Agriculture

1. Agronomy (அக்ரோனமி)

Definition: Agronomy is the science of crop production and soil management. It deals with improving crop yield by adopting scientific cultivation practices.

Objectives

• Increase crop productivity
• Efficient utilization of soil and water
• Weed management
• Nutrient management
• Sustainable agriculture
• Conservation of natural resources

Crop Classification

Based on Season

• Kharif Crops – Grown during June–October. Examples: Paddy, Maize, Cotton, Groundnut, Soybean.
• Rabi Crops – Grown during October–March. Examples: Wheat, Bengal gram, Mustard, Sunflower.
• Summer Crops – Grown during March–June. Examples: Green gram, Black gram, Sesame.

Based on Life Cycle

• Annual Crops – Complete life cycle within one year. Examples: Rice, Wheat, Groundnut.
• Biennial Crops – Require two years. Examples: Carrot, Beetroot.
• Perennial Crops – Live for many years. Examples: Sugarcane, Coconut, Banana.

Based on Economic Importance

• Cereals, Pulses, Oilseeds, Fibre crops, Plantation crops, Spices, Medicinal crops, Fodder crops.

Cropping Systems

• Monocropping – Growing one crop repeatedly. Advantages: Easy management, mechanization possible. Disadvantages: Pest buildup, nutrient depletion.
• Mixed Cropping – Growing two or more crops without row arrangement. Purpose: Risk reduction, stable income. Example: Bajra + Red gram.
• Intercropping – Growing two crops simultaneously in definite row proportion. Advantages: Better land utilization, higher productivity, reduced pest incidence. Example: Maize + Cowpea.
• Crop Rotation – Growing different crops in sequence. Advantages: Improves soil fertility, controls pests, increases yield, reduces weeds. Example: Rice → Black gram.

Tillage

Definition: Mechanical manipulation of soil to create favorable conditions for crop growth.

Objectives

• Seedbed preparation, Weed control, Aeration, Moisture conservation, Mixing fertilizers.

Types

• Primary Tillage – Deep ploughing. Implements: Mouldboard plough, Disc plough.
• Secondary Tillage – Fine seedbed preparation. Implements: Harrow, Cultivator.
• Minimum Tillage – Only essential operations. Advantages: Saves labour, conserves moisture.
• Zero Tillage – Seeds sown without ploughing. Advantages: Prevents erosion, saves fuel, conserves soil moisture.

Sowing

• Broadcasting – Seeds scattered manually.
• Line Sowing – Uniform spacing.
• Drilling – Seed drill used.
• Dibbling – Seeds placed individually.
• Transplanting – Seedlings shifted. Example: Paddy.

Weed Management

Weed: Any unwanted plant growing with crops.

Harmful Effects

• Competes for nutrients, Reduces yield, Hosts pests, Increases harvesting cost.

Weed Control Methods

• Cultural: Crop rotation, Timely sowing, Mulching.
• Mechanical: Hand weeding, Hoeing.
• Biological: Use of insects or pathogens.
• Chemical: Herbicides. Examples: Glyphosate, Butachlor, Atrazine.

Harvesting, Threshing & Storage

• Harvesting: Harvest when crop reaches physiological maturity. Methods: Manual, Mechanical combine harvester.
• Threshing: Separation of grains from straw.
• Storage: Objectives – Prevent insect damage, avoid fungal growth, maintain seed viability. Structures – Silos, Warehouses, Godowns.

2. Soil Science

Definition: Study of soil formation, properties and fertility.

Soil Formation

Factors: Parent material, Climate, Organisms, Relief, Time.

Soil Profile

• O Horizon – Organic matter.
• A Horizon – Topsoil, highest fertility.
• B Horizon – Subsoil, clay accumulation.
• C Horizon – Weathered rocks.
• R Horizon – Bedrock.

Soil Texture

Based on sand, silt and clay.

• Sandy Soil – Advantages: Good drainage. Disadvantages: Poor nutrient holding.
• Clay Soil – Advantages: High fertility. Disadvantages: Poor drainage.
• Loamy Soil – Ideal agricultural soil.

Soil Structure

Arrangement of soil particles. Types: Granular, Blocky, Prismatic, Platy.

Soil pH

• Acidic soil – Below 7
• Neutral – 7
• Alkaline – Above 7
• Most crops prefer 6.5–7.5

Soil Fertility & Essential Nutrients

• Primary: Nitrogen, Phosphorus, Potassium.
• Secondary: Calcium, Magnesium, Sulphur.
• Micronutrients: Zinc, Iron, Copper, Boron, Manganese, Molybdenum, Chlorine.

Organic Manures

• Farmyard manure, Compost, Vermicompost, Green manure.
• Advantages: Improves structure, water holding capacity, microbial activity.

Chemical Fertilizers

• Nitrogen: Urea, Ammonium sulphate.
• Phosphorus: SSP, DAP.
• Potassium: MOP.

Biofertilizers

Living microorganisms. Examples: Rhizobium, Azospirillum, Azotobacter, Blue Green Algae, Phosphate Solubilizing Bacteria.

Advantages: Eco-friendly, Low cost, Improve fertility.

Soil Erosion

Removal of fertile topsoil. Types: Water erosion, Wind erosion.

Control: Contour farming, Terracing, Shelter belts, Cover crops, Afforestation.

3. Irrigation

Definition: Artificial application of water to crops.

Importance

• Maintains moisture, Improves yield, Prevents drought stress, Enhances fertilizer use efficiency.

Sources

• Rivers, Tanks, Wells, Bore wells, Canals.

Methods

• Surface Irrigation: Flooding, Furrow, Basin.
• Sprinkler Irrigation: Advantages – Uniform distribution, suitable for uneven land, saves water.
• Drip Irrigation: Water supplied directly to root zone. Advantages – Saves 40–70% water, reduces weeds, higher yield, suitable for horticultural crops.

Water Use Efficiency

Higher efficiency means more crop yield per unit of water.

Methods to improve: Mulching, Drip irrigation, Proper scheduling, Laser land levelling.

4. Genetics and Plant Breeding (மரபியல் மற்றும் தாவர இனப்பெருக்கம்)

Introduction: Genetics is the branch of biology that deals with heredity and variation. Plant breeding is the science of developing improved crop varieties with higher yield, better quality, disease resistance, pest resistance, and adaptability to different environments.

Basic Genetic Terms

• Gene – Basic unit of heredity that controls a particular character (e.g., plant height, seed colour, flower colour).
• Chromosome – Thread-like structures in the nucleus that carry genes. Humans possess 46 chromosomes.
• DNA – Carries hereditary information and controls protein synthesis.
• RNA – Helps in protein synthesis; types: mRNA, tRNA, rRNA.
• Genotype – Genetic makeup of an organism (e.g., TT).
• Phenotype – Visible appearance (e.g., Tall plant).
• Dominant Character – Expresses even in heterozygous condition (e.g., Tallness in pea).
• Recessive Character – Expresses only in homozygous condition (e.g., Dwarfness).

Mendel's Laws

Gregor Johann Mendel is known as the Father of Genetics. He conducted experiments using pea plants (Pisum sativum).

• Law of Dominance – Dominant characters mask recessive characters. Example: Tall × Dwarf → F₁ generation → All Tall.
• Law of Segregation – Alleles separate during gamete formation; each gamete receives only one allele.
• Law of Independent Assortment – Characters are inherited independently when genes are located on different chromosomes.

Variation

• Genetic Variation – Inherited.
• Environmental Variation – Not inherited.

Mutation

Sudden heritable change in genes or chromosomes. Importance: Development of new crop varieties, disease resistance, early maturity, stress tolerance.

Polyploidy

Presence of more than two sets of chromosomes. Examples: Wheat, Banana. Advantages: Bigger fruits, increased vigour, higher yield.

Plant Breeding

Objectives

• High yield, Early maturity, Pest resistance, Disease resistance, Drought tolerance, Salt tolerance, Better quality, Climate adaptability.

Plant Breeding Methods

• Selection – Choosing superior plants. Types: Mass selection, Pure line selection. Advantages: Simple, Economical.
• Hybridization – Crossing two genetically different parents. Types: Intervarietal, Interspecific, Intergeneric.
• Backcross Method – Used to transfer one desirable character into an already superior variety (e.g., Disease resistance).
• Mutation Breeding – Artificial mutations using Gamma rays, X-rays, Chemicals.
• Tissue Culture – Growing plants in nutrient media under sterile conditions. Advantages: Rapid multiplication, Disease-free plants, Uniform plants.
• Genetic Engineering – Transfer of useful genes between organisms. Examples: Bt Cotton, Golden Rice.

Hybrid Vigour (Heterosis)

Hybrid offspring perform better than parents. Benefits: Higher yield, Better growth, Disease resistance.

Important Agricultural Scientists

• Gregor Mendel – Father of Genetics
• Norman Borlaug – Father of Green Revolution
• M.S. Swaminathan – Father of Indian Green Revolution

5. Seed Technology

Definition: Science dealing with seed production, processing, testing, storage and certification.

Characteristics of Good Seed

• High purity, High germination, Genetic purity, Healthy, Disease free, Proper moisture, High vigour.

Seed Classes

• Nucleus Seed – Produced by breeder; highest purity.
• Breeder Seed – Produced under breeder supervision; golden yellow tag.
• Foundation Seed – Produced from breeder seed; white tag.
• Certified Seed – Produced from foundation seed; blue tag; used by farmers.
• Truthfully Labelled Seed (TL) – Quality declared by producer.

Seed Dormancy

Failure of viable seed to germinate under favourable conditions. Causes: Hard seed coat, Immature embryo, Chemical inhibitors.

Breaking Dormancy

• Scarification, Stratification, Soaking, Chemical treatment.

Seed Germination

Requirements: Water, Oxygen, Suitable temperature, Viable embryo.

Seed Certification & Storage

• Certification Objectives: Genetic purity, Physical purity, Healthy seed, High germination.
• Storage factors: Moisture, Temperature, Insects, Fungi, Rodents.

6. Agricultural Microbiology

Definition: Study of microorganisms useful in agriculture.

Types of Microorganisms

• Bacteria, Fungi, Actinomycetes, Algae, Viruses.

Nitrogen Fixation

Conversion of atmospheric nitrogen into usable forms.

• Symbiotic Bacteria: Rhizobium – works in legume root nodules.
• Free Living Bacteria: Azotobacter, Azospirillum.
• Cyanobacteria: Blue Green Algae – useful in paddy fields.

Mycorrhiza

Association between fungus and plant roots. Advantages: Better phosphorus uptake, Drought tolerance, Better root growth.

Composting

Microorganisms convert organic wastes into compost. Benefits: Improves fertility, Enhances microbial activity.

Biofertilizers & Biopesticides

• Biofertilizers: Rhizobium, Azospirillum, PSB, BGA. Advantages: Eco-friendly, Cost effective, Sustainable agriculture.
• Biopesticides: Bacillus thuringiensis (Bt), Trichoderma, Pseudomonas fluorescens, Neem-based formulations. Advantages: Safe, Environment friendly, Target specific.

7. Agricultural Engineering

Definition: Application of engineering principles in agriculture.

Farm Power

Sources: Human, Animal, Mechanical, Electrical, Solar, Wind.

Farm Machinery

• Tractor, Cultivator, Rotavator, Seed drill, Combine harvester, Power tiller.
• Advantages: Saves labour, Timely operations, Increased productivity.

Land Preparation Implements

• Primary: Mouldboard plough, Disc plough.
• Secondary: Harrow, Cultivator, Rotavator.

Sprayers

Used for pesticide application. Types: Hand sprayer, Knapsack sprayer, Power sprayer.

Renewable Energy

• Solar pumps, Biogas plants, Wind energy.
• Advantages: Low pollution, Sustainable, Reduced fuel cost.

Precision Agriculture

Uses modern technologies like GPS, GIS, Drones, Remote sensing, Sensors.

Benefits: Efficient fertilizer use, Higher productivity, Reduced cost, Better resource management.

8. Agricultural Economics

Definition: Study of efficient use of agricultural resources.

Factors of Production

• Land, Labour, Capital, Management.

Types of Farming

• Subsistence Farming, Commercial Farming, Mixed Farming, Organic Farming, Integrated Farming.

Cost Concepts

• Fixed Cost: Land tax, Machinery depreciation.
• Variable Cost: Seeds, Fertilizers, Labour.

Market Types

• Village Market, Wholesale Market, Retail Market, Regulated Market, Electronic Market.

Minimum Support Price (MSP)

Minimum price announced by the Government for selected crops to protect farmers from distress sales. Objectives: Income security, Price stability, Encourage production.

Crop Insurance

Provides financial protection against drought, flood, cyclone, pest attack, diseases. Benefits: Reduces financial risk, Stabilizes farm income.

Agricultural Credit

• Institutional: Commercial Banks, Cooperative Banks, Regional Rural Banks, NABARD.
• Non-institutional: Money lenders, Traders.

Agricultural Revolutions

• Green Revolution – Food grain production
• White Revolution – Milk
• Blue Revolution – Fisheries
• Yellow Revolution – Oilseeds
• Golden Revolution – Fruits, Honey and Horticulture
• Silver Revolution – Eggs
• Pink Revolution – Meat and Prawn

9. Horticulture (தோட்டக்கலை)

Definition: Horticulture is the branch of agriculture concerned with the cultivation of fruits, vegetables, flowers, spices, plantation crops, medicinal and aromatic plants.

Branches of Horticulture

• Pomology – Study of fruit crops. Examples: Mango, Banana, Guava, Sapota, Citrus.
• Olericulture – Study of vegetable crops. Examples: Tomato, Brinjal, Bhendi, Cabbage, Onion.
• Floriculture – Cultivation of flowers. Examples: Jasmine, Rose, Marigold, Chrysanthemum, Tuberose.
• Plantation Crops – Coconut, Tea, Coffee, Rubber, Cocoa.
• Spices – Pepper, Cardamom, Turmeric, Ginger, Coriander.
• Medicinal & Aromatic Plants – Aloe vera, Tulsi, Ashwagandha, Lemongrass, Mint.

Propagation Methods

• Sexual Propagation – By seeds. Advantages: Simple, Economical. Disadvantages: Variation among plants.
• Asexual (Vegetative) Propagation – Produces genetically identical plants. Methods: Cutting, Layering, Grafting, Budding, Tissue culture. Examples: Mango – Grafting, Rose – Cutting, Jasmine – Layering, Banana – Tissue culture.

Orchard Management

• Proper spacing, Irrigation, Fertilizer application, Weed control, Pruning, Plant protection, Harvesting.

10. Plant Pathology (தாவர நோயியல்)

Definition: Plant pathology is the study of plant diseases and their management.

Causes of Plant Diseases

• Fungi: Rust, Smut, Blast.
• Bacteria: Bacterial leaf blight.
• Viruses: Leaf curl disease.
• Nematodes: Cause root knot disease.

Disease Triangle

Plant disease develops when three factors interact: Susceptible host, Pathogen, Favourable environment.

Disease Symptoms

• Wilting, Leaf spots, Blight, Canker, Rot, Mosaic, Yellowing, Damping off.

Disease Management

• Cultural: Crop rotation, Field sanitation, Resistant varieties.
• Biological: Trichoderma, Pseudomonas fluorescens.
• Chemical: Fungicides, Bactericides.

Common Crop Diseases

• Rice – Blast, Bacterial leaf blight
• Groundnut – Tikka disease
• Sugarcane – Red rot
• Banana – Panama wilt
• Cotton – Wilt

11. Agricultural Entomology (வேளாண் பூச்சியியல்)

Definition: Study of insects affecting crops.

Insect Body Parts & Mouth Parts

• Body Parts: Head, Thorax, Abdomen.
• Mouth Parts: Chewing, Piercing, Sucking, Sponging.

Metamorphosis

• Complete Metamorphosis: Egg → Larva → Pupa → Adult. Examples: Butterfly, Beetle.
• Incomplete Metamorphosis: Egg → Nymph → Adult. Examples: Grasshopper.

Major Crop Pests

• Rice – Stem borer, Brown plant hopper
• Cotton – Bollworm
• Sugarcane – Early shoot borer
• Groundnut – Leaf miner
• Brinjal – Shoot and fruit borer

Pest Management & IPM

• Cultural: Crop rotation, Clean cultivation.
• Mechanical: Hand picking, Light traps.
• Biological: Trichogramma, Ladybird beetle.
• Chemical: Recommended insecticides.
• Integrated Pest Management (IPM) – Combination of cultural, biological, mechanical and chemical control. Advantages: Reduced pesticide use, Environmental safety, Higher profit.

12. Agricultural Extension

Definition: Extension education transfers agricultural technologies from research institutions to farmers.

Objectives

• Improve farm income, Increase production, Transfer new technology, Improve rural livelihood.

Extension Methods

• Individual: Farm visit.
• Group: Farmer meeting, Demonstration.
• Mass: Radio, Television, Internet, Mobile apps.

Front Line Demonstration (FLD)

Conducted to demonstrate newly released crop technologies.

Krishi Vigyan Kendra (KVK)

Functions: Farmer training, Skill development, Demonstrations, Technology assessment.

13. Organic Farming

Definition: Organic farming avoids synthetic fertilizers and pesticides.

Principles

• Healthy soil, Biodiversity, Ecological balance, Recycling farm wastes.

Organic Inputs

• Farmyard manure, Vermicompost, Green manure, Biofertilizers, Biopesticides.

Advantages

• Safe food, Better soil fertility, Less pollution, Sustainable farming, Improved biodiversity.

Limitations

• Lower initial yield, More labour, Certification required.

14. Sustainable Agriculture

Definition: Meeting present food needs without affecting future generations.

• Components: Soil conservation, Water conservation, Crop diversification, Integrated farming, Organic farming, Precision farming.
• Climate Smart Agriculture: Drought-resistant varieties, Efficient irrigation, Carbon reduction, Weather-based farming.

15. Important Agricultural Institutions

• ICAR – Indian Council of Agricultural Research; highest agricultural research organization in India.
• TNAU – Tamil Nadu Agricultural University, located at Coimbatore.
• NABARD – National Bank for Agriculture and Rural Development; provides agricultural finance.
• FCI – Food Corporation of India; procures and stores food grains.
• APEDA – Agricultural and Processed Food Products Export Development Authority; promotes export of agricultural products.

16. Important Government Schemes

• PM-KISAN – Income support to eligible farmers.
• PMFBY – Pradhan Mantri Fasal Bima Yojana; crop insurance scheme.
• Soil Health Card Scheme – Provides soil nutrient status and fertilizer recommendations.
• PMKSY – Pradhan Mantri Krishi Sinchayee Yojana; slogan "More Crop Per Drop"; promotes efficient irrigation.
• NFSM – National Food Security Mission; increase production of Rice, Wheat, Pulses.
• PKVY – Paramparagat Krishi Vikas Yojana; promotes organic farming.
• RKVY – Rashtriya Krishi Vikas Yojana; supports state agricultural development projects.
• e-NAM – Electronic National Agriculture Market; better price discovery, transparent trading, national market access.

TNPSC Frequently Asked One-Liners

• ICAR headquarters – New Delhi
• TNAU is located at Coimbatore.
• Loamy soil is ideal for crop cultivation.
• Rhizobium fixes atmospheric nitrogen in legumes.
• Azospirillum is widely used in cereal crops.
• Blue Green Algae are useful in paddy cultivation.
• Drip irrigation has the highest water-use efficiency.
• Bt Cotton resists bollworm.
• IPM means Integrated Pest Management.
• INM means Integrated Nutrient Management.
• Crop rotation improves soil fertility and breaks pest cycles.
• Soil pH of 6.5–7.5 is suitable for most crops.
• Vermicompost is prepared using earthworms.
• Trichoderma is a beneficial fungus used against plant diseases.
• Pseudomonas fluorescens is a biocontrol agent.
• e-NAM is an electronic agricultural marketing platform.
• PMKSY slogan: More Crop Per Drop.
• PMFBY is the national crop insurance scheme.

Conclusion

Agriculture is an important subject in the TNPSC Combined Technical Services exam. A thorough understanding of agronomy, soil science, irrigation, plant breeding, horticulture, plant pathology, agricultural economics, and government schemes will help you answer objective questions confidently and score well.