Soil Science: Formation, Profile, Texture and Structure MCQs 2026

Regolith is the:

1. A Unconsolidated weathered material overlying bedrock ✓
2. B Pure water table only ✓
3. C Chemical name of gypsum ✓
4. D Crop seed embryo ✓

Organic matter improves soil structure mainly by:

1. A Removing all clay from the profile ✓
2. B Making soil particles radioactive ✓
3. C Increasing salt concentration only ✓
4. D Binding particles into stable aggregates ✓

Soil crusting is especially harmful at crop establishment because it can reduce:

1. A The need for sunlight ✓
2. B The oxygen in the atmosphere ✓
3. C Seedling emergence and water infiltration ✓
4. D The genetic purity of seed ✓

The hydrometer method estimates soil texture based on:

1. A Leaf chlorophyll content ✓
2. B Sedimentation rate of particles in suspension ✓
3. C Seed germination speed only ✓
4. D Root nodulation count only ✓

The soil textural triangle is used to determine:

1. A Textural class from sand, silt and clay percentages ✓
2. B Fertilizer brand from price ✓
3. C Crop maturity group only ✓
4. D Sprayer nozzle color only ✓

A clay loam soil generally contains enough clay to be sticky but:

1. A Contains no sand or silt at all ✓
2. B Is always pure gravel ✓
3. C Cannot hold any water ✓
4. D Is not as heavy-textured as clay ✓

Good soil structure improves crop growth mainly by improving:

1. A Weed seed contamination only ✓
2. B Pesticide label color ✓
3. C Aeration, infiltration and root penetration ✓
4. D Market transportation ✓

Sodic soils have poor structure mainly because excess exchangeable sodium causes:

1. A Permanent aggregation of all sand grains ✓
2. B Dispersion of clay particles ✓
3. C Formation of humus only ✓
4. D Lower pH in all cases ✓

Saline soils are primarily characterized by:

1. A High concentration of soluble salts ✓
2. B No electrical conductivity ✓
3. C Only high exchangeable aluminum ✓
4. D Absence of all ions ✓

Soil pH is a measure of soil:

1. A Texture class only ✓
2. B Particle density only ✓
3. C Organic residue color only ✓
4. D Acidity or alkalinity ✓

Compared with smectite, kaolinite generally has:

1. A Greater shrink-swell capacity always ✓
2. B More interlayer expansion ✓
3. C Lower cation exchange capacity ✓
4. D No clay-sized particles ✓

Smectite clay minerals are known for:

1. A No water adsorption at all ✓
2. B High shrink-swell capacity ✓
3. C Being larger than gravel ✓
4. D Having zero surface area ✓

Cation exchange capacity of soil is contributed mainly by:

1. A Clay minerals and humus ✓
2. B Pure sand and gravel only ✓
3. C Air-filled pores only ✓
4. D Crop canopy height only ✓

Humus is best described as:

1. A Fresh unweathered rock ✓
2. B Pure sodium chloride ✓
3. C A chemical herbicide group ✓
4. D Stable, well-decomposed organic matter in soil ✓

Water erosion of bare soil often begins with detachment of particles by:

1. A Seed certification ✓
2. B Photosynthesis in roots ✓
3. C Raindrop impact or splash ✓
4. D Fertilizer bagging ✓

Soil permeability refers to the ease with which water and air:

1. A Change crop genetics ✓
2. B Move through the soil ✓
3. C Become soil minerals instantly ✓
4. D Destroy organic matter only ✓

Infiltration is the process by which water:

1. A Enters the soil surface ✓
2. B Evaporates from leaves only ✓
3. C Moves through xylem only ✓
4. D Changes into fertilizer ✓

Plant-available water in soil is commonly estimated as the difference between:

1. A Sand and gravel content ✓
2. B pH and EC only ✓
3. C Slope and aspect only ✓
4. D Field capacity and permanent wilting point ✓

Permanent wilting point is the water content at which plants:

1. A Grow at maximum rate ✓
2. B Do not need irrigation forever ✓
3. C Cannot regain turgor even in a humid atmosphere ✓
4. D Produce seed immediately ✓

Field capacity is the soil water content after:

1. A The soil is oven dried ✓
2. B Free drainage of gravitational water has mostly ceased ✓
3. C All plant water has been depleted permanently ✓
4. D Only hygroscopic water remains ✓

Soil consistence describes the soil's:

1. A Resistance to deformation or rupture ✓
2. B Tax invoice number ✓
3. C Crop variety name ✓
4. D Latitude only ✓

Gray or bluish gley colors in soil usually indicate:

1. A Excessive aeration always ✓
2. B Pure sand only ✓
3. C Complete absence of water ✓
4. D Poor drainage and reducing conditions ✓

Red and yellow colors in many well-drained soils are mainly due to:

1. A Fresh plant sap ✓
2. B Calcium nitrate fertilizer ✓
3. C Iron oxides ✓
4. D Pure quartz only ✓

In the Munsell system, soil color is described by:

1. A Sand, silt and clay only ✓
2. B Hue, value and chroma ✓
3. C Nitrogen, phosphorus and potassium only ✓
4. D Slope, aspect and altitude only ✓

Illuviation means:

1. A Accumulation of transported material in a soil horizon ✓
2. B Loss of seed viability during storage ✓
3. C Spray drift from a nozzle ✓
4. D Deep ploughing only ✓

Eluviation is the process of:

1. A Addition of seed to a field ✓
2. B Mixing fertilizer in a bag ✓
3. C Harvesting a crop early ✓
4. D Removal of material from a soil horizon ✓

Podzolization is most closely associated with:

1. A Permanent saltwater flooding only ✓
2. B Desert pavement formation only ✓
3. C Acid forest soils and translocation of humus, iron and aluminum ✓
4. D Pure calcium carbonate deposition only ✓

Calcification is a soil-forming process involving accumulation of:

1. A Fresh leaf litter only ✓
2. B Calcium carbonate ✓
3. C Iron sulfide only ✓
4. D Gypsum boards ✓

Laterization is associated with intense leaching in humid tropics and accumulation of:

1. A Iron and aluminum oxides ✓
2. B Fresh undecomposed straw only ✓
3. C Sodium chloride crystals only ✓
4. D Calcium carbonate nodules only ✓

Capillary water is water held in soil pores:

1. A Only as water vapor above the crop canopy ✓
2. B Only in drainage canals ✓
3. C Only as chemically combined crystal water ✓
4. D Against gravity and available to varying degrees for plants ✓

Soil porosity generally increases when:

1. A Compaction increases sharply ✓
2. B All pores are filled with cement ✓
3. C Aggregation and organic matter improve ✓
4. D Only gravel is removed from roads ✓

Bulk density is the mass of oven-dry soil per unit:

1. A Volume of water only ✓
2. B Bulk volume including pore space ✓
3. C Root length only ✓
4. D Fertilizer bag weight ✓

Platy soil structure is undesirable in many cropped soils because it tends to:

1. A Restrict water movement and root penetration ✓
2. B Increase all root growth instantly ✓
3. C Eliminate erosion completely ✓
4. D Turn sand into clay ✓

Granular soil structure is most commonly found in:

1. A Fresh unweathered bedrock ✓
2. B Deep compacted plough pans only ✓
3. C Pure salt crusts only ✓
4. D Surface horizons rich in roots and organic matter ✓

Soil structure refers to the:

1. A Chemical formula of urea ✓
2. B Number of crops grown per year ✓
3. C Arrangement of primary particles into aggregates or peds ✓
4. D Latitude of the farm ✓

A loam soil is one that has:

1. A Only clay and no sand ✓
2. B A balanced mixture of sand, silt and clay ✓
3. C Only gravel and stones ✓
4. D Only soluble salts ✓

Compared with sandy soils, clayey soils generally have:

1. A Higher water-holding capacity and slower drainage ✓
2. B Lower nutrient retention in all cases ✓
3. C No pore space ✓
4. D No shrink-swell behavior ever ✓

Silt particles are commonly identified in the field by a feel that is:

1. A Sharp and gravelly ✓
2. B Extremely sticky like clay ✓
3. C Woody and fibrous ✓
4. D Smooth or floury ✓

Sandy soil usually feels:

1. A Sticky and plastic only ✓
2. B Silky like flour only ✓
3. C Gritty ✓
4. D Oily and waxy ✓

A catena or toposequence is a sequence of soils related mainly to changes in:

1. A Seed packaging color ✓
2. B Relief, slope position and drainage ✓
3. C Spray tank volume only ✓
4. D Harvest date labels only ✓

In the USDA system, clay particles are smaller than:

1. A 2.0 mm in diameter ✓
2. B 0.002 mm in diameter ✓
3. C 0.05 mm in diameter ✓
4. D 5.0 mm in diameter ✓

Soil texture is determined by the relative proportion of:

1. A Sand, silt and clay ✓
2. B Nitrogen, phosphorus and potassium ✓
3. C Roots, stems and leaves ✓
4. D Pests, diseases and weeds ✓

A soil profile is a:

1. A List of crop prices ✓
2. B Sprayer calibration chart ✓
3. C Single clay mineral particle ✓
4. D Vertical section of soil showing its horizons ✓

The C horizon is usually composed of:

1. A Only fresh leaves ✓
2. B Ploughed topsoil only ✓
3. C Partly weathered parent material ✓
4. D Pure humus ✓

The B horizon is commonly a zone of:

1. A Fresh plant litter only ✓
2. B Illuviation or accumulation of clay, iron, aluminum or humus ✓
3. C Unweathered parent rock only ✓
4. D Permanent snow only ✓

The O horizon consists mainly of:

1. A Organic litter and decomposing plant residues ✓
2. B Unaltered hard bedrock ✓
3. C Only soluble salts ✓
4. D Pure sand grains ✓

The A horizon in a soil profile is generally the:

1. A Unweathered bedrock layer ✓
2. B Deepest groundwater zone only ✓
3. C Pure calcium carbonate layer always ✓
4. D Mineral surface horizon enriched with organic matter ✓

A pedon is best defined as:

1. A A single sand particle ✓
2. B A fertilizer recommendation sheet ✓
3. C The smallest three-dimensional unit of soil used for study ✓
4. D A soil insect larva ✓

Residual parent material is material that has:

1. A Been deposited only by glaciers ✓
2. B Weathered in place from the underlying rock ✓
3. C Been transported only by rivers ✓
4. D Formed only from sea water ✓

The five major soil-forming factors are commonly summarized as climate, organisms, relief, parent material and:

1. A Time ✓
2. B Fertilizer ✓
3. C Tillage ✓
4. D Irrigation ✓

Clay soils generally have

1. A zero water retention ✓
2. B only gravel behavior ✓
3. C high water-holding capacity but may drain slowly ✓
4. D no cation exchange ✓

Balanced fertilization means

1. A supplying nutrients in ratios matching crop needs and soil tests ✓
2. B only urea in maximum dose ✓
3. C ignoring P and K always ✓
4. D applying random micronutrients only ✓

Deep tillage is sometimes used to

1. A break plow pans and improve rooting ✓
2. B increase compaction deliberately ✓
3. C remove all OM ✓
4. D raise water table ✓

Soil fertility differs from soil productivity in that fertility refers to

1. A only rainfall ✓
2. B only management ignoring nutrients ✓
3. C nutrient status/ability to supply nutrients, while productivity includes all growth factors ✓
4. D identical meanings always ✓

Chlorosis is a symptom often linked to

1. A excess green pigment only ✓
2. B deficiency of N, Fe, Mg or other factors reducing chlorophyll ✓
3. C only mechanical lodging ✓
4. D only wind erosion ✓

Secondary nutrients include

1. A Zn Fe Mn only ✓
2. B N P K only ✓
3. C B Mo Cl only ✓
4. D calcium, magnesium and sulfur ✓

Potassium fixation in some soils means

1. A K evaporates as gas ✓
2. B K turns into N ✓
3. C K becomes nitrate ✓
4. D K becomes trapped in clay interlayers less available ✓

Nitrous oxide emissions from soils increase with

1. A zero N inputs always ✓
2. B permanent drought only ✓
3. C excess N fertilizer and wet anaerobic microsites ✓
4. D pure sand with no N ✓

The rhizosphere is

1. A only the plow layer without roots ✓
2. B atmosphere above canopy ✓
3. C the soil zone influenced by roots and root exudates ✓
4. D irrigation canal bed only ✓

Aridisols / desert soils typically have

1. A thick O horizons like forests ✓
2. B low organic matter and may accumulate salts/carbonates ✓
3. C continuous waterlogging ✓
4. D high rainfall leaching always ✓

Vertisols are noted for

1. A never cracking ✓
2. B shrinking and swelling clay behavior ✓
3. C pure sand dunes ✓
4. D permanent frost ✓

Soil survey and mapping help to

1. A ignore spatial variability ✓
2. B apply one rate everywhere blindly ✓
3. C plan land use and management by soil types ✓
4. D replace climate data ✓

Trace element toxicity can occur from

1. A industrial contamination or over-application ✓
2. B balanced micronutrient use only ✓
3. C pure rainwater irrigation only ✓
4. D organic matter alone ✓

Acid sulfate soils problems appear when

1. A lime is applied correctly ✓
2. B pH rises to 8 naturally ✓
3. C gypsum remediates sodicity only ✓
4. D sulfides oxidize and generate sulfuric acidity ✓

Carbon sequestration in soils increases when

1. A all residues are burned ✓
2. B organic inputs rise and decomposition/erosion losses fall ✓
3. C tillage intensifies without cover ✓
4. D OM is mined continuously ✓

Soil health emphasizes

1. A only NPK bag counts ✓
2. B only color charts ✓
3. C biological, chemical and physical functioning together ✓
4. D only tractor horsepower ✓

Band placement of phosphorus is useful because P

1. A leaches as fast as nitrate always ✓
2. B is a gas ✓
3. C needs no soil contact ✓
4. D is relatively immobile in soil ✓

Split application of nitrogen is recommended to

1. A apply all N before sowing only always ✓
2. B never fertilize ✓
3. C apply only at harvest ✓
4. D match crop demand and reduce losses ✓

Nitrogen losses by volatilization are higher when

1. A urea is deep placed in moist soil ✓
2. B urea is surface-applied on alkaline soils without incorporation ✓
3. C temperature is near freezing always ✓
4. D soil is strongly acidic with incorporation ✓

SAR (sodium adsorption ratio) of water indicates

1. A sodicity hazard of irrigation water ✓
2. B only nitrate content ✓
3. C only BOD ✓
4. D only turbidity from clay alone ✓

ESP (exchangeable sodium percentage) is used to diagnose

1. A only nitrogen status ✓
2. B sodicity hazard ✓
3. C only organic carbon ✓
4. D only sand % ✓

Soil salinity management includes

1. A stopping all irrigation forever ✓
2. B adding more NaCl ✓
3. C sealing drains ✓
4. D adequate leaching fraction and drainage ✓

Mycorrhizal fungi help plants mainly by

1. A fixing atmospheric N2 like Rhizobium always ✓
2. B enhancing phosphorus and water uptake ✓
3. C producing urea prills ✓
4. D raising soil pH to 12 ✓

Critical nutrient concentration is

1. A tissue level below which yield declines ✓
2. B soil bulk density threshold ✓
3. C EC of irrigation water only ✓
4. D pH of rain ✓

Luxury consumption refers to

1. A starvation of all nutrients ✓
2. B only foliar feeding ✓
3. C uptake of a nutrient beyond amounts needed for yield ✓
4. D only hydroponics ✓

Integrated nutrient management combines

1. A only urea forever ✓
2. B organic and inorganic nutrient sources judiciously ✓
3. C only FYM with zero mineral fertilizer always ✓
4. D no nutrient inputs ✓

Sulfur deficiency symptoms often include

1. A only purple older leaves like P always ✓
2. B only marginal burn of K only ✓
3. C only Zn rosetting exclusively ✓
4. D yellowing of younger leaves (mobile differently than N patterns vary) ✓

Liming is used to

1. A reclaim sodic soils as the first choice always ✓
2. B add sodium ✓
3. C raise pH of acidic soils ✓
4. D lower pH of alkaline soils ✓

Available water capacity is greater in

1. A pure gravel always ✓
2. B medium-textured soils with good structure than in coarse sands ✓
3. C solid rock ✓
4. D compacted clay with no pores ✓

Permanent wilting point is when

1. A soil is at saturation ✓
2. B soil is oven dry necessarily ✓
3. C plants can no longer extract sufficient water and wilt permanently ✓
4. D EC is zero ✓

Field capacity is the

1. A permanent wilting point ✓
2. B saturation with zero air ✓
3. C water content after excess water has drained by gravity ✓
4. D oven-dry state ✓

Compaction of soil reduces

1. A bulk density ✓
2. B root penetration, infiltration and aeration ✓
3. C strength of plow pan always beneficially ✓
4. D need for any tillage forever ✓

Wind erosion is a major risk in

1. A dense humid forests only ✓
2. B continuously flooded paddies ✓
3. C arid sandy regions with sparse cover ✓
4. D glacial ice fields ✓

Soil erosion by water is reduced by

1. A clean tillage up and down slopes ✓
2. B removing all vegetation ✓
3. C maximizing bare fallow on slopes ✓
4. D cover crops, residue retention and contour practices ✓

Calcareous soils contain

1. A only pure silica sand ✓
2. B zero carbonates ✓
3. C calcium carbonate that can raise pH and affect micronutrients ✓
4. D only sodium chloride crystals ✓

Alluvial soils of the Indus plains are generally

1. A useless for crops ✓
2. B deep and agriculturally important though often calcareous ✓
3. C only volcanic ash ✓
4. D only peat bogs ✓

Parent material influences soil by affecting

1. A only current market prices ✓
2. B only farmer education ✓
3. C mineralogy, texture and inherent fertility ✓
4. D only tractor brand ✓

The topsoil (A horizon) is generally

1. A pure parent rock ✓
2. B richest in organic matter and biological activity ✓
3. C only groundwater ✓
4. D sterile mineral without life ✓

Soil testing is done to

1. A replace the need for any nutrients forever ✓
2. B guide fertilizer and amendment recommendations ✓
3. C measure only air temperature ✓
4. D count insects only ✓

Iron chlorosis in orchards often appears on

1. A high pH calcareous soils ✓
2. B strongly acidic soils with excess Fe ✓
3. C flooded acid sulfate only ✓
4. D organic soils with Fe toxicity always ✓

Zinc deficiency is common in Pakistani soils especially on

1. A strongly acidic forest floors only ✓
2. B peat soils exclusively ✓
3. C pure quartz sand with OM 20% ✓
4. D alkaline calcareous soils ✓

Micronutrients include

1. A Zn, Fe, Mn, Cu, B, Mo, Cl ✓
2. B N, P, K only ✓
3. C C, H, O only ✓
4. D Ca, Mg, S only as micros ✓

Humus is

1. A fresh undecomposed straw only ✓
2. B relatively stable, dark organic matter in soil ✓
3. C pure mineral clay ✓
4. D fertilizer prill coating only ✓

Soil organic matter benefits include

1. A increasing bulk density always ✓
2. B eliminating all microbes ✓
3. C improved structure, water holding and nutrient supply ✓
4. D raising EC permanently ✓

Denitrification under anaerobic conditions converts nitrate to

1. A gaseous N forms (N2/N2O) lost to atmosphere ✓
2. B plant protein directly ✓
3. C rock phosphate ✓
4. D elemental sulfur crystals ✓

Nitrification converts

1. A ammonium to nitrate ✓
2. B nitrate to N2 gas only ✓
3. C organic C to CH4 only ✓
4. D phosphate to PH3 ✓

Biological nitrogen fixation is performed notably by

1. A only nitrifying bacteria making N2 ✓
2. B Rhizobium in legume nodules ✓
3. C denitrifiers creating urea bags ✓
4. D algae making rock phosphate ✓

Green manuring involves

1. A burning all residues always ✓
2. B growing and incorporating leguminous or other plants to enrich soil ✓
3. C removing all organic matter ✓
4. D applying only NaCl ✓

Farmyard manure improves soil mainly by adding

1. A pure sodium chloride ✓
2. B plastic residues as fertilizer ✓
3. C only sand particles ✓
4. D organic matter and some nutrients ✓

SOP and MOP are sources of

1. A only nitrogen ✓
2. B potassium ✓
3. C only phosphorus ✓
4. D only calcium ✓

DAP (diammonium phosphate) mainly supplies

1. A only potassium ✓
2. B only sulfur ✓
3. C only boron ✓
4. D nitrogen and phosphorus ✓

Urea fertilizer supplies

1. A phosphorus only ✓
2. B potassium only ✓
3. C zinc only ✓
4. D nitrogen ✓

Potassium helps plants with

1. A forming chlorophyll as the central atom ✓
2. B N2 fixation enzyme alone ✓
3. C DNA base pairing exclusively ✓
4. D stomatal regulation, disease tolerance and grain quality ✓

Phosphorus is critical for

1. A energy transfer (ATP) and early root development ✓
2. B only leaf green color exclusively ✓
3. C only stomatal opening of K alone ✓
4. D only micronutrient chelation of Fe alone ✓

Nitrogen in plants is especially needed for

1. A only cell wall silica ✓
2. B only fat storage exclusively ✓
3. C only root suberin ✓
4. D proteins, chlorophyll and vegetative growth ✓

Electrical conductivity (EC) of a soil extract is used to assess

1. A salinity level ✓
2. B only organic matter ✓
3. C only texture ✓
4. D only color ✓

Gypsum is commonly used to reclaim

1. A sodic soils ✓
2. B pure sandy deserts overnight without water ✓
3. C peat bogs only ✓
4. D acid sulfate soils exclusively ✓

Sodic soils are problematic mainly due to

1. A excess exchangeable sodium dispersing clay and degrading structure ✓
2. B excess calcium carbonate always improving tilth ✓
3. C lack of any sodium ✓
4. D too much gypsum naturally everywhere ✓

Saline soils are characterized by

1. A zero electrical conductivity ✓
2. B only organic toxicity ✓
3. C absence of Na and Cl ✓
4. D high soluble salt content that reduces water uptake ✓

Most crops grow best in soils that are

1. A extremely acidic pH 2 always ✓
2. B pH 12 always ✓
3. C without any pH relevance ✓
4. D near neutral to slightly acidic/alkaline depending on species ✓

Soil pH indicates

1. A acidity or alkalinity of the soil ✓
2. B only moisture content ✓
3. C only texture class ✓
4. D only organic carbon alone ✓

Cation exchange capacity (CEC) measures

1. A soil's ability to hold and exchange positively charged nutrients ✓
2. B only anion leaching rate ✓
3. C sand percentage ✓
4. D soil temperature ✓

Soil porosity is important because pores hold

1. A only solid minerals ✓
2. B only pure metal ✓
3. C air and water needed by roots ✓
4. D only plastic mulch ✓

Bulk density is

1. A volume of pores only ✓
2. B soil color index ✓
3. C fertilizer grade ✓
4. D mass of dry soil per unit bulk volume ✓

Soil structure describes

1. A only particle size percentages ✓
2. B arrangement of soil particles into aggregates ✓
3. C only pH value ✓
4. D only EC reading ✓

Loam soils are valued because they

1. A balance drainage, aeration and water/nutrient retention ✓
2. B are pure clay only ✓
3. C are pure sand only ✓
4. D contain no silt ✓

Sandy soils typically

1. A drain rapidly and hold fewer nutrients ✓
2. B always waterlog permanently ✓
3. C have the highest CEC always ✓
4. D never need irrigation ✓

Soil is best described as

1. A a natural body of minerals, organic matter, water and air supporting plants ✓
2. B pure solid rock only ✓
3. C only liquid water ✓
4. D only atmospheric gases ✓

The mineral portion of soil is derived mainly from

1. A photosynthesis alone ✓
2. B rainfall nitrogen only ✓
3. C weathering of parent rock and sediments ✓
4. D tractor exhaust ✓

Soil texture refers to

1. A soil color only ✓
2. B organic matter percentage only ✓
3. C relative proportions of sand, silt and clay ✓
4. D bulk density alone ✓