UPHESC Assistant Professor Agronomy PYQs

Concept: Indian rock phosphate (e.g. Mussoorie phos) used for direct application contains about 20–22% P₂O₅ (FCO minimum 18%).

1. DAP – 46%; TSP – 46%; SSP – 16%.
2. 43–47% values belong to TSP/DAP; it is water-insoluble, suited to acid soils.

Short trick: Rock phosphate ≈ 20% P₂O₅, best in acid soils.

Concept: Agricultural grade elemental sulphur contains about 85–90% S (commonly quoted 90%).

1. Gypsum ≈ 13–18.6% S; SSP ≈ 12% S.
2. 99.6% is purified (industrial/chemical) sulphur.

Short trick: Agri-grade S ≈ 90%; gypsum ≈ 18%.

Concept: Nitrification is a two-step biological oxidation.

1. ${\mathrm{NH}}_4^{+}\to {\mathrm{NO}}_2^{-}$ by Nitrosomonas.
2. ${\mathrm{NO}}_2^{-}\to {\mathrm{NO}}_3^{-}$ by Nitrobacter.

Short trick: Nitroso first, Nitro-bacter second.

Concept: Nitrosomonas oxidises NH₄⁺ to NO₂^- (nitritation).

1. Nitrobacter – NO₂^- to NO₃^-.
2. Pseudomonas – denitrification; Bacillus – ammonification, P-solubilisation.

Short trick: Nitroso → nitrite; Nitrobacter → nitrate.

Concept: Recovery of applied P by the first crop is low – about 15–20% even under good management – because P is fixed by Ca, Fe and Al.

1. N use efficiency ≈ 30–50%; K ≈ 60–80%.
2. Residual P benefits later crops.

Short trick: N 50, P 20, K 70 (approx. % recovery).

Concept: India has no commercially exploitable potash reserves; the entire Muriate of Potash (KCl, 60% K₂O) is imported.

1. Urea, DAP and SSP are manufactured in India (though raw materials are partly imported).
2. Main MOP sources: Canada, Russia, Belarus, Jordan, Israel.

Short trick: Potash = 100% import.

Concept: Physical (positional/placement) selectivity is obtained by manipulating the herbicide at the time of application – dose, placement (directed spray, depth), formulation and method – so that the crop escapes contact.

1. Biological/physiological selectivity depends on differential absorption, translocation or metabolism by the plant.
2. Chemical selectivity is inherent to the molecule; 'chronological' is not the standard term for application manipulation.

Short trick: Manipulate application → physical selectivity; plant's own response → physiological.

Concept: Herbicides are sprayed at low pressure (about 10–30 psi, ~1–2 kg/cm²) with flat-fan/flood-jet nozzles to get coarse droplets and avoid drift.

1. High pressure gives fine droplets that drift to nearby crops.
2. Insecticides/fungicides use higher pressure and hollow-cone nozzles.

Short trick: Herbicide: low pressure, big drops, flat-fan nozzle.

Concept: Competition: crop and weed draw on the same limited resources (nutrients, water, light, space); weeds absorb nutrients faster and deprive the crop.

1. Interference = competition + allelopathy together.
2. Association only means growing together.

Short trick: Shared limited resource → competition; plus toxins → interference.

Concept: Glyphosate is a non-selective, systemic (translocated), post-emergence foliar herbicide; it inhibits EPSP synthase (shikimate pathway).

1. It is inactivated on contact with soil (adsorbed), so not soil-active.
2. Contact herbicide example: paraquat.

Short trick: Glyphosate = kills all green, moves inside, dead in soil.

Concept: Bispyribac-sodium (ALS inhibitor) is a post-emergence herbicide for rice (DSR and transplanted) at 20–25 g a.i./ha, 15–25 DAS.

1. Controls Echinochloa, sedges and broadleaf weeds.
2. Wheat uses sulfosulfuron/clodinafop; maize – atrazine/tembotrione.

Short trick: Bispyribac = paddy post-emergence.

Concept: Panicum repens (torpedo grass) is a perennial grass with an extensive creeping rhizome network that binds soil on slopes and bunds.

1. Convolvulus arvensis – bindweed, a problem weed of field crops.
2. Amaranthus viridis, Digera arvensis – annual broadleaf weeds with little soil-binding value.

Short trick: Rhizomatous grasses (Panicum repens, Cynodon) = soil binders.

Concept: Leucas aspera (Thumbai/Guma) leaf juice is used in folk medicine against snake bite and scorpion sting.

1. Phyllanthus niruri (bhui-amla) – jaundice/liver.
2. Abutilon indicum (kanghi) – piles, demulcent; Trianthema – a common kharif weed.

Short trick: Leucas – snake bite; Phyllanthus – liver.

Concept: In drylands crop yields are risky; combining field crops with livestock (dairy, goat, sheep) stabilises income and recycles residues and manure.

1. Fisheries need assured water – unsuitable for dry areas.
2. Crops alone carry the full risk of drought.

Short trick: Dryland IFS = crop + livestock.

Concept: C₄ plants carboxylate twice: first in mesophyll on phosphoenol pyruvate (by PEP carboxylase), then in bundle sheath by RuBP carboxylase (RuBisCO) in the Calvin cycle.

1. Option (A) names the PEP system (PEP carboxylase acting on phosphoenol pyruvate).
2. Both carboxylations are essential, so 'Both (A) and (B)'.

Short trick: C₄ = PEPcase (mesophyll) + RuBisCO (bundle sheath).

Concept: C, H and O (from CO₂ and water) make up about 94–96% of plant dry matter.

1. The remaining ~4–6% is mineral nutrients (N, P, K etc.) – the ash.
2. C ≈ 45%, O ≈ 45%, H ≈ 6%.

Short trick: C-H-O ≈ 96%; minerals ≈ 4%.

Concept: PAR (400–700 nm) is measured with a quantum sensor as photosynthetic photon flux density (µmol m^-2 s^-1); a line quantum sensor measures canopy interception.

1. Pyranometer/solarimeter – total solar radiation.
2. Thermal sensors measure temperature.

Short trick: PAR → quantum (photon) sensor.

Concept: Sun-synchronous satellites are near-polar, low-orbit satellites crossing a place at the same local solar time – used for earth resources (Landsat, IRS, SPOT).

1. GOMS/METEOSAT, INTELSAT and INSAT are geostationary (≈ 36,000 km).
2. Landsat is used for crop acreage and land-use mapping.

Short trick: Resource satellites (Landsat/IRS) = sun-synchronous; communication/weather (INSAT) = geostationary.

Concept: Radiation transfers energy as electromagnetic waves and needs no medium – that is how solar energy crosses space.

1. Conduction – molecule to molecule in solids.
2. Convection – mass movement of fluids (air/water).

Short trick: Sun's heat reaches us through vacuum → radiation.

Concept: Coppicing: trees cut near ground regenerate many shoots from the stump; repeated harvests on short rotation = coppice farming.

1. Examples: Leucaena, Eucalyptus, Sesbania, willow, poplar.
2. Energy plantations often use coppice species, but the practice described is coppicing.

Short trick: Stump re-sprouts → coppice.