Everything you need to know about growing cashew-nut! Learn about: 1. Botany of Cashew-Nut 2. Origin of Cashew-Nut 3. Climate and Soil 4. Orchard Cultural Practices 5. Planting Operation 6. Flowering and Fruiting 7. Training and Pruning 8. Harvesting and Handling 9. Pests and Disease.
Botany of Cashew-Nut:
The cashew-nut belongs to the family Anacardiaceae. According to Bailey, Anacardium is a small genus with few species. As many as 23 species of Anacardium are known to exist in Central and South America.
The important species of Anacardium are as follows:
Anacardium occidentale, A. macrocarpa, A. phemilium, A. orthonianum, A. brasiliense, A. curatellaefolium, A. encardium, A. giganteum, A. humile, A. mediterraneum, A. nanum, A. rhinocarpus, A. spruceanum, A. microsepalum, A. corymbosum, A. excelsum, A. parvifolium, A. amilcarianum, A. kuhlmannianum, A. negrense, A. rondonianum, A. tenuifolium and A. microcarpum.
On the basis of division, Anacardium nanum is referred as ‘Dw+arf’ and Anacardium giganteum as ‘Giant’. Each species is divided into cultivars characterised by colour (yellow or red) and shape (round, pear-shaped or elongated) of apple.
The cashew-nut tree is somewhat straggling with shorter leaves, more distinctly viewed and less strikingly coloured. The flowers are borne in terminal panicles and are usually broader and shorter and less compact than those of mango panicles, with staminate and hermaphrodite flowers in the same panicles. The stamens are nearly all normal and produce pollen. The true fruit is the nut.
Origin of Cashew-Nut:
The cashew, Anacardium occidentale, belongs to the family Anacardiaceae, to which also belong our most important fruit, the mango. It is one of the most delicious and most nutritious nuts of the world. It contains upto 47 per cent fat, 21 per cent protein and 22 per cent carbohydrates and is also rich in minerals like calcium, phosphorus, iron, vitamin and riboflavin. It, therefore, fetches very high price.
Cashew nut shell liquid (CNSL) derived during processing of kernels is corrosive viscous oil which has industrial uses in the manufacture of paints, varnishes and resins etc. India is the largest producer, processor, consumer and exporter of cashew nut in the world. It is one of the important items of export from India. Estimates of export indicate that during 1993-94 the export of cashew kernels and allied products reached 72,450 tonnes, valued at over Rs. 10,440 millions.
The cashew in the shell is a kidney-shaped nut borne on a very much swollen stalk, which is juicy and is called the cashew apple. The cashew apple is sweet but astringent. It is also rich in vitamin C. It makes a very good bottled juice after the removal of the tannins present in it, which cause the astringency. Even the oil extracted from the shells is exported from India.
It was introduced to India by the Portuguese during the 16th century and it was considered a suitable crop for soil conservation, afforestation and also for waste land utilization. The Goan soils were first to receive it. It is generally referred to as a self ploughing crop due to its ability to penetrate even the moderately hard soils. Thus it spread gradually along the coastal regions of East and West India.
The total area under cashew in India is 7,20,000 hectares with a production of 4,50,000 tonnes. Maharashtra stands first with regard to production followed by Kerala and Andhra Pradesh. The plantations of west coasts are considered highly productive as compared to east. It is due to suitable soil condition and fairly well distributed rainfall.
Cashew is a hardy and drought resistant tropical crop. It requires a moist, mild tropical climate. It cannot (withstand extremely low (less than 18°C) and high temperature (more than 40°C) for a prolonged period. It performs generally well upto an altitude of 450 metres and satisfactory upto an altitude of 700 metres. In areas with less than 60% relative humidity, the growth and productivity of cashew is greatly affected.
Areas receiving rainfall of 600 mm to 4500 mm are good for cashew cultivation. It is sensitive to water logging and is tolerant to soil moisture stress to a great extent. Cloudy weather during flowering enhances the mosquito infestation while heavy rain during flowering leads to poor fruit set. High temperature causes fruit drop.
Cashew can be grown on a variety of soils. However, its performance is good in well drained sandy loam and light coastal soil. Heavy clay soil with poor drainage is not suitable.
Though cashew can be propagated by seed, stooling, epicotyl grafting and soft wood grafting, soft wood grafting is advocated as the commercial method. By this method the plants can be multiplied with high success almost throughout the year.
About one and a half to two months old seedlings raised in polythene bags (25 cm x 15 cm size, 300 gauge thickness) are utilized as rootstock. From the selected variety, lateral shoots of current season’s growth (non-flowered, three to five months old, with prominent terminal bud) are used.
These are produced on the mother tree by clipping off leaf blades, leaving behind the petiole stubs. After 10 to 15 days, these are used as scion material for grafting. All the leaves of rootstock are removed except a pair of leaves at the bottom. The rootstock is decapitated at a height of 15 cm from ground level. A cleft of 5 to 6 cm deep is made on the stem.
The procured scion stick is mended into a wedge shape. The graft joint is tied firmly with polythene strip. Covering of these plants with polythene bags (15 cm x 12.5 cm, 100 gauge thickness) and fixing these at the bottom maintains increased temperature and humidity. This enhances sprouting and protects the apical bud from drying. After the sprouting of shoots the polythene cover is removed. The grafts are ready for planting in 5-6 months.
These grafts are planted in previously (May-June) dug pits of 60 x 60 x 60 cm size, filled with a mixture of top soil, compost (5 kg) or poultry manure (2 kg) and rock phosphate (200 g). Monsoon season (July-August) is the ideal time of planting.
A spacing of 7.5 m x 7.5 m or 8 m x 8 m which accommodates 156 to 175 plants/ha is recommended. A closer spacing of 4 m x 4 m has also been recommended with thinning of trees at later stages, thereby maintaining a spacing of 8 m x 8 m by the tenth year. In the early years of planting intercrops like pineapple, pulses, chillies, etc. can be grown.
Initially the plants should be allowed to grow a single stem upto 0.75 to 1.0 metre from the ground level. The flower panicles emerging in first two years should be removed. The plants should be allowed to flower and fruit only from the third year onwards.
From the 4th year onwards 10 to 15 kg FYM per plant should be applied. The fertilizer dose recommended for cashew is 500 g N (1.1 kg urea), 125 g P (625 g rock phosphate) and 125 g K (208 g muriate of potash) per plant per year. It should be applied in two split doses i.e. during pre-monsoon (May-June) and post-monsoon (Sept-Oct) periods.
A number of cashew varieties have been developed. The highest yield has been reported in BPP 5, BPP 6 and Ana (BLA-13) and largest Kernels in NRCC-1, V-3 and V-6.
The trees can start bearing after two years but economic bearing commences after the third year and the plants are in full production by the tenth year and continues for another twenty years. The nuts are usually picked after they fall off from the trees. The mature nuts sink in water while the immature/unfilled float. The nuts are sun dried to reduce the moisture content to below 1 per cent. It is necessary to prevent spoilage during subsequent storage. With proper drying the kernels retain their quality and flavour.
The processing of raw nuts involves roasting, shelling, drying and peeling. A well-managed cashew plantation with high yielding varieties gives nut yield of 100, 400, 800,1200,1600 kg nuts per hectare during 3rd, 4th, 5th, 6th, and 7 year respectively Thereafter a minimum yield of 1600 kg per hectare is expected upto thirty year.
Climate and Soil Required for Growing Cashew-Nut:
Cashew-nut is mainly a tropical plant. It does well under hot and humid climate of the west coast. Cashew-nut is hardy and drought resistant though it is less resistant to frost and chilly weather. It cannot stand dry hot summers. If there is sufficient water supply, it can withstand long period of low relative humidity also. Temperature is a limiting factor in its cultivation and a mild tropical climate is most suitable.
The regions where the temperature ranges from 20 to 30°C with annual rainfall of 1000 – 2000 mm are ideal for cashew cultivation. High temperature (39-42°C) during the marble stage of fruit development causes fruit drop. If the temperature falls below the freezing point, the trees are injured. Its distribution is restricted to altitude in between 700-900 M where temperature does not fall below 20°C for prolonged period.
Cashew-nut seems to thrive on sandy belts along the east coast with about 90 cm of rain per year and with 300-380 cm in the West Coast. It is a sun-loving tree and does not tolerate excessive shade. It is said to be rather highly resistant to strong winds.
Cashew-nut can be grown in wide variety of soils. It can survive even in the waste land with low fertility levels and those which are prone to soil erosion. It is grown widely on laterite, red and coastal soils in Kerala, Maharashtra, Goa, Karnataka, Tamil Nadu, Andhra Pradesh, Orissa and West Bengal. However, the best soil for cashew-nut is deep, well-drained, sandy loam soils without hard pan.
It has been reported that high clay content, high pH more than 8.0, high base saturation, poor drainage or seasonally high water table and the presence of stones or hard pan within 100 cm of soil depth reduced tree size. High sand content and high rainfall are reported favourable.
Orchard Cultural Practices for Growing Cashew-Nut:
i. Irrigation:
Cashew-nut is mostly grown as rainfed crop. But, it responds well to watering during flowering and fruiting. Two or three irrigations during growth and development period of fruits considerably increase the nut yield and reduce fruit drop. Irrigation at the time of flowering should be avoided.
ii. Intercropping:
Intercropping is now becoming more common in cashew-nut plantation. This would enable higher return from the plantation during the first 4 years till the canopy covers the whole area.
Seasonal crops like horse gram, cowpea, groundnut, sweet potato, ginger, black gram, can be raised in cashew plantation as intercrop. In Goa, casuarina trees, teak and eucalyptus are also grown in the cashew plantation. In Andhra Pradesh and some parts of Odisha, cashew, coconut and casuarina form a popular crop combination. The annuals like pigeon pea and tapioca can also be profitably grown in the interspaces in the initial years of orchard establishment.
iii. Weed Control:
Light digging should be done before the end of rainy season to control the growth of weeds- Agrodar-96 (2, 4-D) @ 2 litres in 500 litres of water and subsequently. Gramoxone @ 2.5 1/500 liter of water can effectively check the weeds. The spray with weedicides can be again repeated after the monsoon.
iv. Manuring and Fertilization:
The annual nutrient removal in 30 year old cashew-nut tree is 2.8 kg N, 750 g P2O5 and 1.26 kg K2O. The fertilizers recommended for a mature cashew free are 500 g N, 125 g P2O5 and 125 g K2O per tree per year in two split doses before (May-June) and after the monsoon (August- September). At Konkan (Maharashtra), cashew tree responded to N at 125 kg, P2O5 at 50 kg and K2O at 100 kg per hectare. Under Utkal region, the trees receiving NPK at 250 kg/ha each resulted in the highest yield. In laterite tract of West Bengal, high nut yield has been recorded in trees receiving N 200 g, P2O5 75 g and K2O 100 g per tree at the age of 3 years.
Propagation of Cashew-Nut:
Earlier, cashew was usually propagated through seeds planted in situ with 3 seeds per hole. Now, vegetative propagation by air- layering, budding and grafting is also possible. For raising rootstock seedlings medium sized nut (120 per kg) are selected from heavy and regular bearing trees of known percentage. These are stored in a cool dry place and sown on carefully prepared seed beds in December.
i. Budding:
The seedling takes thickness of lead pencil before rainy season. Patch and forkert methods of budding can be employed. In patch budding, the bud-take is about 90 per cent during May-June. The sprouting of bud takes place after about one month. In case of forkert method, the bark is loosened by two vertical incisions, connecting the two with a transverse cut at the bottom. The bud is inserted into the flap by lifting the flap upward and the bud so covered with the flap is wrapped with polythene tape. The wrapper and the flap are removed after about one month of budding. The exposed bud starts developing further.
ii. Grafting:
Cashew-nut can be successfully grafted by veneer, side, clift and whip grafting. Recently epicotyl and softwood grafting are becoming popular. Softwood grafting is considered the best method suitable for almost all cashew growing states in the country. The epicotyl grafts give only 25-30 per cent success due to mortality of grafts in the nursery. In case of soft grafting over 60 per cent successful grafts are obtained.
iii. Air-Layering:
This is one of the most common methods of cashew propagation. The best time for air-layering is between February and April. Pencil thickness shoots of last season’s growth are selected and a ring of bark about 3 cm long is removed. The ringed portion is applied with IBA @ 500 ppm in lanolin paste. It is then wrapped with polythene sheet. The roots are formed sufficiently within 60-80 days. The layers are separated and planted in pots. The layered plant should be placed under partial shade till transplanting.
iv. Mound-Layering:
The selected trees are cut down at the ground level and cut ends are treated with fungicides to prevent fungal infection. Within two to three months many buds start sprouting from the ground level and they are covered with sand and soil upto 15 – 20 cm. After 30 – 40 days, shoots which turn green to brown are cinctured and treated with IBA and again covered with sand. Cinctured shoots produce roots in 30 – 40 days. Sand mound around the stump is removed and separated for planting.
Planting Operation for Cashew-Nut:
Before raising new plantation of cashew-nut, land should be thoroughly prepared as soon as pre-monsoon showers are received. The pits of 60 cm x 60 cm x 60 cm should be dug atleast 15 days before actual planting. The planting should be made at the distance of 7-8 m depending upon the soil and climatic conditions. It will accommodate 202-140 plants per hectare according to the square system. The planting is done in the beginning of monsoon i.e., May-June or preferably during July-August.
A closer spacing of 4m x 4m in the beginning (625 plants/ha) and thinning out in stages and maintaining a distance of 8m x 8m (156 plants/ha) by the 10th year can be adopted for profitable cultivation. A spacing of 10m x 5m (200 plants/ha) can be adopted in levelled lands planting grafted plants.
Flowering and Fruiting in Cashew-Nut Trees:
The cashew tree starts bearing at the age of 3 to 5 years and attains full bearing by the 10th year and continues to yield usually upto 40 years. The inflorescence is an indeterminate of polygamomonoecious type. Each panicle contains 200 – 1600 flowers. Normally, there are three growth flushes in cashew and in South India the flower bud emergence commences by the middle of September and continues till the end of February, the main season being October- November. The fruit ripens from March to May. In West Bengal, panicles appear in December and flowering continues up to May. Late panicles bear little or no fruits.
Flowering in cashew appears in three distinct phases:
(i) The first male phase with 19-100 per cent male flowers.
(ii) The mixed phase with 0-60 per cent male flowers and 0-20 per cent hermaphrodite flowers.
(iii) The second male phase with 0-6.7 per cent male flowers.
The main duration of flowering was recorded as 85 days in which the duration of the first male phase was 2-4 days, mixed phase 69 days and second male phase 13 days. The percentage of hermaphrodite flowers in the mixed phase was 22.2 and the mean fruit set was 4.6.
The maximum numbers of hermaphrodite flowers are observed in panicles emerging in January which gradually reduced till May. The panicles appearing in the southern side of the tree had the largest number of hermaphrodite flowers. The partially mixed panicles and those appearing on one-month old shoot had longer number of hermaphrodite flowers and were found in the middle portion of the panicles.
The flowers are white to light green at the time of opening, later turning to pink. The flower is typically pentamerous. Number of stamens is 10-11, one or two are large and the remaining small. Yield in cashew is low due to small percentage of hermaphrodite flowers, low fruit set and heavy fruit drop. Average fruit set in cashew is 3-10 per cent. Ovary is superior and is unilocular and it contains a single anatropous ovule.
Growth patterns of the apple, pericarp and kernel are of different types. Initially, the nut grows much faster than the apple but in later stages, the apple increases in size much more rapidly and soon outgrows the nut. The nut reaches their maximum size in about 30 days. Thereafter, the pericarp hardens and its size decreases. The fruit ripens in about 60 days. Protein contents of kernel, increases steadily up to 40 days after fruit set and maintains its level high till harvesting. The sugar also increases upto 40 days, but declines sharply at harvest.
The nut is grey-coloured, kidney shaped and contains a single seed with membranous adherent testa, semi-lunar cotyledons and short hooked radicle. The fleshy peduncle, the cashew apple is juicy, sweet when ripe and rich in vitamin C and sugar. The nut consists of an epicarp, mesocarp, endocarp, testa and kernel.
Training and Pruning of Cashew-Nut:
Normally training and pruning is not practiced in cashew-nut trees. Only, the young trees are trained by providing support at the time of planting and by removing any water sprouts carrying out on the trunk below the union during the first three years of growth. The branches which are hanging and touching the ground are removed. The plant should be allowed to grow by maintaining a single stem up to 0.75 -1.0 m from the ground level.
All the weak and crisscrossed branches are removed. To avoid lodging of the plant by wind, proper staking of plant is needed. After 4-5 years, the main stem attains a height of 4-5 m. After that, the dead and diseased twigs and dried branches should be removed to reduce losses through disease like ‘Die- back’ and also to minimise chance of serious losses due to forest fires. The cut ends should be pasted with Bordeaux paste. The training and pruning of plants is done during August – September.
In cashew-nut, the flowers start opening by 7 AM and continue upto 3 PM, the peak of opening the perfect flowers is between 9 AM – 2 PM. The stigma becomes receptive for about 24 hours before anthesis and continues to be so for about 48 hours after anthesis. The stigma becomes receptive as soon as the flowers open. Pollination is reported to be carried out by the flies, bees and ants as well as the wind.
Fruit setting is poor because percentage of hermaphrodite flower is less. About 3 to 10 per cent fruit set has been reported depending upon climatic conditions. Fruit set can be increased and fruit drop controlled with the use of growth regulators.
Two or three times more nut production can be obtained by spraying 2, 4-D at 10 ppm either at the early or peak stage of flowering. NAA at 10 ppm spraying twice during the flowering period increases fruit set. Two sprays with 50 ppm GA at flowering are the most effective in increasing fruit set and fruit retention.
Harvesting and Handling of Cashew-Nut:
The cashew-nut tree commences economic bearing in third year, attains full bearing by the 10th year and continues to yield for 40 years. The fruit ripens from March to May. It takes two months after pollination for the fruits to be ready. The shell of the nut attains full size in 3- 4 weeks after flowering after which the pedicel swells to produce the Cashew apple. The fruits are harvested when fully ripe. They may be allowed to fall on the ground and collected in dry weather, but in wet weather they must be collected daily and dried in the sun.
Harvesting and collection of nuts are done over a period of 10-12 weeks. When apple is not collected, the fruits may be allowed to fall on the ground and nuts collected periodically during the first 4-6 weeks. Later most of the nuts are collected in one or two major harvests.
Yield varies considerably from tree to tree due to climatic conditions, soil type, age of the tree, management practices, etc. On an average, one tree produces 30-35 kg of apples. At present the average yield of nuts in India is only 2.1 kg per tree per year. Maharashtra records the maximum average yield of 11.8 q/ha followed by Kerala 9.6 q/ha. A well raised plantation should yield 2.5 tons of nuts per hectare. On an average 4.6 tons of raw nuts provides one ton of kernels.
Processing:
Processing of cashew-nuts is the recovery of kernels from raw nuts by manual and mechanical means. Conditioning involves sprinkling of water on dried nuts to bring to an optimum moisture level of 15 – 25 per cent. Roasting makes the shell brittle. Roasting is done with two methods i.e. drum roasting and oil bath roasting. Manual shelling gives higher yield of nuts as compared to mechanical processing.
After shelling, kernels are dried to reduce the moisture and to loosen the adhering testa. After drying for 6-12 hours, peeling is done by hand. The kernels are to be handled carefully to prevent breakage as they are brittle at this stage. The shelling percentage of cashew varies from 20 to 25.
Grading and Packing:
Grading is done for export purpose on the basis of count or number of kernels per pound. Sound kernels are named as “Wholes” and broken ones as “Splits”. The ‘wholes’ are packed in several grades viz. Nos. 210, 240, 280, 320, 400, 459 and 500. The popular grade of kernels is 320. The specification for graded kernels are that they should be fully developed, Ivory white in colour and free from insect damage and spots. Packing is done by Vita pack method. It is exhausting the air inside the packing tin, pumping in carbon dioxide and then sealing.
Pests and Diseases of Cashew-Nut:
Tea Mosquito:
It is a serious pest of cashew, damaging tender shoots, inflorescence and immature nuts at various stages of development. The nymphs inject the toxic saliva into the plant and the affected portion turns brown. The young leaves and inflorescence dry up. The peak-period of infestation is from October to March (flushing, flowering and fruiting season).
Spraying with 5ml Phosphamidon or 15 ml Mono-crotophos or 17ml Dimethoate or 20 ml Endosulfan in 10 litres of water coinciding with new flush, controls the menace.
Leaf Miner (Acrocercops Syngramma):
The caterpillars of this silvery grey moth, mine through the tender leaves and damage them at the time of new flushes. Spraying with 0.05% monocrotophos or phosphamidon or endosulfan at the time of emergence of leaves controls the pest.
The Shoot and Blossom Webber (Macalla Moncusalis):
The caterpillars of the pest attack the shoot and inflorescence together, remain inside and feed on them. Later the shoots dry up. The pest can be controlled by spraying 0.05% phosphamidon or endosulfan.
Diseases:
Dieback Disease:
It is also called the “Pink disease” which is caused by the fungus Pellicularia salmonicolor and is characterised by withering of petals and other parts of the flower. The colour of healthy shoot turns brown and discolouration of sap wood is observed. Spraying with 20 g Copper oxychloride or 10 g Carbendazime or 20 g Captan in 10 litres of water in May-June after pruning the dead wood controls the disease.
The shoot and inflorescence drying is caused by Glocosporium mangiferae and can be controlled by removal of affected parts and application of crude carbolic acid followed by Bordeaux paste. The algal red rust disease on leaves, caused by Cephalurus mycoidia is controlled by dusting nickel chloride in early stages.