Agriculture in your biology syllabus is not about tractors. It is about how biology gets applied to feed 1.4 billion people. The chapter pulls together genetics, plant physiology, ecology and microbiology, which is why CBSE and NEET both like it — they can test six topics through one question on hybrid wheat.
We will walk through the key practices, the science behind each one, and the questions that keep coming back in PYQs.
Key Terms
- Crop variety: a population of a crop species with a specific, heritable set of desirable traits (yield, disease resistance, grain quality).
- Hybridisation: deliberate crossing of two genetically different parents to combine desired traits in the offspring.
- Mutagenesis: inducing mutations with chemicals (EMS) or radiation (gamma rays) to generate variation. Basis of “Sharbati Sonora” wheat.
- Biofortification: breeding crops with higher levels of vitamins, minerals or proteins. Think “Atlas 66” wheat for protein, or golden rice for vitamin A.
- Green Revolution: the 1960s–70s jump in Indian wheat and rice output, driven by Norman Borlaug’s semi-dwarf varieties plus fertilizer and irrigation.
- Integrated Pest Management (IPM): combining biological, mechanical and chemical methods to keep pest damage below an economic threshold.
- Kharif and rabi: monsoon crops (rice, maize, cotton) vs winter crops (wheat, mustard, gram).
Whenever a question names a specific crop variety, it is usually testing one of three points — the trait it was bred for, the breeder who produced it, or the method used. Memorise the trio for about ten famous varieties and you are set.
Core Concepts
Crop improvement — the five steps
Every plant breeding programme, whether for wheat in Ludhiana or tomato in Bangalore, follows the same sequence.
- Collection of variability — gather germplasm from wild relatives, landraces and existing cultivars. This is the raw material.
- Evaluation and parent selection — test accessions for the trait you want (yield, rust resistance, drought tolerance).
- Cross-hybridisation — hand-pollinate the selected parents. Emasculation, bagging and tagging are done to prevent unwanted pollen.
- Selection and testing of superior recombinants — grow the F₁, self to F₂, and pick plants that show the desired trait combinations.
- Testing, release and commercialisation — multi-location trials, yield tests, release by the Central Variety Release Committee.
The mnemonic “Collect Evaluate Cross Select Release” (CECSR) covers the five steps. Any NCERT one-mark question on “steps of plant breeding” is answered straight from this list.
Major Indian crop varieties to remember
| Crop | Variety | Key trait |
|---|---|---|
| Wheat | Sonalika, Kalyan Sona | High yield, semi-dwarf (Green Revolution) |
| Wheat | Atlas 66 | High protein |
| Rice | Jaya, Ratna | High yield, short duration |
| Maize | Shakti, Rattan | High lysine (biofortified) |
| Sugarcane | Saccharum officinarum × S. barberi | Thick stem, high sugar, tropical adaptation |
| Mustard | Pusa Swarnim | Low erucic acid |
| Cauliflower | Pusa Shubhra | Black rot and curl blight resistant |
| Cowpea | Pusa Komal | Bacterial blight resistant |
Nutrient management
Plants need 17 essential elements. The macronutrients N, P, K come in bulk from fertilizers; micronutrients like Fe, Mn, Zn are needed in trace amounts. Urea (46% N), DAP (18% N, 46% P₂O₅) and MOP (60% K₂O) are the three fertilizers every biology student should recognise by formula.
Manures and biofertilizers are the biological alternatives — cow dung compost, vermicompost, Rhizobium in legume root nodules, Azotobacter and Azospirilum free in soil, blue-green algae in paddy fields, and mycorrhiza (Glomus) that help with phosphate uptake.
For a tonne of wheat grain, the crop removes roughly , and from the soil. This is the minimum you must replace to keep yields stable.
Irrigation
India gets 80% of its rainfall in four monsoon months, so irrigation is critical for rabi crops. Major systems:
- Wells and tube wells — most common, groundwater driven.
- Canals — from dammed rivers (Bhakra, Hirakud).
- Tanks — traditional in south India, fed by rainfall.
- Drip and sprinkler — high efficiency, water saving, pushed hard in Rajasthan and Maharashtra.
Storage and pest control
Post-harvest losses in India are 10–15% of production. Biotic causes: insects, rodents, fungi, bacteria, mites. Abiotic: moisture and temperature. Treatment includes drying grain below 14% moisture, fumigation and good storage structures.
For pest control, IPM is the modern answer:
- Biological — Trichogramma wasps against sugarcane borer, Bacillus thuringiensis spray against caterpillars.
- Mechanical — hand picking, light traps, pheromone traps.
- Chemical — pesticides as the last resort, rotated to prevent resistance.
- Cultural — crop rotation, trap crops, resistant varieties.
Animal husbandry as part of agriculture
NCERT groups animal husbandry under agriculture. The high-yield Indian dairy breeds are Sahiwal, Red Sindhi, Gir and Deoni. Exotic breeds are Jersey and Brown Swiss. Cross-breeds like Karan Swiss and Karan Fries combine heat tolerance with high milk yield — a classic breeding goal.
Poultry improvement focuses on broiler (meat) and layer (egg) birds. ILS-82 and B-77 are layer breeds you should know by name.
Worked Examples
Traditional tall wheat varieties lodged — they fell over — when given high nitrogen. Borlaug’s semi-dwarf plants had shorter, thicker stems, so they held up heavy grain heads even with heavy fertilizer. This let farmers push yields from 1 tonne/ha to 4 tonnes/ha. Same genetics, different architecture — the win was structural.
A soybean crop with good Rhizobium nodulation fixes about per hectare per season. At urea cost of roughly ₹30/kg N, that is about ₹3000–₹4500 per hectare saved, plus the soil stays healthier. This is why pulses in the rotation matter economically, not just ecologically.
If a pest causes ₹2000/ha yield loss and a single pesticide spray costs ₹800/ha but recovers the loss, the economic threshold is the pest density at which loss equals control cost. Below it, you save money by not spraying. IPM is built on this number.
Common Mistakes
Writing “Green Revolution was only about wheat”. It was wheat and rice, driven mainly by semi-dwarf varieties plus fertilizer, irrigation, and pesticides — a four-legged stool, not a one-trick pony.
Confusing biofortification with genetic engineering. Biofortification can be done by conventional breeding (Atlas 66) or by GM (golden rice). The word only tells you the goal — higher nutrient content.
Saying Rhizobium fixes nitrogen while free-living in soil. It fixes nitrogen only in symbiosis with legume root nodules. Free-living fixers are Azotobacter, Azospirilum and cyanobacteria.
Mixing up manure and fertilizer. Manure is organic (cow dung, compost) and slow release; fertilizer is inorganic (urea, DAP) and fast release. Both add nutrients, but only manure improves soil structure.
Exam Weightage
| Exam | Typical weight | What they ask |
|---|---|---|
| CBSE Class 9 | 5–6 marks | Crop production practices, storage |
| CBSE Class 12 | 4–5 marks | Plant breeding steps, SCP, biofortification |
| NEET | 1–2 questions | Variety names, biofertilizers, IPM |
| State boards | 5–8 marks | Usually long answer on Green Revolution |
For NEET specifically, PYQs cluster around: which microbe is a biofertilizer, which variety was bred for which trait, the role of emasculation, and the difference between Rhizobium and Azotobacter. Four questions in five years, same four ideas.
If the question mentions “triticale”, remember it is a man-made hybrid of wheat (Triticum) and rye (Secale), created to combine wheat’s productivity with rye’s hardiness. This single fact has appeared in NEET and state PMT papers.
Practice Questions
Q1. Name the five steps of plant breeding.
Collection of variability, evaluation and parent selection, cross-hybridisation, selection and testing of superior recombinants, testing/release/commercialisation. Mnemonic: CECSR.
Q2. What is biofortification? Give one example.
Breeding crops for higher levels of vitamins, minerals or proteins. Example: Atlas 66 wheat bred for high protein content. Golden rice (GM) for vitamin A.
Q3. Differentiate between manure and fertilizer.
Manure is organic (cow dung, compost), slow-release, improves soil structure. Fertilizer is inorganic (urea, DAP), fast-release, does not improve soil structure.
Q4. Name three biofertilizers and their functions.
Rhizobium (nitrogen fixation in legume nodules), Azotobacter (free-living N fixation), Glomus (mycorrhizal phosphorus uptake).
Q5. What is IPM?
Integrated Pest Management — combining biological, mechanical, cultural, and chemical methods to keep pest damage below economic threshold. Chemical pesticides are the last resort.
Q6. Why are pulses important in crop rotation?
Pulses (legumes) have Rhizobium in root nodules that fix atmospheric nitrogen, enriching the soil naturally and reducing fertilizer dependency for the next crop.
FAQs
What was the Green Revolution?
The Green Revolution (1960s–70s) was a dramatic increase in wheat and rice yields in India, driven by semi-dwarf high-yielding varieties developed by Norman Borlaug and adapted by M. S. Swaminathan, combined with irrigation, fertilizers, and pesticides.
What is tissue culture propagation?
Growing plants from small tissue pieces on nutrient media under sterile conditions. This produces genetically identical plants (clones) rapidly. Used for disease-free plants, orchids, and banana.
What is single-cell protein (SCP)?
Protein produced from microorganisms (Spirulina, Methylophilus) grown on industrial substrates. Spirulina has about 60% protein by dry weight and can supplement feed or food.
What is emasculation and why is it done?
Emasculation is the removal of anthers from a bisexual flower before they mature, to prevent self-pollination. The emasculated flower is then bagged and later hand-pollinated with pollen from the desired male parent. This ensures the cross produces only hybrid seeds. It is a critical step in plant breeding — NEET tests it regularly.
What is the difference between hybridisation and genetic engineering?
Hybridisation combines genes from two parents of the same or closely related species through sexual crossing. Genetic engineering transfers specific genes between any organisms (even across kingdoms) using recombinant DNA technology. Bt cotton uses a bacterial gene (from Bacillus thuringiensis) in a plant — impossible through hybridisation.
What is organic farming?
A system that avoids synthetic fertilizers, pesticides, and GMOs. It relies on crop rotation, green manures, compost, biological pest control, and mechanical cultivation. India is the largest producer of organic food by number of farmers (over 3 million). Sikkim became India’s first fully organic state in 2016.
Agriculture looks like a memory chapter at first glance, but the examiner is really testing whether you can connect a practice to the biology behind it. If you can say why nodulation saves fertilizer, or why semi-dwarf wheat doesn’t fall, you are answering the new NCERT pattern correctly.