Lemon/ Citrus Cultivation
1. Introduction
Citrus is native to a large area, which extends from Himalayan foot hills of northeast India to northcentral China, the Philippines in east and Burma, Thailand, Indonesia and New Caledonia in Southeast. In India, in terms of area under cultivation, citrus is the third largest fruit industry after Banana and Mango. Over the last 30 years, the area and production under citrus cultivation has increased at the rate of 11 and 9%, respectively, which shows that the expansion of citrus industry was quite sustainable. The average yield of citrus fruits in India is alarmingly low (10.1 t/ha) compared to other developed countries like Brazil, USA, China, Mexico and Spain (30-40 t/ha). Among mandarins, Nagpur mandarin (Central India), Kinnow mandarin (North–West India), Coorg mandarin (South India) and Khasi mandarin (North-East India) are the commercial cultivars of India. Whereas, Mosambi (Maharashtra), Sathgudi (Andhra Pradesh) and Malta and Jaffa (Punjab) are the sweet orange cultivars traditionally grown.
Citrus cultivation in India is plagued with various problems due to limiting growing conditions, limiting water resources and high incidence of pests and diseases warranting great care from planting till the plants come to bearing in order to sustain a productive life of a minimum of 15-20 years. There is growing interest/awareness among the citrus growers for adoption of latest technologies for commercial cultivation of citrus. The National Research Centre (NRC) for Citrus (ICAR), Nagpur has come out with the package of practices for citrus cultivation in different regions of the country. In the present bankable project on citrus, recommendations of the NRC for Citrus and the views of the citrus growers and their experience has been taken into consideration.
The distribution of major citrus fruits is as under :
Madhya Pradesh, A.P., North Eastern region, Punjab, Rajasthan, U.P., West Bengal and Sikkim
Nagpur mandarin
Khasi mandarin
Kinnow, Nagpur mandarin and local
Darjeeling mandarin
Karnataka and Tamil Nadu
Coorg mandarin
3. Acid lime
Andhra Pradesh, Rajasthan, Karnataka, Uttar Pradesh, Gujarat, Madhya Pradesh, Maharashtra
Kagzi lime, Indore seedling
Baramasi, Kagzi lime
4. Grapefruit
Andhra Pradesh
PKM (Jayadevi)
5. Lemon
Gujarat, Andhra Pradesh, U.P.
Assam
Eureka Hill, Gulgal
Assam lemon
Karnataka
Baramasi, Nepali oblong, Italian lemon, Lisbon lemon, Eureka lemon, Seville
6. Pummelo
Andhra Pradesh, Assam, NEH
Red fleshed, White fleshed
3.1.1 Climate
Citrus trees are evergreen, grown in truly subtropical climates of the world although in tropical regions of the world they tend to produce cyclic growth flushes and hence regulating cropping in tropical areas for forcing them into concentrated bloom needs judicious management of water deficit stress according to soil type and growing season. Citrus fruits grow best between a temperature range of 130C to 370C. Temperatures below – 40C are harmful for the young plants. Soil temperature around 250C seems to be optimum for root growth. High humidity favours spread of many diseases. Frost is highly injurious. Hot wind during summer results in desiccation and drop of flowers and developing fruits. Barring these limitations citrus is grown in all subtropical and tropical areas of the world. The sub-tropical climate is best suited for citrus growth and development. Khasi and Darjeeling mandarins are grown in high altitudes upto 2000 m as it is adapted to a cooler climate.
3.1.2 Soil
Citrus plants are grown in a wide range of soils ranging from sandy loam or alluvial soils of north India to clay loam or deep clay loam or lateritic/acidic soils in the deccan plateau and north-eastern hills. Citrus orchards flourish well in light soils with good drainage properties. Deep soils with pH range of 5.5 to 7.5 are considered ideal. However, they can also be grown in a pH range of 4.0 to 9.0. High calcium carbonate concentration in feeder root zone may adversely affect the growth.
3.2 Planting Material
Availability of quality planting material is of utmost importance in citrus cultivation. Citrus plants are very sensitive to various biotic and abiotic stresses. Therefore selection of an ideal rootstock is a continuing challenge for the citrus industry of India. Currently used rootstocks viz. rough lemon and Rangpur lime have gone through a lot of variation over the last five decades. Therefore ideal selections developed from the conventional rootstocks by National Research Centre for Citrus (NRCC), Nagpur and at other places under State Agriculture Universities may be obtained for propagating quality planting material. For budwood selection, disease free mother plants developed from the elite progeny of known pedigree through shoot tip grafting method available at NRCC, Nagpur may only be used.
Primary nursery beds are prepared on light fertile soils or in the HDPE trays under shade net structures. Selection of nucellar seedlings is done by eliminating weak seedlings, off types and non uniform seedlings in 2-3 stages in the nursery beds. Secondary nursery seedlings may be raised in polythene bags also as they become ready for plantation in the main field after attaining the height of about 30-40 cm after one year.
3.3 Land preparation
Land needs to be thoroughly ploughed and leveled. In hilly areas, planting is done on terraces against the slopes and on such lands, high density planting is possible as more aerial space is available than in flat lands. Since citrus trees are highly sensitive to water logging and water stagnation during rainy season providing drainage channels of 3-4 feet depth along the slopes around the orchard is essential.
3.4 Plant density
a. Mandarin (Citrus reticulata Blanco)
Normal spacing – 6 m x 6 m ; Plant population – 277 / ha
b. Sweet orange (Citrus sinensis osbeck)
Normal spacing - 5 m x 5 m, 5.5 x 5.5 m; Plant population – 400/330 per ha
c. Limes/lemons (Citrus aurantifolia Swingle & Citrus limon)
Normal spacing – 6 x 6 m / 5 x 5 m, Plant population – 277/400 per ha
In light soils, spacing will be 4.5 x 4.5 m or 5 x 5 m
3.5 Planting
The best season of planting is June to August. Pits of the size of 75 cm x 75 cm x 75 cm may be dug for planting seedlings. 15-20 kg of FYM and 500 g of super phosphate is applied per pit while planting. With good irrigation system, planting can be done in other months also.
3.7 Manures & fertilizers
Manuring is done in three equal doses three times in a year in February, June and September. The recommended manurial and fertilizers doses are given in Table
One or two sprays of micro nutrient mixtures if required may be given.
3.8 Interculture
Ploughing, spading of basins, weed control, etc., are important inter-culture operations for soil aeration and health. Chemical control of weeds with pre-emergence weedicides like diuron (3 Kg/ha), simazine (4 Kg/ha), glyphosate 4 l/ha, paraquat (2 l/ha), etc. may also be adopted.
3.9 Intercrops
Leguminous crops like soybean, gram, groundnut, cow peas, french bean, peas etc., may be grown in citrus orchards. Intercropping is advisable during the initial three-four years after planting.
3.10 Training and Pruning
In order to allow the growth of a strong trunk, initially shoots upto 40-50 cm from the ground level should be removed. The centre of the plant should remain open. Branches should be well distributed to all sides. Cross twigs and water suckers are to be removed early. The bearing trees require little or no pruning. All diseased, injured and drooping branches and dead wood are to be removed periodically.
3.11 Pests and Diseases Management
3.11.1 Pests
Important insect-pests of citrus are citrus blackfly and whitefly, citrus psylla, Citrus thrips leaf miner, scale insects, bark eating caterpillar/trunk borer, fruit fly, fruit sucking moth, mites, etc. Other pests attacking citrus particularly mandarin orange, specially in humid climate are mealybug, nematode, etc. Control measures of major pests are indicated below:
3.12 Harvesting
Economic life of plantation: 15 to 25 years
5. Post-harvest management
For imparting uniform yellow-orange colour to the fruits application of ethephon @ 250 ppm along with 1 % calcium acetate as foliar spray at maturity stage is recommended. Sweet oranges and mandarins may be treated with ethylene gas for degreening and development of colour. A temperature of 6-7°C, 5-10 ppm of ethylene and 90-95% RH in a degreening chamber can set a change in colour in about 48 hours. The cold storage conditions for long term storage for different citrus fruits are available. Pre-cooling of citrus is done by forced air system. The storage conditions for each group are stated below. Oranges may be packed in well ventilated CFB boxes - 30 cm x 30 cm x 30 cm.
The storage conditions for various citrus fruits are as under:
Mandarins: Mandarins can be stored at 5- 7°C with 85-90 % RH for 4-8 weeks.
6. Marketing
Citrus fruits being perishable in nature need to be handled delicately and hygienically. Sweet oranges, limes and lemons remain fresh under ambient conditions and hence can be transported to distant places for marketing. More care and attention is required for mandarins during handling and transport.
