Tamil Nadu HSE First Year Agricultural Science cheat sheet

Agriculture = art, science and business of raising crops and livestock for human use; its branches are agronomy, horticulture, forestry, animal husbandry, fishery and agricultural engineering.

Tamil Nadu's net sown area is roughly 5 million hectares, about 55-60% of the geographical area is cultivated, and average rainfall is about 900 mm, of which the northeast monsoon (Oct-Dec) supplies the larger share.

Tamil Nadu is divided into seven agro-climatic zones: Northeast, Northwest, Western, Cauvery Delta, Southern, High Rainfall and Hilly zones.

Major TN crops: rice (Thanjavur, Tiruvarur, Nagapattinam delta), sugarcane, cotton, groundnut, coconut, banana and tapioca; TN leads India in tapioca and is a leading producer of coconut and banana.

Green Revolution inputs = HYV seeds + chemical fertilizers + irrigation + pesticides + credit; in TN it centred on the Cauvery delta rice belt from the late 1960s.

Landholding pattern in TN is dominated by marginal holdings (below 1 ha), which make up the large majority of operational holdings.

Key institutions: TNAU (Coimbatore, est. 1971), Department of Agriculture, Agricultural Engineering Department, TANUVAS (Chennai) for veterinary science, and NABARD for rural credit.

Soil profile horizons: O (organic litter), A (topsoil, humus-rich), E (eluviation), B (illuviation/accumulation), C (weathered parent material), R (bedrock).

Soil texture triangle classifies by % sand, silt and clay; loam is the ideal balance, clay holds water and nutrients but drains poorly, sand drains fast but leaches nutrients.

Bulk density = oven-dry soil mass / total volume (g/cm3); particle density is about 2.65 g/cm3, so porosity % = (1 - bulk density/2.65) x 100.

Soil pH scale: below 6.5 acidic, 6.5-7.5 neutral, above 7.5 alkaline; acidic soils are corrected with lime, alkaline/sodic soils with gypsum.

Cation exchange capacity (CEC) is measured in cmol(+)/kg; high-clay and high-humus soils have higher CEC and retain more nutrients.

Essential nutrients: 16-17 elements; N, P, K are primary macronutrients, Ca, Mg, S secondary, and Fe, Mn, Zn, Cu, B, Mo, Cl (plus Ni) micronutrients.

Tamil Nadu soil types: red loam, laterite, black (vertisol), alluvial, coastal saline, and problem soils (acid saline soils of the coastal belt).

Soil conservation measures: contour bunding, graded bunding, terracing on slopes, check dams, green manuring with daincha (Sesbania) and crop residue mulching.

Cropping seasons in TN: Kharif (June-Sept, southwest monsoon), Rabi (Oct-Jan, northeast monsoon), and summer/June-July special seasons; the northeast monsoon is the main rainy season.

Cropping intensity % = (gross cropped area / net sown area) x 100; multiple cropping raises it above 100.

Seed rate examples: rice (transplanted) 40-60 kg/ha, direct-seeded rice 80-100 kg/ha, groundnut 100-120 kg kernel/ha, cotton 15-20 kg/ha.

Spacing determines plant population: plants/ha = 10,000 / (row spacing in m x plant spacing in m).

Rice nursery: 8-10 day old seedlings for short-duration varieties, 20-25 days for medium/long duration; System of Rice Intensification uses single 8-12 day seedlings with wide spacing.

Fertilizer dose is expressed as N:P2O5:K2O; urea is 46% N, DAP 18% N and 46% P2O5, muriate of potash 60% K2O, single super phosphate 16% P2O5.

Weed control: critical period of crop-weed competition is the first 30-45 days; integrated approach = cultural + mechanical + herbicide (e.g., pre-emergence pendimethalin).

Irrigation scheduling: IW/CPE ratio (irrigation water depth / cumulative pan evaporation), with 0.8-1.0 common for many crops; drip and sprinkler improve water use efficiency.

Horticulture divisions: pomology (fruit), olericulture (vegetables), floriculture (flowers), arboriculture (trees), and plantation crops.

Propagation: sexual (seed) gives variability; asexual (cutting, layering, grafting, budding, tissue culture) preserves true-to-type characters.

Grafting terms: scion is the fruiting top portion, rootstock is the rooted lower portion; mango is propagated by veneer grafting, citrus by budding (T-budding).

Banana is propagated by suckers or tissue-cultured plantlets; it is a herbaceous perennial, not a tree, and TN is a leading banana producer.

Coconut (plantation crop) is propagated by seedlings from mother palms; tall x dwarf hybrids are used; copra and coconut oil are the main products.

Tapioca (cassava) is propagated by stem cuttings; TN dominates Indian tapioca production, grown mainly in Salem, Namakkal and Erode districts.

Protected cultivation: polyhouse, shade net and plastic mulch modify temperature, light and humidity; micro-irrigation with fertigation is standard in high-value horticulture.

Post-harvest: grading, precooling, controlled/modified atmosphere storage, and value addition (jam, squash, dried products) reduce losses, which can exceed 20-30% in fruits and vegetables.

Insect mouthparts determine control: chewing (caterpillars, beetles) suit stomach poisons/contact insecticides; piercing-sucking (aphids, hoppers) suit systemic insecticides.

Metamorphosis: complete (egg-larva-pupa-adult, e.g., butterflies, beetles) versus incomplete (egg-nymph-adult, e.g., hoppers, bugs).

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

Major TN pests: brown plant hopper and yellow stem borer in rice, American bollworm in cotton, leaf-eating caterpillar in banana, rhinoceros beetle and red palm weevil in coconut.

Disease triangle: susceptible host + virulent pathogen + favourable environment; removing any one factor prevents disease.

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

Rice blast (Magnaporthe oryzae) causes spindle-shaped lesions; bacterial leaf blight (Xanthomonas oryzae) causes water-soaked margins and wilting; tungro is a virus spread by green leafhopper.

Integrated Pest Management (IPM): cultural, mechanical, biological (Trichogramma, NPV, Bacillus thuringiensis), chemical as last resort, and avoiding resistance by rotating insecticide groups.

Ruminant digestion: four-chambered stomach (rumen, reticulum, omasum, abomasum); rumen microbes ferment cellulose and synthesize B vitamins and microbial protein.

Cattle breeds: indigenous milch (Sahiwal, Red Sindhi, Gir), draught (Kangayam, Umblachery, Hallikar) and exotic (Holstein Friesian, Jersey); Kangayam is a native TN draught breed.

Buffalo breeds: Murrah (high milk), Surti, Jaffarabadi; TN has the Toda buffalo of the Nilgiris.

Poultry: layers vs broilers; incubation period of chicken eggs is 21 days; indigenous breeds include Aseel and Kadaknath.

Artificial insemination uses diluted, frozen semen and oestrus detection; the oestrous cycle in cattle is about 21 days and gestation about 280-285 days.

Common diseases: foot-and-mouth disease (viral), mastitis (bacterial), anthrax (bacterial, zoonotic), Newcastle disease (Ranikhet) in poultry; vaccination is the main control.

Feed: concentrate mixture plus roughage; balanced ration supplies energy, protein, minerals and vitamins; urea/molasses treatment improves straw digestibility.

Zoonoses (e.g., rabies, anthrax, brucellosis) transmit from animals to humans; pasteurization and vaccination reduce risk.

Tillage operations: primary (mouldboard plough, disc plough) break and invert soil; secondary (cultivator, harrow, rotavator) pulverize and level the seedbed.

Sowing implements: seed drill places seed in rows, dibbler places seed at spots; transplanters are used for rice and vegetables.

Power sources: human, animal, and mechanical (tractor, power tiller); tractor power is rated in horsepower (hp), 1 hp = 0.746 kW.

Irrigation systems: surface (flood, furrow), sprinkler (suitable for undulating land), and drip (saves water, suits orchards and vegetables).

Water pumps: centrifugal pumps for shallow lifts, submersible pumps for deep wells; pump efficiency = water horsepower / brake horsepower x 100.

Processing equipment: thresher separates grain from chaff, winnower cleans by air, and rice mill converts paddy to rice; drying reduces moisture to safe storage levels (about 12-14%).

Farm machinery selection depends on farm size, soil type, crop, and available power; custom hiring centres provide machinery to small farmers.

Farm management decisions rest on the principle of equi-marginal returns: allocate resources so the marginal return per unit is equal across uses.

Cost concepts: fixed cost (does not vary with output) versus variable cost (varies with output); total cost = fixed + variable.

Gross income = yield x price; net income = gross income - total cost; farm profitability is judged by net income and benefit-cost ratio.

Benefit-cost ratio = total benefits / total costs; a ratio above 1 indicates profitability.

Law of diminishing returns: as a variable input is added to fixed inputs, marginal product eventually declines.

Marketing channels, marketable surplus, and price spread (producer price vs consumer price) determine farmer's share of the consumer rupee.

Credit sources: institutional (cooperative banks, commercial banks, RRBs, NABARD) and non-institutional (moneylenders); crop insurance (PMFBY) and minimum support price protect income.

Farm records: physical (area, yield, inputs) and financial (receipts, expenses) help evaluate efficiency and plan the next season.

Extension is the process of transferring technology from research to farmers and feedback from farmers to research; it is education, not mere information supply.

Extension methods: individual (farm visit, home visit), group (demonstration, field day, method demonstration), and mass (radio, TV, print, social media).

Teaching methods: result demonstration shows a proven practice, method demonstration teaches a skill step by step; both are more effective than lectures alone.

Adoption process stages: awareness, interest, evaluation, trial, adoption; innovators and early adopters lead, laggards follow last.

Diffusion of innovations: communication channels and change agents speed adoption; local leaders and farmer interest groups are effective multipliers.

Rural development programmes: panchayat raj institutions, self-help groups (SHGs), National Rural Livelihood Mission and MGNREGA support rural incomes and employment.

Extension worker qualities: technical competence, empathy, communication skill and local language ability; participatory approaches (PRA) build trust.

Sustainable agriculture balances productivity, profitability and environmental protection; it uses organic matter, crop rotation and integrated nutrient management.

Soil erosion types: sheet, rill, gully and wind erosion; erosion reduces topsoil, organic matter and productivity.

Greenhouse gases from agriculture: methane (ruminants, flooded paddy) and nitrous oxide (excess nitrogen fertilizer); CO2 from fuel and land clearing.

Organic farming avoids synthetic fertilizers and pesticides; it uses compost, vermicompost, green manure, biofertilizers (Rhizobium, Azospirillum, phosphobacteria) and biocontrol agents.

Integrated Nutrient Management (INM) combines organic manures, chemical fertilizers and biofertilizers to maintain soil health and yields.

Water conservation: rainwater harvesting, farm ponds, check dams, and micro-irrigation reduce runoff and improve groundwater recharge.

Biodiversity and agroforestry: trees on farms provide shade, fodder, fuel and habitat; crop rotation and intercropping reduce pest outbreaks.

Pollution sources: pesticide residue, fertilizer runoff causing eutrophication, and stubble burning; safe disposal and integrated pest management reduce harm.

Soil sampling: collect from several spots in a zig-zag pattern, mix, quarter to about 500 g, air-dry, label with location, depth and date, and send for analysis.

Soil pH and EC can be measured in the field with a portable meter or in the lab with a pH meter and conductivity meter; record units (pH unitless, EC in dS/m).

Seed germination test: place counted seeds on moist filter paper or sand, keep in a warm place, count germinated seedlings after the specified period, and calculate germination % = (germinated/total) x 100.

Field visit observations: record crop, variety, growth stage, spacing, irrigation method, pest/disease symptoms, and soil type; compare with recommended practices.

Project activity format: title, objective, materials, procedure, observations, results, conclusion and suggestions; keep a dated field diary.

Pest and disease diagnosis: examine leaves, stems and roots for symptoms and signs (lesions, webbing, insects), collect specimens in labelled bags, and confirm with the teacher or extension officer.

Farm machinery observation: note the implement, its function, power source and field capacity; record safety precautions during operation.

Data handling: tabulate observations, compute averages and percentages, and present results in tables and simple graphs for the project report.