Infiltration rate, backwash frequency, and fertigation dose are separate concepts.

Question 29Micro-Irrigation Systems: Types, Components and Layout

A grower lays drip laterals on the soil surface along vegetable rows. Which term best describes this layout?

  1. Bubbler irrigation
  2. Surface drip irrigation Correct answer.
  3. Micro-sprinkler irrigation
  4. Subsurface drip irrigation

Explanation

When laterals and emitters rest on or just above the soil surface, the method is surface drip irrigation. Subsurface drip places the tubing below the root zone surface. Micro-sprinklers and bubblers are different emission devices, not lateral placement methods.

Question 30Micro-Irrigation Systems: Types, Components and Layout

Why are drip laterals often laid in paired rows with the lateral between them in some row-crop layouts?

  1. It prevents the emitters from ever clogging
  2. It eliminates the need for a pump
  3. One lateral can wet the root zones of two adjacent rows, reducing pipe cost per hectare Correct answer.
  4. It raises the operating pressure of the system

Explanation

Placing a single lateral between two crop rows lets the wetted bulbs overlap both root zones, cutting the length of pipe and number of emitters needed. This lowers capital cost while still meeting crop water needs. It does not prevent clogging, remove the need for a pump, or increase pressure.

Question 31Micro-Irrigation Systems: Types, Components and Layout

A drip system shows emitters near the head discharging more water than those at the far end of long laterals. What is the most likely cause?

  1. The flush valves are closed during irrigation
  2. The emitters are all oversized for the design flow
  3. Excessive friction head loss along the lateral causing pressure to drop toward the end Correct answer.
  4. The filter is removing too many particles

Explanation

As water travels along a lateral, friction causes the pressure to decrease from the inlet toward the far end, so emitters near the head discharge more. This is why lateral length and diameter are limited in design and why pressure-compensating emitters are sometimes used. Filtration, closed flush valves, and emitter size do not explain the head-to-tail gradient.

Question 32Micro-Irrigation Systems: Types, Components and Layout

What is the primary advantage of pressure-compensating emitters in a micro-irrigation layout?

  1. They eliminate friction losses in the lateral
  2. They require no filtration to operate reliably
  3. They deliver a nearly constant discharge over a wide range of inlet pressures Correct answer.
  4. They increase the flow rate as pressure rises

Explanation

Pressure-compensating emitters contain a flexible element that adjusts the flow passage so discharge stays nearly constant across a broad pressure range. This allows longer laterals and more uniform application on uneven terrain. They still need filtration, cannot remove friction losses, and do not increase flow with pressure.

Question 33Micro-Irrigation Systems: Types, Components and Layout

In fertigation with a drip system, why is the fertilizer injection point placed upstream of the filter?

  1. To prevent the fertilizer from mixing with water
  2. To reduce the flow rate of the emitters
  3. So the filter can capture any undissolved fertilizer particles before they reach the emitters Correct answer.
  4. To allow the fertilizer to raise the system pressure

Explanation

Injecting fertilizer before the filter ensures that any precipitate or undissolved material is trapped rather than carried into the laterals and emitters. This placement protects the small emitter passages. Injection does not pressurize the system, prevent mixing, or change emitter flow.

Question 34Micro-Irrigation Systems: Types, Components and Layout

Which combination correctly represents the usual order of head components in a drip system, from the water source toward the laterals?

  1. Pump, then filter, then pressure regulator, then mainline Correct answer.
  2. Filter, then pump, then mainline, then pressure regulator
  3. Mainline, then filter, then pump, then pressure regulator
  4. Pressure regulator, then mainline, then pump, then filter

Explanation

Water is first pressurized by the pump, then cleaned by the filter, then regulated to the design pressure before entering the mainline and sub-mains. This sequence protects downstream components and maintains the emitter design pressure. Placing the pump after the filter or the regulator before the pump would not deliver filtered, regulated water correctly.

Question 35Micro-Irrigation Systems: Types, Components and Layout

A field has a gentle slope, and the grower wants uniform emission along laterals running downhill. Which design choice best helps achieve this?

  1. Using pressure-compensating emitters or installing pressure regulators on the laterals Correct answer.
  2. Removing the filter to reduce head loss
  3. Increasing the emitter spacing to double the design spacing
  4. Shortening the laterals to a single emitter

Explanation

On sloping ground, elevation change adds to or subtracts from friction losses, making pressure non-uniform. Pressure-compensating emitters or lateral-level regulators maintain steady discharge despite this. Widening spacing, removing filtration, or using a single emitter do not solve the pressure variation.

Question 36Micro-Irrigation Systems: Types, Components and Layout

What is the function of a sand media filter in a micro-irrigation system using canal or reservoir water?

  1. To add nutrients to the irrigation water
  2. To measure the flow rate into each block
  3. To increase the water pressure before the mainline
  4. To trap fine organic and inorganic particles that screen filters would pass Correct answer.

Explanation

Sand media filters pass water through a bed of graded sand that captures fine organic matter and silt, which is common in canal or reservoir supplies. They are often used ahead of screen filters as a primary stage. They do not add nutrients, boost pressure, or measure flow.

Question 37Micro-Irrigation Systems: Types, Components and Layout

In a subsurface drip irrigation (SDI) layout, why are emitters usually spaced further apart than in surface drip for the same crop?

  1. Buried emitters discharge much higher flow rates than surface emitters
  2. Subsurface laterals operate at much higher pressure than surface laterals
  3. Water spreads laterally and upward from the buried emitter, wetting a larger soil volume per emission point Correct answer.
  4. SDI systems do not require filtration so spacing is arbitrary

Explanation

In SDI the emitter is below the surface, so water moves outward and upward through the soil, forming a wider wetted bulb. This allows wider emitter spacing while still wetting the root zone. Emitter discharge and operating pressure are not inherently higher, and filtration is still required.

Question 38Micro-Irrigation Systems: Types, Components and Layout

A grower notices algae and slime buildup inside the drip laterals. Which management measure most directly addresses this problem?

  1. Increasing the emitter flow rate by raising pressure
  2. Shortening the irrigation duration
  3. Chlorination of the system combined with filtration of the organic load Correct answer.
  4. Removing the screen filter to increase flow

Explanation

Algae and bacterial slime are organic clogging agents, so treating the water with chlorine and filtering out organic matter controls them. Raising pressure or removing filtration would worsen clogging, and shortening irrigation does not remove the organisms.

Question 39Micro-Irrigation Systems: Types, Components and Layout

What role does the sub-main play in a drip irrigation layout?

  1. It holds the emitters that discharge water to the plants
  2. It filters the water before it enters the mainline
  3. It distributes water from the mainline to groups of laterals within a block Correct answer.
  4. It regulates the pressure at the pump outlet

Explanation

The sub-main (or manifold) carries water from the mainline and feeds a set of laterals, often through a valve that controls a block. Emitters sit on laterals, filtration is at the head, and pressure regulation is a head function.

Question 40Micro-Irrigation Systems: Types, Components and Layout

A drip block is designed with 16 mm laterals 80 m long and emitters rated 2 L/h at 1 bar. If the measured pressure at the lateral inlet is 1.4 bar and at the far end is 0.7 bar, what does this indicate about the design?

  1. Pressure variation exceeds the allowable range, so emission uniformity will be poor Correct answer.
  2. The filter is over-performing and must be removed
  3. The system is operating exactly at design pressure throughout
  4. The emitters are compensating perfectly for pressure differences

Explanation

A drop from 1.4 to 0.7 bar is a 50 percent variation along the lateral, which is far beyond the small variation non-compensating emitters tolerate for good uniformity. Such a gradient means head-end emitters will over-irrigate and tail-end emitters under-irrigate. The design should be revised with shorter laterals, larger diameter, or pressure-compensating emitters.

Question 41Micro-Irrigation Systems: Types, Components and Layout

Why is a vacuum relief valve sometimes installed on subsurface drip laterals?

  1. To filter fine particles from the water
  2. To inject fertilizer into the buried line
  3. To admit air and prevent soil or water from being sucked back into the emitters when the system shuts down Correct answer.
  4. To increase the operating pressure of the buried laterals

Explanation

When a buried lateral is shut off, water can drain and create negative pressure that draws soil particles or dirty water back into the emitters, causing clogging. A vacuum relief (air/vacuum) valve admits air to break the vacuum. It does not raise pressure, inject fertilizer, or filter water.

Question 42Micro-Irrigation Systems: Types, Components and Layout

A designer must choose between a screen filter and a sand media filter for a surface reservoir supply carrying heavy organic load. Which reasoning is most sound?

  1. Sand media should be the primary filter because screens clog rapidly with organic matter, with a screen as a secondary safety stage Correct answer.
  2. No filter is needed if the emitters are pressure-compensating
  3. A screen alone is best because it has the finest openings of any filter
  4. A sand filter should be placed after the emitters to catch debris

Explanation

Heavy organic loads blind screen filters quickly, requiring frequent cleaning, whereas sand media filters are designed to hold such loads and are backwashed periodically. A screen downstream then serves as a safety catch for any media or remaining particles. Emitter type does not remove the need for filtration, and filters are never placed after emitters.

Question 43Micro-Irrigation Systems: Types, Components and Layout

In a drip system, two laterals of equal length and emitter spacing are compared: one 12 mm and one 16 mm internal diameter. Which statement best explains the expected difference in emission uniformity?

  1. The smaller-diameter lateral has lower friction loss and therefore better uniformity
  2. Diameter has no effect on friction loss in micro-irrigation laterals
  3. Both laterals will show identical pressure profiles because emitter spacing is the same
  4. The larger-diameter lateral has lower friction loss, so pressure and discharge vary less along its length Correct answer.

Explanation

Friction head loss in a pipe decreases as diameter increases for a given flow, so the 16 mm lateral maintains a more even pressure profile and better emission uniformity. The smaller lateral suffers greater friction loss and a steeper pressure decline. Emitter spacing does not cancel this diameter effect.

Question 44Micro-Irrigation Systems: Types, Components and Layout

A grower plans a micro-sprinkler system for an orchard instead of drip. Which characteristic justifies this choice?

  1. Micro-sprinklers deliver water only below the soil surface
  2. Micro-sprinklers wet a larger soil surface area, which suits widely spaced tree roots and can aid frost protection Correct answer.
  3. Micro-sprinklers use less water than drip under all conditions
  4. Micro-sprinklers require no filtration or pressure regulation

Explanation

Micro-sprinklers spread water over a wider wetted pattern, which can better match the root spread of widely spaced trees and can provide limited frost protection. They generally use more water than drip and still need filtration and pressure control. They operate above the surface, not below it.

Question 45Micro-Irrigation Systems: Types, Components and Layout

During a system evaluation, emitters in one block show widely different discharges while inlet pressure is uniform and the filter is clean. What is the most probable explanation?

  1. The flush valves are opened too frequently
  2. Partial clogging or manufacturing variation among individual emitters Correct answer.
  3. The pump is delivering too little pressure to the whole system
  4. The sub-main diameter is too large for the block

Explanation

With uniform inlet pressure and clean filtration, variation among emitters points to partial clogging or differences in emitter manufacturing (coefficient of variation). Individual emitters can block or wear differently. Pump pressure, oversized sub-main, and flushing frequency would not produce this localized scatter.

Question 46Micro-Irrigation Systems: Types, Components and Layout

Which component in a micro-irrigation head assembly protects the system by admitting air into the pipeline when internal pressure drops below atmospheric?

  1. Air release valve
  2. Non-return check valve
  3. Vacuum relief valve Correct answer.
  4. Pressure gauge

Explanation

A vacuum relief valve opens when internal pressure falls below atmospheric and admits air, preventing back-siphonage of soil, mud, or chemical through emitters and avoiding lateral collapse. Air release valves work in the opposite direction, venting trapped air during pressurization. These are two distinct devices and are often both fitted at the head or high points.

Question 47Micro-Irrigation Systems: Types, Components and Layout

A grower wants a micro-irrigation system in which each plant receives water from its own small spray jet with a wetted pattern of roughly 1.5 m diameter, and the jets are mounted on rigid risers above the canopy. Which system type does this describe?

  1. Surface drip with inline emitters
  2. Micro-sprinkler (micro-jet) system Correct answer.
  3. Bubbler system
  4. Subsurface drip irrigation

Explanation

Micro-sprinklers and micro-jets discharge through small nozzles on risers and wet a circular area around each plant, which is typical for orchards and tree crops. Drip systems deliver water through point emitters with a much smaller wetted pattern, and bubblers apply water in a small basin at low head without a spray pattern. The description of a spray jet on a riser above the canopy matches micro-sprinklers.

Question 48Micro-Irrigation Systems: Types, Components and Layout

A drip lateral is to be sized so that friction loss along it does not exceed the allowable pressure variation for good emission uniformity. Which change most reduces friction loss along the lateral while keeping its length, emitter spacing, and emitter flow rate unchanged?

  1. Shortening the emitter spacing
  2. Increasing the lateral internal diameter Correct answer.
  3. Reducing the lateral internal diameter
  4. Increasing the number of emitters per lateral

Explanation

Friction loss in a pipe falls steeply as internal diameter increases, so a larger-diameter lateral carries the same total flow with a much smaller head loss along its length. Keeping length and emitter flow constant means total lateral flow is fixed, so diameter is the controlling variable. Smaller diameter, closer spacing, or more emitters all raise friction loss rather than lower it.

Question 49Micro-Irrigation Systems: Types, Components and Layout

In a drip block, fertilizer is to be injected and the designer must place the injection point correctly. Which placement is standard practice in a micro-irrigation head?

  1. Downstream of the last lateral, at the flush manifold
  2. Downstream of the filters but upstream of the mainline valves
  3. Directly into each lateral at the field edge
  4. Upstream of the filters so the filters remove any precipitates or undissolved particles Correct answer.

Explanation

The injection point is placed upstream of the filters so that any undissolved fertilizer particles or precipitates formed during mixing are trapped before the water reaches the emitters. This protects the small emitter orifices from clogging. Injection downstream of the filters would let those particles pass straight into the laterals.

Question 50Micro-Irrigation Systems: Types, Components and Layout

A designer compares two layouts for the same orchard block: a micro-sprinkler system with one jet per tree and a drip system with two drippers per tree. Which statement best captures the hydraulic and agronomic trade-off that favors the micro-sprinkler option?

  1. Micro-sprinklers apply water more uniformly than drippers at any given pressure because spray patterns overlap.
  2. Micro-sprinklers eliminate the need for any filtration because their nozzles are larger than emitter orifices.
  3. Micro-sprinklers wet a larger soil volume and can leach salts away from the root zone, but they need higher flow and more robust filtration than drippers. Correct answer.
  4. Micro-sprinklers operate at lower pressure than drippers and therefore always use less energy per unit area.

Explanation

Micro-sprinklers spread water over a wider surface area, which wets a larger root-zone volume and helps move accumulated salts outward and downward, a real advantage in orchards on saline soils. The trade-off is higher discharge per unit and larger openings that still require good filtration to avoid nozzle wear and blockage. Drippers use less water per plant and are generally more efficient in application.