UPHESC Assistant Professor Agronomy PYQs

Concept: Bunch (erect) groundnut: 30 cm between rows × 10 cm between plants (≈ 3.3 lakh plants/ha).

1. Spreading types: 45–60 × 10–15 cm.
2. Seed rate for bunch types ≈ 100 kg kernels/ha.

Short trick: Bunch 30 × 10; spreading 45–60 × 15.

Concept: Percolation depends on macropores; sandy soils have large pores and highest hydraulic conductivity.

1. Clay has many fine pores – slowest percolation.
2. Loam and alluvium are intermediate.

Short trick: Sand drains, clay holds.

Concept: Australia has the largest organic agricultural area in the world (about 35 million ha, mostly extensive grazing land) – FiBL/IFOAM surveys.

1. Argentina is second; India has the largest number of organic producers.
2. USA and Canada have much smaller areas.

Short trick: Area → Australia; Producers → India.

Concept: Moisture equivalent (Briggs & McLane): water retained by a 1 cm soil layer after centrifuging at 1000 × g; this force corresponds to a soil water potential of about −1 bar.

1. It approximates field capacity in medium/fine textured soils.
2. Field capacity −0.1 to −0.33 bar; wilting point −15 bar; hygroscopic coefficient −31 bar.

Short trick: Moisture equivalent: 1000 g → about −1 bar.

Concept: Hypoxia = partial deficiency of O₂ (early/short waterlogging); Anoxia = complete absence of O₂.

1. Acclimation – adjustment to stress.
2. Anoxemia – lack of O₂ in blood (animal term).

Short trick: Hypo = less; An = none.

Concept: Chickpea (desi, medium seeded) seed rate is 75–80 kg/ha at 30 × 10 cm spacing.

1. Bold-seeded kabuli types need 90–100 kg/ha; small-seeded 60–65 kg/ha.
2. Seed is treated with Rhizobium and Trichoderma before sowing.

Short trick: Gram ≈ 75–80 kg/ha, row 30 cm.

Concept: Water films around particles and in small pores are held by surface tension (cohesion) together with adhesion – the capillary forces.

1. Gravity removes water, it does not retain it.
2. Osmotic tension arises from solutes, not from films around particles.

Short trick: Thin film = surface tension + adhesion.

Concept: Standard moisture extraction pattern (40-30-20-10): of the water used by roots, 40% comes from the upper quarter of the root zone.

1. Next quarters supply 30%, 20% and 10%.
2. Hence irrigation is scheduled mainly on the upper root-zone moisture.

Short trick: 40-30-20-10 rule.

Concept: In acid soils Fe and Al fix applied P strongly; band placement concentrates the fertilizer in a narrow band, reducing soil contact and fixation.

1. It keeps P available near roots for longer.
2. Subsoil placement is used for acid subsoils of humid regions only with deep placement machinery; broadcast increases fixation.

Short trick: High fixing (acid) soils → band placement.

Concept: DAP (18-46-0) contains P in water-soluble (monocalcium-type ammonium phosphate) form.

1. Water soluble: SSP, TSP, DAP, MAP.
2. Citrate soluble: dicalcium phosphate, basic slag; Insoluble: rock phosphate, bone meal.

Short trick: DAP, SSP, TSP → water soluble; rock phosphate → insoluble.

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.