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

Regolith is the:

1. AUnconsolidated weathered material overlying bedrock✓
2. BPure water table only✓
3. CChemical name of gypsum✓
4. DCrop seed embryo✓

Organic matter improves soil structure mainly by:

1. ARemoving all clay from the profile✓
2. BMaking soil particles radioactive✓
3. CIncreasing salt concentration only✓
4. DBinding particles into stable aggregates✓

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

1. AThe need for sunlight✓
2. BThe oxygen in the atmosphere✓
3. CSeedling emergence and water infiltration✓
4. DThe genetic purity of seed✓

The hydrometer method estimates soil texture based on:

1. ALeaf chlorophyll content✓
2. BSedimentation rate of particles in suspension✓
3. CSeed germination speed only✓
4. DRoot nodulation count only✓

The soil textural triangle is used to determine:

1. ATextural class from sand, silt and clay percentages✓
2. BFertilizer brand from price✓
3. CCrop maturity group only✓
4. DSprayer nozzle color only✓

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

1. AContains no sand or silt at all✓
2. BIs always pure gravel✓
3. CCannot hold any water✓
4. DIs not as heavy-textured as clay✓

Good soil structure improves crop growth mainly by improving:

1. AWeed seed contamination only✓
2. BPesticide label color✓
3. CAeration, infiltration and root penetration✓
4. DMarket transportation✓

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

1. APermanent aggregation of all sand grains✓
2. BDispersion of clay particles✓
3. CFormation of humus only✓
4. DLower pH in all cases✓

Saline soils are primarily characterized by:

1. AHigh concentration of soluble salts✓
2. BNo electrical conductivity✓
3. COnly high exchangeable aluminum✓
4. DAbsence of all ions✓

Soil pH is a measure of soil:

1. ATexture class only✓
2. BParticle density only✓
3. COrganic residue color only✓
4. DAcidity or alkalinity✓

Compared with smectite, kaolinite generally has:

1. AGreater shrink-swell capacity always✓
2. BMore interlayer expansion✓
3. CLower cation exchange capacity✓
4. DNo clay-sized particles✓

Smectite clay minerals are known for:

1. ANo water adsorption at all✓
2. BHigh shrink-swell capacity✓
3. CBeing larger than gravel✓
4. DHaving zero surface area✓

Cation exchange capacity of soil is contributed mainly by:

1. AClay minerals and humus✓
2. BPure sand and gravel only✓
3. CAir-filled pores only✓
4. DCrop canopy height only✓

Humus is best described as:

1. AFresh unweathered rock✓
2. BPure sodium chloride✓
3. CA chemical herbicide group✓
4. DStable, well-decomposed organic matter in soil✓

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

1. ASeed certification✓
2. BPhotosynthesis in roots✓
3. CRaindrop impact or splash✓
4. DFertilizer bagging✓

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

1. AChange crop genetics✓
2. BMove through the soil✓
3. CBecome soil minerals instantly✓
4. DDestroy organic matter only✓

Infiltration is the process by which water:

1. AEnters the soil surface✓
2. BEvaporates from leaves only✓
3. CMoves through xylem only✓
4. DChanges into fertilizer✓

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

1. ASand and gravel content✓
2. BpH and EC only✓
3. CSlope and aspect only✓
4. DField capacity and permanent wilting point✓

Permanent wilting point is the water content at which plants:

1. AGrow at maximum rate✓
2. BDo not need irrigation forever✓
3. CCannot regain turgor even in a humid atmosphere✓
4. DProduce seed immediately✓

Field capacity is the soil water content after:

1. AThe soil is oven dried✓
2. BFree drainage of gravitational water has mostly ceased✓
3. CAll plant water has been depleted permanently✓
4. DOnly hygroscopic water remains✓

Soil consistence describes the soil's:

1. AResistance to deformation or rupture✓
2. BTax invoice number✓
3. CCrop variety name✓
4. DLatitude only✓

Gray or bluish gley colors in soil usually indicate:

1. AExcessive aeration always✓
2. BPure sand only✓
3. CComplete absence of water✓
4. DPoor drainage and reducing conditions✓

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

1. AFresh plant sap✓
2. BCalcium nitrate fertilizer✓
3. CIron oxides✓
4. DPure quartz only✓

In the Munsell system, soil color is described by:

1. ASand, silt and clay only✓
2. BHue, value and chroma✓
3. CNitrogen, phosphorus and potassium only✓
4. DSlope, aspect and altitude only✓

Illuviation means:

1. AAccumulation of transported material in a soil horizon✓
2. BLoss of seed viability during storage✓
3. CSpray drift from a nozzle✓
4. DDeep ploughing only✓

Eluviation is the process of:

1. AAddition of seed to a field✓
2. BMixing fertilizer in a bag✓
3. CHarvesting a crop early✓
4. DRemoval of material from a soil horizon✓

Podzolization is most closely associated with:

1. APermanent saltwater flooding only✓
2. BDesert pavement formation only✓
3. CAcid forest soils and translocation of humus, iron and aluminum✓
4. DPure calcium carbonate deposition only✓

Calcification is a soil-forming process involving accumulation of:

1. AFresh leaf litter only✓
2. BCalcium carbonate✓
3. CIron sulfide only✓
4. DGypsum boards✓

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

1. AIron and aluminum oxides✓
2. BFresh undecomposed straw only✓
3. CSodium chloride crystals only✓
4. DCalcium carbonate nodules only✓

Capillary water is water held in soil pores:

1. AOnly as water vapor above the crop canopy✓
2. BOnly in drainage canals✓
3. COnly as chemically combined crystal water✓
4. DAgainst gravity and available to varying degrees for plants✓

Soil porosity generally increases when:

1. ACompaction increases sharply✓
2. BAll pores are filled with cement✓
3. CAggregation and organic matter improve✓
4. DOnly gravel is removed from roads✓

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

1. AVolume of water only✓
2. BBulk volume including pore space✓
3. CRoot length only✓
4. DFertilizer bag weight✓

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

1. ARestrict water movement and root penetration✓
2. BIncrease all root growth instantly✓
3. CEliminate erosion completely✓
4. DTurn sand into clay✓

Granular soil structure is most commonly found in:

1. AFresh unweathered bedrock✓
2. BDeep compacted plough pans only✓
3. CPure salt crusts only✓
4. DSurface horizons rich in roots and organic matter✓

Soil structure refers to the:

1. AChemical formula of urea✓
2. BNumber of crops grown per year✓
3. CArrangement of primary particles into aggregates or peds✓
4. DLatitude of the farm✓

A loam soil is one that has:

1. AOnly clay and no sand✓
2. BA balanced mixture of sand, silt and clay✓
3. COnly gravel and stones✓
4. DOnly soluble salts✓

Compared with sandy soils, clayey soils generally have:

1. AHigher water-holding capacity and slower drainage✓
2. BLower nutrient retention in all cases✓
3. CNo pore space✓
4. DNo shrink-swell behavior ever✓

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

1. ASharp and gravelly✓
2. BExtremely sticky like clay✓
3. CWoody and fibrous✓
4. DSmooth or floury✓

Sandy soil usually feels:

1. ASticky and plastic only✓
2. BSilky like flour only✓
3. CGritty✓
4. DOily and waxy✓

In the USDA system, clay particles are smaller than:

1. A2.0 mm in diameter✓
2. B0.002 mm in diameter✓
3. C0.05 mm in diameter✓
4. D5.0 mm in diameter✓

Soil texture is determined by the relative proportion of:

1. ASand, silt and clay✓
2. BNitrogen, phosphorus and potassium✓
3. CRoots, stems and leaves✓
4. DPests, diseases and weeds✓

A soil profile is a:

1. AList of crop prices✓
2. BSprayer calibration chart✓
3. CSingle clay mineral particle✓
4. DVertical section of soil showing its horizons✓

The C horizon is usually composed of:

1. AOnly fresh leaves✓
2. BPloughed topsoil only✓
3. CPartly weathered parent material✓
4. DPure humus✓

The B horizon is commonly a zone of:

1. AFresh plant litter only✓
2. BIlluviation or accumulation of clay, iron, aluminum or humus✓
3. CUnweathered parent rock only✓
4. DPermanent snow only✓

The O horizon consists mainly of:

1. AOrganic litter and decomposing plant residues✓
2. BUnaltered hard bedrock✓
3. COnly soluble salts✓
4. DPure sand grains✓

The A horizon in a soil profile is generally the:

1. AUnweathered bedrock layer✓
2. BDeepest groundwater zone only✓
3. CPure calcium carbonate layer always✓
4. DMineral surface horizon enriched with organic matter✓

A pedon is best defined as:

1. AA single sand particle✓
2. BA fertilizer recommendation sheet✓
3. CThe smallest three-dimensional unit of soil used for study✓
4. DA soil insect larva✓

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

1. ASeed packaging color✓
2. BRelief, slope position and drainage✓
3. CSpray tank volume only✓
4. DHarvest date labels only✓

Residual parent material is material that has:

1. ABeen deposited only by glaciers✓
2. BWeathered in place from the underlying rock✓
3. CBeen transported only by rivers✓
4. DFormed only from sea water✓

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

1. ATime✓
2. BFertilizer✓
3. CTillage✓
4. DIrrigation✓

Clay soils generally have

1. Azero water retention✓
2. Bonly gravel behavior✓
3. Chigh water-holding capacity but may drain slowly✓
4. Dno cation exchange✓

Balanced fertilization means

1. Asupplying nutrients in ratios matching crop needs and soil tests✓
2. Bonly urea in maximum dose✓
3. Cignoring P and K always✓
4. Dapplying random micronutrients only✓

Deep tillage is sometimes used to

1. Abreak plow pans and improve rooting✓
2. Bincrease compaction deliberately✓
3. Cremove all OM✓
4. Draise water table✓

Soil fertility differs from soil productivity in that fertility refers to

1. Aonly rainfall✓
2. Bonly management ignoring nutrients✓
3. Cnutrient status/ability to supply nutrients, while productivity includes all growth factors✓
4. Didentical meanings always✓

Chlorosis is a symptom often linked to

1. Aexcess green pigment only✓
2. Bdeficiency of N, Fe, Mg or other factors reducing chlorophyll✓
3. Conly mechanical lodging✓
4. Donly wind erosion✓

Secondary nutrients include

1. AZn Fe Mn only✓
2. BN P K only✓
3. CB Mo Cl only✓
4. Dcalcium, magnesium and sulfur✓

Potassium fixation in some soils means

1. AK evaporates as gas✓
2. BK turns into N✓
3. CK becomes nitrate✓
4. DK becomes trapped in clay interlayers less available✓

Nitrous oxide emissions from soils increase with

1. Azero N inputs always✓
2. Bpermanent drought only✓
3. Cexcess N fertilizer and wet anaerobic microsites✓
4. Dpure sand with no N✓

The rhizosphere is

1. Aonly the plow layer without roots✓
2. Batmosphere above canopy✓
3. Cthe soil zone influenced by roots and root exudates✓
4. Dirrigation canal bed only✓

Aridisols / desert soils typically have

1. Athick O horizons like forests✓
2. Blow organic matter and may accumulate salts/carbonates✓
3. Ccontinuous waterlogging✓
4. Dhigh rainfall leaching always✓

Vertisols are noted for

1. Anever cracking✓
2. Bshrinking and swelling clay behavior✓
3. Cpure sand dunes✓
4. Dpermanent frost✓

Soil survey and mapping help to

1. Aignore spatial variability✓
2. Bapply one rate everywhere blindly✓
3. Cplan land use and management by soil types✓
4. Dreplace climate data✓

Trace element toxicity can occur from

1. Aindustrial contamination or over-application✓
2. Bbalanced micronutrient use only✓
3. Cpure rainwater irrigation only✓
4. Dorganic matter alone✓

Acid sulfate soils problems appear when

1. Alime is applied correctly✓
2. BpH rises to 8 naturally✓
3. Cgypsum remediates sodicity only✓
4. Dsulfides oxidize and generate sulfuric acidity✓

Carbon sequestration in soils increases when

1. Aall residues are burned✓
2. Borganic inputs rise and decomposition/erosion losses fall✓
3. Ctillage intensifies without cover✓
4. DOM is mined continuously✓

Soil health emphasizes

1. Aonly NPK bag counts✓
2. Bonly color charts✓
3. Cbiological, chemical and physical functioning together✓
4. Donly tractor horsepower✓

Band placement of phosphorus is useful because P

1. Aleaches as fast as nitrate always✓
2. Bis a gas✓
3. Cneeds no soil contact✓
4. Dis relatively immobile in soil✓

Split application of nitrogen is recommended to

1. Aapply all N before sowing only always✓
2. Bnever fertilize✓
3. Capply only at harvest✓
4. Dmatch crop demand and reduce losses✓

Nitrogen losses by volatilization are higher when

1. Aurea is deep placed in moist soil✓
2. Burea is surface-applied on alkaline soils without incorporation✓
3. Ctemperature is near freezing always✓
4. Dsoil is strongly acidic with incorporation✓

SAR (sodium adsorption ratio) of water indicates

1. Asodicity hazard of irrigation water✓
2. Bonly nitrate content✓
3. Conly BOD✓
4. Donly turbidity from clay alone✓

ESP (exchangeable sodium percentage) is used to diagnose

1. Aonly nitrogen status✓
2. Bsodicity hazard✓
3. Conly organic carbon✓
4. Donly sand %✓

Soil salinity management includes

1. Astopping all irrigation forever✓
2. Badding more NaCl✓
3. Csealing drains✓
4. Dadequate leaching fraction and drainage✓

Mycorrhizal fungi help plants mainly by

1. Afixing atmospheric N2 like Rhizobium always✓
2. Benhancing phosphorus and water uptake✓
3. Cproducing urea prills✓
4. Draising soil pH to 12✓

Critical nutrient concentration is

1. Atissue level below which yield declines✓
2. Bsoil bulk density threshold✓
3. CEC of irrigation water only✓
4. DpH of rain✓

Luxury consumption refers to

1. Astarvation of all nutrients✓
2. Bonly foliar feeding✓
3. Cuptake of a nutrient beyond amounts needed for yield✓
4. Donly hydroponics✓

Integrated nutrient management combines

1. Aonly urea forever✓
2. Borganic and inorganic nutrient sources judiciously✓
3. Conly FYM with zero mineral fertilizer always✓
4. Dno nutrient inputs✓

Sulfur deficiency symptoms often include

1. Aonly purple older leaves like P always✓
2. Bonly marginal burn of K only✓
3. Conly Zn rosetting exclusively✓
4. Dyellowing of younger leaves (mobile differently than N patterns vary)✓

Liming is used to

1. Areclaim sodic soils as the first choice always✓
2. Badd sodium✓
3. Craise pH of acidic soils✓
4. Dlower pH of alkaline soils✓

Available water capacity is greater in

1. Apure gravel always✓
2. Bmedium-textured soils with good structure than in coarse sands✓
3. Csolid rock✓
4. Dcompacted clay with no pores✓

Permanent wilting point is when

1. Asoil is at saturation✓
2. Bsoil is oven dry necessarily✓
3. Cplants can no longer extract sufficient water and wilt permanently✓
4. DEC is zero✓

Field capacity is the

1. Apermanent wilting point✓
2. Bsaturation with zero air✓
3. Cwater content after excess water has drained by gravity✓
4. Doven-dry state✓

Compaction of soil reduces

1. Abulk density✓
2. Broot penetration, infiltration and aeration✓
3. Cstrength of plow pan always beneficially✓
4. Dneed for any tillage forever✓

Wind erosion is a major risk in

1. Adense humid forests only✓
2. Bcontinuously flooded paddies✓
3. Carid sandy regions with sparse cover✓
4. Dglacial ice fields✓

Soil erosion by water is reduced by

1. Aclean tillage up and down slopes✓
2. Bremoving all vegetation✓
3. Cmaximizing bare fallow on slopes✓
4. Dcover crops, residue retention and contour practices✓

Calcareous soils contain

1. Aonly pure silica sand✓
2. Bzero carbonates✓
3. Ccalcium carbonate that can raise pH and affect micronutrients✓
4. Donly sodium chloride crystals✓

Alluvial soils of the Indus plains are generally

1. Auseless for crops✓
2. Bdeep and agriculturally important though often calcareous✓
3. Conly volcanic ash✓
4. Donly peat bogs✓

Parent material influences soil by affecting

1. Aonly current market prices✓
2. Bonly farmer education✓
3. Cmineralogy, texture and inherent fertility✓
4. Donly tractor brand✓

The topsoil (A horizon) is generally

1. Apure parent rock✓
2. Brichest in organic matter and biological activity✓
3. Conly groundwater✓
4. Dsterile mineral without life✓

Soil testing is done to

1. Areplace the need for any nutrients forever✓
2. Bguide fertilizer and amendment recommendations✓
3. Cmeasure only air temperature✓
4. Dcount insects only✓

Iron chlorosis in orchards often appears on

1. Ahigh pH calcareous soils✓
2. Bstrongly acidic soils with excess Fe✓
3. Cflooded acid sulfate only✓
4. Dorganic soils with Fe toxicity always✓

Zinc deficiency is common in Pakistani soils especially on

1. Astrongly acidic forest floors only✓
2. Bpeat soils exclusively✓
3. Cpure quartz sand with OM 20%✓
4. Dalkaline calcareous soils✓

Micronutrients include

1. AZn, Fe, Mn, Cu, B, Mo, Cl✓
2. BN, P, K only✓
3. CC, H, O only✓
4. DCa, Mg, S only as micros✓

Humus is

1. Afresh undecomposed straw only✓
2. Brelatively stable, dark organic matter in soil✓
3. Cpure mineral clay✓
4. Dfertilizer prill coating only✓

Soil organic matter benefits include

1. Aincreasing bulk density always✓
2. Beliminating all microbes✓
3. Cimproved structure, water holding and nutrient supply✓
4. Draising EC permanently✓

Denitrification under anaerobic conditions converts nitrate to

1. Agaseous N forms (N2/N2O) lost to atmosphere✓
2. Bplant protein directly✓
3. Crock phosphate✓
4. Delemental sulfur crystals✓

Nitrification converts

1. Aammonium to nitrate✓
2. Bnitrate to N2 gas only✓
3. Corganic C to CH4 only✓
4. Dphosphate to PH3✓

Biological nitrogen fixation is performed notably by

1. Aonly nitrifying bacteria making N2✓
2. BRhizobium in legume nodules✓
3. Cdenitrifiers creating urea bags✓
4. Dalgae making rock phosphate✓

Green manuring involves

1. Aburning all residues always✓
2. Bgrowing and incorporating leguminous or other plants to enrich soil✓
3. Cremoving all organic matter✓
4. Dapplying only NaCl✓

Farmyard manure improves soil mainly by adding

1. Apure sodium chloride✓
2. Bplastic residues as fertilizer✓
3. Conly sand particles✓
4. Dorganic matter and some nutrients✓

SOP and MOP are sources of

1. Aonly nitrogen✓
2. Bpotassium✓
3. Conly phosphorus✓
4. Donly calcium✓

DAP (diammonium phosphate) mainly supplies

1. Aonly potassium✓
2. Bonly sulfur✓
3. Conly boron✓
4. Dnitrogen and phosphorus✓

Urea fertilizer supplies

1. Aphosphorus only✓
2. Bpotassium only✓
3. Czinc only✓
4. Dnitrogen✓

Potassium helps plants with

1. Aforming chlorophyll as the central atom✓
2. BN2 fixation enzyme alone✓
3. CDNA base pairing exclusively✓
4. Dstomatal regulation, disease tolerance and grain quality✓

Phosphorus is critical for

1. Aenergy transfer (ATP) and early root development✓
2. Bonly leaf green color exclusively✓
3. Conly stomatal opening of K alone✓
4. Donly micronutrient chelation of Fe alone✓

Nitrogen in plants is especially needed for

1. Aonly cell wall silica✓
2. Bonly fat storage exclusively✓
3. Conly root suberin✓
4. Dproteins, chlorophyll and vegetative growth✓

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

1. Asalinity level✓
2. Bonly organic matter✓
3. Conly texture✓
4. Donly color✓

Gypsum is commonly used to reclaim

1. Asodic soils✓
2. Bpure sandy deserts overnight without water✓
3. Cpeat bogs only✓
4. Dacid sulfate soils exclusively✓

Sodic soils are problematic mainly due to

1. Aexcess exchangeable sodium dispersing clay and degrading structure✓
2. Bexcess calcium carbonate always improving tilth✓
3. Clack of any sodium✓
4. Dtoo much gypsum naturally everywhere✓

Saline soils are characterized by

1. Azero electrical conductivity✓
2. Bonly organic toxicity✓
3. Cabsence of Na and Cl✓
4. Dhigh soluble salt content that reduces water uptake✓

Most crops grow best in soils that are

1. Aextremely acidic pH 2 always✓
2. BpH 12 always✓
3. Cwithout any pH relevance✓
4. Dnear neutral to slightly acidic/alkaline depending on species✓

Soil pH indicates

1. Aacidity or alkalinity of the soil✓
2. Bonly moisture content✓
3. Conly texture class✓
4. Donly organic carbon alone✓

Cation exchange capacity (CEC) measures

1. Asoil's ability to hold and exchange positively charged nutrients✓
2. Bonly anion leaching rate✓
3. Csand percentage✓
4. Dsoil temperature✓

Soil porosity is important because pores hold

1. Aonly solid minerals✓
2. Bonly pure metal✓
3. Cair and water needed by roots✓
4. Donly plastic mulch✓

Bulk density is

1. Avolume of pores only✓
2. Bsoil color index✓
3. Cfertilizer grade✓
4. Dmass of dry soil per unit bulk volume✓

Soil structure describes

1. Aonly particle size percentages✓
2. Barrangement of soil particles into aggregates✓
3. Conly pH value✓
4. Donly EC reading✓

Loam soils are valued because they

1. Abalance drainage, aeration and water/nutrient retention✓
2. Bare pure clay only✓
3. Care pure sand only✓
4. Dcontain no silt✓

Sandy soils typically

1. Adrain rapidly and hold fewer nutrients✓
2. Balways waterlog permanently✓
3. Chave the highest CEC always✓
4. Dnever need irrigation✓

Soil is best described as

1. Aa natural body of minerals, organic matter, water and air supporting plants✓
2. Bpure solid rock only✓
3. Conly liquid water✓
4. Donly atmospheric gases✓

The mineral portion of soil is derived mainly from

1. Aphotosynthesis alone✓
2. Brainfall nitrogen only✓
3. Cweathering of parent rock and sediments✓
4. Dtractor exhaust✓

Soil texture refers to

1. Asoil color only✓
2. Borganic matter percentage only✓
3. Crelative proportions of sand, silt and clay✓
4. Dbulk density alone✓