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Tamil Nadu HSE First Year Agricultural Science study materials
Tamil Nadu HSE First Year Agricultural Science study resources

Tamil Nadu HSE First Year Agricultural Science practice questions

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Question 1Introduction to Agriculture and Agricultural Development in Tamil Nadu

Agriculture is best described as which of the following activities?

  1. The manufacture of cloth from synthetic polymer fibres in mills
  2. The cultivation of crops and the rearing of livestock for human use Correct answer.
  3. The extraction of minerals from rock deposits for industrial use
  4. The trading of shares and securities in financial markets

Explanation

Agriculture covers both crop production and animal husbandry, together with the allied operations that support them. It is distinguished from mining, manufacturing and commerce because its core is the managed production of plants and animals. This combined crop-and-livestock meaning is the standard definition used in the Tamil Nadu higher secondary syllabus.

Question 2Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which branch of agriculture deals specifically with the scientific rearing of cattle, goats, sheep and poultry?

  1. Horticulture
  2. Animal husbandry Correct answer.
  3. Agronomy
  4. Sericulture

Explanation

Animal husbandry is the branch that applies breeding, feeding, health care and housing practices to domesticated livestock. Agronomy and horticulture are concerned with field crops and garden crops respectively, while sericulture is restricted to silkworm rearing. Recognising these boundaries is essential for classifying farm enterprises correctly.

Question 3Introduction to Agriculture and Agricultural Development in Tamil Nadu

In the classification of crops by season in Tamil Nadu, which crop group is sown with the onset of the southwest monsoon and harvested around September to October?

  1. Kar crops Correct answer.
  2. Sornavarappu crops
  3. Navarai crops
  4. Pishanam crops

Explanation

Tamil Nadu traditionally recognises six cropping seasons, and the kar season corresponds to the southwest monsoon period from June to September. Sornavarappu and Navarai belong to the later northeast monsoon and summer periods, while Pishanam falls in the post-monsoon window. Matching a crop to its season determines irrigation and variety choice.

Question 4Introduction to Agriculture and Agricultural Development in Tamil Nadu

The Green Revolution in Tamil Nadu is most closely associated with which combination of inputs and crop?

  1. Organic manures and cotton
  2. High-yielding varieties, chemical fertilizers and assured irrigation in rice Correct answer.
  3. Drought-tolerant millets under rainfed conditions
  4. Salt-tolerant varieties and coastal saline soils

Explanation

The Green Revolution of the 1960s and 1970s depended on semi-dwarf high-yielding varieties that responded to fertilizer and water. In Tamil Nadu, the impact was greatest in irrigated rice tracts such as the Cauvery delta, where canal water made the package workable. The technology spread only where irrigation and credit were available.

Question 5Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which of the following is the correct expansion of the cropping term 'cropping intensity'?

  1. The ratio of gross cropped area to net sown area, usually expressed as a percentage Correct answer.
  2. The proportion of the net sown area that is irrigated
  3. The number of different crops grown on a farm in one year
  4. The quantity of seed required per hectare of a given crop

Explanation

Cropping intensity measures how many times the net sown area is cropped in a year, calculated as gross cropped area divided by net sown area multiplied by one hundred. A value above one hundred indicates more than one crop in the same field. It is a key indicator of land-use efficiency in intensive farming districts.

Question 6Introduction to Agriculture and Agricultural Development in Tamil Nadu

A farmer in the Cauvery delta grows paddy from June to October and then raises pulses on the same land using residual moisture. This practice is best described as which form of cropping?

  1. Relay cropping
  2. Mixed cropping
  3. Monoculture
  4. Sequence cropping Correct answer.

Explanation

Sequence cropping, also called multiple cropping in sequence, means raising two or more crops one after another on the same field in the same year. The paddy-then-pulses pattern fits this definition because the second crop follows the harvest of the first. Residual moisture from the paddy season supports the pulse crop without additional irrigation.

Question 7Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which soil group covers the largest area of Tamil Nadu and is noted for its black colour and high moisture retention?

  1. Laterite soils
  2. Alluvial soils
  3. Black cotton soils Correct answer.
  4. Red loamy soils

Explanation

Black soils, also called regur or cotton soils, are formed from the weathering of basaltic rock and are widely distributed in the western and northwestern parts of Tamil Nadu. Their clay content gives them high water-holding capacity and their colour comes from iron and magnesium compounds. They are valued for cotton and sorghum cultivation.

Question 8Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which of the following combinations correctly matches an agricultural zone of Tamil Nadu with a crop for which it is well known?

  1. Cauvery delta zone with apple and pear orchards
  2. Western zone with tea and coffee on the Nilgiri slopes Correct answer.
  3. Southern zone with wheat as the principal cereal
  4. Northeastern zone with saffron as the main cash crop

Explanation

The western zone includes the Nilgiris and adjoining hill areas where cool, high-rainfall conditions suit plantation crops such as tea and coffee. Tamil Nadu is divided into agro-climatic zones precisely because rainfall, soil and temperature differ sharply across the state. Zone-crop matching guides variety selection and extension advice.

Question 9Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which agency is the principal institutional source of agricultural credit at the village level in Tamil Nadu, providing short-term crop loans through Primary Agricultural Cooperative Credit Societies?

  1. The Tamil Nadu Agricultural University
  2. The Food Corporation of India
  3. NABARD
  4. The cooperative credit structure Correct answer.

Explanation

The short-term cooperative credit structure runs from Primary Agricultural Cooperative Credit Societies at village level through district central cooperative banks to the state cooperative bank. These societies provide crop loans, input credit and often link farmers to subsidy schemes. NABARD refinances and supervises but does not lend directly to individual farmers.

Question 10Introduction to Agriculture and Agricultural Development in Tamil Nadu

A farmer wants to sell paddy at the assured minimum price announced by the government. Which mechanism is intended to provide this price support in Tamil Nadu?

  1. The regulated market yard auction system with no floor price
  2. Minimum Support Price procurement through designated agencies such as the Food Corporation of India and state cooperatives Correct answer.
  3. Direct cash transfer of input subsidy to the farmer's bank account
  4. Crop insurance payouts after a notified yield loss

Explanation

Minimum Support Price is announced by the central government for major crops, and procurement is carried out by designated agencies so that farmers receive the announced price. In Tamil Nadu, the Food Corporation of India and state cooperative marketing bodies operate procurement centres. The system protects farmers against distress sales when market prices fall below the support level.

Question 11Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which of the following best explains why the System of Rice Intensification differs from conventional paddy cultivation?

  1. It requires continuous submergence of the field throughout the crop period
  2. It relies on very high seed rates and dense transplanting to suppress weeds
  3. It replaces paddy with a dryland millet in the same field
  4. It uses younger single seedlings, wider spacing and intermittent irrigation instead of continuous flooding Correct answer.

Explanation

The System of Rice Intensification raises yields by transplanting young single seedlings at wide spacing and keeping the soil moist rather than flooded. Aerobic soil conditions encourage vigorous root growth and tillering, and the wider spacing reduces competition. The method also reduces seed requirement and irrigation water compared with conventional practice.

Question 12Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which of these is the primary reason for including a legume such as black gram in a cereal-based rotation in Tamil Nadu?

  1. Legumes fix atmospheric nitrogen through root nodule bacteria and enrich soil fertility Correct answer.
  2. Legumes eliminate the need for any potassium or phosphorus application
  3. Legumes require more irrigation than cereals and improve water infiltration
  4. Legumes deplete soil nitrogen and therefore reduce weed growth

Explanation

Legumes form a symbiotic association with Rhizobium bacteria in root nodules, which convert atmospheric nitrogen into forms the plant can use. When the legume residues are incorporated, part of this nitrogen becomes available to the following cereal crop. This biological nitrogen fixation lowers fertilizer cost and improves soil health.

Question 13Introduction to Agriculture and Agricultural Development in Tamil Nadu

In Tamil Nadu agriculture, what does the term 'dry farming' specifically refer to?

  1. Cultivation of crops using only well water without any canal supply
  2. Cultivation of crops in a field that has been left fallow for one season
  3. Cultivation of crops entirely under rainfed conditions in areas receiving less than about 750 mm annual rainfall Correct answer.
  4. Cultivation of crops after draining a flooded paddy field

Explanation

Dry farming, or dryland agriculture, is practised in low-rainfall tracts where the entire crop water requirement is met from rainfall. It relies on moisture conservation practices such as contour bunding, mulching and drought-tolerant varieties. The distinction from irrigated farming rests on the source of water, not on the type of irrigation structure.

Question 14Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which statement correctly describes the role of the Tamil Nadu Agricultural University in the state's agricultural development?

  1. It distributes subsidized food grains through fair price shops
  2. It fixes the Minimum Support Price for all notified crops
  3. It conducts research, develops crop varieties and provides extension education to farmers Correct answer.
  4. It regulates the licensing of pesticide dealers across the state

Explanation

The agricultural university system combines teaching, research and extension, releasing improved varieties and transferring technology to farmers through Krishi Vigyan Kendras and demonstration plots. Price policy and food distribution are handled by other agencies. Pesticide regulation falls under the state agriculture department under central legislation.

Question 15Introduction to Agriculture and Agricultural Development in Tamil Nadu

A delta farmer observes that yields have stagnated despite heavy fertilizer use, and soil tests show a declining organic carbon level. Which corrective measure is most appropriate?

  1. Flooding the field continuously throughout the fallow period
  2. Continuous paddy monoculture without any intervening crop
  3. Increasing urea application further to compensate for low yields
  4. Incorporating green manure crops and farmyard manure with balanced fertilizer based on soil test Correct answer.

Explanation

Declining organic carbon indicates loss of soil organic matter, which reduces nutrient availability and soil structure. Green manuring with crops such as daincha and applying farmyard manure restore organic carbon, while soil-test-based balanced fertilization corrects nutrient imbalance. Together these measures address the cause rather than the symptom of stagnation.

Question 16Introduction to Agriculture and Agricultural Development in Tamil Nadu

Which of the following correctly pairs a Tamil Nadu agricultural research station or institution with its specialized mandate?

  1. Central Marine Fisheries Research Institute, Kochi, with paddy breeding
  2. Sugarcane Breeding Institute, Coimbatore, with sugarcane varietal improvement Correct answer.
  3. Tamil Nadu Rice Research Institute, Aduthurai, with cotton breeding
  4. Indian Institute of Horticultural Research, Bengaluru, with sericulture research

Explanation

The Sugarcane Breeding Institute at Coimbatore is a national institute dedicated to sugarcane improvement and is a landmark of Tamil Nadu's agricultural research base. Each institution has a defined commodity or discipline mandate, which is why matching institute to mandate requires care. Knowing these mandates helps a student interpret technology transfer and variety release information.

Question 17Soil Science and Soil Management

In soil science, the term 'soil texture' refers to the relative proportion of which soil separates?

  1. Gravel, pebbles and stones
  2. Humus, peat and compost
  3. Nitrogen, phosphorus and potassium
  4. Sand, silt and clay Correct answer.

Explanation

Soil texture is defined by the relative proportions of the three mineral separates sand, silt and clay, each with a defined particle size range. Gravel and stones are coarse fragments excluded from the texture class, while humus and nutrients are not particle-size separates at all.

Question 18Soil Science and Soil Management

Which soil separate has particles smaller than 0.002 mm in diameter and is mainly responsible for the soil's plasticity when wet?

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

Explanation

Clay is conventionally the fraction with particles below 0.002 mm, and its plate-like minerals and large surface area give wet soil its stickiness and plasticity. Sand and silt particles are larger and non-plastic, so they cannot produce this behaviour.

Question 19Soil Science and Soil Management

A soil sample feels gritty, has very low water-holding capacity and dries out quickly. Which texture class best matches this description?

  1. Clayey soil
  2. Sandy soil Correct answer.
  3. Loamy soil
  4. Silty soil

Explanation

Dominance of sand gives a gritty feel, large pore spaces and rapid drainage, so the soil holds little water and dries fast. Clay and silt fractions are what give smoothness and greater retention, so those classes do not fit the description.

Question 20Soil Science and Soil Management

Which of the following is a primary macronutrient that leguminous crops obtain largely through symbiotic nitrogen fixation?

  1. Nitrogen Correct answer.
  2. Molybdenum
  3. Zinc
  4. Boron

Explanation

Nitrogen is a primary macronutrient required in large amounts, and legumes can meet much of that need through Rhizobium bacteria in root nodules. Zinc, boron and molybdenum are micronutrients needed only in trace amounts.

Question 21Soil Science and Soil Management

Which soil organism group is chiefly responsible for decomposing organic residues and producing humus in cultivated soil?

  1. Algae only
  2. Bacteria and fungi Correct answer.
  3. Earthworms only
  4. Nematodes only

Explanation

Bacteria and fungi are the main decomposers that break down organic residues and build humus, with bacteria dominating in neutral moist soils and fungi in acidic or dry ones. The other groups assist in soil processes but are not the principal decomposers.

Question 22Soil Science and Soil Management

A farmer wants to reduce soil erosion on a gentle slope with regular crop rows. Which practice directly slows runoff by following the contour?

  1. Removing all vegetation from the bunds
  2. Contour ploughing and contour bunding Correct answer.
  3. Ploughing up and down the slope
  4. Burning crop residues before sowing

Explanation

Contour ploughing and bunding run across the slope, so runoff is intercepted and given time to infiltrate instead of accelerating downhill. Ploughing along the slope creates channels that speed erosion, and removing cover or burning residues destroys the protection.

Question 23Soil Science and Soil Management

Which soil structure type is described as roughly cube-shaped aggregates with flat faces and sharp edges, commonly found in the B horizon of many soils?

  1. Blocky Correct answer.
  2. Platy
  3. Granular
  4. Prismatic

Explanation

Blocky structure consists of block-like aggregates whose length, breadth and thickness are similar, with flat faces and sharp edges, and it is typical of subsoil horizons. Platy, prismatic and granular structures each have a distinctly different shape.

Question 24Soil Science and Soil Management

A soil has a bulk density of 1.4 g/cm³ and a particle density of 2.8 g/cm³. What is its porosity?

  1. 40 per cent
  2. 50 per cent Correct answer.
  3. 25 per cent
  4. 60 per cent

Explanation

Porosity is calculated as one minus the ratio of bulk density to particle density, so 1 minus 1.4/2.8 equals 0.5, or 50 per cent. The other values come from incorrect arithmetic or from confusing the two densities.

Question 25Soil Science and Soil Management

Which statement correctly explains why a soil with a high cation exchange capacity holds plant nutrients better?

  1. It has more negatively charged clay and humus surfaces that attract and retain cations Correct answer.
  2. It contains more gravel that stores nutrients
  3. It has a lower pH in every case
  4. It has more sand particles that chemically bind anions

Explanation

Cation exchange capacity depends on negatively charged surfaces on clay minerals and humus, which adsorb cations such as calcium, magnesium and potassium against leaching. Sand and gravel have little charge, and pH is not automatically lowered by high exchange capacity.

Question 26Soil Science and Soil Management

Which chemical reaction describes the acidification of soil when ammonium fertiliser is nitrified?

  1. Formation of carbonates that neutralise acidity
  2. Release of hydroxyl ions that raise pH
  3. Conversion of nitrate back to ammonium
  4. Release of hydrogen ions during nitrification that lower pH Correct answer.

Explanation

Nitrification converts ammonium to nitrite and then nitrate, releasing hydrogen ions and thereby lowering soil pH. This is why long-term use of ammonium fertilisers can make soil acidic.

Question 27Soil Science and Soil Management

Which practice is the most direct way to reclaim an acidic soil for crops that need near-neutral pH?

  1. Flooding with saline water
  2. Adding common salt
  3. Adding lime Correct answer.
  4. Adding gypsum

Explanation

Lime, usually ground limestone or calcium carbonate, neutralises soil acidity and raises pH. Gypsum is used for sodic soils and does not correct acidity, while salt and saline water worsen the problem.

Question 28Soil Science and Soil Management

Which soil water form is held so tightly by soil particles that plants cannot absorb it?

  1. Gravitational water
  2. Hygroscopic water Correct answer.
  3. Capillary water
  4. Field capacity water

Explanation

Hygroscopic water forms a thin film bound strongly by adsorption forces and is unavailable to plants. Capillary water is the main available reserve, and gravitational water drains away rapidly after rain.

Question 29Soil Science and Soil Management

A soil has 30 per cent sand, 30 per cent silt and 40 per cent clay. Using the standard textural triangle, which class does it fall in?

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

Explanation

Clay loam occupies the middle of the textural triangle where clay is between about 27 and 40 per cent and sand is between about 20 and 45 per cent, so 30 sand, 30 silt and 40 clay fits. The other classes require either much more sand or much more clay.

Question 30Soil Science and Soil Management

Which statement about soil organic matter is correct?

  1. It lowers the cation exchange capacity of the soil
  2. It increases bulk density in all soils
  3. It decreases the activity of soil microorganisms
  4. It improves water-holding capacity and aggregate stability Correct answer.

Explanation

Organic matter improves water retention, binds particles into stable aggregates and supplies nutrients and energy to microbes. It also lowers bulk density and raises cation exchange capacity, so the other statements are reversed.

Question 31Soil Science and Soil Management

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

  1. Nitrification Correct answer.
  2. Ammonification
  3. Denitrification
  4. Leaching

Explanation

Nitrification is the two-step microbial oxidation of ammonium to nitrite and then nitrate under aerobic conditions. Ammonification releases ammonium from organic matter, denitrification converts nitrate to nitrogen gas in anaerobic conditions, and leaching is the movement of dissolved ions downward.

Question 32Soil Science and Soil Management

A farmer notices a white crust on the surface of an irrigated field and poor germination. Which soil problem is most likely?

  1. High organic matter content
  2. Accumulation of soluble salts Correct answer.
  3. Severe phosphorus deficiency
  4. Excess soil acidity

Explanation

A white surface crust with poor germination is the classic sign of salinity, where soluble salts accumulate and raise osmotic pressure so seedlings take up water poorly. Acidity does not produce a white crust, and the other options do not fit the visible symptom.

Question 33Soil Science and Soil Management

Which reclamation practice is specifically appropriate for a sodic soil with high exchangeable sodium?

  1. Applying gypsum with provision for drainage Correct answer.
  2. Applying ammonium sulphate
  3. Adding lime only
  4. Increasing irrigation without drainage

Explanation

Gypsum supplies calcium that replaces exchangeable sodium on the clay complex, and drainage is essential to remove the displaced sodium salts from the root zone. Lime does not displace sodium effectively, and irrigation without drainage simply raises the water table.

Question 34Soil Science and Soil Management

Why does the addition of organic matter improve the structure of a heavy clay soil?

  1. It dissolves the clay minerals completely
  2. It removes all pore space from the soil
  3. It increases the clay content of the soil
  4. It binds clay particles into stable aggregates through cementing and biological activity Correct answer.

Explanation

Organic matter and the polysaccharides and microbial products formed during its decomposition act as binding agents that hold clay particles into water-stable aggregates, improving aeration and drainage. It does not dissolve clay or increase the clay fraction.

Question 35Soil Science and Soil Management

Two soils have the same total porosity, but one has many fine pores and the other many large pores. Which statement is correct?

  1. The soil with fine pores retains more water at field capacity but drains more slowly Correct answer.
  2. The soil with fine pores has higher aeration at the same moisture content
  3. The soil with large pores retains more water at field capacity
  4. Both soils have identical water retention because porosity is equal

Explanation

Pore size, not total porosity alone, governs water behaviour: fine pores hold water strongly against drainage and conduct it slowly, while large pores drain quickly and favour aeration. Equal total porosity therefore does not mean equal retention or aeration.

Question 36Soil Science and Soil Management

A farmer continuously grows a single cereal crop with no organic manure and removes all residues. Which consequence is most likely over several seasons?

  1. Decline in organic matter, weaker structure and reduced nutrient-holding capacity Correct answer.
  2. Permanent rise in cation exchange capacity
  3. Increase in soil organic carbon and improved aggregation
  4. Elimination of all soil erosion risk

Explanation

Removing residues and adding no organic matter depletes the carbon supply to soil, so organic matter declines, aggregates become less stable and cation exchange capacity falls. Continuous cereal cropping also increases erosion risk rather than removing it.

Question 37Crop Production and Agronomy

In Tamil Nadu HSE Agricultural Science, which crop is classified as a cereal grain grown primarily for its starchy endosperm?

  1. Sugarcane
  2. Groundnut
  3. Paddy Correct answer.
  4. Cotton

Explanation

Cereals are grasses cultivated for their edible starchy grains, and paddy (rice) is the principal cereal of Tamil Nadu. Groundnut and cotton are oilseed and fibre crops respectively, while sugarcane is a sugar crop.

Question 38Crop Production and Agronomy

Which soil texture is generally best suited for irrigated paddy cultivation in the delta regions of Tamil Nadu?

  1. Sandy soil
  2. Rocky soil
  3. Heavy clay soil Correct answer.
  4. Gravelly soil

Explanation

Paddy requires a soil that holds standing water and reduces percolation losses. Heavy clay soils with high water-holding capacity and poor drainage are ideal for puddling and maintaining a submerged root zone.

Question 39Crop Production and Agronomy

What is the recommended seed rate for direct-sown rice under dry conditions per hectare?

  1. 40 kg
  2. 80 kg Correct answer.
  3. 150 kg
  4. 20 kg

Explanation

Direct dry sowing of rice requires a higher seed rate than transplanted rice because of greater mortality and uneven establishment. About 80 kg per hectare is the standard recommendation for dry direct sowing.

Question 40Crop Production and Agronomy

Which operation is performed to break soil clods and level the field before transplanting paddy seedlings?

  1. Ridging
  2. Puddling Correct answer.
  3. Earthing up
  4. Mulching

Explanation

Puddling is the churning of saturated soil to destroy structure, reduce percolation and create a soft mud for transplanting. Ridging, mulching and earthing up serve different purposes in other crops.

Question 41Crop Production and Agronomy

In Tamil Nadu, which season is referred to as the 'Samba' season for paddy cultivation?

  1. August to September Correct answer.
  2. February to May
  3. October to January
  4. June to July

Explanation

Samba is the main paddy season in Tamil Nadu, with nursery sowing around August and harvesting in the following months. The other seasons are Sornavari and Navarai, each with distinct sowing windows.

Question 42Crop Production and Agronomy

Which of the following is a leguminous pulse crop commonly grown as a rainfed crop in the black cotton soils of Tamil Nadu?

  1. Ragi
  2. Sesame
  3. Maize
  4. Black gram Correct answer.

Explanation

Black gram is a short-duration legume that fixes atmospheric nitrogen through root nodules and suits rainfed black soils. Maize and ragi are cereals, while sesame is an oilseed.

Question 43Crop Production and Agronomy

What is the primary purpose of treating paddy seeds with a fungicide before sowing?

  1. To control seed-borne diseases Correct answer.
  2. To hasten maturity
  3. To increase seed weight
  4. To improve grain colour

Explanation

Seed treatment with fungicides such as carbendazim controls seed-borne pathogens like blast and sheath blight. It does not alter seed weight, grain colour or the crop duration.

Question 44Crop Production and Agronomy

Which spacing is generally recommended for transplanting paddy seedlings of a medium-duration variety?

  1. 5 cm x 5 cm
  2. 20 cm x 10 cm Correct answer.
  3. 60 cm x 30 cm
  4. 50 cm x 50 cm

Explanation

A spacing of about 20 cm between rows and 10 cm between hills provides adequate plant population and light penetration for medium-duration paddy. Closer spacing causes overcrowding, and wider spacing reduces yield.

Question 45Crop Production and Agronomy

Which nutrient is most commonly deficient in Tamil Nadu paddy soils and is supplied through urea?

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

Explanation

Nitrogen is the most frequently deficient nutrient in paddy soils and is applied mainly as urea in split doses. Phosphorus and potassium are supplied through complex fertilisers, and zinc deficiency is corrected with zinc sulphate.

Question 46Crop Production and Agronomy

A farmer applies 50 kg of urea to a field. Approximately how much nitrogen does this supply?

  1. 11.5 kg
  2. 50 kg
  3. 23 kg Correct answer.
  4. 46 kg

Explanation

Urea contains about 46 per cent nitrogen, so 50 kg of urea supplies roughly 23 kg of nitrogen. This calculation is essential for matching fertiliser doses to soil test recommendations.

Question 47Crop Production and Agronomy

Which irrigation practice is recommended for paddy to reduce water use without significant yield loss?

  1. Alternate wetting and drying Correct answer.
  2. Continuous deep submergence
  3. Flooding once at planting only
  4. Irrigating only at harvest

Explanation

Alternate wetting and drying allows the field to dry to a safe threshold before re-flooding, saving water while maintaining yield. Continuous deep submergence wastes water, and irrigating only at planting or harvest is agronomically inadequate.

Question 48Crop Production and Agronomy

The critical period for weed competition in a transplanted paddy crop generally falls within which window after transplanting?

  1. 90 to 110 days
  2. 0 to 10 days
  3. 20 to 45 days Correct answer.
  4. 60 to 80 days

Explanation

The critical weed-free period for paddy usually lies between about 20 and 45 days after transplanting, when the crop is small and weed growth is vigorous. Early and late windows have less impact on final yield.

Question 49Crop Production and Agronomy

Which herbicide is a pre-emergence herbicide commonly used in direct-sown paddy?

  1. Pendimethalin Correct answer.
  2. Glyphosate
  3. Paraquat
  4. 2,4-D

Explanation

Pendimethalin is applied to the soil before weed emergence to prevent germination of grassy and broadleaf weeds. Glyphosate and paraquat are non-selective contact herbicides used mainly for stale seedbed or inter-row control.

Question 50Crop Production and Agronomy

In a paddy field, which pest causes 'dead heart' symptoms in the vegetative stage?

  1. Brown planthopper
  2. Gall midge
  3. Yellow stem borer Correct answer.
  4. Leaf folder

Explanation

Yellow stem borer larvae bore into the central shoot and kill it, producing characteristic dead hearts. Brown planthopper causes hopperburn, leaf folder rolls leaves, and gall midge produces silver shoots.