Cashew is native of South Eastern Brazil, from where it was introduced to Malabar coast of India in the sixteenth century to cover bare hillside for soil conservation. It gained commercial importance in 1920. African countries produce large quantities of cashewnut, but they are not processed into consumable products because of difficulties in organising the native labour. India imports raw cashewnuts, which are processed and converted into cashew kernels and cashew shell liquid and re-exported to the countries, like USA, Canada, United Kingdom, Australia and Russia.
Cashew crop plantation Guidence
The cashew tree is a low spreading, evergreen tree with a number of primary and secondary branches and with a very prominent tap root and a well developed and extensive network of lateral and sinker roots. The fleshy peduncle the ‘cashew apple’ is juicy and sweet when ripe. The apple varies in size, colour, juice content and taste. It is a rich source of vitamin C and sugar. The cashew fruit is a kidney shaped drupaceous nut, greenish grey in colour. The nuts vary in size, shape, weight (3 to 20g) and shelling percentage (15-30 per cent)
Climate and Soil
It is a hardy tropical plant and does not exact a very specific, climate. It can come up in places situated within 35 latitude on either side of the equator and also in the hill ranges upto 700 m MSL. It can grow well in places receiving rainfall from 50 cm to 250 cm and tolerate a temperature range of 25 to 49 C. it requires a bright weather and does not tolerate excessive shade.
Cashew is cultivated on a wide variety of soils in India like laterite, red and coastal sandy soil. To a limited extent, it is also grown on black soils. It can be also grown in hill slopes in virgin organic matter rich soils. They do not prefer water logged or saline soils.
Propagation
Seed propagation is seldom practised now except to raise the rootstock materials. Seeds should be collected during the month of March to May and the heavy seed nuts, which sink in water, are alone mixed with 2 parts of fine sand. They take normally 15 to 20 days for germination.
Vegetative propagation
One year old shoots as well as current season shoots are used for air-layering. Though there is good root development in this method, heavy mortality occurs both at nursery stage and on the main field. Other drawbacks of this method are that it is cumbersome, time consuming and production of a limited number of layers per tree and as such layers are also not suitable for cyclone prone areas as they do not have a tap root providing less anchorage to soil.
The vegetative propagation through cuttings is seldom practised, as success is very less. Similarly veneer grafting, side grafting and patch budding are also reported to be successful but the nursery period is quite long, 3 to 4 years. Recently ‘epicotyl grafting’ and ‘soft wood grafting’ are recommended for commercial scale adoption. In the case of epicotyl grafting, tender seedlings with height of 15 cm are selected as root stocks and a ‘V’ shaped cut is made after beheading it at a height of 4 to6 cm from the cotyledons connective. The precured scion is collected and a wedge is made at the base of it, so as to exactly fit in the cut made in the stock. The scion is exactly fitted in the stock and tied with polythene strips. The success of epicotyl grafting varies from 50 to 60 per cent and depends upon high humidity, temperature, freedom from fungal disease, number of rainy days and rate of cambial growth. When the above method is adopted in 30 to 40 days old seedling, it is known as soft wood grafting. The success varies from 40 to 50 per cent.
Planting
Pits of 45x45x45 cm are dug and filled with a mixture of top soil, 10 kg of farm yard manure and one kg of neem cake at a distance of 7m x7m either way during June July and planted. In the case of seedling, 45 days old seedlings are transplanted.
Cashew plants respond well to the application of manure and fertilizers. These compounds are applied at various stages of the plant. Manure is applied during the first 15 days of planting. Fertilizer is applied to the plant at the base with a radius of 22.5 m and depth of 15 cm. The fertilizer quantity of the 1st year of planting per plant is 50 g of urea, 175 g of rock phosphate and 85 g of muriate of potash. Similarly the nutrients for the plant during 1st year of planting are 15 kg of FYM, 250 g of nitrogen, 50 g of P₂O₅ and 50 g of K₂O. If cashew is being cultivated as organic plant then nutrients are supplied in the form of oil cakes, green leaf compost, vermicompost, poultry manure etc.
Cashew plants are basically rain fed variety. The plants require water for up to 3 years. Irrigation during the flowering and fruiting increases productivity and quality. When cashew is being cultivated in sandy soils, then irrigation is needed during summer months. Proper drainage should be provided to avoid water stagnation. Drip irrigation with drippers at a distance of 1 m from the crop during the flowering months (second fortnight of December to march) is observed to produce higher yields.
Once the harvest is done the cashew is processed through the following
methods: Cleaning, Roasting, Shell separation, Drying, Peeling, Grading, Packing.
Manual picking is done and the nuts are cleaned. Open pans or hot oil bath is done to clean the nuts. The roasting of nuts using the rotary method is efficient and hygienic. Manual shelling recovers the kernels as a whole and then they are air dried in hot chambers to facilitate peeling. Kernels that are sound are called whole kernels and that which are broken are called splits. Again the grading is done as white, scorched, dessert, etc. The whole nuts are graded differently and the splits are graded differently. The cashews are packed by the Vita Pack Method, which involves removing the air from the packing tin and pumping CO₂ and sealing the pack.
The best harvest is obtained from the 4th year of planting. Harvesting should be done from February till May. The harvest of the crop depends on the varieties used for planting and it is observed that the trees give complete yield almost in the 10th year and it keeps increasing until the tree reaches 20 years. Fruit of the tree is removed and the nuts are separated. Harvesting is done on a weekly basis and on a clean land.
In the beginning for about 3 or 4 years other crops can be cultivated in the space between the cashew plants. Commonly cultivated intercrops are turmeric, groundnut, chillies, papaya, bhendi etc. This intercropping facilitates extra income to the farmers.
Processing consists of roasting, shelling, extracting the oil, peeling, grading and packing.
Roasting makes the shells brittle, besides making the extraction of kernels easier. A slight underoasting or overroasting adversely affects the quality and recovery of kernels. In the open pan roasting method, one kilogram of nuts are kept in shallow iron pans or earthen pots and are heated over an open fire. The nuts are rapidly turned to prevent charring. The roasted nuts are then removed from the pan and thrown on the floor. They are quickly covered with earth, which would absorb shell oil adhering to the roasting nuts and also cool them. The nuts are then subjected to subsequent operations. The cashew nuts are also roasted by drying under sun for two to three days when they lose much of the moisture contents and become brittle enough for shelling. The other improved methods of roasting cashewnuts are
Tea mosquito bug
Adults and nymphs suck the sap from the tender plant parts. Spraying endosulfan 0.05% thrice, first at the time of emergence of new flushes, the second at floral formation and third at fruit set is recommended. Die back or Pink disease Spraying any copper fungicides besides pruning the dead twigs are suggested.
Grading
Grading is done based on “counts” or number of kernels per pound. The kernels, which have no split, are separated as ‘wholes’. These are again separated into six grades as 210,240,280,320,400 and 430 whole nuts per pound. The graded kernels should be fully developed, ivory white in colour and free from insect damage and black or brown spots. The broken and split kernels are then separated and classified as standard and scorched pieces, splits, butts, small pieces and each grade is separately packed.
Shelling
After roasting, shelling is done by labour. Each nut is placed edgewise and cracked open with a light wooden mallet and the kernel extracted with or without the help of a wire prong. Care has to be taken that the inner kernel is intact and is not broken into bits.
Packing
Packing is done in this. In this method, the air inside the tine is exhausted and they are recharged with Co2 before they are sealed air-tight.
Continuous roasting process
The principle adopted in this system is the same as in the case of open pan roasting method. This plant consists of a single walled or double walled rotating metallic drum. In the case of double walled drum, the smoke or gases produced during roasting escape through the interspace between the two walls of the drum and are condensed to shell oil by a cooling system but in the case of single walled drum, the gases that escape from the nuts during the process of roasting are allowed to escape through a chimney provided at the lower end and there is no provision for collecting shell liquid.
Peeling
Removal of a thin outer brown skin is done by hand with the help of a safety pin or small hand knife. Peeling is made easier when the kernels are subjected to a heat treatment for about four hours in a drying chamber. After peeling, the kernels are spread out indoors on cement flooring so that they may absorb some moisture and become less brittle. This prevents the tendency to break easily during grading.
Oil bath process
In this method, the nuts are held in wire trays and are passed through a bath of cashew shell oil maintained at a temperature of 200 to 2020C for a period of three minutes whereby the shell oil is recovered from the shells to the maximum possible extent. This process ensures uniform roasting of nuts and eliminates charring of kernels.
The yield depends upon many factors. Individual trees, which yield more than 6 kg after 15 years, are considered as good yielders.
The following two pests are economically important in cashew plantations.
The grub bores into the trunk and the roots. Swabing the trunk with BHC 50% and drenching the soil around the base of the tree with BHC 50% are recommended.