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Maharashtra HSC Crop Science (Bifocal B4) study materials
Maharashtra HSC Crop Science (Bifocal B4) study resources

Maharashtra HSC Crop Science (Bifocal B4) practice questions

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Question 1Introduction to Crop Science and Crop Classification

Which branch of agriculture deals with the scientific study of crops and their improvement for human use?

  1. Apiculture
  2. Sericulture
  3. Horticulture
  4. Agronomy Correct answer.

Explanation

Agronomy is the branch of agricultural science concerned with field crops, their cultivation, management and improvement. Horticulture deals with garden crops such as fruits and vegetables, while sericulture and apiculture are allied activities involving silkworms and honeybees respectively.

Question 2Introduction to Crop Science and Crop Classification

In the binomial system of nomenclature followed for crop plants, the name Oryza sativa denotes which crop?

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

Explanation

Oryza sativa is the scientific name of cultivated Asian rice, where Oryza is the genus and sativa the species epithet. Wheat belongs to the genus Triticum, maize to Zea and sorghum to Sorghum, so none of them matches the given binomial.

Question 3Introduction to Crop Science and Crop Classification

A crop that completes its life cycle within a single growing season and must be re-sown each year is best described as which type?

  1. Ephemeral
  2. Perennial
  3. Biennial
  4. Annual Correct answer.

Explanation

Annual crops germinate, flower, set seed and die within one season, so the next crop must be raised from fresh seed. Biennials need two seasons and perennials persist for several years, which does not match the description given.

Question 4Introduction to Crop Science and Crop Classification

Crops grown primarily for their edible seeds belonging to the grass family, such as wheat, rice and maize, are grouped together as which class?

  1. Fibre crops
  2. Pulses
  3. Oilseeds
  4. Cereals Correct answer.

Explanation

Cereals are grasses cultivated for their starchy grains, which form the staple food of most populations. Pulses are leguminous seed crops, oilseeds are grown for edible or industrial oil, and fibre crops are grown for textile or cordage fibre.

Question 5Introduction to Crop Science and Crop Classification

Which of the following is a kharif season crop normally sown with the onset of the south-west monsoon in Maharashtra?

  1. Cotton Correct answer.
  2. Mustard
  3. Wheat
  4. Chickpea

Explanation

Kharif crops are sown at the beginning of the monsoon and harvested in autumn, and cotton is a typical kharif crop of the Deccan region. Chickpea, wheat and mustard are rabi crops grown on residual moisture in the cooler post-monsoon season.

Question 6Introduction to Crop Science and Crop Classification

A grower wants to classify a crop according to the part of the plant harvested. Groundnut and mustard would fall into which group on this basis?

  1. Tuber crops
  2. Oilseed crops Correct answer.
  3. Forage crops
  4. Root crops

Explanation

Classification by economic produce places crops in groups such as cereals, pulses, oilseeds and fibres according to the harvested part or product. Groundnut and mustard are grown for their oil-bearing seeds, so they belong to the oilseed group rather than root, tuber or forage groups.

Question 7Introduction to Crop Science and Crop Classification

Which pair correctly matches a crop with the plant family to which it belongs?

  1. Cotton and Malvaceae Correct answer.
  2. Mustard and Solanaceae
  3. Rice and Fabaceae
  4. Chickpea and Poaceae

Explanation

Cotton (Gossypium) belongs to the family Malvaceae, so that pairing is botanically correct. Chickpea is a legume of Fabaceae, rice is a grass of Poaceae, and mustard belongs to Brassicaceae, which makes the other pairings incorrect.

Question 8Introduction to Crop Science and Crop Classification

A crop scientist describes a plant as having a C4 photosynthetic pathway. Which crop below is the most appropriate example of such a plant?

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

Explanation

Sugarcane is a well-known C4 grass that fixes carbon dioxide through the Hatch-Slack pathway, giving high photosynthetic efficiency in hot climates. Rice, wheat and soybean are C3 plants that use the Calvin cycle and are generally less efficient under high temperature.

Question 9Introduction to Crop Science and Crop Classification

Which statement best explains why pulses are valued in a crop rotation with cereals?

  1. They deplete soil nitrogen faster than cereals and require heavy urea
  2. They suppress all weeds by releasing root exudates
  3. They grow only in sandy soils where cereals cannot survive
  4. They add nitrogen to the soil through symbiotic rhizobia in root nodules Correct answer.

Explanation

Pulses form a symbiosis with Rhizobium bacteria in root nodules, which fix atmospheric nitrogen and leave part of it in the soil for the following crop. This biological nitrogen contribution is the main reason pulses are placed in rotation with nitrogen-demanding cereals.

Question 10Introduction to Crop Science and Crop Classification

A farmer keeps a field free of cultivation for one season to restore fertility and moisture. This practice is termed which kind of cropping?

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

Explanation

Fallow cropping deliberately leaves the land uncropped for a season so that soil fertility, organic matter and moisture can be restored. Mixed and intercropping involve growing two or more crops together, and relay cropping overlaps the sowing of a second crop before the first is harvested.

Question 11Introduction to Crop Science and Crop Classification

Which of the following crops is best classified as a plantation crop in the Indian context?

  1. Lentil
  2. Bajra
  3. Tea Correct answer.
  4. Jowar

Explanation

Plantation crops are perennial crops grown on large estates and usually processed at or near the field, with tea being a classic example. Bajra and jowar are annual cereal staples, and lentil is an annual pulse, so they do not fit the plantation category.

Question 12Introduction to Crop Science and Crop Classification

A crop is described as having a short duration, a dense canopy and the ability to smother weeds when grown between rows of a main crop. This describes its role as which type of crop?

  1. Border crop
  2. Trap crop
  3. Cover crop Correct answer.
  4. Catch crop

Explanation

A cover crop is grown to protect the soil surface, reduce erosion and suppress weeds through dense ground cover. Trap crops attract pests away from the main crop, catch crops use residual moisture in a short window, and border crops are planted around field edges.

Question 13Introduction to Crop Science and Crop Classification

Which of these crops is grown chiefly for its underground modified stem rather than for a true root?

  1. Potato Correct answer.
  2. Carrot
  3. Radish
  4. Sweet potato

Explanation

The potato tuber is a swollen underground stem bearing eyes or buds, which is why it is botanically a stem tuber. Sweet potato is a swollen root, and carrot and radish are true taproots, so they do not fit the description.

Question 14Introduction to Crop Science and Crop Classification

In crop classification, crops such as sunhemp and dhaincha are grouped as green manure crops mainly because they are

  1. Used as ornamental plants in gardens
  2. Harvested for grain and sold in the market
  3. Grown only for livestock grazing
  4. Ploughed into the soil while still green to enrich organic matter Correct answer.

Explanation

Green manure crops are raised specifically to be incorporated into the soil in the vegetative stage, adding organic matter and, in legumes, nitrogen. They are not harvested for grain, grazing or ornamental use, which distinguishes them from other crop groups.

Question 15Introduction to Crop Science and Crop Classification

A crop grown in a region receives irrigation only from stored rainwater collected in a farm pond, with no canal or well supply. Under the standard classification of agriculture, this practice belongs to which category?

  1. Protected cultivation
  2. Hydroponics
  3. Rainfed or dryland farming Correct answer.
  4. Irrigated farming

Explanation

When crop water needs are met from conserved rainfall rather than from canals, wells or other assured sources, the practice falls under rainfed or dryland farming. Irrigated farming depends on assured water supply, while protected cultivation and hydroponics are entirely different production systems.

Question 16Introduction to Crop Science and Crop Classification

Two crops are sown in separate rows in the same field in the same season, with row proportions such as 2:1. This system is best described as which of the following?

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

Explanation

Intercropping is the growing of two or more crops simultaneously in the same field in definite row proportions, which spreads risk and uses resources more efficiently. Sequence cropping is growing crops one after another, monocropping is a single crop, and fallow cropping leaves land uncropped.

Question 17Soil Science and Soil Fertility Management

Which soil particle size fraction, according to the International (Atterberg) system used in Indian soil science, has a diameter range of 0.002 to 0.02 mm?

  1. Fine sand
  2. Silt Correct answer.
  3. Clay
  4. Coarse sand

Explanation

In the International system, silt is defined as particles between 0.002 mm and 0.02 mm. Clay is below 0.002 mm, while fine sand spans 0.02 to 0.2 mm and coarse sand 0.2 to 2.0 mm.

Question 18Soil Science and Soil Fertility Management

A soil sample contains 30% clay, 20% silt and 50% sand. Using the standard textural triangle, into which class does this soil fall?

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

Explanation

With 50% sand, 30% clay and 20% silt, the plotted point lies in the sandy clay loam class, which requires roughly 20-35% clay and more than 45% sand with limited silt. Loam needs far more silt, and clay loam needs over 27% clay with less sand.

Question 19Soil Science and Soil Fertility Management

Which soil structure type is most favourable for root penetration and aeration in black cotton soils of Maharashtra?

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

Explanation

Granular (crumb) structure creates small rounded aggregates with abundant pore space, favouring root growth, aeration and drainage. Single grain, platy and massive structures either lack aggregation or compact the profile, restricting air and water movement.

Question 20Soil Science and Soil Fertility Management

A farmer's field shows a compacted layer with very low infiltration. Which structural problem most directly explains reduced water entry?

  1. Higher organic matter content
  2. Increased macroporosity
  3. Presence of granular aggregates
  4. Formation of a plough pan Correct answer.

Explanation

Repeated tillage at a constant depth forms a dense plough pan with few continuous pores, sharply reducing infiltration and root penetration. Macroporosity, organic matter and granular aggregation all improve rather than restrict water entry.

Question 21Soil Science and Soil Fertility Management

Which soil water potential component represents the attraction of water molecules to soil particle surfaces and to ions?

  1. Osmotic potential
  2. Matric potential Correct answer.
  3. Gravitational potential
  4. Pressure potential

Explanation

Matric potential arises from adsorption of water onto particle surfaces and capillary forces within micropores. Osmotic potential results from dissolved solutes, pressure potential from hydrostatic pressure, and gravitational potential from elevation.

Question 22Soil Science and Soil Fertility Management

A soil has field capacity of 28% and permanent wilting point of 12% on a weight basis, with a bulk density of 1.4 g/cm3. What is the available water capacity in the top 15 cm layer, in mm?

  1. 16.8 mm
  2. 11.2 mm
  3. 33.6 mm Correct answer.
  4. 22.4 mm

Explanation

Available water on a weight basis is 28 - 12 = 16%, i.e. 0.16 g/g. Multiply by bulk density (1.4) and depth (15 cm = 150 mm): 0.16 x 1.4 x 150 = 33.6 mm.

Question 23Soil Science and Soil Fertility Management

Which soil moisture constant is measured after a soil is saturated and then allowed to drain freely under gravity for 2-3 days?

  1. Hygroscopic coefficient
  2. Permanent wilting point
  3. Field capacity Correct answer.
  4. Saturation percentage

Explanation

Field capacity is the water retained after gravitational water has drained from a saturated soil, typically reached in 2-3 days. Saturation percentage is the fully waterlogged state, and the hygroscopic coefficient refers to air-dry moisture held very tightly.

Question 24Soil Science and Soil Fertility Management

Which soil colloid is described as a 2:1 expanding lattice mineral with high shrink-swell capacity and high cation exchange capacity?

  1. Kaolinite
  2. Illite
  3. Iron oxide
  4. Montmorillonite Correct answer.

Explanation

Montmorillonite is a 2:1 expanding lattice clay with a large internal surface, giving high CEC and pronounced swelling on wetting. Kaolinite is 1:1 non-expanding, illite is 2:1 non-expanding, and iron oxide has little CEC.

Question 25Soil Science and Soil Fertility Management

Which cation, when dominant on the exchange complex, causes dispersion of clay and poor soil structure?

  1. Magnesium
  2. Sodium Correct answer.
  3. Calcium
  4. Aluminium

Explanation

Sodium is a highly hydrated, weakly held cation that disperses clay particles and destroys aggregates, producing sodic soils with poor infiltration. Calcium and magnesium flocculate clays and stabilise structure.

Question 26Soil Science and Soil Fertility Management

Cation exchange capacity is conventionally expressed in which unit?

  1. kg per hectare
  2. dS per m of soil
  3. cmol(p+) per kg of soil Correct answer.
  4. mg per kg of soil

Explanation

CEC is expressed as centimoles of charge per kilogram of soil, written cmol(p+)/kg (formerly meq/100 g). The other units describe nutrient mass, electrical conductivity or field application rates, not exchange capacity.

Question 27Soil Science and Soil Fertility Management

A soil has a CEC of 20 cmol(p+)/kg and 60% base saturation. What is the approximate exchangeable base content?

  1. 20 cmol(p+)/kg
  2. 32 cmol(p+)/kg
  3. 8 cmol(p+)/kg
  4. 12 cmol(p+)/kg Correct answer.

Explanation

Exchangeable bases equal CEC multiplied by base saturation: 20 x 0.60 = 12 cmol(p+)/kg. The remaining 8 cmol(p+)/kg represents exchangeable acidity.

Question 28Soil Science and Soil Fertility Management

Which soil reaction range is generally considered most favourable for availability of most plant nutrients in mineral soils?

  1. pH 4.0 to 4.5
  2. pH above 9.0
  3. pH 7.5 to 8.5
  4. pH 6.0 to 7.0 Correct answer.

Explanation

A pH near 6.0-7.0 balances nutrient solubility: phosphorus, nitrogen and micronutrients are reasonably available while aluminium toxicity is minimal. Strongly acidic and strongly alkaline ranges reduce availability of several nutrients.

Question 29Soil Science and Soil Fertility Management

A farmer applies elemental sulphur to an alkaline calcareous soil. By which process does this amendment lower soil pH?

  1. Volatilisation of sulphur dioxide
  2. Microbial oxidation of sulphur to sulphuric acid Correct answer.
  3. Exchange of sodium by calcium
  4. Direct neutralisation of carbonate by sulphate

Explanation

Sulphur-oxidising bacteria convert elemental sulphur to sulphuric acid, which neutralises carbonates and lowers pH. Sulphate itself does not neutralise carbonate, and sodium exchange or volatilisation do not acidify the soil.

Question 30Soil Science and Soil Fertility Management

Which reclamation measure is most appropriate for a sodic soil with high exchangeable sodium percentage and poor infiltration?

  1. Flooding with saline water and drying
  2. Applying gypsum followed by leaching with good-quality water Correct answer.
  3. Deep ploughing without any amendment
  4. Adding common salt to the surface

Explanation

Gypsum supplies calcium, which replaces exchangeable sodium on the clay complex; the displaced sodium is then removed by leaching with good-quality water. Adding salt or saline water worsens the sodic condition, and ploughing alone cannot remove sodium.

Question 31Soil Science and Soil Fertility Management

A soil has an electrical conductivity of 5 dS/m, an exchangeable sodium percentage of 8 and a pH of 8.1. Into which class does it fall?

  1. Sodic soil
  2. Saline-sodic soil
  3. Saline soil Correct answer.
  4. Normal soil

Explanation

Saline soils have EC above 4 dS/m with ESP below 15 and pH usually below 8.5, which matches this sample. Sodic soils show high ESP, and saline-sodic soils combine both high EC and high ESP.

Question 32Soil Science and Soil Fertility Management

Which essential plant nutrient is classified as a primary macronutrient in Indian fertilizer recommendations?

  1. Potassium Correct answer.
  2. Iron
  3. Boron
  4. Zinc

Explanation

Potassium is one of the three primary macronutrients, along with nitrogen and phosphorus. Zinc, boron and iron are micronutrients required in much smaller quantities.

Question 33Soil Science and Soil Fertility Management

Which deficiency symptom is most characteristic of nitrogen deficiency in a growing cereal crop?

  1. Interveinal chlorosis of young leaves
  2. Purple colouration of older leaves
  3. White necrotic spots on young leaves
  4. General yellowing starting from older leaves Correct answer.

Explanation

Nitrogen is mobile in the plant, so deficiency causes general chlorosis beginning in older leaves as nitrogen is remobilised to growing points. Purple older leaves indicate phosphorus deficiency, and interveinal chlorosis of young leaves suggests iron or zinc shortage.

Question 34Soil Science and Soil Fertility Management

Urea contains about 46% nitrogen. How much urea is needed to supply 92 kg N per hectare?

  1. 200 kg Correct answer.
  2. 150 kg
  3. 46 kg
  4. 92 kg

Explanation

Urea required equals nitrogen needed divided by the fraction of N: 92 / 0.46 = 200 kg per hectare. The other values either supply too little nitrogen or ignore the 46% concentration.

Question 35Soil Science and Soil Fertility Management

Which fertilizer is correctly matched with its nutrient content?

  1. Urea - about 20% N
  2. Muriate of potash - about 60% K2O Correct answer.
  3. Single superphosphate - about 46% P2O5
  4. Diammonium phosphate - about 46% N and 0% P2O5

Explanation

Muriate of potash (potassium chloride) contains about 60% K2O. Single superphosphate carries about 16% P2O5, DAP about 18% N and 46% P2O5, and urea about 46% N.

Question 36Soil Science and Soil Fertility Management

Why is urea usually incorporated into the soil rather than left on the surface in warm, moist conditions?

  1. Ammonia formed by hydrolysis can volatilise and be lost Correct answer.
  2. It is fixed rapidly by clay minerals
  3. It leaches completely within hours of application
  4. It is converted to nitrate before dissolving

Explanation

Urease hydrolyses surface-applied urea to ammonium carbonate, and in warm moist conditions ammonia can escape to the atmosphere, especially on alkaline soils. Incorporation places urea where hydrolysis products are retained on the exchange complex.

Question 37Soil Science and Soil Fertility Management

In the nitrogen cycle, which process converts ammonium to nitrate and is carried out by Nitrosomonas and Nitrobacter?

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

Explanation

Nitrification is the two-step microbial oxidation of ammonium to nitrite and then nitrate. Ammonification releases ammonium from organic matter, denitrification reduces nitrate to gaseous nitrogen, and fixation converts atmospheric nitrogen into combined forms.

Question 38Soil Science and Soil Fertility Management

A paddy field kept continuously submerged shows substantial gaseous nitrogen loss. Which process best explains this loss?

  1. Leaching of nitrate through the puddled layer
  2. Direct volatilisation of ammonium from the flooded surface
  3. Nitrification in the aerobic surface layer followed by denitrification in the reduced subsoil Correct answer.
  4. Fixation of ammonium by expanding clay minerals

Explanation

In flooded paddies an oxidised surface layer supports nitrification, and the nitrate formed diffuses into the reduced layer where denitrification converts it to N2 and N2O. This coupled pathway causes large gaseous losses in submerged soils.

Question 39Soil Science and Soil Fertility Management

Which practice is the most direct way to build soil organic matter and improve fertility in a rainfed field?

  1. Applying only inorganic nitrogen fertilizer
  2. Repeated deep ploughing and leaving soil bare
  3. Burning crop residues after harvest
  4. Incorporating well-decomposed farmyard manure Correct answer.

Explanation

Adding well-decomposed farmyard manure supplies organic carbon and nutrients, improving aggregation, water holding and biological activity. Burning residues, bare fallow and sole inorganic nitrogen deplete or fail to build organic matter.

Question 40Soil Science and Soil Fertility Management

In a long-term field trial, continuous application of ammonium sulphate without lime has markedly acidified the soil. Which mechanism best explains this acidification?

  1. Ammonium is fixed irreversibly by clay and releases acid
  2. The fertilizer adds calcium carbonate that reacts with water
  3. Nitrification of ammonium releases hydrogen ions and the sulphate residue leaves no base to neutralise them Correct answer.
  4. Sulphate ions directly replace hydroxyl ions in the soil solution

Explanation

Nitrification of ammonium produces hydrogen ions, and because sulphate is a non-basic anion, the soil's base reserves are depleted over time, lowering pH. This acidifying effect is characteristic of ammonium-based fertilizers.

Question 41Plant Nutrition, Manures and Fertilizers

Which essential nutrient is absorbed by plants mainly as the divalent cation Mg²⁺ and forms the central atom of the chlorophyll molecule?

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

Explanation

Magnesium is taken up as Mg²⁺ and occupies the centre of the porphyrin ring of every chlorophyll molecule, so its deficiency produces interveinal chlorosis in older leaves. Calcium and boron are not constituents of chlorophyll, and sulphur is absorbed as sulphate and used in proteins.

Question 42Plant Nutrition, Manures and Fertilizers

A soil test reports 0.4 per cent organic carbon. Using the standard conversion factor, what is the approximate organic matter content of this soil?

  1. 0.23 per cent
  2. 1.72 per cent
  3. 0.69 per cent Correct answer.
  4. 0.40 per cent

Explanation

Organic matter is conventionally estimated by multiplying organic carbon by the Van Bemmelen factor of 1.724, because humus contains roughly 58 per cent carbon. Hence 0.4 × 1.724 gives about 0.69 per cent organic matter.

Question 43Plant Nutrition, Manures and Fertilizers

Which fertilizer is correctly described as a straight nitrogenous fertilizer containing about 46 per cent N?

  1. Ammonium sulphate
  2. Single superphosphate
  3. Urea Correct answer.
  4. Muriate of potash

Explanation

Urea, CO(NH₂)₂, is the most concentrated solid straight nitrogen fertilizer, carrying about 46 per cent nitrogen. Superphosphate supplies phosphorus, muriate of potash supplies potassium, and ammonium sulphate, though nitrogenous, carries only about 20 to 21 per cent N.

Question 44Plant Nutrition, Manures and Fertilizers

In the nitrogen cycle, the conversion of ammonium to nitrate by Nitrosomonas and Nitrobacter is termed

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

Explanation

Nitrification is the two-step microbial oxidation of ammonium to nitrite and then to nitrate, carried out by Nitrosomonas and Nitrobacter respectively. The other processes release ammonium from organic matter, reduce nitrate to nitrogen gas, or convert atmospheric nitrogen into combined forms.

Question 45Plant Nutrition, Manures and Fertilizers

Which group of organisms is chiefly responsible for converting atmospheric nitrogen into combined forms in the root nodules of legumes?

  1. Nitrosomonas
  2. Azotobacter
  3. Mycorrhiza
  4. Rhizobium Correct answer.

Explanation

Rhizobium bacteria enter legume roots, form nodules, and reduce atmospheric nitrogen to ammonia using nitrogenase, supplying combined nitrogen to the host. Azotobacter fixes nitrogen but is free-living in soil, whereas Nitrosomonas nitrifies and mycorrhiza mainly aids nutrient uptake.

Question 46Plant Nutrition, Manures and Fertilizers

Farmyard manure is best classified as which type of organic input?

  1. Biofertilizer
  2. Bulky organic manure Correct answer.
  3. Complex chemical fertilizer
  4. Concentrated organic manure

Explanation

Farmyard manure is a bulky organic manure because it is applied in large quantities and is low in nutrient concentration, though it improves soil physical condition. Concentrated organic manures such as oil cakes and biofertilizers such as Rhizobium cultures are quite different in nature.

Question 47Plant Nutrition, Manures and Fertilizers

Which of the following is a micronutrient essential for plants and normally supplied through soil application of borax?

  1. Calcium
  2. Potassium
  3. Nitrogen
  4. Boron Correct answer.

Explanation

Boron is a micronutrient required in very small amounts, and borax (sodium tetraborate) is a common carrier used to supply it. Nitrogen, potassium and calcium are macronutrients needed in much larger quantities.

Question 48Plant Nutrition, Manures and Fertilizers

A grower applies 100 kg of urea to one hectare. Approximately how much nitrogen does this supply?

  1. 60 kg N
  2. 100 kg N
  3. 20 kg N
  4. 46 kg N Correct answer.

Explanation

Urea contains about 46 per cent nitrogen, so 100 kg of urea supplies roughly 46 kg of actual nitrogen. The remaining mass is largely carbon, oxygen and hydrogen in the urea molecule.

Question 49Plant Nutrition, Manures and Fertilizers

In fertilizer grade notation such as 10:26:26, the three figures represent the percentages of

  1. N, S and K₂O
  2. N, P₂O₅ and K₂O Correct answer.
  3. N, CaO and MgO
  4. N, P and K in elemental form

Explanation

Fertilizer grades are always expressed as nitrogen, available phosphorus as phosphorus pentoxide, and potassium as potassium oxide. Elemental phosphorus and potassium values are lower because the oxide forms are heavier.

Question 50Plant Nutrition, Manures and Fertilizers

Which fertilizer is distinctly acidic in its residual effect on soil and is therefore used on alkaline soils?

  1. Diammonium phosphate
  2. Calcium ammonium nitrate
  3. Ammonium sulphate Correct answer.
  4. Basic slag

Explanation

Ammonium sulphate leaves an acidifying residue because the ammonium is nitrified and the sulphate remains with hydrogen ions, so it suits alkaline soils. Calcium ammonium nitrate is neutral and basic slag is alkaline in reaction.