RBSE SS Agriculture cheat sheet

Cropping intensity (%) = (total cropped area ÷ net sown area) × 100; it exceeds 100 when land is double-cropped.

Crop period for a sequence = sum of individual crop durations; relay and intercropping overlap durations, so the field stays occupied longer than a single crop.

Land equivalent ratio (LER) = Σ (intercrop yield of each species ÷ its sole-crop yield); LER > 1 indicates an intercropping advantage.

C3 crops (wheat, rice, mustard) generally saturate at lower temperatures and photorespire more than C4 crops (maize, sorghum, pearl millet), which have higher water-use efficiency.

Kharif crops are sown with monsoon onset (June–July) and harvested September–October; rabi crops are sown October–November and harvested March–April.

Seed rate (kg/ha) = (desired plant population per ha × test weight in g) ÷ (1000 × germination fraction × field establishment fraction).

Growing degree days (GDD) = Σ [(Tmax + Tmin)/2 − base temperature] over days when mean temperature exceeds the base.

Vernalization requirement: winter wheat and barley need low-temperature exposure to initiate flowering; spring types lack this requirement.

Bulk density (g/cm³) = oven-dry soil mass ÷ total soil volume; particle density of most mineral soils is about 2.65 g/cm³.

Porosity (%) = [1 − (bulk density ÷ particle density)] × 100.

Soil textural class is assigned from the percentages of sand, silt and clay using the textural triangle; clay dominance gives high water-holding and high plasticity.

Cation exchange capacity (CEC) is expressed in cmol(+)/kg (numerically equal to meq/100 g); humus and smectite clays contribute the highest CEC.

Base saturation (%) = (sum of exchangeable bases ÷ CEC) × 100; soils with high base saturation are generally less acidic.

Fertilizer nutrient conversion: urea (46% N), DAP (18% N, 46% P2O5), single superphosphate (16% P2O5), muriate of potash (60% K2O).

P2O5 × 0.44 = P; K2O × 0.83 = K; use these factors to convert oxide-labelled recommendations to elemental nutrient.

Nitrogen fixation by Rhizobium on legumes and by free-living Azotobacter is biologically mediated; denitrification converts nitrate to N2 or N2O under anaerobic conditions.

Mendel's law of segregation applies to alleles at one locus; independent assortment applies to loci on different chromosomes or far apart on the same chromosome.

Test cross: crossing an individual of unknown genotype with a homozygous recessive reveals whether the unknown is homozygous or heterozygous.

Backcross involves crossing a hybrid to one of its parents; the recurrent parent is restored genetically while the donor trait is introgressed.

Heterosis (%) = [(F1 − better parent) ÷ better parent] × 100 for heterobeltiosis; use mid-parent value for standard heterosis.

Seed germination (%) = (number of normal seedlings ÷ number of seeds sown) × 100; test in four replicates of 100 seeds.

Pure live seed (%) = (germination % × purity %) ÷ 100; used to adjust seeding rates for lot quality.

Self-pollinated crops are usually improved by pure-line selection, pedigree or bulk methods; cross-pollinated crops by mass selection, recurrent selection or synthetic variety formation.

Mutation breeding uses physical (gamma rays, X-rays) or chemical (EMS, sodium azide) mutagens; induced mutants are often polyploid or chimeric.

Vegetables are grouped by edible part: leafy (spinach, cabbage), root (carrot, radish), fruit (tomato, brinjal), flower (cauliflower, broccoli), pod (pea, bean), bulb (onion, garlic).

Nursery bed area for transplanting is usually 1/10 to 1/20 of the main field area, depending on crop and spacing.

Pruning and training regulate light interception and fruit load in orchards; bearing habit (terminal vs lateral) determines pruning severity.

Sex expression in cucurbits: ethephon promotes female flowers, gibberellic acid promotes male flowers in cucurbits such as cucumber.

Vegetative propagation methods: cutting (sugarcane, rose), layering (guava, litchi), grafting (mango, citrus), budding (rose, citrus), sucker (banana, pineapple).

Fruit set in tomato improves with 2,4-D or NAA sprays at low concentration; excess causes epinasty and fruit distortion.

Post-harvest cooling: precooling removes field heat; storage life of most tropical fruits is short below 10–13 °C because of chilling injury.

Kitchen garden planning: quick-maturing leafy vegetables (spinach, coriander) are intercropped with long-duration crops such as tomato or brinjal.

Economic threshold level (ETL) is the pest density at which control measures should begin to prevent economic injury level from being reached.

Insecticide dose calculation: quantity of commercial formulation (L or kg) = (recommended active ingredient rate × area) ÷ formulation concentration.

IPM sequence: host resistance and cultural methods first, biological agents next, chemical control last as a rescue measure.

Koch's postulates: the pathogen must be consistently associated with the disease, isolated in pure culture, reproduce symptoms on a healthy host, and be re-isolated.

Disease triangle: disease occurs when a virulent pathogen, a susceptible host and favourable environment coincide over time.

Biological control agents: Trichoderma (soil-borne fungal antagonists), Bacillus thuringiensis (lepidopteran larvae), NPV (Helicoverpa), Trichogramma (egg parasitoid).

Seed treatment with carbendazim or thiram controls seed-borne smut and damping-off; soil solarization reduces soil-borne inoculum.

Pest monitoring uses light traps (nocturnal moths), pheromone traps (species-specific) and yellow sticky traps (aphids, whiteflies).

Lactation yield estimate: daily milk yield × lactation length; standard lactation is usually taken as 305 days.

Feed conversion ratio (FCR) = feed consumed ÷ live weight gain or milk produced; lower FCR is better.

Pearson square method balances two feedstuffs to a target crude protein percentage; the difference diagonals give the parts of each feed.

Total digestible nutrients (TDN) and crude protein (CP) are the main measures used to balance ruminant rations; roughage-to-concentrate ratio varies with production level.

Gestation periods: cattle about 280 days, buffalo about 310 days, goat about 150 days, sheep about 148 days.

Colostrum should be fed within the first hours after birth; it supplies immunoglobulins because the newborn has no placental antibody transfer.

Milk composition: cow milk about 3.5–4.0% fat, 3.2–3.5% protein; buffalo milk is higher in fat and total solids.

Crossbreeding programmes (e.g., exotic dairy breeds with local cattle) improve milk yield but require planned selection for adaptation and heat tolerance.

Gross margin = gross output value − variable costs; fixed costs are excluded because they do not change with the enterprise.

Net farm income = gross receipts − total costs (variable + fixed), including depreciation and imputed family labour.

Benefit-cost ratio = present value of benefits ÷ present value of costs; a ratio above 1 indicates a viable investment.

Internal rate of return is the discount rate at which net present value equals zero.

Payback period = initial investment ÷ annual net cash inflow; shorter periods indicate faster recovery.

Cost of production per unit = total cost ÷ total output; compare across enterprises to decide crop allocation.

Law of diminishing returns: as a variable input increases on fixed land, marginal returns eventually decline; optimum input use occurs where marginal value product equals marginal factor cost.

Farm records: physical records (yield, inputs), financial records (cash book, ledger) and inventory records are the three basic types.

Extension teaching methods: individual (farm visit, office call), group (demonstration, field day) and mass (radio, television, print).

Adoption stages: awareness, interest, evaluation, trial and adoption; innovators and early adopters lead the diffusion curve.

Demonstration plots compare a recommended practice with the farmer's practice; the yield difference is the demonstrable gain.

Communication model: sender, message, channel, receiver and feedback; absence of feedback causes message distortion.

Participatory rural appraisal tools include transect walks, seasonal calendars, resource mapping and focus group discussion.

Rural development indicators include literacy, per capita income, infrastructure access and employment diversification.

Farmers' organizations and self-help groups improve input purchase, credit access and collective marketing.

Diffusion of innovations: adoption rate is influenced by relative advantage, compatibility, complexity, trialability and observability.

Field capacity (ha/h) = (implement width in m × forward speed in km/h) ÷ 10.

Field efficiency (%) = (effective field capacity ÷ theoretical field capacity) × 100.

Wheel slip (%) = [(no-load wheel revolutions − load wheel revolutions) ÷ load wheel revolutions] × 100.

Draft requirement rises with soil resistance and implement width; power (kW) = draft (kN) × speed (m/s).

Moisture content (dry basis) = (mass of water ÷ mass of dry matter) × 100; wet basis = (mass of water ÷ total mass) × 100.

Irrigation water requirement = crop evapotranspiration − effective rainfall + losses; drip irrigation typically achieves higher application efficiency than surface flooding.

Seed drill calibration: seed rate (kg/ha) = (seed collected in g × 10) ÷ (effective width in m × distance travelled in m).

Tractor PTO power is measured at the power take-off shaft; drawbar power is measured at the hitch and is lower because of transmission losses.

Agroforestry systems: agrisilviculture (crops + trees), silvopasture (trees + pasture/livestock), agrisilviculture combined with livestock, and tree-based boundary plantings.

Alley cropping alternates rows of trees or shrubs with crop strips; prunings provide mulch and green manure.

Land equivalent ratio also applies to agroforestry; a ratio above 1 indicates greater combined productivity than sole cropping.

Nitrogen-fixing tree species such as Leucaena and Gliricidia supply nitrogen through leaf litter and prunings.

Tree-crop competition occurs mainly for light, water and nutrients; root and canopy pruning reduces below-ground and above-ground competition.

Windbreaks reduce wind speed and evaporation; spacing depends on tree height, with effective protection extending several tree heights downwind.

Multipurpose trees provide fuelwood, fodder, fruit and timber while conserving soil; selection depends on climate and farmer needs.

Soil erosion control: contour hedgerows of grasses or shrubs slow runoff and trap sediment on sloping land.

Sustainable agriculture integrates economic viability, environmental quality and social equity; it is assessed across all three, not yield alone.

Organic farming excludes synthetic fertilizers and pesticides; nutrient supply relies on compost, green manure, crop rotation and biological fixation.

Greenhouse gases from agriculture: methane from flooded rice and ruminants, nitrous oxide from nitrogen fertilizer and manure, carbon dioxide from land-use change.

Carbon sequestration in soil increases with organic matter addition, reduced tillage and permanent cover.

Integrated nutrient management combines organic sources, mineral fertilizers and biofertilizers to match crop demand and reduce losses.

Water quality risk: nitrate leaching and pesticide runoff are reduced by split fertilizer application, buffer strips and controlled irrigation.

Crop rotation and diversification interrupt pest and disease cycles and reduce reliance on chemical control.

Conservation tillage reduces soil erosion and fuel use but may increase dependence on herbicides and initial weed pressure.