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UPMSP Intermediate Agronomy study materials
UPMSP Intermediate Agronomy study resources

UPMSP Intermediate Agronomy practice questions

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Question 1Agronomy Fundamentals, Cropping Systems and Farming Types

In the classification of cropping systems, which term describes growing two or more crops simultaneously in the same field in distinct rows or strips?

  1. Mixed cropping
  2. Sequence cropping
  3. Sole cropping
  4. Intercropping Correct answer.

Explanation

Intercropping places two or more crops together in the same season but in separate rows or strips, so each crop keeps its own planting geometry. Mixed cropping differs because the seeds are broadcast together without a row arrangement. Sequence cropping involves crops following one another in time rather than sharing the field simultaneously.

Question 2Agronomy Fundamentals, Cropping Systems and Farming Types

A farmer harvests rice in kharif and then raises chickpea on the same land in rabi using residual soil moisture. This practice is best described as:

  1. Alley cropping
  2. Strip cropping
  3. Double cropping Correct answer.
  4. Relay cropping

Explanation

Double cropping means raising two crops in sequence on the same field within one agricultural year, which matches rice followed by chickpea. Relay cropping would require the second crop to be sown into the standing first crop before harvest. Alley and strip cropping are spatial arrangements, not seasonal sequences.

Question 3Agronomy Fundamentals, Cropping Systems and Farming Types

Which cropping intensity value results when a farmer grows three crops on one hectare in a single year?

  1. 200 per cent
  2. 300 per cent Correct answer.
  3. 400 per cent
  4. 100 per cent

Explanation

Cropping intensity is the total cropped area expressed as a percentage of the net sown area. Three crops on one hectare give a cropped area of three hectares against a net sown area of one hectare, so intensity is 300 per cent. Each additional crop in the year adds 100 percentage points.

Question 4Agronomy Fundamentals, Cropping Systems and Farming Types

Which of the following is a characteristic feature of plantation agriculture?

  1. Large estates raise a single cash crop for processing and export Correct answer.
  2. Fields are shifted every two years to restore fertility
  3. Crops are grown mainly for household consumption
  4. Livestock rearing is combined with subsistence grain growing

Explanation

Plantation agriculture is capital-intensive estate farming that concentrates on one or a few perennial cash crops such as tea, rubber or sugarcane, grown for processing and sale rather than home use. It requires large holdings, hired labour and good transport links to markets or factories.

Question 5Agronomy Fundamentals, Cropping Systems and Farming Types

In a crop rotation, which group of crops is grown primarily to restore soil nitrogen for the following cereal?

  1. Fibre crops such as jute and cotton
  2. Fodder maize and sorghum
  3. Legumes such as gram and lentil Correct answer.
  4. Oilseeds such as mustard and linseed

Explanation

Legumes host Rhizobium in root nodules, which fixes atmospheric nitrogen and enriches the soil for the next crop. Including a legume in the rotation therefore reduces the nitrogen requirement of the succeeding cereal. Non-legume groups do not add nitrogen and usually deplete it.

Question 6Agronomy Fundamentals, Cropping Systems and Farming Types

Which soil-and-water practice is designed specifically to conserve moisture in the root zone of a rainfed crop by breaking capillary continuity at the surface?

  1. Summer ploughing
  2. Dust mulching Correct answer.
  3. Broad bed furrowing
  4. Contour bunding

Explanation

Dust mulching creates a loose, dry surface layer that breaks the continuous capillary pores through which water rises and evaporates. This surface barrier reduces evaporation loss from the moist layer below. Contour bunding and broad bed furrowing mainly manage runoff rather than checking capillary rise.

Question 7Agronomy Fundamentals, Cropping Systems and Farming Types

A grower wants to reduce risk of total failure in a rainfed field by sowing sorghum and pigeonpea together in alternate rows. Which benefit of intercropping is being exploited?

  1. Higher yield of the dominant crop alone
  2. Complete elimination of weeds without tillage
  3. Insurance against failure of one component crop Correct answer.
  4. Uniform maturity of all component crops

Explanation

Intercropping spreads production risk because the component crops differ in drought tolerance and duration, so if one fails the other still yields. This stability is a recognised advantage of intercropping in rainfed areas. It does not guarantee uniform maturity or eliminate weeds.

Question 8Agronomy Fundamentals, Cropping Systems and Farming Types

Which of the following pairs correctly matches a farming system with its typical location in India?

  1. Commercial grain farming - Kerala backwaters
  2. Plantation agriculture - Assam and Kerala Correct answer.
  3. Shifting cultivation - Punjab plains
  4. Intensive subsistence rice - Rajasthan desert

Explanation

Tea, rubber, coffee and similar estate crops are grown in the humid hill and coastal tracts of Assam, Kerala and neighbouring states, so plantation agriculture matches those regions. The other pairs place a system in a climate that cannot support it.

Question 9Agronomy Fundamentals, Cropping Systems and Farming Types

In a multiple cropping programme, which sequence gives the highest land-use efficiency when water and nutrients are non-limiting?

  1. Cotton - fallow - wheat
  2. Rice - fallow - fallow
  3. Fallow - wheat - fallow
  4. Maize - potato - moong Correct answer.

Explanation

A three-crop sequence such as maize, potato and moong keeps the land occupied for most of the year, raising the total cropped area and hence land-use efficiency. Sequences containing fallow leave the land idle and reduce cropping intensity.

Question 10Agronomy Fundamentals, Cropping Systems and Farming Types

Which statement correctly distinguishes dry farming from dryland farming as used in Indian agronomy?

  1. Dry farming receives more than 750 mm annual rainfall
  2. Dryland farming is practised where rainfall exceeds 1,000 mm
  3. Dryland farming excludes the use of moisture conservation measures
  4. Dry farming is practised in areas receiving less than 500 mm annual rainfall Correct answer.

Explanation

In Indian usage, dry farming refers to crop production in tracts receiving less than about 500 mm of annual rainfall, where moisture is severely limiting. Dryland farming covers the somewhat wetter rainfed belt, roughly 500 to 750 mm, where moisture conservation can support more stable yields.

Question 11Agronomy Fundamentals, Cropping Systems and Farming Types

A farmer practising mixed farming in a peri-urban area keeps two buffaloes and grows fodder maize and berseem. Which feature makes this a mixed farming system rather than a specialised one?

  1. Only livestock are kept and all fodder is purchased
  2. Land is left fallow for two consecutive years
  3. Only crops are grown and all residues are sold
  4. Livestock and crop enterprises are combined on the same farm Correct answer.

Explanation

Mixed farming combines crop production with livestock rearing on the same holding, so crop residues and fodder support the animals and manure returns to the fields. This integration of enterprises distinguishes it from specialised crop or livestock farms.

Question 12Agronomy Fundamentals, Cropping Systems and Farming Types

Which agronomic practice most directly reduces the risk of crop failure from a mid-season dry spell in a rainfed sorghum field?

  1. Delaying sowing until the rains end
  2. Increasing the seed rate at sowing
  3. Applying a protective irrigation at the critical growth stage Correct answer.
  4. Removing all crop residues from the surface

Explanation

A protective or life-saving irrigation applied at the critical stage, such as flowering, buffers the crop against a dry spell at the point when moisture stress is most damaging. This is a standard contingency measure in rainfed agronomy.

Question 13Agronomy Fundamentals, Cropping Systems and Farming Types

Which sequence represents a valid crop rotation rather than a cropping pattern?

  1. Sugarcane planted in strips between jute strips
  2. Sole cotton grown continuously for ten years
  3. Rice - wheat - rice - wheat on the same field over years Correct answer.
  4. Maize and cowpea in alternate rows in one season

Explanation

A crop rotation is the ordered succession of different crops on the same field over successive seasons or years, so an alternating rice-wheat sequence qualifies. Simultaneous arrangements in one season are intercropping or strip cropping, and continuous sole cropping is monoculture without rotation.

Question 14Agronomy Fundamentals, Cropping Systems and Farming Types

Which combination of crops is most suitable for a sequential triple-cropping system in the Indo-Gangetic plains under assured irrigation?

  1. Bajra - fallow - fallow
  2. Rice - potato - moong Correct answer.
  3. Sugarcane - sugarcane - fallow
  4. Cotton - fallow - gram

Explanation

Assured irrigation in the Indo-Gangetic plains allows a short-duration kharif cereal, a rabi tuber or cereal and a short summer pulse, so rice, potato and moong fit a three-crop year. The other options include long-duration crops or fallow periods that prevent three harvests.

Question 15Agronomy Fundamentals, Cropping Systems and Farming Types

In a strip cropping layout, what is the primary purpose of arranging alternate strips of a close-growing crop with an erosion-susceptible row crop?

  1. To increase the seed rate of the row crop
  2. To slow runoff and trap soil moving from the row-crop strips Correct answer.
  3. To eliminate the need for contour layout on slopes
  4. To ensure both crops mature on the same date

Explanation

Close-growing strips act as filters that slow surface runoff and trap soil eroding from adjacent strips of row crops, thereby checking water erosion. Strips are normally laid across the slope or on the contour so their filtering action works.

Question 16Agronomy Fundamentals, Cropping Systems and Farming Types

Which statement best explains why legume-based intercropping often gives a higher land equivalent ratio than sole cropping of either component?

  1. The cereal suppresses the legume completely during the season
  2. The legume transfers some fixed nitrogen and the two crops exploit different canopy and root zones Correct answer.
  3. The legume competes more strongly for light than the cereal
  4. Both crops require identical spacing and nutrient schedules

Explanation

Component crops with different canopy heights and rooting depths partition light, water and nutrients, and the legume can transfer part of its fixed nitrogen to the companion. Together these complementary effects raise total productivity per unit land, giving a land equivalent ratio above one.

Question 17Agronomy Fundamentals, Cropping Systems and Farming Types

A rainfed farmer in a 450 mm rainfall tract wants to stabilise yields across good and bad years. Which cropping strategy is agronomically most sound?

  1. Include a drought-tolerant contingency crop and a short-duration variety in the plan Correct answer.
  2. Increase fertiliser doses to compensate for uncertain rainfall
  3. Abandon moisture conservation and rely on rainfall alone
  4. Grow a single long-duration high-yielding variety every year

Explanation

In low-rainfall tracts, stability comes from matching crop duration and drought tolerance to the expected moisture supply and keeping a contingency crop ready if the season fails. This hedges against variability instead of betting on one long-duration variety.

Question 18Agronomy Fundamentals, Cropping Systems and Farming Types

Which of the following best explains the difference between crop diversification and crop substitution?

  1. Both terms refer only to changing the variety within a single crop
  2. Diversification adds new crops or enterprises to the system, while substitution replaces one crop with another Correct answer.
  3. Diversification replaces one crop with another, while substitution adds new enterprises
  4. Both terms mean growing only one crop over a larger area

Explanation

Diversification broadens the farm portfolio by adding crops or enterprises, which spreads risk and income sources. Substitution swaps the existing crop for a different one without necessarily increasing the number of enterprises.

Question 19Agronomy Fundamentals, Cropping Systems and Farming Types

In a farming systems context, which practice exemplifies integrated farming rather than a specialised system?

  1. A tea estate processing its own leaf for export
  2. A cotton farm buying all inputs and selling all lint
  3. A 200-hectare wheat farm using only hired machinery
  4. A poultry unit, fish pond and vegetable plot linked so wastes from one enterprise fertilise another Correct answer.

Explanation

Integrated farming deliberately links crop, livestock, fishery and other enterprises so that the waste or by-product of one becomes an input for another, improving resource use efficiency. Specialised systems concentrate on one enterprise and do not rely on such internal recycling.

Question 20Agronomy Fundamentals, Cropping Systems and Farming Types

Which of the following describes the primary agronomic purpose of a cover crop in a rotation?

  1. To provide a marketable grain in the same season
  2. To replace all fertiliser requirements of the next crop
  3. To protect the soil surface and suppress weeds between main crops Correct answer.
  4. To increase the depth of ploughing before sowing

Explanation

Cover crops are grown mainly to shield the soil from erosion, suppress weeds and improve organic matter during otherwise idle periods. Their biomass may be incorporated, but they are not grown as a marketable main crop.

Question 21Agronomy Fundamentals, Cropping Systems and Farming Types

Which of the following best states the principle behind crop rotation for disease management?

  1. Rotating crops always eliminates all soil-borne pathogens permanently
  2. The same pathogen builds up when a susceptible host is grown repeatedly Correct answer.
  3. Rotation works only when the same crop is returned every third year
  4. Disease control in rotation depends solely on higher seed rates

Explanation

Continuous cropping of a susceptible host allows its specific pathogen or pest to multiply in soil and residues, so rotating with a non-host breaks the build-up cycle. Rotation reduces inoculum but does not permanently eradicate all pathogens.

Question 22Agronomy Fundamentals, Cropping Systems and Farming Types

A grower in a high-rainfall coastal area wants to reduce runoff and soil loss on a gentle slope while continuing to grow annual crops. Which measure is most appropriate?

  1. Continuous sole cropping without any bund
  2. Burning crop residues before sowing
  3. Contour bunding with a grassed waterway Correct answer.
  4. Summer ploughing along the slope

Explanation

Contour bunds laid across the slope intercept runoff and store it, while a grassed waterway safely carries away excess water, so the combination controls soil loss on gently sloping cropland. Ploughing along the slope and residue burning both increase erosion.

Question 23Agronomy Fundamentals, Cropping Systems and Farming Types

Which factor most strongly limits the adoption of multiple cropping in a rainfed region with a short growing season?

  1. Large market demand for the produce
  2. Short moisture availability period and limited irrigation Correct answer.
  3. Abundance of soil nutrients
  4. High labour availability

Explanation

Multiple cropping needs a growing period long enough and moisture available long enough to fit two or more crops. In a short-season rainfed region the moisture window is brief and irrigation is limited, so an extra crop cannot be supported.

Question 24Agronomy Fundamentals, Cropping Systems and Farming Types

Which statement correctly describes relay cropping as a form of multiple cropping?

  1. The second crop is sown into the standing first crop before it is harvested Correct answer.
  2. Two crops are sown together and harvested on the same day
  3. One crop is grown alone and the field is left fallow afterwards
  4. Crops are grown in alternate strips across the slope

Explanation

In relay cropping the second crop is sown into the standing first crop shortly before its harvest, so the two overlap briefly and the land is never idle. This shortens the turnaround time and raises cropping intensity compared with a pure sequence.

Question 25Soil Science, Soil Fertility and Plant Nutrition

Which soil textural class generally holds the greatest total pore space and therefore the highest water-holding capacity at field capacity?

  1. Loamy sand
  2. Clay Correct answer.
  3. Coarse sand
  4. Sandy loam

Explanation

Fine-textured soils dominated by clay particles pack with abundant, narrow micropores, so total porosity and retained water at field capacity are highest. Sands have large but few pores that drain freely under gravity.

Question 26Soil Science, Soil Fertility and Plant Nutrition

A farmer applies urea to a flooded paddy field and broadcasts it on the surface. Which nitrogen loss pathway is most favored by this practice?

  1. Ammonia volatilization after hydrolysis Correct answer.
  2. Denitrification of applied urea directly
  3. Nitrate leaching below the root zone
  4. Fixation of ammonium by potassium minerals

Explanation

Urea hydrolyses to ammonium carbonate, raising pH at the floodwater-soil interface, and ammonium converts to ammonia gas that escapes to the atmosphere. Surface broadcasting without incorporation maximizes this loss.

Question 27Soil Science, Soil Fertility and Plant Nutrition

Which soil reaction range is generally considered most favorable for availability of most plant nutrients while avoiding micronutrient deficiency?

  1. pH 6.0 to 7.0 Correct answer.
  2. pH 4.0 to 4.5
  3. pH 3.0 to 3.5
  4. pH 8.0 to 8.5

Explanation

Near-neutral pH around 6.0 to 7.0 balances availability of macronutrients such as phosphorus with adequate solubility of micronutrients. Strongly acid or alkaline reactions reduce availability of several nutrients and can cause toxicity.

Question 28Soil Science, Soil Fertility and Plant Nutrition

A soil test reports 0.5 percent organic carbon. Using the standard Van Bemmelen factor, what is the approximate organic matter content?

  1. 0.86 percent Correct answer.
  2. 1.72 percent
  3. 5.00 percent
  4. 0.50 percent

Explanation

The conventional Van Bemmelen factor assumes organic matter contains about 58 percent carbon, so organic matter equals organic carbon multiplied by 1.724. Multiplying 0.5 by 1.724 gives roughly 0.86 percent.

Question 29Soil Science, Soil Fertility and Plant Nutrition

Which cation is held most strongly on negatively charged soil exchange sites under comparable conditions?

  1. Al3+ Correct answer.
  2. K+
  3. Ca2+
  4. Na+

Explanation

Complementary cation exchange follows the lyotropic series, in which ions of higher charge and larger hydrated size are held more strongly. Trivalent aluminium is adsorbed far more tightly than divalent or monovalent cations.

Question 30Soil Science, Soil Fertility and Plant Nutrition

In a soil with a high cation exchange capacity dominated by calcium and magnesium, which management practice best maintains base saturation on an acid soil?

  1. Adding elemental sulfur before each crop
  2. Applying agricultural lime to neutralize exchangeable acidity Correct answer.
  3. Flooding the field continuously to leach bases
  4. Applying ammonium sulfate fertilizer year after year

Explanation

Lime supplies calcium carbonate that neutralizes exchangeable aluminium and hydrogen and replaces them with calcium, raising base saturation. Acidifying or base-leaching practices instead lower base saturation.

Question 31Soil Science, Soil Fertility and Plant Nutrition

Which essential element is classified as a macronutrient although it is not a constituent of any organic compound in the plant?

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

Explanation

Potassium is required in large amounts but functions largely as an osmoticum and enzyme activator rather than as a structural component of organic molecules. Nitrogen, phosphorus and sulfur are all incorporated into organic compounds.

Question 32Soil Science, Soil Fertility and Plant Nutrition

A maize field shows interveinal chlorosis on younger leaves while veins remain green, consistent with a deficiency of a mobile element.

  1. Nitrogen
  2. Potassium
  3. Iron Correct answer.
  4. Magnesium

Explanation

Iron is immobile in the phloem, so deficiency symptoms appear first on young leaves as interveinal chlorosis. Mobile elements such as magnesium and nitrogen are retranslocated and show symptoms on older leaves.

Question 33Soil Science, Soil Fertility and Plant Nutrition

Which fertilizer material has the highest nitrogen content on a percentage basis?

  1. Calcium ammonium nitrate
  2. Anhydrous ammonia Correct answer.
  3. Ammonium nitrate
  4. Urea

Explanation

Anhydrous ammonia contains about 82 percent nitrogen, the highest of the common straight nitrogen fertilizers. Urea contains about 46 percent and ammonium nitrate about 34 percent.

Question 34Soil Science, Soil Fertility and Plant Nutrition

A soil has an electrical conductivity of 8 dS/m in the saturation extract and an exchangeable sodium percentage of 4. How should this soil be classified?

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

Explanation

Saline soils have an electrical conductivity above 4 dS/m with exchangeable sodium percentage below 15. This soil meets the salinity criterion while remaining below the sodicity threshold.

Question 35Soil Science, Soil Fertility and Plant Nutrition

Which reclamation amendment is most appropriate for a sodic soil containing free calcium carbonate?

  1. Gypsum Correct answer.
  2. Sodium chloride
  3. Hydrochloric acid
  4. Ammonium chloride

Explanation

Gypsum supplies soluble calcium that replaces exchangeable sodium, and the released sodium is leached with good-quality water. Where free lime is present, gypsum is the standard amendment.

Question 36Soil Science, Soil Fertility and Plant Nutrition

Which biological process converts ammonium to nitrate in well-aerated soil?

  1. Nitrogen fixation by Rhizobium
  2. Nitrification by Nitrosomonas and Nitrobacter Correct answer.
  3. Ammonification by heterotrophs
  4. Denitrification by Pseudomonas

Explanation

Nitrification is a two-step aerobic process in which Nitrosomonas oxidizes ammonium to nitrite and Nitrobacter oxidizes nitrite to nitrate. It requires adequate aeration and a near-neutral pH.

Question 37Soil Science, Soil Fertility and Plant Nutrition

A farmer wants to grow a legume to add nitrogen to the soil. Which practice best supports effective nodulation?

  1. Flooding the field after sowing
  2. Applying a high rate of urea at sowing
  3. Inoculating seed with the appropriate Rhizobium strain Correct answer.
  4. Liming the soil to pH 8.5

Explanation

Effective nodulation requires compatible rhizobia in the root zone, which seed inoculation supplies when native populations are inadequate. High nitrogen, extreme pH and waterlogging all suppress nodulation.

Question 38Soil Science, Soil Fertility and Plant Nutrition

Which soil property is measured by the amount of water retained at 1500 kPa tension?

  1. Saturation percentage
  2. Field capacity
  3. Infiltration rate
  4. Permanent wilting point Correct answer.

Explanation

The water retained at 1500 kPa (15 bar) tension approximates the permanent wilting point, the lower limit of plant-available water. Field capacity corresponds to about 33 kPa tension in most soils.

Question 39Soil Science, Soil Fertility and Plant Nutrition

A soil has field capacity of 30 percent and permanent wilting point of 12 percent on a weight basis, with a bulk density of 1.3 g/cm3. What is the approximate available water capacity in millimeters for a 60 cm root zone?

  1. 230 mm
  2. 140 mm Correct answer.
  3. 42 mm
  4. 18 mm

Explanation

Available water on a weight basis is 30 minus 12, or 18 percent, which equals 0.18 g/g. Multiplying by bulk density 1.3 gives 0.234 cm3/cm3, and multiplying by 600 mm depth gives about 140 mm.

Question 40Soil Science, Soil Fertility and Plant Nutrition

Which soil structure type is most favorable for root penetration and water movement in a cultivated field?

  1. Massive
  2. Platy
  3. Granular Correct answer.
  4. Columnar

Explanation

Granular structure consists of small, rounded aggregates with abundant interconnected pores, favoring aeration, drainage and root growth. Platy, columnar and massive structures restrict these processes.

Question 41Soil Science, Soil Fertility and Plant Nutrition

Which practice is the most direct way to increase soil organic carbon in a rice-wheat rotation?

  1. Repeated deep tillage to bury residues
  2. Burning residues after each harvest
  3. Removing all straw for fodder
  4. Incorporating crop residues instead of burning them Correct answer.

Explanation

Retaining and incorporating crop residues adds carbon inputs that build soil organic matter over time. Burning, excessive tillage and complete removal reduce carbon inputs and accelerate decomposition.

Question 42Soil Science, Soil Fertility and Plant Nutrition

Which form of soil nitrogen is most susceptible to leaching loss in a sandy soil?

  1. Nitrogen in crop residues
  2. Organic nitrogen in humus
  3. Ammonium adsorbed on exchange sites
  4. Nitrate Correct answer.

Explanation

Nitrate carries a negative charge and is not retained by negatively charged soil colloids, so it moves freely with drainage water. Adsorbed ammonium and organic nitrogen are largely immobile.

Question 43Soil Science, Soil Fertility and Plant Nutrition

A soil test shows a high phosphorus level, but the crop shows phosphorus deficiency in a calcareous soil at pH 8.2. Which explanation is most plausible?

  1. Phosphorus is volatilized as phosphine gas
  2. Phosphorus is fixed by exchangeable sodium
  3. Phosphorus is leached rapidly as phosphate anions
  4. Phosphorus is fixed as calcium phosphates and unavailable Correct answer.

Explanation

In calcareous soils, soluble phosphate reacts with calcium to form sparingly soluble calcium phosphates, reducing availability even when total phosphorus is high. Leaching and gaseous loss of phosphorus are negligible in field soils.

Question 44Soil Science, Soil Fertility and Plant Nutrition

Which liming material is characterized by the highest calcium carbonate equivalent among common sources?

  1. Dolomite
  2. Basic slag
  3. Calcium carbonate
  4. Calcium oxide Correct answer.

Explanation

Calcium oxide, or quicklime, has a neutralizing value of about 179 percent calcium carbonate equivalent, the highest among common liming materials. Calcium carbonate is the standard at 100 percent.

Question 45Soil Science, Soil Fertility and Plant Nutrition

Which micronutrient deficiency is most likely in a highly leached sandy soil with high pH?

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

Explanation

Boron is highly mobile in sandy soils and readily leached, and its availability declines at high pH, making deficiency common. Molybdenum availability, by contrast, increases with pH.

Question 46Soil Science, Soil Fertility and Plant Nutrition

Which statement correctly describes the role of vesicular-arbuscular mycorrhizae in plant nutrition?

  1. They convert ammonium into nitrate in the rhizosphere
  2. They fix atmospheric nitrogen in root nodules
  3. They decompose soil organic matter into humus
  4. They extend hyphae that improve phosphorus uptake Correct answer.

Explanation

Arbuscular mycorrhizal fungi form extensive hyphal networks that explore soil beyond the root depletion zone, enhancing uptake of relatively immobile nutrients such as phosphorus and zinc. Nitrogen fixation and nitrification are carried out by other organisms.

Question 47Soil Science, Soil Fertility and Plant Nutrition

A farmer applies 120 kg of urea containing 46 percent nitrogen. How much nitrogen is supplied?

  1. 46 kg
  2. 276 kg
  3. 55.2 kg Correct answer.
  4. 120 kg

Explanation

Nitrogen supplied equals the fertilizer quantity multiplied by its nitrogen percentage, so 120 multiplied by 0.46 gives about 55.2 kg of nitrogen. The remaining mass is largely the carrier material.

Question 48Soil Science, Soil Fertility and Plant Nutrition

Which management strategy best reduces nitrate contamination of groundwater in an irrigated field?

  1. Irrigating heavily immediately after fertilizer application
  2. Using only nitrate-based fertilizers at high rates
  3. Splitting nitrogen applications to match crop demand Correct answer.
  4. Applying the full nitrogen dose before sowing

Explanation

Splitting applications synchronizes nitrogen supply with crop uptake, reducing the amount of nitrate left in the soil for leaching. Pre-plant single doses and heavy irrigation increase nitrate movement below the root zone.

Question 49Tillage, Seedbed Preparation and Soil Conservation

Primary tillage in seedbed preparation is best described as the operation that:

  1. levels and firms the surface after ploughing
  2. compacts the subsoil to improve capillary rise
  3. applies herbicides uniformly over the field
  4. breaks and loosens the soil to full working depth, burying residues and weeds Correct answer.

Explanation

Primary tillage is the first, deep operation such as ploughing, which inverts and loosens soil to full depth and buries crop residues and weeds. Secondary tillage follows to refine, level and firm the seedbed. Compaction and spraying are not tillage objectives.

Question 50Tillage, Seedbed Preparation and Soil Conservation

A farmer wants a fine, firm seedbed with good seed-to-soil contact after deep ploughing. The most appropriate implement sequence is:

  1. subsoiler, then chisel plough
  2. rotavator, then subsoiler
  3. mouldboard plough, then mouldboard plough again
  4. harrow, then plank or roller Correct answer.

Explanation

Secondary tillage implements such as harrows break clods and the plank or roller firms and levels the surface, giving the fine tilth and seed contact that small seeds require. Repeating primary ploughing or deep loosening does not refine the surface.