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BSEB Inter Agriculture study materials
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BSEB Inter Agriculture practice questions

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Question 1Principles of Agronomy and Crop Production

Which agronomic practice involves growing two or more crops together in the same field during the same season with a definite row arrangement?

  1. Fallow cropping
  2. Sequential cropping
  3. Intercropping Correct answer.
  4. Monocropping

Explanation

Intercropping places two or more crops in the same field in the same season with a defined row geometry, so the crops share light, water and nutrients but remain spatially separate. Monocropping uses a single crop, while sequential cropping separates crops in time rather than space.

Question 2Principles of Agronomy and Crop Production

In a crop rotation, a legume such as lentil is included mainly because it contributes to the following crop through which process?

  1. Deep ploughing of the subsoil
  2. Production of allelopathic root exudates
  3. Rapid depletion of soil potassium
  4. Biological nitrogen fixation in root nodules Correct answer.

Explanation

Rhizobia in root nodules of legumes fix atmospheric nitrogen, and the nitrogen-rich residues left after harvest raise available soil nitrogen for the following cereal. The benefit is a nutrient contribution, not tillage or weed suppression.

Question 3Principles of Agronomy and Crop Production

A seed lot has 92 percent purity and 85 percent germination. What is its germination percentage adjusted for purity (pure live seed percentage)?

  1. 92.0 percent
  2. 78.2 percent Correct answer.
  3. 88.5 percent
  4. 85.0 percent

Explanation

Pure live seed is calculated as purity multiplied by germination divided by 100, that is 92 × 85 / 100 = 78.2 percent. This value reflects only the viable seed of the desired species present in the lot.

Question 4Principles of Agronomy and Crop Production

Which soil moisture condition is most suitable for puddling before transplanting rice seedlings?

  1. Soil at permanent wilting point
  2. Soil at field capacity without free water
  3. Dry soil with cracks
  4. Saturated soil with standing water Correct answer.

Explanation

Puddling destroys soil aggregates in saturated, waterlogged conditions, creating a soft mud and a compacted layer that reduces percolation losses. Rice transplants then establish easily and standing water suppresses many weeds.

Question 5Principles of Agronomy and Crop Production

For a crop with a recommended seed rate of 100 kg per hectare and a row spacing of 25 cm, which factor most directly determines the number of plants established per unit area?

  1. Depth of sowing alone
  2. Colour of the seed coat
  3. Seed rate combined with germination and field establishment percentage Correct answer.
  4. Row spacing alone irrespective of seed size

Explanation

Plant population is set by the seed rate adjusted for purity, germination and field establishment, while row spacing only distributes that population. Seed size affects the number of seeds per kilogram but is already captured in the calibrated seed rate.

Question 6Principles of Agronomy and Crop Production

Which irrigation scheduling approach is based on the ratio of water applied to the water required by the crop?

  1. Consumptive use
  2. Water use efficiency
  3. Duty of water
  4. Irrigation efficiency Correct answer.

Explanation

Irrigation efficiency compares the water beneficially used by the crop with the water delivered to the field. It is expressed as a ratio or percentage and indicates how well applied water is converted into crop use.

Question 7Principles of Agronomy and Crop Production

Which weed control measure is an example of a cultural method rather than a chemical method?

  1. Growing a smother crop such as cowpea to suppress weeds Correct answer.
  2. Using a flame weeder between crop rows
  3. Spraying pendimethalin as a pre-emergence herbicide
  4. Applying glyphosate as a directed spray

Explanation

Cultural weed control manipulates the cropping system, for example by using competitive smother crops, closer spacing or timely sowing, to suppress weeds through crop dominance. Herbicide spraying and flaming are chemical and physical methods respectively.

Question 8Principles of Agronomy and Crop Production

Which of the following describes the critical period of crop-weed competition for a cereal crop?

  1. The period after crop harvest
  2. The period when weeds have already set seed
  3. The entire crop growth period from sowing to harvest
  4. The early period when the crop is most sensitive to weed competition Correct answer.

Explanation

The critical period is the interval during which weed competition causes the greatest yield loss, generally early in crop growth when the crop canopy is open. Weed control outside this window gives less economic return.

Question 9Principles of Agronomy and Crop Production

Which nutrient is most commonly deficient in flooded paddy soils because of its conversion to unavailable forms under reduced conditions?

  1. Phosphorus
  2. Potassium
  3. Zinc Correct answer.
  4. Nitrogen

Explanation

Under submerged, reduced soil conditions zinc precipitates as insoluble sulphides and carbonates, making it unavailable and causing khaira disorder in rice. Nitrogen becomes more available as ammonium under reduction, and potassium remains comparatively mobile.

Question 10Principles of Agronomy and Crop Production

What is the main agronomic purpose of applying a green manure crop such as dhaincha before rice transplanting?

  1. To reduce soil microbial activity
  2. To increase soil bulk density
  3. To add organic matter and nitrogen to the soil Correct answer.
  4. To lower the soil organic carbon content

Explanation

Green manure crops are grown and incorporated into the soil while still succulent, adding organic matter and, for legumes, biologically fixed nitrogen. This improves soil physical condition and nutrient supply for the succeeding crop.

Question 11Principles of Agronomy and Crop Production

Which tillage operation is performed to break the hard pan formed below the plough layer in a compacted field?

  1. Planking
  2. Rolling
  3. Harrowing
  4. Subsoiling Correct answer.

Explanation

Subsoiling uses a heavy tine implement that penetrates below the normal plough depth to shatter compacted layers without inverting the soil. Harrowing and planking only work the surface layers.

Question 12Principles of Agronomy and Crop Production

A farmer wants to sow a crop in a field where the previous crop was harvested late and the soil is dry. Which practice best conserves moisture for the next crop?

  1. Flooding the field and leaving it open
  2. Deep ploughing immediately after harvest
  3. Frequent shallow intercultivation to create a dust mulch Correct answer.
  4. Burning the crop residues

Explanation

Shallow intercultivation breaks the capillary continuity at the surface, forming a dust mulch that reduces evaporation losses from the soil below. This is a standard moisture conservation practice in dryland farming.

Question 13Principles of Agronomy and Crop Production

Which cropping system is described as growing a crop in a field for a short period and then leaving the land uncropped for the rest of the year?

  1. Ratooning
  2. Fallow cropping Correct answer.
  3. Mixed cropping
  4. Relay cropping

Explanation

Fallow cropping leaves the land uncultivated for part of the year to conserve moisture and restore fertility. The crop occupies the field for a short period while the remaining period is a managed fallow.

Question 14Principles of Agronomy and Crop Production

Which of the following best explains why a legume-cereal rotation improves cereal yield compared with continuous cereal cropping?

  1. Legume residues add nitrogen and break pest and disease cycles Correct answer.
  2. Legumes increase soil pH to a fixed level
  3. Legumes eliminate the need for any phosphorus fertiliser
  4. Legumes remove all weeds from the field permanently

Explanation

Rotating a cereal with a legume combines nitrogen input from fixed nitrogen in residues with a break in host-specific pathogens and pests. Both effects together typically raise the following cereal yield.

Question 15Principles of Agronomy and Crop Production

Which of the following is the correct order of operations for raising a transplanted rice crop?

  1. Nursery sowing, transplanting, puddling, harvesting
  2. Puddling, transplanting, nursery sowing, harvesting
  3. Nursery sowing, puddling, transplanting, harvesting Correct answer.
  4. Transplanting, nursery sowing, puddling, harvesting

Explanation

Seedlings are first raised in a nursery, the main field is then puddled and levelled, and seedlings of the right age are transplanted before harvest. Puddling must precede transplanting to create the soft mud that supports establishment.

Question 16Principles of Agronomy and Crop Production

What does the term 'land equivalent ratio' quantify in an intercropping system?

  1. The proportion of land left fallow between rows
  2. The yield advantage of intercropping relative to sole cropping Correct answer.
  3. The ratio of seed rate to plant population
  4. The amount of irrigation water saved

Explanation

The land equivalent ratio compares the land area needed under sole cropping with the area of intercropping that produces the same yield. A ratio above one indicates a yield advantage for the intercrop.

Question 17Principles of Agronomy and Crop Production

A crop has a consumptive use of 500 mm over its season and receives 300 mm of effective rainfall and 300 mm of irrigation water. What is the irrigation efficiency in terms of water beneficially used?

  1. About 50 percent
  2. About 60 percent
  3. About 100 percent
  4. About 83 percent Correct answer.

Explanation

Beneficial use is 500 mm against a total supply of 600 mm, giving 500/600 × 100, which is about 83 percent. The excess 100 mm represents losses through deep percolation, runoff or evaporation.

Question 18Principles of Agronomy and Crop Production

Which factor most strongly determines the choice of sowing time for a rainfed kharif crop in Bihar?

  1. Price of the seed in the market
  2. Onset of the monsoon rains Correct answer.
  3. Date of the previous harvest
  4. Colour of the soil

Explanation

In rainfed kharif cultivation, sowing must follow adequate monsoon rainfall so that germination and early establishment succeed. Sowing too early risks dry spells, and too late shortens the growing season.

Question 19Principles of Agronomy and Crop Production

Which practice is an example of biological control of insect pests in an agronomic crop?

  1. Releasing Trichogramma egg parasitoids in the field Correct answer.
  2. Flooding the field to drown larvae
  3. Burning crop residues after harvest
  4. Spraying carbaryl dust on the crop

Explanation

Biological control uses living natural enemies such as parasitoids, predators or pathogens to suppress pest populations. Trichogramma wasps parasitise the eggs of lepidopteran pests and reduce larval numbers.

Question 20Principles of Agronomy and Crop Production

Which statement correctly describes the difference between dryland farming and rainfed farming?

  1. Rainfed farming is practised only in areas with less than 500 mm annual rainfall
  2. Dryland farming requires more irrigation than rainfed farming
  3. Dryland farming excludes the use of any soil moisture conservation measures
  4. Dryland farming is practised in low-rainfall areas with moisture conservation, while rainfed farming depends on rainfall in higher-rainfall regions Correct answer.

Explanation

Dryland farming refers to crop production in arid and semi-arid regions with less than about 500 mm annual rainfall, where moisture conservation is central. Rainfed farming depends on rainfall but occurs in regions with higher and more dependable precipitation.

Question 21Principles of Agronomy and Crop Production

Which of the following is a long-duration intercrop combination commonly recommended for maintaining soil fertility in a cereal-based system?

  1. Wheat with mustard
  2. Barley with oats
  3. Rice with wheat
  4. Maize with cowpea Correct answer.

Explanation

A cereal-legume intercrop such as maize with cowpea adds biologically fixed nitrogen through the legume while the cereal provides the main yield. Wheat with mustard or barley with oats are not legume combinations, and rice with wheat is sequential rather than an intercrop.

Question 22Principles of Agronomy and Crop Production

A soil test recommends 120 kg nitrogen per hectare for a maize crop, to be split into a basal dose and a top dressing. Which split is most appropriate for a light-textured soil?

  1. The entire dose one week before harvest
  2. One third at sowing and two thirds at knee-high stage Correct answer.
  3. The entire dose at sowing
  4. Half at sowing and half after harvest

Explanation

Light soils retain little nitrogen, so the dose is split to reduce leaching losses and match crop uptake. Applying a smaller basal dose and a larger top dressing at the knee-high stage supplies nitrogen when demand is highest.

Question 23Principles of Agronomy and Crop Production

Which of the following is the primary reason for treating seed with a fungicide before sowing in a cereal crop?

  1. To increase the seed rate per hectare
  2. To increase the germination percentage of dead seeds
  3. To protect germinating seeds and seedlings from seed-borne and soil-borne pathogens Correct answer.
  4. To improve the cooking quality of the grain

Explanation

Seed treatment with fungicides controls pathogens carried on or in the seed and those in the soil that attack germinating seeds and young seedlings. It protects established plants but does not change viability of already dead seeds.

Question 24Principles of Agronomy and Crop Production

Which agronomic term describes the sequence of crops grown on the same field over a defined number of years?

  1. Crop sequence
  2. Crop rotation Correct answer.
  3. Cropping pattern
  4. Cropping scheme

Explanation

Crop rotation is the planned succession of different crops on the same land over a period of years, designed to maintain fertility and interrupt pest cycles. A cropping pattern refers to the spatial and temporal arrangement of crops in a region.

Question 25Principles of Agronomy and Crop Production

Which of the following best explains why zero tillage can reduce soil erosion in a maize-wheat system?

  1. Zero tillage increases the soil bulk density to prevent infiltration
  2. Crop residues left on the surface intercept raindrops and slow runoff Correct answer.
  3. Zero tillage increases the number of ploughings
  4. Zero tillage removes all crop residues from the field

Explanation

Retaining residues on the soil surface under zero tillage protects the soil from raindrop impact, slows runoff and improves infiltration, which together reduce erosion. The undisturbed soil structure also resists detachment.

Question 26Principles of Agronomy and Crop Production

In agronomic terminology, what does the term 'cropping intensity' express for a cultivated field?

  1. The depth of soil disturbed by ploughing before each sowing operation
  2. The total weight of produce removed from the field per hectare in one season
  3. The number of crops harvested from the same field in a year expressed as a percentage of the sole-crop area Correct answer.
  4. The proportion of the field area that remains fallow during the monsoon season

Explanation

Cropping intensity compares the total cropped area harvested in a year with the net sown area, and is normally written as a percentage; growing two crops on the same land gives about 200 per cent. It is a measure of land use efficiency over time, not of yield weight, fallow share, or tillage depth.

Question 27Principles of Agronomy and Crop Production

A grower plans a maize–potato–moong sequence on the same plot in one agricultural year. Which term best classifies this arrangement?

  1. Mixed cropping
  2. Relay cropping
  3. Sole cropping
  4. Sequential multiple cropping Correct answer.

Explanation

Growing two or more crops in succession on the same land within one year, one after the other, is sequential multiple cropping, and a three-crop sequence of this type is a typical intensive form. The crops do not share the field at the same time, which separates it from mixed, relay, and sole cropping.

Question 28Principles of Agronomy and Crop Production

A crop removed 150 kg N, 30 kg P and 120 kg K per hectare, and the field received 100 kg N, 40 kg P and 40 kg K per hectare as fertiliser. Using the nutrient balance approach, which statement about the potassium recommendation for the next crop is most sound?

  1. Fertiliser potassium should be halved, because crop removal figures already include soil reserves
  2. The potassium deficit of about 80 kg per hectare should be compensated in the next fertiliser dose Correct answer.
  3. Potassium is in surplus, so no potassium fertiliser is required for the following crop
  4. Only the nitrogen gap matters, because potassium is never limiting in cereal soils

Explanation

The balance approach compares nutrients removed in the harvest with nutrients added, so potassium shows a deficit of roughly 120 minus 40, that is about 80 kg per hectare. That gap must be made up in the next dose if soil fertility is to be maintained, since a negative balance steadily depletes available soil potassium.

Question 29Soil Science and Soil Fertility Management

In soil science, the term 'soil texture' refers to the relative proportions of which particle size groups?

  1. Pore space, air and water
  2. Sand, silt and clay Correct answer.
  3. Calcium, magnesium and potassium
  4. Humus, sand and gravel

Explanation

Soil texture is defined by the relative proportions of the three mineral particle separates: sand, silt and clay. These separates are distinguished mainly by their equivalent diameters, not by their chemical composition or by the amount of pore space present.

Question 30Soil Science and Soil Fertility Management

Which soil particle size separate generally has the greatest specific surface area per unit weight?

  1. Fine gravel
  2. Coarse silt
  3. Clay Correct answer.
  4. Fine sand

Explanation

Specific surface area increases sharply as particle size decreases, and clay has by far the smallest particles among the separates. Its large surface area per gram is the basis of clay's high water-holding and cation exchange capacity.

Question 31Soil Science and Soil Fertility Management

A soil sample contains 40% sand, 40% silt and 20% clay. Using the standard texture triangle, this soil falls in which textural class?

  1. Silt loam
  2. Loam Correct answer.
  3. Clay loam
  4. Sandy clay loam

Explanation

The loam class occupies the central region of the texture triangle, roughly where sand, silt and clay are in moderate and fairly balanced proportions. A composition of 40% sand, 40% silt and 20% clay plots inside that central loam area.

Question 32Soil Science and Soil Fertility Management

Which type of soil structure is generally considered most favourable for plant growth in the surface horizon?

  1. Single grain
  2. Platy
  3. Massive
  4. Granular Correct answer.

Explanation

Granular structure consists of small, rounded, porous aggregates that allow good aeration, water infiltration and root penetration. It is typical of well-managed surface soils rich in organic matter and biological activity.

Question 33Soil Science and Soil Fertility Management

The process by which soluble salts accumulate in the root zone and raise the electrical conductivity of the soil solution is called:

  1. Salinization Correct answer.
  2. Leaching
  3. Laterization
  4. Podzolization

Explanation

Salinization is the accumulation of soluble salts such as chlorides and sulphates in the root zone, which raises the electrical conductivity of the soil solution. It commonly develops under irrigation with poor drainage in arid and semi-arid regions.

Question 34Soil Science and Soil Fertility Management

Which soil horizon is typically the zone of maximum organic matter accumulation in an undisturbed grassland soil?

  1. R horizon
  2. C horizon
  3. A horizon Correct answer.
  4. Bedrock layer

Explanation

The A horizon is the surface mineral horizon where organic matter from roots and litter is incorporated, giving it the darkest colour and highest biological activity. It overlies the subsoil B horizon and the weathered C horizon.

Question 35Soil Science and Soil Fertility Management

Which of the following is a leguminous green manure crop commonly grown to add atmospheric nitrogen to soil?

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

Explanation

Sunhemp is a fast-growing legume often ploughed in as green manure, and its root nodules host rhizobia that fix atmospheric nitrogen. Cereals such as maize, wheat and rice are non-legumes and do not fix nitrogen symbiotically.

Question 36Soil Science and Soil Fertility Management

The cation exchange capacity of a soil is expressed in which unit?

  1. Megapascals (MPa)
  2. Decisiemens per metre (dS m-1)
  3. Centimoles of charge per kilogram (cmol(c) kg-1) Correct answer.
  4. Kilograms per hectare (kg ha-1)

Explanation

Cation exchange capacity measures the quantity of exchangeable positive charge held per unit mass of soil, reported as centimoles of charge per kilogram. It reflects the number of negatively charged exchange sites on clay and organic matter.

Question 37Soil Science and Soil Fertility Management

Compared with a sandy soil, a clayey soil typically shows which combination of properties?

  1. Lower water-holding capacity and higher cation exchange capacity
  2. Higher water-holding capacity and lower cation exchange capacity
  3. Lower water-holding capacity and lower cation exchange capacity
  4. Higher water-holding capacity and higher cation exchange capacity Correct answer.

Explanation

Clay particles have very large specific surface areas and many negatively charged sites, so clayey soils retain more water and hold more exchangeable cations than sandy soils. Sandy soils drain freely but store little water or nutrients.

Question 38Soil Science and Soil Fertility Management

A soil has a pH of 5.2 and a high exchangeable aluminium content. Which amendment is most appropriate to correct this condition?

  1. Elemental sulphur
  2. Gypsum
  3. Ammonium sulphate
  4. Agricultural lime Correct answer.

Explanation

Agricultural lime raises soil pH by neutralising acidity and precipitating toxic exchangeable aluminium. This improves root growth and nutrient availability in strongly acid soils.

Question 39Soil Science and Soil Fertility Management

Which essential plant nutrient is taken up mainly as the anion H2PO4- and is often poorly available because it is fixed by iron and aluminium oxides in acid soils?

  1. Magnesium
  2. Phosphorus Correct answer.
  3. Potassium
  4. Calcium

Explanation

Phosphorus is absorbed mainly as dihydrogen phosphate and becomes strongly adsorbed or precipitated by iron and aluminium oxides in acid soils. This fixation reduces its availability to crops and explains the low recovery of applied phosphate fertiliser.

Question 40Soil Science and Soil Fertility Management

In the nitrogen cycle, the conversion of ammonium to nitrate by soil bacteria is known as:

  1. Ammonification
  2. Nitrification Correct answer.
  3. Denitrification
  4. Nitrogen fixation

Explanation

Nitrification is the microbial oxidation of ammonium to nitrite and then to nitrate, carried out by specialised chemoautotrophic bacteria. The resulting nitrate is mobile in soil and readily taken up by crops or lost by leaching.

Question 41Soil Science and Soil Fertility Management

Which practice is most effective for conserving soil moisture in a rainfed field during a dry spell?

  1. Mulching the soil surface with crop residues Correct answer.
  2. Removing all plant residues after harvest
  3. Compacting the surface with heavy machinery
  4. Frequent deep ploughing to expose fresh soil

Explanation

A surface mulch of crop residues reduces evaporation, moderates soil temperature and protects the surface from crusting. This conserves stored moisture for the crop during dry periods.

Question 42Soil Science and Soil Fertility Management

The water held in soil between field capacity and permanent wilting point is best described as:

  1. Gravitational water
  2. Capillary fringe water
  3. Available water Correct answer.
  4. Hygroscopic water

Explanation

Available water is the portion held between field capacity and permanent wilting point, which plants can absorb through their roots. Water above field capacity drains as gravitational water, while water below the wilting point is tightly bound and unavailable.

Question 43Soil Science and Soil Fertility Management

Which organism group is chiefly responsible for converting organic nitrogen in crop residues into ammonium?

  1. Nitrifying bacteria
  2. Denitrifying bacteria
  3. Heterotrophic decomposer microorganisms Correct answer.
  4. Rhizobia in root nodules

Explanation

Ammonification is carried out by a wide range of heterotrophic bacteria and fungi that decompose organic matter and release ammonium. Nitrifying, rhizobial and denitrifying organisms perform different steps of the nitrogen cycle.

Question 44Soil Science and Soil Fertility Management

A farmer applies 120 kg of urea (46% N) per hectare. Approximately how much nitrogen is applied?

  1. 120 kg N per hectare
  2. 55 kg N per hectare Correct answer.
  3. 276 kg N per hectare
  4. 46 kg N per hectare

Explanation

The nitrogen content is found by multiplying the fertiliser mass by its nitrogen percentage: 120 kg multiplied by 0.46 equals about 55 kg N per hectare. This calculation lets fertiliser doses be compared on an elemental nutrient basis.

Question 45Soil Science and Soil Fertility Management

Which statement best explains why the availability of most plant nutrients is greatest at a soil pH near neutral?

  1. At extreme pH values nutrients are fixed or precipitated into less soluble forms Correct answer.
  2. Cation exchange capacity becomes zero at neutral pH
  3. Microbial activity ceases entirely at pH values below 7
  4. Neutral pH maximises the solubility of every nutrient equally

Explanation

At very low pH, elements such as phosphorus, molybdenum and calcium become less available through fixation or precipitation, while at high pH iron, zinc and manganese become insoluble. Near neutrality the balance of these effects gives the widest overall nutrient availability.

Question 46Soil Science and Soil Fertility Management

Which soil colour is most commonly associated with a well-drained, well-aerated soil containing oxidised iron compounds?

  1. Greenish grey
  2. Yellowish brown to reddish Correct answer.
  3. Bluish grey
  4. Pale white

Explanation

Oxidised iron compounds such as haematite and goethite give well-drained soils yellowish brown to reddish colours. These colours indicate that oxygen is present and iron is in the ferric state.

Question 47Soil Science and Soil Fertility Management

Which of the following is a secondary plant nutrient required in moderate amounts but not classified as a macronutrient in the primary group?

  1. Copper
  2. Molybdenum
  3. Sulphur Correct answer.
  4. Boron

Explanation

Sulphur is classed as a secondary nutrient along with calcium and magnesium because plants need it in moderate amounts. Boron, molybdenum and copper are micronutrients required only in very small quantities.

Question 48Soil Science and Soil Fertility Management

A laboratory reports a soil with 2.5% organic carbon. Using the common conversion factor, the approximate organic matter content is:

  1. 25%
  2. 2.5%
  3. 1.45%
  4. 4.3% Correct answer.

Explanation

Soil organic matter is commonly estimated by multiplying organic carbon by the Van Bemmelen factor of about 1.724. Thus 2.5% organic carbon corresponds to roughly 4.3% organic matter.

Question 49Soil Science and Soil Fertility Management

Which management practice would most directly reduce nitrate leaching into groundwater beneath a cropped field?

  1. Applying all nitrogen fertiliser in a single dose before heavy rains
  2. Growing a deep-rooted catch crop after the main harvest Correct answer.
  3. Flood-irrigating immediately after nitrogen application
  4. Leaving the field fallow and bare through the rainy season

Explanation

A deep-rooted catch crop scavenges residual nitrate from the soil profile after the main crop is harvested, reducing the amount that can leach into groundwater. It also protects the surface from erosion and adds organic matter when incorporated.

Question 50Soil Science and Soil Fertility Management

In a soil with high cation exchange capacity dominated by calcium and magnesium, which process best explains the reduced availability of potassium to plants?

  1. Competitive displacement of potassium from exchange sites by the dominant cations Correct answer.
  2. Rapid conversion of potassium to nitrate by nitrifying bacteria
  3. Volatilisation of potassium as a gas at neutral pH
  4. Complete chemical destruction of potassium in the soil

Explanation

When calcium and magnesium saturate most exchange sites, potassium is held less strongly and can be displaced into the soil solution, where it may be leached or taken up in proportions affected by the balance of cations. This competition among cations influences potassium availability.