Scientific Officer-Agronomy-Practice-1

Prepare for the SPSC Scientific Officer Agronomy examination with 20 MCQs on soil science, crop nutrition, irrigation, weed management, plant physiology and agricultural research, with answers and explanations.

Practice questions

A wheat crop shows yellowing of older leaves, beginning at the leaf tips. Which nutrient deficiency is most consistent with this symptom?
- Nitrogen
- Calcium
- Iron
- Boron
A soil has a high cation exchange capacity (CEC). What does this generally indicate?
- It cannot retain plant nutrients
- It has a greater capacity to retain exchangeable cations
- It always has a neutral pH
- It contains no organic matter
Which process converts atmospheric nitrogen into ammonia through the action of nitrogen-fixing microorganisms?
- Nitrification
- Denitrification
- Biological nitrogen fixation
- Ammonia volatilization
In a field trial, why are treatments commonly randomized within experimental blocks?
- To eliminate the need for replication
- To reduce systematic bias and account for field variability
- To guarantee identical yields
- To prevent all weather effects
Which soil property most directly describes the distribution of sand, silt and clay particles?
- Soil texture
- Soil structure
- Soil colour
- Soil consistency
A farmer applies excessive nitrogen fertilizer to a cereal crop. Which outcome is a plausible risk?
- Guaranteed improvement in grain quality
- Increased lodging risk and possible nutrient losses
- Complete elimination of weeds
- Permanent prevention of soil salinity
Which instrument is commonly used to measure photosynthetically active radiation (PAR) in crop research?
- PAR quantum sensor
- Barometer
- Rain gauge
- Soil penetrometer
What is the main agronomic purpose of growing a legume as a green manure crop?
- To remove all phosphorus from the soil
- To add organic matter and potentially contribute biologically fixed nitrogen
- To permanently eliminate the need for irrigation
- To prevent every soil-borne disease
Which indicator is commonly used to evaluate the salinity of irrigation water?
- Electrical conductivity
- Wind speed
- Soil bulk density alone
- Leaf area index
Why can waterlogging reduce crop growth in many upland crops?
- It always increases oxygen supply to roots
- It restricts oxygen diffusion into the root zone
- It permanently increases photosynthesis
- It prevents all nutrient transformations
In crop science, harvest index is generally calculated as:
- Total above-ground biomass divided by grain yield
- Economic yield divided by total above-ground biological yield
- Root length divided by plant height
- Grain moisture divided by soil moisture
Which weed characteristic most directly contributes to the development of herbicide resistance in a weed population?
- Selection and reproduction of resistant individuals under repeated herbicide use
- The absence of genetic variation in every population
- Complete prevention of seed production
- Uniform susceptibility of all plants over generations
Which soil amendment is commonly used to supply calcium and help reclaim sodic soil?
- Gypsum
- Sodium chloride
- Urea
- Elemental nitrogen gas
Which process converts ammonium into nitrite and then nitrate under suitable aerobic conditions?
- Denitrification
- Nitrification
- Biological nitrogen fixation
- Ammonia volatilization
Why is a soil test useful before recommending fertilizer application?
- It measures every plant disease directly
- It helps estimate nutrient status and guide fertilizer recommendations
- It guarantees the same yield in every field
- It eliminates the need to consider crop requirements
Which crop response is most likely when plant population exceeds the optimum density?
- Competition among plants for light, water and nutrients may reduce individual plant growth
- Each plant receives unlimited resources
- Competition disappears completely
- Yield per plant must increase indefinitely
What is the principal function of stomata in most terrestrial crop plants?
- Regulating gas exchange and water vapour loss
- Absorbing mineral nutrients directly from the soil
- Fixing atmospheric nitrogen in all leaves
- Producing seeds without reproduction
Which practice is most likely to reduce soil erosion on sloping cultivated land?
- Continuous bare fallow without protection
- Cultivation up and down the slope
- Contour farming combined with suitable soil cover
- Removal of all crop residues
In a fertilizer experiment, why should an untreated control plot be included?
- To provide a comparison for estimating treatment effects
- To guarantee that the fertilizer treatment wins
- To remove the need for statistical analysis
- To ensure all plots have identical soil conditions
Which strategy best supports sustainable nutrient management in irrigated agriculture?
- Applying the same excessive fertilizer rate to every field
- Using soil and crop information to match nutrient sources, rates, timing and placement to crop needs
- Ignoring irrigation-water quality
- Applying nutrients without considering crop uptake