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Maharashtra HSC NSQF Micro Irrigation Technician study materials
Maharashtra HSC NSQF Micro Irrigation Technician study resources

Maharashtra HSC NSQF Micro Irrigation Technician practice questions

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Question 1Micro Irrigation Fundamentals and System Types

In a drip irrigation system, what is the primary function of the emitter (dripper)?

  1. To regulate water flow to a small, controlled discharge at the plant root zone Correct answer.
  2. To boost line pressure at the head of each lateral
  3. To inject fertilizer into the irrigation water
  4. To filter suspended particles before water enters the mainline

Explanation

The emitter is the terminal discharge device of a drip system and its job is to release water slowly and uniformly at a controlled rate near the root zone. Filtration, pressure boosting and fertigation are handled by separate components at the head control unit, not by the emitter.

Question 2Micro Irrigation Fundamentals and System Types

Which micro irrigation method delivers water as a small spray or jet over the soil surface around each plant without pressurising the whole field?

  1. Subsurface drip irrigation
  2. Surface furrow flooding
  3. Basin irrigation
  4. Micro sprinkler irrigation Correct answer.

Explanation

Micro sprinklers (micro jets and micro sprays) throw water as fine sprays or jets over a limited wetted area around each plant and operate at low discharge compared with conventional sprinklers. Furrow, basin and subsurface drip are different methods with different delivery mechanisms.

Question 3Micro Irrigation Fundamentals and System Types

What does the term 'wetted percentage' (wetted area fraction) represent in the design of a drip irrigation system?

  1. The proportion of the field area wetted by the emitters relative to the total area Correct answer.
  2. The percentage of emitters that are clogged at any time
  3. The fraction of applied water lost to deep percolation
  4. The ratio of night-time irrigation hours to total pumping hours

Explanation

Wetted percentage describes how much of the cropped area receives water from the emitters and is a key design parameter affecting root development and irrigation scheduling. It is a geometric coverage measure, not a measure of losses, clogging or timing.

Question 4Micro Irrigation Fundamentals and System Types

A farmer wants to irrigate a closely spaced vegetable crop where laterals can be laid on the soil surface and moved between beds. Which system best matches this requirement?

  1. A solid-set overhead sprinkler system
  2. A lined canal gravity supply
  3. A portable surface drip system with removable laterals Correct answer.
  4. A permanently buried subsurface drip system

Explanation

Portable surface drip systems use laterals that lie on the surface and can be lifted and shifted between beds, which suits closely spaced vegetables and changing layouts. Buried, solid-set and canal systems are fixed or gravity-based and do not offer this flexibility.

Question 5Micro Irrigation Fundamentals and System Types

Why is a pressure-compensating emitter preferred on long laterals laid on undulating terrain?

  1. It increases the discharge as pressure rises to flush the lateral
  2. It works only under gravity flow without a pump
  3. It eliminates the need for any filtration in the system
  4. It maintains a nearly constant discharge over a wide range of inlet pressures Correct answer.

Explanation

Pressure-compensating emitters contain a flexible or moving element that adjusts the flow path so discharge stays nearly constant despite pressure variations along the lateral or due to elevation changes. This improves uniformity on long or sloping laterals without removing the need for filtration.

Question 6Micro Irrigation Fundamentals and System Types

What is the main purpose of flushing the laterals and sub-mains of a drip irrigation system periodically?

  1. To sterilise the soil around the emitters
  2. To raise the operating pressure of the system
  3. To remove accumulated sediment and biological slime from the pipelines Correct answer.
  4. To increase the emitter discharge rate permanently

Explanation

Flushing opens line ends at higher velocity to carry out settled silt, sand and biofilm that would otherwise clog emitters. It is a maintenance practice for pipeline cleanliness and does not change pressure settings, soil condition or emitter ratings.

Question 7Micro Irrigation Fundamentals and System Types

In a drip system layout, what is the role of the sub-main?

  1. It stores water for night-time irrigation
  2. It filters the water before the pump
  3. It emits water directly to the plant roots
  4. It carries water from the mainline to the laterals through a control valve or manifold Correct answer.

Explanation

The sub-main (or manifold) distributes water from the mainline to groups of laterals and usually carries a valve or control point for each block. Emitting water is the emitter's job, while filtration and storage occur at other components.

Question 8Micro Irrigation Fundamentals and System Types

Which factor most directly determines the spacing of emitters along a lateral in a drip design for a widely spaced orchard crop?

  1. The wetting pattern and root spread of each tree Correct answer.
  2. The colour of the lateral tubing
  3. The size of the fertilizer tank
  4. The length of the mainline

Explanation

Emitter spacing in orchards is set so the wetted bulbs overlap enough to cover the tree's active root zone, based on soil wetting pattern and root spread. Tubing colour, mainline length and tank size do not govern emitter spacing.

Question 9Micro Irrigation Fundamentals and System Types

What distinguishes subsurface drip irrigation (SDI) from surface drip irrigation?

  1. Water is applied only at night
  2. Emitters are replaced by sprinklers
  3. Laterals are buried below the soil surface at the root zone Correct answer.
  4. It operates without any filter

Explanation

SDI places drip tubing below the soil surface, typically 15 to 30 cm deep, so water is delivered directly to the root zone with reduced evaporation and no surface wetting. Timing, emitter type and filtration requirements are not what define SDI.

Question 10Micro Irrigation Fundamentals and System Types

A grower wants to apply soluble fertilizer uniformly through a drip system. Which component is required for this?

  1. A non-return valve only
  2. A fertigation unit such as a venturi injector or dosing pump Correct answer.
  3. A sand separator cyclone
  4. A pressure relief valve only

Explanation

Fertigation requires a metering device, such as a venturi injector or a dosing pump, to introduce the nutrient solution into the irrigation water at a controlled rate. Cyclones, relief valves and check valves perform other hydraulic functions and do not dose fertilizer.

Question 11Micro Irrigation Fundamentals and System Types

Which statement correctly describes the difference between drip irrigation and conventional sprinkler irrigation?

  1. Drip applies water slowly and locally, while sprinklers apply water over a broad area at higher rates Correct answer.
  2. Drip cannot be used with soluble fertilizers
  3. Drip wets the entire field uniformly while sprinklers wet only the root zone
  4. Drip requires higher operating pressure than sprinklers

Explanation

Drip irrigation delivers small, frequent amounts of water directly near each plant, whereas sprinklers broadcast water over a wide area at higher application rates. Drip generally operates at lower pressure and is well suited to fertigation.

Question 12Micro Irrigation Fundamentals and System Types

What is the purpose of an air release valve installed at high points of a micro irrigation pipeline network?

  1. To inject air into the water for aeration
  2. To measure the flow rate in the pipeline
  3. To drain water from the pipeline for storage
  4. To vent trapped air that would otherwise disturb flow and damage components Correct answer.

Explanation

Air trapped at high points can cause erratic flow, water hammer and reduced emitter performance, so air release valves vent it automatically. They do not drain, aerate or measure flow.

Question 13Micro Irrigation Fundamentals and System Types

A field has a sandy soil with very low water-holding capacity. How should a drip irrigation schedule be adjusted compared with a loamy soil?

  1. Apply larger, less frequent irrigations to save labour
  2. Stop irrigating because sandy soil drains too fast
  3. Apply smaller, more frequent irrigations to reduce deep percolation Correct answer.
  4. Use the same schedule because soil type does not affect drip scheduling

Explanation

Sandy soils hold little water and have high infiltration, so water moves quickly below the root zone. Smaller, more frequent applications keep moisture in the root zone and minimise deep percolation losses, unlike loamy soils that can store more water between events.

Question 14Micro Irrigation Fundamentals and System Types

What does emission uniformity (EU) of a drip system indicate?

  1. The pressure at the pump outlet
  2. The total volume of water pumped per season
  3. The percentage of fertilizer in the water
  4. How evenly water is discharged across the emitters in a field Correct answer.

Explanation

Emission uniformity expresses how uniformly emitters discharge water across a field, combining manufacturer variation and pressure differences. It is not a measure of total volume, pump pressure or nutrient concentration.

Question 15Micro Irrigation Fundamentals and System Types

Why are inline drip tapes with turbulent-flow emitters often chosen for row crops such as maize and cotton?

  1. They operate without any pressure at all
  2. They provide economical, closely spaced emission points along a single disposable lateral Correct answer.
  3. They are designed only for tree crops
  4. They require no filtration and can use muddy water

Explanation

Inline drip tape integrates emitters at close spacing inside a thin-walled lateral, giving an economical option for dense row crops where the tape may be used for one or a few seasons. It still needs filtration and operating pressure and is not restricted to orchards.

Question 16Micro Irrigation Fundamentals and System Types

What is the function of a screen (screen mesh) filter in the head control unit of a drip system?

  1. To measure the total volume of water applied
  2. To add nutrients to the water
  3. To raise the water pressure for the laterals
  4. To trap suspended particles larger than the mesh opening before water reaches the emitters Correct answer.

Explanation

Screen filters use a mesh that captures particles larger than the openings, protecting fine emitters from clogging. Nutrient addition, pressure boosting and volume measurement are handled by other components.

Question 17Micro Irrigation Fundamentals and System Types

In a drip system, why should the operating pressure at the head be checked against the emitter manufacturer's recommended range?

  1. Lower pressure always increases discharge
  2. Pressure has no effect on emitter performance
  3. Higher pressure always improves emitter life
  4. Discharge and uniformity depend on operating within the specified pressure range Correct answer.

Explanation

Each emitter is rated for a pressure range within which its discharge and uniformity are as designed. Operating outside this range causes either under- or over-discharge and poor uniformity, so head pressure must be matched to the emitter specification.

Question 18Micro Irrigation Fundamentals and System Types

Which of the following best describes a 'micro jet' as used in micro irrigation?

  1. A device that injects fertilizer into the mainline
  2. A large impact sprinkler covering a whole field
  3. A buried emitter that releases water drop by drop
  4. A small device that throws a jet of water a short distance around a plant Correct answer.

Explanation

A micro jet is a small low-volume device that projects water as a short jet around a plant, often used in orchards and nurseries. Buried emitters, large impact sprinklers and fertilizer injectors are different devices.

Question 19Micro Irrigation Fundamentals and System Types

A farmer observes that emitters at the far end of a lateral discharge much less water than those near the head. Which is the most likely cause?

  1. Emitter spacing that is too close
  2. Excessive filtration removing too many particles
  3. Too much fertilizer in the water
  4. Excessive friction loss along the lateral causing a large pressure drop Correct answer.

Explanation

Friction along the lateral reduces pressure progressively, so downstream emitters on a long or undersized lateral discharge less, causing poor uniformity. This is a hydraulic design issue, not a filtration, fertigation or spacing problem.

Question 20Micro Irrigation Fundamentals and System Types

Which combination correctly pairs a micro irrigation system type with a typical application?

  1. Micro sprinkler with paddy rice grown under standing water
  2. Subsurface drip with deep-rooted orchards and row crops needing root-zone delivery Correct answer.
  3. Drip tape with large shade trees only
  4. Micro jet with flood irrigation of lowland fields

Explanation

Subsurface drip places water directly in the root zone and suits orchards and row crops where evaporation and surface wetting are to be minimised. Paddy rice, flood irrigation and large shade trees do not match the other pairings given.

Question 21Micro Irrigation Fundamentals and System Types

What is the main advantage of using a venturi injector for fertigation compared with a simple bypass tank?

  1. It increases the emitter discharge rate
  2. It filters the water while injecting fertilizer
  3. It eliminates the need for a pump in the system
  4. It draws fertilizer solution into the water at a controllable rate using the pressure difference Correct answer.

Explanation

A venturi injector uses the pressure difference across a constriction to suck fertilizer solution into the flow at a rate that can be adjusted with a valve. It does not filter, change emitter ratings or remove the need for a pump.

Question 22Micro Irrigation Fundamentals and System Types

A designer must choose between surface drip and micro sprinklers for a closely planted leafy vegetable crop on a site prone to strong winds. Which consideration is most relevant?

  1. Surface drip requires higher pressure than micro sprinklers
  2. Wind improves the uniformity of micro sprinkler sprays
  3. Micro sprinklers are unaffected by wind because of their low volume
  4. Micro sprinkler spray is more affected by wind drift, reducing uniformity, so surface drip may be preferred Correct answer.

Explanation

Wind distorts and drifts micro sprinkler sprays, lowering distribution uniformity, whereas drip applies water at the soil surface and is largely unaffected by wind. Low volume does not make micro sprinklers immune to wind, and drip generally operates at lower pressure.

Question 23Micro Irrigation Fundamentals and System Types

Which of these is a correct statement about the relationship between emitter discharge rate and wetted soil volume in a given soil?

  1. Emitter discharge has no effect on the wetted pattern
  2. A higher discharge rate generally produces a wider, shallower wetted pattern than a lower rate Correct answer.
  3. A higher discharge rate produces a deeper, narrower wetted bulb
  4. A lower discharge rate always wets a larger surface area

Explanation

At higher discharge the water spreads more horizontally near the surface because it exceeds the soil's ability to move it downward quickly, giving a wider and shallower wetted pattern. Lower rates favour deeper, narrower wetting, so discharge does influence the wetted shape.

Question 24Micro Irrigation Fundamentals and System Types

What is the purpose of a backflow prevention device in a drip fertigation system?

  1. To release air from the pipeline
  2. To prevent water from flowing forward into the laterals
  3. To stop fertilizer-contaminated water from flowing back into the water source Correct answer.
  4. To regulate the pressure at the emitters

Explanation

Backflow prevention keeps fertilizer-laden water from siphoning back into a well, canal or municipal supply, protecting the water source from contamination. It does not stop forward flow, vent air or regulate emitter pressure.

Question 25Soil-Water-Plant Relationships and Irrigation Scheduling

A soil sample weighs 150 g wet and 120 g after oven drying at 105 °C. What is its gravimetric moisture content on a dry-weight basis?

  1. 25 % Correct answer.
  2. 20 %
  3. 30 %
  4. 80 %

Explanation

Gravimetric moisture on a dry basis equals the mass of water lost divided by the oven-dry soil mass, multiplied by 100. Water lost is 150 − 120 = 30 g, and the dry mass is 120 g, so the value is (30 ÷ 120) × 100 = 25 %.

Question 26Soil-Water-Plant Relationships and Irrigation Scheduling

Which soil water category is held so tightly by soil particles that plants cannot absorb it and it remains after plants wilt permanently?

  1. Hygroscopic water Correct answer.
  2. Gravitational water
  3. Field capacity water
  4. Capillary water

Explanation

Hygroscopic water forms a thin film bound by strong adhesion to soil particle surfaces and is unavailable to roots. Capillary and gravitational water are the plant-available and draining fractions respectively, while field capacity describes a moisture state rather than a tightly bound film.

Question 27Soil-Water-Plant Relationships and Irrigation Scheduling

For a soil at field capacity, which statement correctly describes the matric potential?

  1. It is positive and equal to the depth of the water table
  2. It is negative because capillary and adsorptive forces hold water against gravity Correct answer.
  3. It is positive because roots actively push water upward
  4. It is zero because all pores are saturated

Explanation

Unsaturated soil holds water under tension, so matric potential is negative relative to free water. This suction is created by capillarity in fine pores and adsorption on particle surfaces, and it is the driving force that draws water toward roots.

Question 28Soil-Water-Plant Relationships and Irrigation Scheduling

A soil has field capacity of 30 % and permanent wilting point of 12 % (both gravimetric). What is the available water content?

  1. 2.5 %
  2. 42 %
  3. 12 %
  4. 18 % Correct answer.

Explanation

Available water content is the difference between field capacity and permanent wilting point. Subtracting 12 % from 30 % gives 18 %, which represents the moisture range that plant roots can actually extract.

Question 29Soil-Water-Plant Relationships and Irrigation Scheduling

Which soil texture generally holds the greatest total available water per unit depth of soil?

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

Explanation

Silt loam combines moderate porosity with good pore-size distribution, giving a high available water capacity. Very sandy and gravelly soils drain rapidly and store little water, so their available water per unit depth is low.

Question 30Soil-Water-Plant Relationships and Irrigation Scheduling

A crop root zone is 600 mm deep and the soil available water capacity is 150 mm per metre. If irrigation is applied when 50 % of available water is depleted, what is the net irrigation depth?

  1. 45 mm Correct answer.
  2. 30 mm
  3. 150 mm
  4. 90 mm

Explanation

Available water in the 600 mm root zone is 150 mm/m × 0.6 m = 90 mm. Depleting half of that means the net irrigation depth is 90 × 0.5 = 45 mm.

Question 31Soil-Water-Plant Relationships and Irrigation Scheduling

What does the term reference evapotranspiration (ET₀) represent?

  1. Total water applied through a drip system
  2. Evapotranspiration from a standardized well-watered grass or alfalfa surface Correct answer.
  3. Water lost by a specific crop at any growth stage
  4. Water stored in the soil after rainfall

Explanation

ET₀ is the evapotranspiration from a defined reference surface, typically well-watered grass, under specified climatic conditions. Crop water use is then obtained by multiplying ET₀ by a crop coefficient that accounts for species and growth stage.

Question 32Soil-Water-Plant Relationships and Irrigation Scheduling

A crop has a crop coefficient of 0.8 and reference evapotranspiration is 6 mm/day. What is the crop evapotranspiration?

  1. 4.8 mm/day Correct answer.
  2. 0.48 mm/day
  3. 7.5 mm/day
  4. 6.8 mm/day

Explanation

Crop evapotranspiration is calculated by multiplying ET₀ by the crop coefficient. Here 6 mm/day × 0.8 gives 4.8 mm/day, the estimated daily water use of the crop.

Question 33Soil-Water-Plant Relationships and Irrigation Scheduling

Which pan-evaporation factor explains why a Class A pan reading usually overestimates crop water use?

  1. Pan readings are taken only at night
  2. Pan evaporation excludes any radiation effect
  3. Pan water is warmer and the pan has exposed sides that add advective heat Correct answer.
  4. Pan water is always colder than the surrounding air

Explanation

A Class A pan absorbs extra heat through its exposed metal sides and stores warmer water than a crop canopy, so evaporation is enhanced. A pan coefficient below one is therefore applied to convert pan evaporation to reference evapotranspiration.

Question 34Soil-Water-Plant Relationships and Irrigation Scheduling

In a soil moisture tension measurement, a tensiometer reading of 40 kPa indicates what about the soil?

  1. The soil is saturated and water is draining freely
  2. The soil is at about field capacity or slightly drier and suction is moderate Correct answer.
  3. The soil has reached permanent wilting point
  4. The soil contains no water at all

Explanation

Tensiometers measure matric suction, and values around 10 to 50 kPa indicate moist to moderately dry soil in the readily available range. A reading of 40 kPa therefore signals moderate suction rather than saturation or the wilting point, which occurs near 1500 kPa.

Question 35Soil-Water-Plant Relationships and Irrigation Scheduling

A farmer irrigates when the soil moisture depletion reaches the management allowed depletion (MAD). What is the purpose of setting MAD below 100 %?

  1. To avoid crop water stress and yield loss before the wilting point is reached Correct answer.
  2. To ensure the soil is always fully saturated
  3. To reduce the soil's available water capacity
  4. To increase the leaching requirement

Explanation

MAD is kept below full depletion because crops begin to suffer stress and lose yield before all available water is exhausted. Irrigating at a moderate depletion threshold maintains readily available water and protects yield.

Question 36Soil-Water-Plant Relationships and Irrigation Scheduling

Which irrigation scheduling approach directly uses daily crop evapotranspiration and rainfall to track the soil water balance?

  1. Feel-and-appearance method
  2. Checkbook or water-balance method Correct answer.
  3. Calendar-date method
  4. Soil colour comparison

Explanation

The checkbook method maintains a running account of soil water, adding rainfall and irrigation and subtracting crop evapotranspiration. When the balance reaches the depletion threshold, irrigation is scheduled, making it a quantitative and crop-specific approach.

Question 37Soil-Water-Plant Relationships and Irrigation Scheduling

Why is drip irrigation often scheduled more frequently than surface flooding for the same crop?

  1. Drip applies water only at night
  2. Drip cannot deliver enough water per event
  3. Drip eliminates the need for any scheduling
  4. Drip wets only part of the root zone, so the stored water buffer is smaller Correct answer.

Explanation

Drip irrigation wets a limited soil volume around emitters, so the total available water buffer within the wetted root zone is smaller. Smaller, more frequent applications are therefore needed to prevent depletion and stress.

Question 38Soil-Water-Plant Relationships and Irrigation Scheduling

A field has a root zone of 900 mm, available water capacity of 120 mm/m, and irrigation is triggered at 60 % depletion. What net depth should be applied?

  1. 120 mm
  2. 108 mm
  3. 72 mm
  4. 64.8 mm Correct answer.

Explanation

Total available water in the root zone is 120 mm/m × 0.9 m = 108 mm. At 60 % depletion the net application depth is 108 × 0.6 = 64.8 mm.

Question 39Soil-Water-Plant Relationships and Irrigation Scheduling

If the net irrigation requirement is 45 mm and the application efficiency of the system is 75 %, what gross depth must be applied?

  1. 33.75 mm
  2. 60 mm Correct answer.
  3. 45 mm
  4. 120 mm

Explanation

Gross application equals net requirement divided by application efficiency. Dividing 45 mm by 0.75 gives 60 mm, which accounts for losses such as deep percolation and evaporation.

Question 40Soil-Water-Plant Relationships and Irrigation Scheduling

Which condition most directly increases reference evapotranspiration on a clear summer day?

  1. High soil salinity
  2. High wind speed, high temperature, and low humidity Correct answer.
  3. Heavy overnight rainfall
  4. Low wind speed, low temperature, and high humidity

Explanation

Evaporative demand rises with warm air, dry air, and wind because these increase the vapour pressure deficit and remove moisture from the boundary layer. Cool, calm, humid conditions reduce ET₀, while rainfall and salinity act through other mechanisms.

Question 41Soil-Water-Plant Relationships and Irrigation Scheduling

A tensiometer installed at 30 cm depth reads 55 kPa while one at 15 cm reads 20 kPa. What is the most reasonable interpretation?

  1. The entire root zone is saturated
  2. The deeper layer has no roots
  3. The shallow tensiometer is faulty because it reads lower
  4. The surface layer is wetter, suggesting recent irrigation or rain that has not yet penetrated deeply Correct answer.

Explanation

A lower suction near the surface indicates higher moisture there, consistent with a recent wetting event that has not yet moved deeper. The higher suction at 30 cm shows the subsoil is still drier, which is useful information for deciding whether to irrigate again.

Question 42Soil-Water-Plant Relationships and Irrigation Scheduling

What is the main reason for measuring soil moisture at more than one depth in an orchard?

  1. To measure soil temperature
  2. To track water depletion across the active root zone and avoid under- or over-irrigation Correct answer.
  3. To confirm the pH profile
  4. To estimate the emitter discharge rate

Explanation

Roots are distributed over depth, and moisture can differ markedly between shallow and deep layers. Multi-depth monitoring shows where water is being used and helps adjust irrigation depth so the whole root zone is adequately supplied.

Question 43Soil-Water-Plant Relationships and Irrigation Scheduling

Which statement best explains why heavy clay soils need lower irrigation application depths but more frequent events than sandy soils?

  1. Clay drains faster than sand
  2. Clay has higher available water capacity but lower infiltration rate Correct answer.
  3. Clay has lower available water capacity and higher infiltration rate
  4. Clay contains no capillary water

Explanation

Clay soils retain more water per unit depth because of fine pores, so the same depletion corresponds to a larger stored reserve. However, their low infiltration rate limits how much can be applied at once, so smaller, more frequent applications avoid runoff.

Question 44Soil-Water-Plant Relationships and Irrigation Scheduling

A crop uses 5 mm/day and the effective rainfall over a week is 14 mm. Ignoring other losses, what net irrigation is needed for that week?

  1. 21 mm Correct answer.
  2. 49 mm
  3. 14 mm
  4. 35 mm

Explanation

Weekly crop water use is 5 mm/day × 7 days = 35 mm. Subtracting effective rainfall of 14 mm leaves a net irrigation requirement of 21 mm.

Question 45Soil-Water-Plant Relationships and Irrigation Scheduling

Which practice improves the accuracy of a tensiometer reading in a drip-irrigated field?

  1. Filling the tube with soil slurry
  2. Reading it only after heavy rain
  3. Ensuring good contact between the ceramic cup and undisturbed soil Correct answer.
  4. Installing it far from the wetted zone

Explanation

A tensiometer measures the suction of the soil in contact with its ceramic cup, so poor contact gives misleading readings. Installing it within the wetted root zone with firm soil contact ensures the measured suction reflects the root environment.

Question 46Soil-Water-Plant Relationships and Irrigation Scheduling

What does the term readily available water (RAW) describe?

  1. Water lost to deep percolation
  2. The total porosity of the soil
  3. The portion of available water that plants can extract without significant stress Correct answer.
  4. Water held below permanent wilting point

Explanation

Readily available water is the fraction of the available water range that crops can use before stress begins to reduce transpiration and growth. It is commonly taken as a set proportion of total available water depending on crop sensitivity.

Question 47Soil-Water-Plant Relationships and Irrigation Scheduling

Why does mulching the soil surface reduce irrigation frequency?

  1. It increases the soil's wilting point
  2. It reduces evaporation from the soil surface and conserves moisture Correct answer.
  3. It increases the crop coefficient
  4. It raises the reference evapotranspiration

Explanation

A mulch layer limits direct evaporation from the soil surface, so more of the stored water remains for transpiration. Lower evaporative loss slows depletion of the root zone and lengthens the interval between irrigations.

Question 48Soil-Water-Plant Relationships and Irrigation Scheduling

A grower's tensiometer at 20 cm reads 15 kPa one day after irrigation and 65 kPa five days later. What does this trend indicate?

  1. The root zone is drying and the next irrigation is approaching Correct answer.
  2. The soil is becoming wetter over time
  3. The soil has become saturated
  4. The crop has stopped transpiring

Explanation

Increasing suction over successive days shows that water is being removed from the soil by roots and evaporation faster than it is replenished. Tracking this trend allows the grower to schedule the next irrigation before the depletion threshold is exceeded.

Question 49Water Source, Pumping, Filtration and Fertigation Equipment

In a drip irrigation system supplied from an open well, which component protects the pump from running dry when the water level falls below the suction pipe?

  1. Dry-run (low-level) cut-off sensor with control panel Correct answer.
  2. Venturi injector on the bypass
  3. Pressure-compensating dripper
  4. Air release valve on the mainline

Explanation

A low-level or dry-run protection device senses the falling water level in the well or sump and switches off the pump before the impeller runs without water, which would cause overheating and seal damage. Air release valves, drippers and venturis serve hydraulic or fertigation functions and cannot stop the pump.

Question 50Water Source, Pumping, Filtration and Fertigation Equipment

A farmer's borewell yields 4,000 litres per hour. Which pump selection principle best avoids over-extraction while meeting the drip system design flow?

  1. Choose the pump with the largest suction pipe diameter regardless of head
  2. Choose a pump rated far above the yield and throttle it with a gate valve
  3. Choose a pump whose duty point matches the design flow and total head, not the maximum possible yield Correct answer.
  4. Choose the highest-capacity pump available so the system can be expanded later

Explanation

Pump selection should be based on the required design flow and the total head (suction lift, delivery head and friction losses) so the duty point falls on the system curve. Oversizing forces throttling, wastes energy and can over-extract a low-yielding borewell.