Citrus Cultivation: Production Technology of Citrus

Citrus spp.; Rutaceae; 

2n=18

INTRODUCTION:

Citrus is the leading tree fruit crop globally. In India, it ranks second in area with 12.8% share under fruit crops and 9.6% share in production. Among citrus, mandarins dominate with 50% area followed by sweet orange and limes. Major citrus growing states are Maharashtra, Andhra Pradesh, Punjab, Karnataka, and the North-Eastern region. Citrus is micro-nutrient loving. Trifoliate orange is resistant to Phytophthora and nematodes. Limolin is the glycoside responsible for the bitter taste in citrus juice. Nagpur mandarin was introduced by Shriji Raja Bhosle in 1894. High-density planting of Kinnow is possible using Troyer Citrange rootstock (1.8 x 1.8 m spacing). Citrus classification is given by Tanaka and Swingle. Grapefruit is also called Forbidden fruit or breakfast food. Citron is referred to as Persian apple.

ORIGIN & DISTRIBUTION:

Originates in South-East Asia and tropical/sub-tropical Indochina. Grown between 40°N to 40°S latitudes. Major producers: USA, Spain, India, Italy, Japan, Brazil, South Africa, etc. USA contributes 35-40% of world citrus production.

CLIMATE AND SOIL:

• Thrives in dry semi-arid climate for quality fruits.
• Tolerates light frosts.
• Optimum temperature: 16–20°C (range 17–40°C).
• Annual rainfall: 500–775 mm.
• Grows in well-drained sandy or clay loams.

SPECIES AND CULTIVARS:

Classification:
Swingle (1948) – 16 species: Eucitrus (10), Papeda (6).
Tanaka (1954) – 144 species: Archicitrus (98), Metacitrus (46).
Swingle is preferred for practical utility due to less confusion.

Major species:

1. MANDARIN GROUP:

• C. reticulata: Polyembryonic. Nagpur, Coorg, Khasi (India), Ponkan (China).
• C. unshu: Seedless. Satsuma, Owari, Kara, Silver hill (Japan).
• C. deliciosa: Willow leaf, Kinnow, King, Blinda (Mediterranean).
• C. nobilis: Tangor type. Kunembo, King Orange (Indo-China).

2. ORANGE GROUP:

• C. sinensis (Sweet orange): Mosambi, Blood Red, Sathgudi, Valencia, Pineapple, Washington Navel, etc.
• C. aurantium (Sour orange)

3. GRAPEFRUIT & PUMMELO GROUP:

• C. grandis (Pummelo): Monoembryonic. Kaopan, Buntan.
• C. paradisica (Grapefruit): Polyembryonic. Ruby, Marsh, Duncan, etc.

4. ACID LIME GROUP:

• C. limon (Lemon): Eureka, Lisbon, Feminello, etc.
• C. jambheri (Rough lemon): Indian rootstock.
• C. aurantifolia (Acid lime): Kagzi lime – canker susceptible.
• C. medica (Citron): Monoembryonic.
• C. karna (Kharna Khatta): Rootstock.
• C. limonica (Rangpur lime): Tolerant to tristeza and salt.

Other wild species: C. indica, C. latipes, C. macroptera, C. ichangensis, C. assamensis

Related genera:

• Poncirus: Trifoliate orange – inedible, rootstock.
• Fortunella (Kumquat): Ornamental. Margarita, Japonica, etc.

INTERGENERIC HYBRIDS:

• Citrange: Trifoliate x C. sinensis (Troyer, Carriyo, etc.)
• Citrangequat: Citrange x Fortunella
• Citrangedin: (P. trifoliata x C. sinensis) x C. mitis
• Others: Citrangor, Cicitrange, Citrandarin, Citrumelo, Citermon, Citrumquat

FORTUNELLA HYBRIDS:

• Procimequat: F. japonica x C. aurantifolia x F. hindisi
• Limequat: C. reticulata x F. japonica x F. margarita

INTRAGENERIC HYBRIDS:

• Tangor: C. reticulata x C. sinensis (Temple, Clementine, etc.)
• Tangelo: C. reticulata x C. paradise (Orlando, Sampson, etc.)
• Lemonima: C. limon x C. aurantifolia
• Lemmonnage: C. limon x C. reticulata

SWEET ORANGE:

Grown commercially in Andhra Pradesh, Maharashtra, Karnataka, Punjab, Haryana, Rajasthan.

Cultivars: Blood Red (Punjab), Jaffa, Hamlin, Mosambi (Maharashtra), Sathgudi (AP)

Propagation: Budding (T or Patch) in Jan-Mar or Sep-Oct. Popular rootstocks: Jatti Khatti, Rangpur lime.

Land Preparation & Planting:

• Pits of 60 cm³, filled with soil + FYM + Carbofuron
• Monsoon planting at spacing of 6m x 6m

Manuring:

550:370:550 gm NPK/tree/year. Apply fertilizers in a 30–40 cm ring, 1–2 m away from trunk.

Irrigation:

• Regular during fruit development
• Avoid direct trunk contact (double ring method best)
• Drip irrigation preferred
• Stop irrigation 1–2 months before flowering

Interculture:

• Legumes and cucurbits can be intercropped
• Avoid solanaceous crops
• Weed control: diuron @ 3 kg/ha (2 sprays at 120-day intervals), simazine, atrazine, 2,4-D, etc.

Pruning and Training:

No regular pruning. Remove dead/diseased branches after harvest. Train to single trunk up to 1m in first 3 years.

Harvesting and Yield:

• 9–12 months to mature
• Harvest when fully ripe (non-climacteric)
• North India: Dec–Feb; South India: Oct–Mar; Central India: Nov–Jan, Mar–May
• Yield: 500–2000 fruits/tree

Post-harvest Handling and Storage:

• Wash, dry, grade, wrap in tissue, pack in corrugated boxes
• Dip in 500 ppm Benlate or 0.1% carbendazim
• Storage: Malta (2–3 months @ 4.4°C), Sathgudi (4 months @ 2°C), Mosambi (3 months @ 5°C and 85–90% RH)

Physiological Disorders – Fruit Drop:

• Natural shedding of flowers/fruits
• Pre-harvest drop is serious
• Causes: Climate, water stress, nutrition, seed-fruit link
• Control: Spray 10 ppm 2,4-D 2 months before harvest, 1% Bordeaux mixture for disease prevention

Soil

Mandarins adapt well to various well-drained soils, though light loamy soils are most suitable. They can tolerate a pH range from 4.5 to 9.0, but the ideal range is between 6.0 and 8.0.

Cultivars

• Coorg: Medium to large-sized bright orange fruits, obvate-globose shape with thin rind. Common in Coorg and Wynad, harvested in February-March.
• Khasi: Depressed globose to ovate fruits, smooth and orange-yellow, grown in Assam, Meghalaya, and NE India.
• Nagpur: Popular subglobose fruits with a smooth surface and a slightly extended base. Ripens between January and February.
• Kinnow: Hybrid of King Mandarin × Willow Leaf. Medium obvate fruits with deep orange-yellow color. Known for irregular bearing, matures mid-January.

Propagation

Mandarins are propagated by seeds (nucellar seedlings) and T-budding on rootstocks such as Rangpur lime, Rough lemon, Cleopatra, Troyer Citrange, and Kharna Khatta.

Planting

Planting is done during monsoon using 50 cm³ pits with 4–6 m spacing. Kinnow on Troyer Citrange allows 1.8 m spacing with 3000 plants/ha.

Manuring

Each plant requires 450 g nitrogen, 450 g phosphorus, and 900 g potassium in two splits (May and post-harvest). Micronutrient spray includes zinc sulphate, copper sulphate, magnesium sulphate, manganese sulphate, ferrous sulphate, boric acid, slaked lime, and urea mixed in 450 liters of water annually.

Irrigation

Irrigation frequency is every 10–15 days in winter and 5–7 days in summer. Drip irrigation is highly effective. Avoid water stress during key stages. In South India, mandarins grow rainfed in high rainfall zones.

Interculture

Intercropping with pea, cowpea, and gram is beneficial. Weeds can be controlled with diuron (5 kg/ha) pre-emergence and atrazine (5–6 kg/ha) post-emergence.

Training & Pruning

Train as low-headed plants (50 cm) with single stem. Prune after fruiting to remove dead or diseased branches, suckers, and water shoots.

Crop Regulation (Bahar Treatment)

Flowering occurs three times annually:

• Ambebahar – February
• Mrigbahar – June (preferred)
• Hastbahar – October

Regulated by withholding water before flowering to induce stress, followed by manure and irrigation to stimulate blooming.

Harvesting and Yield

Harvest at full maturity. Fruiting begins by year 4; commercial yields from year 10–12. Yields range from 500 to 1000 fruits per plant. Ethrel (50 ppm) treatment accelerates color development. Storage is possible for several months at 8–10°C and 85–90% RH.

Citrus Decline

Caused by tristeza virus, leading to leaf yellowing, root decay, dieback, and tree death. Often seen in poorly managed orchards. Management includes pruning deadwood, spraying Bordeaux mixture, organic manuring, and using tolerant rootstock like Rangpur lime.

Granulation

Seen in Mosambi, Hamlin, and Blood Red. Characterized by hardening of juice vesicles and reduced juice content. Influenced by variety, climate, nutrition, and age. Managed by lime/Zn/Cu sprays, early harvest, reduced irrigation, and 200–500 ppm lead arsenate sprays.

Fruit Drop

Preharvest drop can reduce yields. Controlled through proper practices and spraying with 2,4-D (10 ppm), NAA (5 ppm), 2,4,5-T (5 ppm), and Aureofungin (20 ppm).

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Limes and Lemons

India leads global acid lime production and ranks fifth in lime and lemon output. Cultivated widely across A.P., Maharashtra, Tamil Nadu, Karnataka, Gujarat, Bihar, Himachal Pradesh, Punjab, Rajasthan, and U.P.

Origin

Limes – India, Lemons – Malaya

Climate and Soil

Acid limes prefer warm, frost-free, moderately humid climates up to 1000 m elevation. Sweet limes tolerate frost better. Lemons thrive in both humid and semi-humid areas up to 1200 m. Soil must be deep, well-drained, and rich in organic matter with a pH of 6.5–7.0.

Varieties

• Kagzi Lime: Most common variety.
• Pramalini, Vikram, Saisarbat: High yielding and disease resistant.
• Selection 49: Tolerant to canker and leaf miner.
• Seedless Lime: Oblong, prolific bearer.
• Tahiti Lime: Large, triploid, nearly thornless.
• Sweet Limes: Mithachikna (thin rind), Mithotra (thick rind).

Lemon Varieties

• Eureka, Lisbon, Villafranka: Commercially grown types.
• Lucknow Seedless, Nepali Round, Kagzikalan: Local selections with good traits.
• Plant Lemon 1: Canker and tristeza tolerant, self-compatible.

Propagation

Acid lime: through seeds (nucellar) or budding on Rangpur lime. Sweet lime: by cuttings, layering or budding. Lemons: by budding on trifoliate orange or Rangpur lime.

Planting

Done before/after rains depending on rainfall. Pits of 1 m³ are filled with soil-manure mix. Spacing: 4–6 m (limes), 6–8 m (lemons).

Training and Pruning

Limes are trained as low-headed. Prune annually to remove fruited shoots and unhealthy branches.

Manuring

Lime: 5 kg FYM + 900 g N + 250 g P + 500 g K/plant/year. Lemons need 500 g N/plant/year. Apply micronutrient sprays as in oranges.

Irrigation

Irrigate when the top 25 cm soil dries. Drip system enhances yield. Avoid stem contact by using check bunds.

Interculture

Mulching is effective. Weeds can be managed using Monuron, Diuron, or Gramoxone.

Harvesting and Yield

Harvest from Jan–Sept (limes), May (lemons), June–Aug (Rangpur lime). Lime yields 2000–5000 fruits/plant. Storage: Limes (6–8 weeks at 8.3–10°C), Lemons (8–12 weeks at 7.2–8.6°C).

Citrus Canker

Caused by a Gram-negative bacterium. Symptoms include water-soaked lesions on various plant parts leading to corky spots. Spreads via leaf miner, rain, and wind. Controlled through pruning, Bordeaux spray, and streptomycin (500 ppm) or streptocycline on new flushes.

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