Crop Science — Applied Agronomy & Production
Kharif vs Rabi vs Zaid Crops
| Season | Sown | Harvested | Examples |
|---|
|--------|------|-----------|---------|
| Kharif | June–July (monsoon onset) | Sept–Oct | Rice, Maize, Sorghum, Cotton, Groundnut, Soybean, Tur |
|---|---|---|---|
| Rabi | Oct–Nov (post-monsoon) | March–April | Wheat, Mustard, Barley, Chickpea (Gram), Peas, Linseed |
| Zaid | March–June (summer) | June–July | Watermelon, Muskmelon, Cucumber, Vegetables |
Major Crop Production — India
Rice (Paddy) — Oryza sativa
•Area: 44 million hectares (largest in world)
•Top producers: West Bengal, UP, Andhra Pradesh, Punjab, Bihar
•Water requirement: 1200–2000 mm (highly water-intensive)
•Varieties: IR-36, Jaya (high yielding), Basmati (export quality), Swarna (flood tolerant)
•Soils: Clay loam to clay (high water retention), pH 5.5–6.5
•Nutrients: High N requirement (split dose), P at basal, K for grain filling
•Pests: Brown planthopper (BPH) — most serious; stem borer, leaf folder
•Diseases: Blast (Pyricularia oryzae), Sheath blight, Bacterial leaf blight (BLB)
Wheat — Triticum aestivum
•Area: 32 million hectares
•Top producers: UP, Punjab, Haryana, MP, Rajasthan
•Water requirement: 450–650 mm (5–6 irrigations)
•Critical irrigation stages: CRI (21 days), Tillering (40 days), Jointing (60 days), Boot, Heading, Dough stage
•Varieties: HD-2967, GW-322, DBW-17, K-307; MACS-6222 (rust resistant)
•Nutrients: 120 N, 60 P, 40 K kg/ha (split nitrogen: half basal, half at CRI)
•Diseases: Yellow rust (most important), Brown rust, Black rust, Loose smut, Karnal bunt
Cotton — Gossypium hirsutum (American) / G. arboreum (Desi)
•Area: 12 million hectares
•Top producers: Gujarat, Maharashtra, Telangana, AP, Rajasthan
•Soil: Deep black cotton soil (regur), well-drained
•Season: Kharif (sown May–June, picked Oct–Feb)
•Critical pest: Bollworm complex (American bollworm, Spotted bollworm, Pink bollworm), Whitefly
•Bt Cotton: 95%+ of India's cotton is Bt hybrid — introduced 2002, controls bollworms
•Irrigation: 6–8 irrigations; critical at squaring, flowering, boll development
Soil Nutrients — NPK Functions
| Nutrient | Primary Function | Deficiency Symptom |
|---|
|----------|-----------------|-------------------|
| N (Nitrogen) | Chlorophyll, protein synthesis, vegetative growth | Yellowing from older leaves (bottom up), stunted growth |
|---|---|---|
| P (Phosphorus) | Root development, flowering, seed formation, energy (ATP) | Purple/reddish discolouration of leaves, poor root growth |
| K (Potassium) | Stomatal regulation, disease resistance, enzyme activation | Marginal leaf scorch (browning at leaf edges), starting from older leaves |
| Ca (Calcium) | Cell wall formation, meristem growth | Tip burn, blossom end rot (tomato), apical damage |
| Mg (Magnesium) | Chlorophyll (central atom), enzyme cofactor | Interveinal chlorosis — veins remain green, rest yellows |
| S (Sulphur) | Protein synthesis (cysteine, methionine), oil crops | Yellowing of young leaves (unlike N which starts from old) |
| Fe (Iron) | Chlorophyll synthesis, enzyme cofactor | Interveinal chlorosis on young leaves |
| Zn (Zinc) | Enzyme activation, IAA synthesis | White bud in maize, Khaira disease in rice |
Fertiliser Forms and Application
| Fertiliser | N% | P% | K% | Application |
|---|
|-----------|----|----|----|----|
| Urea | 46 | 0 | 0 | Most concentrated N, split dose |
|---|---|---|---|---|
| DAP | 18 | 46 | 0 | Basal application |
| MOP (Muriate of Potash) | 0 | 0 | 60 | Basal or at tillering |
| 20:20:0:13 (Complex) | 20 | 20 | 0 | Basal, S-containing |
| 10:26:26 (Complex) | 10 | 26 | 26 | Basal for K + P |
| Ammonium Sulphate | 20.6 | 0 | 0 | Acidic soils, S supply |
| SSP (Single Superphosphate) | 0 | 16 | 0 | Contains S and Ca also |
Integrated Pest Management (IPM)
IPM Principles (WHO definition)
Compatible combination of pest control tactics that minimize economic, health, and environmental risks.
IPM Components (in order of preference)
1.Cultural control: Crop rotation, resistant varieties, sowing time adjustment, sanitation
2.Mechanical/Physical: Yellow sticky traps, light traps, pheromone traps, hand picking
3.Biological control: Natural enemies (predators, parasitoids, pathogens)
- Chrysoperla (predator): aphids, whitefly, mites
- Trichogramma (egg parasitoid): lepidopteran pests
- Beauveria bassiana (entomopathogenic fungus): various insects
- NPV (Nuclear Polyhedrosis Virus): bollworm, Spodoptera
4.Chemical control (last resort): Use only when pest crosses Economic Threshold Level (ETL)
Economic Thresholds (ETL) Examples
| Crop-Pest | ETL |
|---|
|-----------|-----|
| Rice — BPH | 5–10 insects per hill |
|---|---|
| Cotton — Bollworm | 5–8% damage or 5 eggs/25 plants |
| Wheat — Aphid | 100 aphids per 10 tillers |
| Tomato — Whitefly | 20 adults per plant |