Cultivation of Rice

Botanical & Taxonomic Information

• Scientific Name: Oryza sativa (Asian rice), Oryza glaberrima (African rice)
• Family: Poaceae (Gramineae)
• Chromosome Number: 2n = 24
• Inflorescence Type: Panicle
• Pollination Type: Self-pollinated crop (cleistogamous flowers)
• Center of Origin:
  • Oryza sativa: India, China, and Thailand (Indo-Burma region)
  • Oryza glaberrima: West Africa

Nutritional & Chemical Facts

Rice grain composition:

• Carbohydrates: 78-80%
• Protein: 6-8%
• Fat: 2-2.5%
• Fiber: 0.5-1%
• Ash: 0.3-0.8%
• Rice bran oil: Contains Oryzanol, which lowers cholesterol.
• Thiamine (Vitamin B1) Deficiency: Causes Beri-Beri disease (common in populations consuming polished rice).

Leading Rice Producing States & Countries

• Top Rice-Producing States in India: West Bengal, Uttar Pradesh, Punjab, Odisha, Andhra Pradesh
• Top Rice-Producing Countries (2023): China, India, Indonesia, Bangladesh, Vietnam
• Top Rice Exporting Countries: India (Largest exporter globally), Thailand, Vietnam, Pakistan, United States

Types of Rice Seasons in India

India has three major rice-growing seasons:

• Aus (Autumn) Rice: The term ‘aus’ originates from Sanskrit (‘ashu’ meaning quick). It refers to pre-monsoon rice grown and harvested in August-September, hence called autumn rice.
• Aman (Kharif/Winter) Rice: Derived from Arabic (‘Aman’ meaning safety), it signifies the stability of the crop. This is the main rice crop, harvested in winter.
• Boro (Summer) Rice: Grown in submerged lands during January-February to April-May. It is harvested in summer.

• Varietal Types of Oryza sativa:
  1. Indica Rice: Grown in tropical regions like India; late-maturing, tall, and mostly awnless.
  2. Japonica Rice: Grown in temperate regions (Japan, China); early-maturing, short-stemmed, high nitrogen efficiency.
  3. Javanica Rice: Wild form, cultivated in Indonesia.

Breeding History of High-Yielding Rice

• TN-1 (Taichung Native-1): Developed in Taiwan post-WWII. Introduced in India (1964-65) by G.V. Chalam (NSC GM).
• IR-8 (Miracle Rice): Developed at IRRI, Manila by breeder Henry M. Beachell. Introduced in India (1966), outyielded TN-1.
• Parentage: Dee-geo-woo-gen × Peta (Indonesia).
• Jaya: First Indian rice variety under India’s rice breeding program, developed by Dr. Shastry.
• Parentage: TN-1 × T-141. Outyielded TN-1 & IR-8, hence called “Miracle Rice” in India.
• Padma: Reverse cross of Jaya (T-141 × TN-1).
• Jagannath: Mutant of T-141.
• CR-1014: T-90 × Urang Urangan (Indica × Javanica). Released in 1988, popular in Odisha, Andhra Pradesh, West Bengal.

Important Rice Varieties

• Deep Water Rice: Chakia-59, Madhukar, Jalamagan, Jaisuria, Jaladhi 1 & 2, Pantdhan II, Jalapriya.
• Aromatic (Scented) Rice: Sabarmati, Basmati-370, Karnal Local, Dehradun Basmati, Pusa Basmati-1, Kasturi, Taraori Basmati.
• Non-Basmati Superfine Rice: IR-64, PR-106, Gaurav, Punjab No.1.

Hybrid Rice Development

• First developed in China (1970s) using the Cytoplasmic Male Sterility (CMS) and Fertility Restorer Gene system.
• India started hybrid rice commercialization in 1994, releasing five hybrids:
• APRH-1, APRH-2 (Andhra Pradesh)
• KRH-1 (Karnataka), MGR-1 (Tamil Nadu)
• PHB-71 (Only hybrid released by the private sector).
• Further releases: CNRH-1, KRH-3, DRRH-1 (West Bengal & Andhra Pradesh, 1996).
• Hybrid rice provides higher yields and better disease resistance but requires higher management inputs.

Important Rice Varieties & Their Characteristics

• Jaya: Known as the miracle rice of India
• IR-8: First semi-dwarf high-yielding variety (HYV), called miracle rice
• Swarna: High-yielding variety, flood-resistant
• Sahbhagi Dhan: Drought-resistant variety
• Pusa Basmati-1: Popular Basmati rice variety
• MTU-7029 (Swarna Masuri): One of the most widely grown HYVs
• Sampada, Pusa 44: High-yielding long-duration rice varieties
• CR Dhan 201 & 205: Flood-resistant rice developed by ICAR-CRRI
• Lalat & Naveen: Popular in Eastern India

Weed Control in Rice Cultivation

• Propanil (Stam F-34): 3 kg a.i/ha (8 liters) at 6-8 DAT (days after transplanting) when weeds are 1-3 leaf stage.
• Butachlor (Machete): 2 kg a.i/ha pre-emergence herbicide.
• Fluchloralin (Basalin): Soil incorporated at puddling or 1-3 DAT, applied at 1 kg a.i/ha.
• Nitrofen (TOK-E-25): Pre-emergence application @ 2 kg a.i/ha.

Water Management in Rice Cultivation

• Critical Water Stages:
  • Tillering stage (0-20 days) → Needs 5 cm standing water.
  • Booting stage → Most critical stage for water supply.
  • Primordia growth to flowering (40-60 days) → Essential submergence required.

Transplanting in Rice

• Ideal seedling age:
  • Kharif season: 20-30 days old, with 20×15 cm spacing.
  • Rabi season: 30-35 days old, with 15×15 cm spacing.
• Seedling leaf count:
  • Best: 4 leaves.
  • Acceptable: 3 leaves.
  • Not recommended: 5 leaves (as it leads to delayed growth)
  • Proper spacing and seedling age ensure optimal tillering and higher yields.

Dapog Method of Rice Cultivation

• Origin: Developed in Philippines & Japan

Key Features:

• Seedlings are ready within 12 days, much earlier than traditional methods.
• Higher seed rate: 1.5-3 kg/m², 50 times of test weight per m².
• Grown on wooden planks, trays, concrete floors, or polythene-covered seedbeds.
• 1 m² nursery can transplant 200 m² field (hence, 45-50 m² nursery needed for 1 ha).
• Results in 4-day early flowering compared to conventional methods.
• This method is suitable for intensive rice production systems and reduces transplanting shock.

V-Shaped Rice Cultivation

• Developed by Matsushima (1967)
• Concept: A V-shaped curve is obtained when plotting grain yield per hill against nitrogen application at successive growth stages.
• Reason: This is due to heavy nitrogen fertilization at 5-day intervals, which initially reduces yield but later increases it, forming a V-shaped trend.

This technique optimizes fertilizer use efficiency in rice.

Beushening in Rice

• Definition: A technique where the young rice crop is cross-ploughed 4-6 weeks after sowing in 5-10 cm standing water.
• Purpose:
  • Weed control.
  • Soil aeration.
  • Optimization of crop stand.

This practice is common in broadcasted direct-seeded rice fields.

Puddling in Rice Cultivation

• Definition: Mechanically breaking soil aggregates in excess moisture conditions to create a soft, leveled field.
• Key Benefits:
  • Reduces percolation losses (main objective).
  • Improves nutrient retention.
  • Helps in weed suppression.
• Impact:
  • Increases soil bulk density from 1.4 to 1.7 g/cc.
  • Hampers root penetration for upland crops grown after rice.

Puddling is widely practiced in lowland rice fields to ensure better water retention and yield.

Processing of Rice

1. Milling:
   • Removes aleurone layer and embryo during polishing, reducing non-carbohydrate nutrients.
   • Vitamin B1 (Thiamine) deficiency from polished rice causes Beri-Beri disease.
2. Polishing: Removes fine bran residues and smoothens rice grains.
3. Parboiling: A hydrothermal treatment where starch transforms from a crystalline to amorphous form.
   • Helps in nutrient retention and easier milling.

Parboiled rice is more nutritious than raw milled rice.

Important Agronomic Facts

• Sowing time:
  • Aus (Autumn) Rice: April-May
  • Boro Rice: November-December
• Inflorescence type: Panicle
• Plant type: Short-day crop
• Cardinal temperature: 30-32°C
• Hulling %: 65%
• Fruit type: Caryopsis
• Most used nitrogen fertilizer: Ammonium sulfate
• Optimal pH for rice: 4-6
• Most dominant weed: Echinochloa sp.
• Iron deficiency symptom: White eye in rice
• Gas emitted from rice fields: Methane
• Nutrient loss in rice (highest): Denitrification
• Dwarfing gene: Dee-Gee-Woo-Gen
• Spacing for seedlings: 20×10 cm
• Khaira disease cause: Zinc deficiency
• Miracle rice of India: Jaya
• Largest rice exporter: Thailand
• ICAR-CRRI (Central Rice Research Institute, Cuttack): Leading rice research institute in India.
• Hull Composition: Lemma + Palea together form the husk.
• Pollination: Rice is self-pollinated and a short-day plant.
• Hulling %: 70-75% (Weight of hulled rice ÷ Weight of paddy grain × 100).
• Cardinal Temperature: 30-32°C.
• Test Weight: 25g per 1,000 grains.

Important Rice Production Facts

• Optimum pH for Rice: 4.0 – 6.5
• Seed Rate: Direct-seeded rice: 50-75 kg/ha, Transplanted rice: 30-40 kg/ha
• Spacing: Normal transplanting: 20 × 15 cm, Hybrid rice: 15 × 15 cm
• Rice Yield: Irrigated HYVs: 5-6 t/ha, Rainfed upland rice: 1-2 t/ha
• Moisture Content for Safe Storage: 13-14%
• Duration of Different Rice Types:
  • Short duration: 100-120 days
  • Medium duration: 120-140 days
  • Long duration: 140-160 days

Major Pests & Diseases of Rice

Pests

• Brown Plant Hopper (BPH) (Nilaparvata lugens) – Major vector of Rice Tungro Virus
• Rice Stem Borer (Scirpophaga incertulas) – Causes dead hearts and whiteheads
• Gall Midge (Orseolia oryzae) – Produces silver shoots
• Rice Leaf Folder (Cnaphalocrocis medinalis) – Rolls leaves, reducing photosynthesis

Diseases

• Blast (Magnaporthe oryzae) – Causes leaf blast and neck blast
• Bacterial Leaf Blight (BLB) (Xanthomonas oryzae pv. oryzae) – Leads to yellowing and drying of leaves
• Sheath Blight (Rhizoctonia solani) – Causes necrotic lesions on leaves
• False Smut (Ustilaginoidea virens) – Produces greenish spore balls on grains
• Tungro Disease – Virus disease transmitted by BPH

Important Agronomic Practices

• System of Rice Intensification (SRI):
  • Uses young seedlings (8-12 days old)
  • Wider spacing (25 × 25 cm)
  • Alternate Wetting and Drying (AWD) method to conserve water
  • Improves yield by 20-30%

• Direct Seeded Rice (DSR):
  • Requires less water and saves labor costs
  • Herbicide dependency increases for weed management
  • Ideal for areas with water scarcity

• Aerobic Rice Cultivation:
  • Grown without standing water (like wheat)
  • Saves 50% of irrigation water
  • Suitable for upland and rainfed areas

Environmental Impact & Greenhouse Gas Emissions

• Rice contributes to global warming due to methane (CH₄) emissions from flooded fields.
• Methane emission reduction strategies:
  • Alternate Wetting and Drying (AWD)
  • Direct Seeded Rice (DSR)
  • Use of biochar and organic amendments

Important Genetic & Breeding Facts

• Dwarfing Gene: Dee-Gee-Woo-Gen (introduced in IR-8)
• Hybrid Rice:
  • First developed in China (1974)
  • India introduced hybrids in 1994 (e.g., APRH-1, KRH-1, PHB-71)
• Golden Rice: Genetically engineered rice with β-carotene (Vitamin A precursor)

India’s Average Yield: 2.9–3.5 t/ha