UPHESC Assistant Professor Agronomy PYQs

Concept: Light compensation point: light intensity at which gross photosynthesis = respiration, so net CO₂ exchange is zero.

1. Saturation point – intensity beyond which photosynthesis no longer rises.
2. Shade plants have low compensation points.

Short trick: Compensation = 'balance' (P = R); Saturation = 'no more rise'.

Concept: CAM plants open stomata at night and close them by day, giving the highest water-use efficiency.

1. Transpiration ratio: CAM ≈ 50–100, C₄ ≈ 250–350, C₃ ≈ 450–950 g water/g DM.
2. Examples: pineapple, agave, cacti.

Short trick: CAM = night-shift stomata = desert survivors.

Concept: Broad Bed and Furrow (BBF), developed at ICRISAT, is meant for deep Vertisols (black soils).

1. Beds ~1.0 m wide with 0.5 m furrows on 0.4–0.8% grade drain excess water safely and conserve moisture.
2. Black soils have low infiltration when wet, so surface drainage is essential.

Short trick: BBF – ICRISAT – Black cotton soil.

Concept: Abscisic acid (ABA), the 'stress hormone', is synthesised in roots under drying soil and signals stomatal closure.

1. Betaine is an osmolyte (osmotic adjustment), not the sensor/signal.
2. Cytokinin declines under stress; ethylene is mainly a ripening/senescence hormone.

Short trick: ABA = Anti-transpirant Big Alarm – closes stomata.

Concept: Neutron moisture meter: fast neutrons from Am-Be source are slowed by hydrogen of soil water; counts of slow neutrons give volumetric moisture in situ, repeatedly at the same spot.

1. Gravimetric – standard but destructive, not in situ.
2. Tensiometer and gypsum blocks measure tension/resistance and need calibration; limited range.

Short trick: Hydrogen slows neutrons → neutron probe = advanced in-situ method (TDR is newer still).

Concept: ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2\to 6{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}$, ΔG ≈ −686 kcal per mole (≈ 2870 kJ).

1. About 38 ATP (×7.3 kcal ≈ 277 kcal) are conserved – ~40% efficiency.
2. The rest is lost as heat.

Short trick: Glucose = 686 kcal = 38 ATP.

Concept: Conveyance efficiency $E_c=\frac{W_f}{W_d}\times 100$ (water reaching field ÷ water delivered at source).

1. $E_c=\frac{3,60,000}{5,00,000}\times 100$
2. = 0.72 × 100 = 72%.
3. 28% is lost in seepage/evaporation in the channels.

Short trick: Conveyance = received ÷ released.

Concept: Percolation: downward movement of water through saturated soil under gravity, below the root zone.

1. Infiltration – entry of water into the soil surface.
2. Seepage – lateral/downward loss from channels; Interflow – lateral subsurface flow.

Short trick: Infiltration = entry; Percolation = going deeper.

Concept: Drip systems are low-pressure systems working at about 1–3 kg/cm² (≈ 15–45 psi) at the head, against 2.5–5 kg/cm² for sprinklers.

1. 1 kg/cm² ≈ 14.2 psi, so 1–3 kg/cm² ≈ 14–43 psi.
2. Pressure-compensating emitters work within this range.

Short trick: Drip ≈ 1–3 bar ≈ 15–45 psi.

Concept: Fisher's rule of thumb: an experiment should have at least 12 error degrees of freedom for a reliable estimate of error.

1. In RBD error df = (t − 1)(r − 1).
2. E.g. 4 treatments need at least 5 replications: 3 × 4 = 12.

Short trick: Error df ≥ 12 decides the minimum replications.

Concept: Probability lies between 0 (impossible event) and 1 (certain event).

1. −1 to +1 is the range of the correlation coefficient.
2. Probability can never be negative.

Short trick: Probability 0→1; correlation −1→+1.

Concept: Mode is the value that occurs most often (repeatedly) in the data.

1. Mean – arithmetic average; Median – middle value of ordered data.
2. Mode can be read from the highest point of the frequency curve.

Short trick: Mode = 'most often' (fashion).

Concept: Latin Square Design controls variation in two directions by blocking along both rows and columns.

1. RBD – one-way gradient.
2. CRD – homogeneous material (lab/pot); Split plot – factors needing different plot sizes.

Short trick: Two gradients → Latin square (each treatment once in each row and column).

Concept: Fineness (micronaire, µg/inch): very fine < 3.0; fine 3.0–3.9; medium 4.0–4.9; slightly coarse 5.0–5.9; coarse ≥ 6.0.

1. Lower micronaire = finer fibre.
2. Very fine fibres are typical of long-staple G. barbadense types.

Short trick: Below 3 very fine, 3s fine, 4s medium, 5s slightly coarse, 6+ coarse.

Concept: M.Y. Nuttonson (1955), 'Wheat–climate relationships and the use of phenology in ascertaining the thermal and photo-thermal requirements of wheat', fixed the base temperature used for wheat heat units (growing degree days).

1. Base temperature for wheat ≈ 4.5 °C (≈ 40 °F) in this work; GDD = Σ(T_mean − T_base).
2. The other authors are not associated with the wheat base temperature.

Short trick: Nuttonson 1955 – wheat GDD base.

Concept: Soybean is a warm-season crop; optimum 26–30 °C; growth is badly hampered below about 10 °C (and above ~40 °C).

1. Germination is poor in cold soil.
2. 25–30 °C lie in the optimum range, so they are wrong.

Short trick: Soybean: below 10 °C stop, 26–30 °C best.

Concept: Organic farming rests on a living, biologically active soil ('feed the soil, not the plant'); IFOAM principles: health, ecology, fairness, care.

1. Agrochemicals are excluded.
2. Yield is not the only goal; all nutrients are supplied through organic sources and recycling.

Short trick: Organic = living soil.

Concept: Ley farming: growing grasses/legume forage (ley) for some years in rotation with arable crops.

1. It restores soil structure, organic matter and N.
2. Silviculture – raising forest trees; agroforestry – trees with crops.

Short trick: Ley = temporary grass/legume pasture in rotation.

Concept: Ideal agroforestry trees: fast growing, light/narrow crown, deep roots, coppicing ability, N-fixing, multipurpose.

1. Small crown lets light reach the intercrop.
2. Fast growth gives early returns (e.g. poplar, eucalyptus, Leucaena).

Short trick: Fast growth + less shade.

Concept: Timely sown irrigated wheat: N 120–150, P₂O₅ 40–60, K₂O 40 kg/ha (common recommendation 120:60:40).

1. Full P and K are applied basally at sowing.
2. Higher P (80+) is not recommended for normal soils.

Short trick: Wheat 120:60:40 – P up to 60.