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MSCE Agriculture practice questions

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Question 1Crop Science and Crop Production

Which soil characteristic most directly governs the plant-available water holding capacity of a loam-textured topsoil?

  1. The concentration of exchangeable sodium on the clay complex
  2. The depth of the water table below the rooting zone
  3. The proportion of sand-sized particles
  4. The balance of micropores and macropores created by particle aggregation Correct answer.

Explanation

Available water is held in micropores and released from macropores, so a well-aggregated loam with a balanced pore-size distribution stores more plant-available water than a single-textured soil. Sand content reduces retention while sodium and water-table depth affect drainage and aeration rather than the pore-size balance itself.

Question 2Crop Science and Crop Production

A grower wants to break hardpan compaction at 25 cm depth before establishing a deep-rooted legume. Which tillage operation targets that layer with least surface disturbance?

  1. Disk harrowing to 15 cm
  2. Moldboard ploughing to 30 cm
  3. Rotary hoeing of the top 10 cm
  4. Subsoiling with a tined implement to 30 cm Correct answer.

Explanation

Subsoiling uses narrow tines working below the surface to shatter compacted layers while leaving most surface residue in place. Ploughing and harrowing disturb or invert the topsoil but do not specifically fracture a pan at 25 cm.

Question 3Crop Science and Crop Production

Which process converts atmospheric dinitrogen into plant-usable ammonia within legume root nodules?

  1. Ammonification by saprophytic fungi
  2. Nitrification by Nitrosomonas
  3. Denitrification by Pseudomonas
  4. Biological nitrogen fixation by rhizobia Correct answer.

Explanation

Rhizobia in symbiotic nodules reduce atmospheric N2 to ammonia using nitrogenase, supplying nitrogen directly to the host legume. Nitrification, denitrification and ammonification act on nitrogen already present in the soil rather than fixing atmospheric gas.

Question 4Crop Science and Crop Production

A cereal crop shows interveinal chlorosis on older leaves first, with healthy green veins. Which nutrient deficiency best fits this pattern?

  1. Calcium
  2. Iron
  3. Boron
  4. Magnesium Correct answer.

Explanation

Magnesium is a mobile nutrient and a core component of chlorophyll, so deficiency appears as interveinal chlorosis on older leaves as the plant redistributes magnesium to new growth. Iron, boron and calcium are largely immobile and show symptoms on young tissue first.

Question 5Crop Science and Crop Production

Which crop is botanically a legume and therefore capable of forming nitrogen-fixing symbioses?

  1. Rice
  2. Maize
  3. Soybean Correct answer.
  4. Wheat

Explanation

Soybean belongs to the Fabaceae and forms nodules with Bradyrhizobium species that fix atmospheric nitrogen. Maize, wheat and rice are grasses and do not form symbiotic nitrogen-fixing nodules.

Question 6Crop Science and Crop Production

What is the primary purpose of applying a pre-emergence herbicide in a crop production system?

  1. To increase the crop's tolerance to post-emergence herbicides
  2. To create a soil residue barrier that controls weeds before or during seedling emergence Correct answer.
  3. To sterilise the soil and prevent all seed germination
  4. To kill weeds that have already emerged and tillered

Explanation

Pre-emergence herbicides are applied to the soil surface and form a residue layer that kills germinating weed seedlings before they compete with the crop. They act on emerging weeds rather than established ones and do not sterilise soil.

Question 7Crop Science and Crop Production

Which crop rotation principle most effectively reduces the build-up of a soil-borne pathogen specific to one crop family?

  1. Growing the same crop continuously with higher fertiliser rates
  2. Rotating between two cultivars of the same species
  3. Leaving the field fallow but allowing host weeds to grow
  4. Alternating with unrelated crop species that are non-hosts to the pathogen Correct answer.

Explanation

A non-host break starves host-specific pathogens of a food base and lets their populations decline in soil. Continuous cropping or same-species cultivar rotation maintains the host, while weedy fallow can sustain the pathogen.

Question 8Crop Science and Crop Production

Which seed quality attribute is measured by a standard germination test in a seed laboratory?

  1. The proportion of seeds producing normal seedlings under specified conditions Correct answer.
  2. The percentage of pure seed by weight
  3. The moisture content of the seed lot
  4. The thousand-seed weight of the sample

Explanation

A germination test reports the percentage of seeds that develop into normal seedlings under controlled temperature, moisture and light conditions. Purity, moisture and seed weight are separate quality parameters assessed by other tests.

Question 9Crop Science and Crop Production

A field trial compares two maize hybrids and reports a significant genotype-by-environment interaction for grain yield. What does this result imply for varietal recommendation?

  1. The ranking of hybrids may change across environments, so recommendations should consider specific environments Correct answer.
  2. Yield differences are due entirely to random error
  3. The trial should be discarded because interactions invalidate yield data
  4. One hybrid will always outyield the other regardless of location

Explanation

A significant genotype-by-environment interaction means the performance difference between hybrids depends on the growing environment, so a single broad recommendation may mislead. Breeders and agronomists respond by testing across sites and recommending varieties for defined environments.

Question 10Crop Science and Crop Production

A grower irrigates a clay soil daily with small volumes, and the crop shows wilting despite wet surface soil. Which explanation is most consistent with this observation?

  1. The crop has developed resistance to water uptake
  2. Frequent small applications wet only the surface and fail to refill the root zone Correct answer.
  3. The clay has low total porosity
  4. The irrigation water has a high calcium content

Explanation

Light, frequent applications on a clay soil may only wet the top few centimetres while the deeper root zone remains dry, so plants wilt even though the surface looks moist. The remedy is to apply enough water to refill the effective root depth.

Question 11Crop Science and Crop Production

Which practice best reduces nitrate leaching after harvest of a high-nitrogen cereal crop in a humid region?

  1. Deep ploughing to bury crop residues
  2. Leaving the soil bare over winter to allow evaporation
  3. Applying additional nitrogen fertiliser in late autumn
  4. Establishing a fast-growing cover crop to scavenge residual soil nitrogen Correct answer.

Explanation

A rapidly establishing cover crop takes up residual nitrate and holds it in biomass over winter, reducing leaching losses. Additional autumn nitrogen or bare fallow increases the pool of mobile nitrate available for leaching.

Question 12Crop Science and Crop Production

In a rice paddy, ammonium-based fertiliser is generally more efficient than nitrate-based fertiliser. Which mechanism explains this?

  1. Flooded, anaerobic soil favours denitrification of nitrate to gaseous nitrogen Correct answer.
  2. Ammonium is taken up only by roots while nitrate is not
  3. Ammonium is more soluble in water than nitrate
  4. Nitrate is rapidly fixed by clay minerals in paddy soils

Explanation

In the reduced, waterlogged layer of a paddy, nitrate is readily denitrified to N2 and N2O and lost to the atmosphere, whereas ammonium is stable in the reduced zone. This is why ammonium or urea sources are preferred for flooded rice.

Question 13Crop Science and Crop Production

Which factor most strongly determines the critical period for weed competition in a grain maize crop?

  1. The number of herbicide passes in the previous season
  2. The colour of the maize leaves
  3. The early crop growth stage before canopy closure Correct answer.
  4. The market price of the grain

Explanation

Maize is most sensitive to weed competition during early vegetative growth before the canopy closes and shades the soil. Weeds emerging in this window reduce yield most, so control is timed to protect that phase.

Question 14Crop Science and Crop Production

A soil test reports a cation exchange capacity of 12 cmol(+)/kg and 70 percent base saturation dominated by calcium. What does this indicate about the soil?

  1. It is a highly weathered, strongly acidic soil with low fertility
  2. It has a moderate nutrient-holding capacity with adequate calcium and limited exchangeable acidity Correct answer.
  3. It is a sandy soil with negligible nutrient retention
  4. It is a saline soil dominated by sodium

Explanation

A CEC of 12 cmol(+)/kg is moderate, typical of loamy soils, and 70 percent base saturation dominated by calcium means most exchange sites are occupied by basic cations with little aluminium or hydrogen. This indicates reasonable nutrient retention and low acidity.

Question 15Crop Science and Crop Production

Which crop establishment method is most appropriate for a smallholder aiming to reduce soil erosion on a sloping field with limited mechanisation?

  1. Continuous flood irrigation of the slope
  2. Conservation tillage with residue retention along the contour Correct answer.
  3. Deep ripping followed by bare fallow
  4. Conventional mouldboard ploughing up and down the slope

Explanation

Conservation tillage that retains residues and follows the contour slows runoff and protects the soil surface, which suits low-input systems. Ploughing up and down the slope accelerates erosion, and bare fallow or flooding is unsuitable on sloping land.

Question 16Crop Science and Crop Production

What is the main agronomic advantage of planting a nitrogen-fixing legume in rotation before a cereal crop?

  1. It guarantees complete control of all cereal pests
  2. It eliminates the need for all other nutrients
  3. It reduces the soil organic matter content
  4. It adds fixed nitrogen to the system and can reduce fertiliser nitrogen requirements for the following crop Correct answer.

Explanation

Legumes fix atmospheric nitrogen that remains in residues and soil, providing a nitrogen credit to the following cereal and reducing fertiliser demand. They do not supply all nutrients or provide complete pest control and generally help maintain organic matter.

Question 17Crop Science and Crop Production

Which physiological process is directly reduced when stomata close in response to drought stress during grain filling?

  1. Photosynthetic carbon dioxide uptake and transpiration Correct answer.
  2. Root hair formation
  3. Seed dormancy
  4. Nitrogen fixation in the soil

Explanation

Stomatal closure restricts the diffusion of carbon dioxide into the leaf and reduces transpiration, lowering photosynthetic rate and biomass accumulation. This directly limits carbohydrate supply to developing grain under drought.

Question 18Crop Science and Crop Production

A grower applies a systemic insecticide as a seed treatment to control an early-season sucking pest. Which property of seed treatment makes it effective against that pest?

  1. The active ingredient is taken up by the seedling and translocated, protecting developing tissue Correct answer.
  2. The chemical sterilises the seed and prevents pest feeding
  3. The treatment attracts natural enemies to the crop
  4. The chemical remains on the soil surface and kills pests by contact

Explanation

Systemic seed treatments are absorbed by the germinating seedling and translocated through its tissues, so sap-feeding pests are exposed to the active ingredient as they feed. This protects early growth that would otherwise be vulnerable before foliar sprays are practical.

Question 19Crop Science and Crop Production

Which practice is most likely to reduce the development of herbicide-resistant weed populations in a continuous cropping system?

  1. Applying herbicide only when resistance is already visible
  2. Rotating herbicide modes of action and integrating mechanical or cultural control Correct answer.
  3. Increasing the application rate of a single herbicide
  4. Using the same herbicide with the same mode of action every season

Explanation

Resistance management relies on diversifying selection pressure, so rotating modes of action and combining chemical control with mechanical or cultural tactics slows the selection of resistant biotypes. Repeated use of one mode of action or higher rates of a single product accelerates resistance.

Question 20Crop Science and Crop Production

A crop shows stunted growth, purple-tinged older leaves and poor root development, and a soil test shows adequate total phosphorus but cold, compacted soil. What is the most likely cause?

  1. Excess phosphorus toxicity
  2. Restricted phosphorus uptake because cold, compacted soil limits root exploration Correct answer.
  3. Nitrogen deficiency
  4. Absolute phosphorus deficiency in the soil

Explanation

Phosphorus is relatively immobile in soil, so uptake depends on root exploration; cold, compacted soil restricts root growth and phosphorus acquisition even when total soil phosphorus is adequate. The symptoms reflect a supply problem rather than an absolute soil deficit.

Question 21Crop Science and Crop Production

In a seed production programme, why is isolation distance between fields of the same cross-pollinated crop important?

  1. To ensure uniform soil moisture across fields
  2. To prevent mechanical damage from farm machinery
  3. To reduce the cost of fertiliser application
  4. To limit cross-pollination and maintain genetic purity of the seed lot Correct answer.

Explanation

Cross-pollinated crops can receive pollen from neighbouring fields, so isolation distance limits gene flow and preserves the genetic identity of the seed crop. This is a central requirement for certified seed production.

Question 22Crop Science and Crop Production

A farmer wants to reduce post-harvest losses in a cereal grain store in a humid climate. Which combination of practices is most effective?

  1. Storing grain at high moisture with good ventilation
  2. Sealing undried grain in airtight bags immediately after harvest
  3. Mixing fresh and old grain to equalise moisture
  4. Drying grain to a safe moisture level and storing it in a cool, dry, insect-proof facility Correct answer.

Explanation

Safe storage depends on drying grain to a moisture level that prevents mould growth and insect activity, combined with a cool, dry, pest-exclusion facility. High-moisture or sealed undried grain heats and spoils rapidly.

Question 23Crop Science and Crop Production

Which factor most directly limits the use of a high-yielding cereal variety in a low-rainfall environment?

  1. The number of tillers produced in irrigated trials
  2. The cost of seed packaging
  3. The variety's maturity duration and water requirement relative to the season length Correct answer.
  4. The colour of the grain

Explanation

In low-rainfall environments, a variety whose maturity and water use exceed the available season risks terminal drought and poor grain filling. Matching maturity duration to the rainfall pattern is a primary adaptation criterion.

Question 24Crop Science and Crop Production

A soil profile shows a dense, platy structure at 20-30 cm with standing water after rain and poor root penetration. Which combination of causes is most consistent with this diagnosis?

  1. Long-term traffic or tillage compaction combined with low organic matter Correct answer.
  2. High calcium carbonate content and good aggregation
  3. Excess earthworm activity and high organic matter
  4. Recent application of gypsum to a sodic soil

Explanation

Platy structure at shallow depth with restricted infiltration and rooting is a classic sign of compacted soil, often from machinery traffic or repeated tillage at the same depth, worsened by low organic matter. Organic matter and biological activity usually improve structure rather than create pans.

Question 25Crop Science and Crop Production

In a crop simulation model, a genotype is described by parameters for thermal time to flowering and for photoperiod sensitivity. Why must both parameters be estimated together when predicting adaptation across latitudes?

  1. Because thermal time alone always predicts flowering date accurately
  2. Because flowering date depends on the interaction of temperature accumulation and daylength Correct answer.
  3. Because genotype parameters are independent of environment
  4. Because photoperiod sensitivity is irrelevant in field crops

Explanation

Flowering time results from the combined effect of temperature-driven development and daylength sensitivity, so a genotype calibrated only on thermal time can mispredict at latitudes with different photoperiods. Joint estimation captures the interaction and improves predictions of adaptation.

Question 26Crop Science and Crop Production

Which measure expresses the percentage of viable seeds that produce normal seedlings under standard laboratory conditions?

  1. Thousand-grain weight
  2. Test weight
  3. Seed moisture content
  4. Seed germination percentage Correct answer.

Explanation

Germination percentage is determined by counting normal seedlings produced from a defined number of seeds under controlled temperature and moisture, and it directly expresses seed lot viability. The other measures describe seed size, water status or bulk density rather than the capacity to establish seedlings.

Question 27Crop Science and Crop Production

Which soil condition most directly reduces the availability of phosphorus to a growing cereal crop?

  1. High organic matter content in the plough layer
  2. Low soil pH causing fixation with iron and aluminium Correct answer.
  3. Low soil temperature in early spring
  4. High calcium saturation at near-neutral pH

Explanation

In acid soils, soluble phosphate reacts with iron and aluminium oxides to form less soluble compounds, sharply reducing phosphorus availability. Organic matter and near-neutral calcium saturation generally favour or maintain phosphorus supply, while cool temperatures slow root growth and uptake but do not cause the chemical fixation that acidity does.

Question 28Crop Science and Crop Production

A cereal crop is sown at a lower seed rate than recommended but with uniform row spacing. Which outcome is most likely?

  1. Earlier maturity with no change in yield
  2. Fewer ears per unit area and lower yield potential Correct answer.
  3. Increased lodging risk from taller stems
  4. Larger individual grains but unchanged yield

Explanation

Cereal yield is largely built from the number of fertile ears per unit area, so a reduced plant population lowers the ear population and the yield ceiling even if individual plants tiller more. Grain size may rise slightly, but this rarely compensates fully for the missing ears, and lodging risk is not increased by thinner stands.

Question 29Crop Science and Crop Production

Which practice best protects a cereal crop from frost damage during the sensitive flowering stage?

  1. Applying extra nitrogen immediately before flowering
  2. Adjusting sowing date so flowering avoids the local frost window Correct answer.
  3. Irrigating heavily the day before flowering
  4. Increasing seed rate to raise canopy density

Explanation

Matching sowing date to the local climate shifts flowering away from the period when frost is most likely, which is the most reliable way to protect the sensitive reproductive stage. Extra nitrogen, denser canopies and heavy irrigation do not raise the crop's frost tolerance and can even increase damage or lodging.

Question 30Crop Science and Crop Production

Which characteristic distinguishes a determinate crop cultivar from an indeterminate one in terms of canopy management?

  1. Determinate types stop vegetative growth at flowering, so canopy size is fixed early Correct answer.
  2. Indeterminate types stop vegetative growth at flowering and mature uniformly
  3. Determinate types continue producing new leaves throughout grain filling
  4. Indeterminate types require no support or staking in any production system

Explanation

Determinate cultivars cease vegetative growth when flowering begins, so canopy size and the number of fruiting sites are largely fixed early in the season. Indeterminate cultivars keep producing new vegetative growth and flowers over a longer period, which affects pruning, support and harvest timing decisions.

Question 31Crop Science and Crop Production

Which cropping practice most directly improves soil organic carbon in a continuously cropped arable field?

  1. Retaining crop residues and adding a cover crop in the rotation Correct answer.
  2. Burning residues to speed seedbed preparation
  3. Deep mouldboard ploughing after each harvest
  4. Increasing mineral nitrogen rates without adding organic matter

Explanation

Returning residues and growing a cover crop adds fresh organic material to the soil, which is the main pathway for building soil organic carbon in arable systems. Ploughing, burning and relying only on mineral fertiliser either remove carbon inputs or accelerate the loss of existing organic matter.

Question 32Crop Science and Crop Production

Which statement correctly describes the role of a catch crop in a nutrient management plan?

  1. It sterilises the soil against root pathogens
  2. It takes up residual soil nitrogen and holds it against leaching over winter Correct answer.
  3. It raises soil pH by releasing carbonate during decomposition
  4. It fixes atmospheric nitrogen for the following cereal crop

Explanation

A catch crop is established after the main crop to scavenge residual nitrate from the soil profile and hold it in plant tissue over the leaching season. It is not primarily a nitrogen-fixing crop, does not raise pH, and does not sterilise soil against pathogens.

Question 33Crop Science and Crop Production

Which factor most strongly determines the choice of plant population density for a grain sorghum crop in a semi-arid environment?

  1. Number of previous crops in the rotation
  2. Height of the surrounding windbreak
  3. Expected water supply available through the season Correct answer.
  4. Colour of the grain at maturity

Explanation

In semi-arid conditions, the amount of stored and in-season water sets the upper limit on the plant population that can be supported without exhausting soil moisture before grain filling. Grain colour, windbreak height and rotation length do not determine the water-limited carrying capacity of the stand.

Question 34Crop Science and Crop Production

Which is the main agronomic reason for applying lime to an acid mineral soil before sowing a sensitive crop?

  1. To supply phosphorus directly to the crop
  2. To reduce soil organic matter content
  3. To raise pH and reduce aluminium and manganese toxicity Correct answer.
  4. To increase soil bulk density for better anchorage

Explanation

Liming neutralises acidity and precipitates exchangeable aluminium and manganese, which are toxic to roots at low pH, while also improving conditions for nutrient availability. Lime does not supply phosphorus, is not applied to increase bulk density, and does not aim to reduce organic matter.

Question 35Crop Science and Crop Production

A grower observes dark, water-soaked lesions spreading rapidly on leaves after several days of high humidity. Which management measure is most appropriate for a foliar bacterial disease?

  1. Increasing nitrogen application to stimulate rapid regrowth
  2. Applying a broad-spectrum herbicide to burn off infected leaves
  3. Improving air movement and avoiding overhead irrigation to reduce leaf wetness Correct answer.
  4. Withholding all irrigation until the lesions disappear

Explanation

Bacterial foliar diseases spread mainly through water splash and prolonged leaf wetness, so reducing canopy humidity and avoiding overhead irrigation limits new infections. Herbicide burn-off, extra nitrogen and total irrigation withdrawal do not control the pathogen and may weaken the crop.

Question 36Crop Science and Crop Production

Which practice most effectively reduces the risk of soil compaction from field traffic in a wet season?

  1. Restricting traffic to designated tramlines and avoiding passes on wet soil Correct answer.
  2. Ploughing immediately after each rainfall event
  3. Applying gypsum to the soil surface before traffic
  4. Increasing tyre pressure to spread the load

Explanation

Confining traffic to tramlines and keeping heavy machinery off wet soil limits the area affected and the depth of compaction. Higher tyre pressure concentrates stress, ploughing wet soil can create smearing, and surface gypsum does not protect the subsoil from wheel loads.

Question 37Crop Science and Crop Production

Which statement best explains why a legume in rotation can increase the yield of a following non-legume crop beyond the nitrogen it supplies?

  1. It removes excess phosphorus from the soil
  2. It can break disease and pest cycles and improve soil structure Correct answer.
  3. It eliminates the need for any further fertiliser
  4. It always raises soil pH to an optimal level

Explanation

Legume rotation benefits include breaking the host continuity of soil-borne pathogens and pests, improving aggregation and water infiltration, and diversifying the root environment, which can lift yield beyond the nitrogen contribution alone. Legumes do not reliably raise pH, do not remove phosphorus, and do not remove the need for balanced nutrition.

Question 38Crop Science and Crop Production

Which factor is most important when deciding the harvest date of a grain crop that is to be stored for several months?

  1. Number of tillers produced per plant
  2. Length of the previous fallow period
  3. Colour of the straw in the field
  4. Grain moisture content at harvest Correct answer.

Explanation

Grain moisture at harvest governs the risk of mould, heating and insect damage during storage, so it is the key criterion for deciding when to harvest a crop intended for long storage. Straw colour, fallow length and tiller number do not determine storage safety.

Question 39Crop Science and Crop Production

In a crop rotation with a host and a non-host crop, which mechanism explains the decline of a specialised soil-borne pathogen during the non-host phase?

  1. The pathogen switches to the non-host and becomes harmless
  2. The non-host crop releases antibiotics that sterilise the soil
  3. The non-host crop increases soil pH to a lethal level
  4. The pathogen population declines because its host is absent and resting structures lose viability Correct answer.

Explanation

A pathogen specialised to one crop family cannot multiply without a susceptible host, so its population and resting structures decline over successive non-host seasons. Antibiotic sterilisation, host switching and pH change are not the mechanisms by which rotation reduces such pathogens.

Question 40Crop Science and Crop Production

Which irrigation scheduling approach most directly matches water application to crop demand in a drip-irrigated vegetable crop?

  1. Irrigating at a fixed time every day regardless of weather
  2. Applying water only when leaves show permanent wilting
  3. Flooding the field whenever the surface appears dry
  4. Replacing the estimated crop evapotranspiration at intervals set by soil moisture monitoring Correct answer.

Explanation

Scheduling that replaces estimated crop evapotranspiration and is checked against soil moisture monitoring matches supply to actual demand and avoids both under- and over-irrigation. Fixed daily timing, surface appearance and waiting for permanent wilting all lead to inefficient or damaging water management.

Question 41Crop Science and Crop Production

Which statement correctly describes the purpose of hardening off seedlings before field transplanting?

  1. To gradually adapt seedlings to outdoor conditions and reduce transplant shock Correct answer.
  2. To increase seedling height before transplanting
  3. To sterilise the root system against pathogens
  4. To speed up flowering after transplanting

Explanation

Hardening off gradually exposes seedlings to lower temperatures, stronger light and reduced water so that their tissues adapt before field transplanting, reducing shock and mortality. It does not aim to increase height, sterilise roots or accelerate flowering.

Question 42Crop Science and Crop Production

Which factor most directly explains why a crop grown in a shaded intercrop produces taller, thinner stems than the same crop in full sun?

  1. Reduced transpiration causing cell expansion
  2. Increased photosynthesis from diffuse light in the shade
  3. Shade avoidance through stem elongation in response to reduced red to far-red light Correct answer.
  4. Higher soil temperature under the intercrop canopy

Explanation

Canopy shade lowers the red to far-red ratio, which triggers shade-avoidance responses including stem elongation and reduced stem thickness. Photosynthesis is generally lower in shade, and transpiration and soil temperature changes do not explain the elongation response.

Question 43Crop Science and Crop Production

Which measure is most appropriate for managing a soil-borne nematode problem in a high-value root crop?

  1. Increasing the plant population to dilute the nematodes
  2. Applying a foliar fungicide during the growing season
  3. Rotating with a non-host crop and using resistant cultivars where available Correct answer.
  4. Irrigating more frequently to wash nematodes from the soil

Explanation

Nematode populations are managed most effectively by breaking the host cycle through rotation with non-host crops and by deploying resistant cultivars where these exist. Foliar fungicides do not reach soil nematodes, denser planting does not dilute them, and irrigation does not remove them from the root zone.

Question 44Crop Science and Crop Production

Which crop trait is most important when selecting a variety for mechanical combine harvesting of grain?

  1. Very tall stems and late maturity
  2. Large leaf area retained at harvest
  3. Uniform maturity and resistance to shattering Correct answer.
  4. High susceptibility to lodging

Explanation

Combine harvesting requires a crop that matures evenly and holds its grain until the header passes, so uniform maturity and shatter resistance are essential. Tall late stems, retained leaf area and lodging susceptibility all interfere with efficient mechanical harvest.

Question 45Crop Science and Crop Production

A farmer applies urea to the soil surface of a flooded rice paddy and observes poor nitrogen recovery. Which management change is most likely to improve recovery?

  1. Incorporating urea into the reduced soil layer before flooding or using a coated urea Correct answer.
  2. Applying urea only at the panicle initiation stage without incorporation
  3. Applying urea to the dry soil surface and leaving it uncovered
  4. Applying urea together with lime

Explanation

Surface-applied urea in flooded soil is vulnerable to ammonia volatilisation and to algal immobilisation, so placing it into the reduced soil layer or using a coated product improves nitrogen recovery. Leaving it on the surface, mixing it with lime, or delaying application without placement does not solve the loss pathway.

Question 46Crop Science and Crop Production

Which statement correctly describes the function of a windbreak in a crop production system?

  1. It increases wind speed to improve pollination of cereal crops
  2. It reduces wind speed and can lower evaporation and mechanical damage near the protected area Correct answer.
  3. It raises soil temperature to accelerate germination
  4. It eliminates the need for irrigation in dry regions

Explanation

A windbreak slows wind near the protected zone, reducing evaporation, wind erosion and physical damage to crops, with benefits extending a limited distance downwind. It does not increase wind speed, remove the need for irrigation, or deliberately raise soil temperature.

Question 47Crop Science and Crop Production

Which factor most directly determines the length of the grain-filling period in a determinate cereal crop?

  1. The number of seeds set per ear only
  2. The depth of sowing
  3. The colour of the awns
  4. Temperature and the timing of senescence of the flag leaf and canopy Correct answer.

Explanation

Grain filling lasts as long as the canopy, especially the flag leaf, remains photosynthetic and green, and it is shortened by high temperature and early senescence. Seed number per ear affects sink size but not the duration, while sowing depth and awn colour do not govern the period.

Question 48Crop Science and Crop Production

Which practice best reduces the risk of lodging in a high-yielding wheat crop?

  1. Applying nitrogen in split doses matched to growth stage and avoiding excessive early nitrogen Correct answer.
  2. Irrigating heavily just before harvest
  3. Applying all nitrogen at sowing to maximise early growth
  4. Increasing seed rate above the recommended level

Explanation

Splitting nitrogen and avoiding excess early supply keeps stems shorter and stronger while still meeting crop demand, which lowers lodging risk. A single large sowing-time dose, excessive seed rate and late heavy irrigation all increase stem height or weight and worsen lodging.

Question 49Crop Science and Crop Production

Which statement correctly describes the relationship between soil water potential and plant water uptake?

  1. Uptake is highest at the permanent wilting point
  2. Uptake declines as soil water potential becomes more negative and approaches the wilting point Correct answer.
  3. Uptake is independent of soil water potential once roots are present
  4. Uptake increases as soil water potential becomes more negative

Explanation

As soil dries, water is held more tightly and its potential becomes more negative, so the gradient driving water into roots shrinks and uptake declines toward the wilting point. Uptake does not increase with more negative potential, is not independent of it, and is negligible at the permanent wilting point.

Question 50Crop Science and Crop Production

Which approach is most appropriate for controlling a grass weed that has developed resistance to a single herbicide mode of action in a continuous cereal rotation?

  1. Integrating cultural controls with herbicides that have different modes of action Correct answer.
  2. Applying the same herbicide more frequently
  3. Doubling the rate of the same herbicide
  4. Replacing the herbicide with a foliar fungicide

Explanation

Resistance management relies on reducing selection pressure by combining cultural measures such as rotation, stale seedbeds and delayed sowing with herbicides from different mode-of-action groups. Raising the rate or frequency of the same herbicide increases selection for resistance, and a fungicide has no herbicidal activity.