Tamil Nadu HSE Second Year Agricultural Science cheat sheet

Cropping intensity (%) = (sum of area under all crops in a year ÷ net sown area) × 100.

Land equivalent ratio (LER) = sum of (intercrop yield ÷ sole crop yield) of each component; LER > 1 indicates intercropping advantage.

Crop rotation with a legume fixes 20–60 kg N/ha for the succeeding cereal through Rhizobium symbiosis.

Critical period of crop-weed competition is generally the first 30–45 days after sowing for most annual field crops.

Rice requires puddling and 5–10 cm standing water; dryland crops such as sorghum and millets follow C4 photosynthesis with higher water-use efficiency.

Seed rate (kg/ha) = (desired plant population/m² × test weight in g) ÷ (germination % × purity % × 100).

Sole cropping, sequential cropping, relay cropping and intercropping are distinguished by whether crop life cycles overlap in time.

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 pH below 5.5 favours Al and Mn toxicity; liming with CaCO₃ raises pH, and lime requirement rises with clay and organic matter content.

Cation exchange capacity (cmol(+)/kg) is measured by ammonium acetate (pH 7) displacement; montmorillonite > illite > kaolinite in CEC.

Available N by alkaline permanganate, available P by Olsen (neutral–alkaline soils) or Bray-1 (acid soils), available K by neutral ammonium acetate.

Fertilizer dose for a nutrient = (recommended nutrient kg/ha × 100) ÷ % nutrient content of the fertilizer.

C:N ratio above about 30 in residues causes temporary immobilization of nitrogen; below 20 favours net mineralization.

Net photosynthesis = gross photosynthesis − respiration; C4 plants avoid photorespiration because PEP carboxylase concentrates CO₂ in bundle-sheath cells.

Transpiration ratio = mass of water transpired ÷ mass of dry matter produced; lower values indicate better water-use efficiency.

Photosynthetically active radiation spans 400–700 nm; chlorophyll a and b absorb mainly red (about 660 nm) and blue (about 450 nm).

Crop growth rate (g/m²/day) = (W₂ − W₁) ÷ (t₂ − t₁); relative growth rate = (ln W₂ − ln W₁) ÷ (t₂ − t₁).

Leaf area index = total leaf area ÷ ground area; values of 3–5 are typical optima for many field crops.

Vernalization is low-temperature promotion of flowering (e.g., wheat); photoperiodism classifies crops as short-day, long-day or day-neutral.

Seed germination requires imbibition, then enzyme activation; gibberellic acid mobilizes endosperm starch via α-amylase in cereals.

The 17 essential elements: C, H, O, N, P, K, Ca, Mg, S (macronutrients) and Fe, Mn, Zn, Cu, B, Mo, Cl, Ni (micronutrients).

Mobile nutrients (N, P, K, Mg) show deficiency first in older leaves; immobile nutrients (Ca, B, Fe, S) show it in younger leaves.

Irrigation water requirement = consumptive use + percolation + seepage losses − effective rainfall.

Duty of water (ha/cumec) = irrigated area ÷ discharge; delta (m) = depth of water applied over the base period.

Furrow irrigation suits row crops on medium soils; drip achieves 85–95% application efficiency and is suited to wide-row and horticultural crops.

Fertigation delivers soluble fertilizer through drip lines; urea, potassium nitrate and monoammonium phosphate are commonly used.

Zinc deficiency in rice (Khaira disease) is corrected by soil application of ZnSO₄ at 20–25 kg/ha or foliar spray of 0.5% solution.

Economic threshold level (ETL) is the pest density at which control measures are justified to prevent economic loss; economic injury level is the density causing loss equal to control cost.

Insecticide dose (ml or g per litre) = (recommended dose per ha ÷ spray volume per ha) × 1000 for unit conversion.

Rice stem borer is managed by clipping seedling tips before transplanting and by releasing Trichogramma japonicum egg parasitoids.

Koch's postulates link a pathogen to a disease: constant association, isolation, pure-culture inoculation reproducing symptoms, and re-isolation.

Biological control agents include Trichoderma viride against soil-borne pathogens and Bacillus thuringiensis against lepidopteran larvae.

Damping-off in nurseries is controlled by seed treatment with carbendazim or Trichoderma and by avoiding excess irrigation.

Blight, wilt and rust are fungal; mosaic, leaf curl and yellow vein are viral; bacterial wilt shows vascular oozing in water.

Vegetative propagation methods: cutting, layering (air and ground), grafting, budding and tissue culture; seed propagation is sexual.

Apical dominance is broken by pinching and pruning to induce lateral branching in chrysanthemum and rose.

Coconut is propagated by seedlings from elite palms; mango by veneer or epicotyl grafting; banana by sword suckers or tissue culture.

Floriculture crops: jasmine (Jasminum sambac), chrysanthemum, rose, marigold, tuberose and crossandra are important in Tamil Nadu.

Post-harvest storage life is extended by pre-cooling, controlled atmosphere (low O₂, elevated CO₂) and ethylene scrubbing.

Kitchen garden layout follows crop rotation and companion planting; vegetable yields are expressed as t/ha and horticultural crops often as kg per tree.

Pollen viability and stigma receptivity timing determine hand-pollination success in hybrid seed production of horticultural crops.

Cattle gestation period is about 280–285 days; buffalo about 305–310 days; goat about 150 days.

Estrus cycle length: cattle 18–24 days (average 21), buffalo 21–23 days, sheep 16–17 days.

Milk composition: cow milk about 3.5–4.5% fat, buffalo milk 6–7% fat; solids-not-fat about 8.5–9%.

Poultry incubation is 21 days for chicken, 28 days for duck and 28–30 days for turkey and guinea fowl.

Balanced cattle ration: maintenance plus production; roughage-to-concentrate ratio commonly 60:40 to 70:30.

Colostrum feeding within the first hour after birth provides immunoglobulins; calf mortality is reduced by timely colostrum intake.

Common dairy cattle breeds in Tamil Nadu include Jersey crossbreds, Holstein Friesian crossbreds and indigenous Kangayam and Umblachery.

Gross income = sum of (quantity of each product × its price); net income = gross income − total cost.

Benefit–cost ratio = total returns ÷ total cost; a ratio above 1 indicates profitability.

Farm management decisions use marginal analysis: add input while marginal value product exceeds marginal factor cost.

Cost concepts: fixed cost, variable cost, total cost, average cost and marginal cost are used to compute break-even output.

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

Diffusion of innovation stages: knowledge, persuasion, decision, implementation and confirmation; adopter categories are innovators, early adopters, early majority, late majority and laggards.

Cooperative societies and Farmer Producer Organizations provide input supply, credit and collective marketing to smallholders.

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

Field capacity (ha/h) = (implement width in m × speed in km/h) ÷ 10; field efficiency = effective field capacity ÷ theoretical field capacity × 100.

Seed drill calibration: seed rate (kg/ha) = (seed collected in g × 10,000) ÷ (area covered in m² × 1000).

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

Safe grain storage moisture: paddy about 13–14%, wheat 12%, maize 13%; higher moisture promotes mould and insect attack.

Drying rate depends on air temperature, humidity and airflow; sun drying is cheap but slower and weather-dependent.

Tractor PTO power is measured at the power take-off shaft; rated engine power is measured at the flywheel.

Mulberry (Morus alba) is the primary food plant; silkworm Bombyx mori passes through egg, larva (5 instars), pupa and adult moth.

Larval duration is about 24–28 days; the fifth instar consumes the majority of leaf and is the most economically important stage.

Rearing houses require 24–28 °C and 70–85% relative humidity; high humidity predisposes to flacherie and muscardine.

Silk fibre is a protein (fibroin core, sericin gum); one cocoon yields roughly 800–1,500 m of filament depending on race.

Diseases: pebrine (protozoan Nosema), flacherie (bacteria/virus), muscardine (fungus Beauveria) and grasserie (nuclear polyhedrosis virus).

Disinfection of rearing equipment with bleaching powder or formalin reduces disease incidence between crops.

Tasar, eri and muga are non-mulberry silks reared on castor, oak and other host plants in different Indian regions.

Composite fish culture uses Indian major carps (catla, rohu, mrigal) with exotic carps (silver carp, grass carp, common carp) in different feeding niches.

Stocking density in composite culture is typically 5,000–8,000 fingerlings per hectare with a species ratio matched to feeding habits.

Pond productivity depends on dissolved oxygen (above 4 mg/L), pH 6.5–8.5 and adequate natural plankton.

Fish seed production relies on hypophysation using pituitary extract or synthetic hormone to induce breeding.

Common fish diseases include epizootic ulcerative syndrome, fin rot and argulosis; water quality management is the first control measure.

Cage and pen culture allow intensive production in reservoirs, lakes and coastal waters.

Fisheries contribute to nutrition through protein-rich fish and by-products such as fish meal and fish oil.

Social forestry includes farm forestry, community forestry and strip plantations along roads and canals.

Agroforestry combines trees with crops or livestock; nitrogen-fixing species such as Leucaena and Gliricidia improve soil fertility.

Afforestation and reforestation differ: afforestation establishes forest on non-forest land, reforestation restores degraded forest.

Silvicultural systems include clear felling, shelterwood, selection and coppice systems, chosen by species and management objective.

Forest products are classified as major (timber) and minor (bamboo, honey, gums, resins, medicinal plants, tendu leaves).

Windbreaks and shelterbelts reduce wind erosion and protect crops; species selection depends on rainfall and soil depth.

Joint Forest Management involves local communities in protection and benefit-sharing of degraded forest land.

Soil sampling uses a zig-zag pattern; a composite sample from 10–15 spots is mixed, quartered and about 500 g sent for analysis.

Seed germination test: place 100 seeds on moist filter paper, count normal seedlings after the prescribed period, and express as percentage.

Plant protection spray volume for a knapsack sprayer is calibrated by spraying water on a measured area and measuring the volume used.

Field layout records plot size, replication, randomization and treatment number; a randomized block design requires at least three replications.

Herbarium specimen preparation requires pressing, drying and labelling with botanical name, family, locality and date.

Farm records for a project include input costs, labour days, yields and prices, from which gross margin is calculated.

Water sample testing for irrigation checks pH, electrical conductivity and sodium adsorption ratio to judge suitability.