ASRB NET cheat sheet

Law of minimum (Liebig): yield is limited by the nutrient in shortest supply relative to need, not by total nutrient abundance.

Mendel's first law (segregation) applies to single-gene traits; the 9:3:3:1 F2 ratio needs independent assortment plus complete dominance in a dihybrid cross.

Cytoplasmic male sterility is maternally inherited and is used to produce hybrid seed without emasculation; restorer (Rf) genes suppress it in the F1.

Koch's postulates: constant association with disease, isolation in pure culture, reproduction of symptoms on reinoculation, and re-isolation.

Rice is a C3 crop; maize, sorghum and sugarcane are C4 with PEP carboxylase as the first carboxylating enzyme and low photorespiration.

Insecticide resistance management: rotate mode-of-action groups (IRAC classification) and maintain untreated refuges to slow selection.

In horticulture, the climacteric rise in respiration and ethylene marks ripening in banana, mango and tomato; non-climacteric crops include citrus and grape.

Photosynthetic rate is limited by stomatal conductance under drought; ABA closes stomata and raises root-to-shoot signalling under water deficit.

Selection response R = i·h²·σP, where i is selection intensity, h² heritability and σP phenotypic standard deviation.

Inbreeding coefficient rises by 1/(2Ne) per generation; Ne is reduced by unequal sex ratio and few breeding sires.

BLUP breeding values use an animal model with pedigree-based numerator relationship matrix to separate genetic from environmental effects.

Rumen microbes ferment fibre to volatile fatty acids; ammonia from protein degradation is the main N source for microbial protein synthesis.

Crude protein = N × 6.25; true protein digestibility corrects for metabolic faecal nitrogen.

Vaccination with modified-live vaccines mimics natural infection and gives stronger cell-mediated immunity than killed vaccines.

Anthrax: Gram-positive, spore-forming Bacillus; spores persist in soil and infection is typically peracute with sudden death.

Mastitis diagnosis: somatic cell count above threshold plus culture; Streptococcus agalactiae and Staphylococcus aureus are common contagious causes.

Cation exchange capacity is measured in cmol(+)/kg; base saturation is exchangeable bases as a percentage of CEC.

Soil pH measured in 1:2.5 soil:water; a decrease of one pH unit means a tenfold rise in H+ activity.

Bulk density = oven-dry mass / total volume; particle density of mineral soil is about 2.65 g/cm³, so porosity = 1 − (BD/PD).

Field capacity is water held at about −33 kPa; permanent wilting point is about −1500 kPa; available water is the difference.

Rhizobium forms root nodules on legumes and fixes N2 via nitrogenase; the symbiosis is host-specific.

Nitrification is oxidation of ammonium to nitrate by Nitrosomonas then Nitrobacter; it acidifies soil.

Liebig's law and Mitscherlich's diminishing returns describe crop response to added nutrients; soil test calibration sets critical levels.

Heavy metal mobility rises as pH falls; liming reduces bioavailability of Cd, Pb and Zn in contaminated soils.

Drawbar power (kW) = draft (kN) × speed (m/s); tractive efficiency is drawbar power divided by axle power.

Implement draft scales with soil texture, depth and width; specific draft (kN/m²) is used to size implements.

Irrigation application efficiency = water stored in root zone / water delivered; drip typically exceeds sprinkler and furrow.

Reference evapotranspiration (ETo) is computed by the FAO-56 Penman-Monteith equation; ETc = ETo × Kc.

Universal soil loss equation: A = R·K·LS·C·P, where each factor is dimensionless or in standard units.

Contour bunds and terraces reduce slope length (LS) and slow runoff; check dams trap sediment in gullies.

Thermal processing: D-value is time at a given temperature to reduce microbial population by 90%; z-value is temperature change for a tenfold D change.

Blanching inactivates enzymes (peroxidase, polyphenol oxidase) before freezing or drying to prevent browning and off-flavours.

Gross margin = gross output − variable costs; fixed costs are excluded when comparing enterprises in the short run.

Benefit-cost ratio = present value of benefits / present value of costs; NPV = benefits − costs discounted at the opportunity cost of capital.

Price elasticity of demand = % change in quantity / % change in price; inelastic demand means revenue rises when supply falls.

Marketing margin = consumer price − farm-gate price; the producer share is farm-gate price as a percentage of retail price.

ANOVA partitions total sum of squares into treatment and error; F = treatment mean square / error mean square.

Coefficient of variation = (standard deviation / mean) × 100, used to compare variability across trials with different means.

Type I error rejects a true null hypothesis; power = 1 − probability of Type II error.

Diffusion of innovations: innovators, early adopters, early and late majority, laggards; adoption follows an S-curve.

Water activity (aw) below 0.6 halts most microbial growth; below 0.85 most bacteria stop growing but xerophilic moulds persist.

HACCP has seven principles: hazard analysis, CCP identification, critical limits, monitoring, corrective actions, verification, record keeping.

Pasteurisation of milk: 63 °C for 30 min (LTLT) or 72 °C for 15 s (HTST); UHT is about 135-150 °C for a few seconds.

Milk composition averages 3.5% fat, 3.3% protein, 4.8% lactose; casein micelles precipitate at pH 4.6.

Cheddar cheese making relies on rennet coagulation, whey drainage, cheddaring and ripening; starter cultures produce lactic acid.

Maillard browning is a reaction between reducing sugars and amino groups, accelerated by heat and intermediate aw.

Rigor mortis in meat resolves with glycolysis and pH fall to about 5.5; cold shortening occurs when carcasses chill too fast.

Food preservation by canning uses 12-D reduction of Clostridium botulinum spores as the reference process.

Fish gills counter-current exchange of water and blood maximises oxygen uptake; hypoxia drives surface gasping.

Pond carrying capacity depends on dissolved oxygen; feeding above assimilation capacity causes ammonia accumulation.

Dietary protein requirement of fish is higher than in warm-blooded animals because protein is used for energy.

Fish are poikilothermic; metabolic rate and feed intake scale with water temperature and body weight (metabolic scope).

Induced breeding uses pituitary extract or synthetic hormones such as ovaprim to trigger spawning.

Aeromonas hydrophila and Edwardsiella cause motile aeromonad septicaemia and enteric septicaemia in freshwater fish.

Nitrogenous waste is excreted mainly as ammonia through gills; unionised ammonia (NH3) is more toxic than NH4+ and rises with pH.

Composite fish culture in India mixes surface, column and bottom feeders (catla, rohu, mrigal) to use all pond niches.

Agroforestry systems include agrisilviculture, silvopasture and agrihortisilviculture; multipurpose trees provide fuel, fodder and shade.

Nitrogen-fixing trees such as Leucaena and Gliricidia supply prunings as green leaf manure in alley cropping.

Biological oxygen demand measures oxygen consumed by microbes over 5 days; chemical oxygen demand is a faster, less specific measure.

Eutrophication follows nutrient enrichment (N, P), causing algal blooms and oxygen depletion in aquatic systems.

Carbon sequestration in agroforestry is estimated from biomass allometry plus soil organic carbon stocks.

Windbreaks reduce wind speed and evaporation, protecting crops and reducing soil erosion on exposed land.

Bioaccumulation is uptake of a pollutant by an organism; biomagnification is its increase along trophic levels (e.g., DDT, mercury).

Biodiversity indices: Shannon index weights evenness and richness; Simpson index emphasises dominance.

Green Revolution in India relied on semi-dwarf wheat and rice varieties with irrigation and fertiliser responsive traits.

ICAR is the apex body coordinating agricultural research and education in India; SAUs handle state-level research.

Minimum Support Price is announced by the CACP for major crops to protect farmers from price crashes.

Kisan Credit Card provides short-term credit for crop production; PM-KISAN gives direct income support to small farmers.

Soil Health Card reports 12 parameters including pH, EC, organic carbon and available N, P, K, S and micronutrients.

Integrated Pest Management combines biological, cultural, mechanical and chemical control, with chemicals as a last resort.

National Food Security Mission targets rice, wheat and pulses to raise production and productivity.

Organic farming certification in India follows NPOP standards; the Jaivik Bharat logo identifies certified organic produce.

A hypothesis must be testable and falsifiable; a null hypothesis states no effect or no difference.

Randomisation, replication and local control are the three principles of experimental design (Fisher).

In a randomised block design, blocks control field heterogeneity; treatments are randomised within each block.

Correlation measures association, not causation; regression estimates the change in one variable per unit of another.

Sampling error decreases with the square root of sample size; doubling precision requires four times the sample.

Valid research requires informed consent, confidentiality and honest reporting; plagiarism and data fabrication are misconduct.

A p-value is the probability of observed or more extreme data under the null, not the probability the null is true.

Chi-square goodness of fit compares observed and expected frequencies: χ² = Σ(O − E)²/E.