The cashew-nut tree is a fast grower and an evergreen tropical tree. It grows to a height of 12 m. Blossoming takes place between November and January. Seedling trees flower in the third year after planting. The fruit ripens fully within 2 months.
Cashewnut (Anacardium occidentale L.)
Family: Anacardiaceae
Variety
Tamil Nadu Varieties : Vridhachalam-1,Vridhachalam-2,Vridhachalam-3,VRI 4,VRI (CW) H1
Kerala Varieties : Akshaya (H-7-6),Amrutha (H-1597),Anagha (H-8-1),Anakkayam-1 (BLA-139-1),Dhana (H-1608),Dharasree (H-3-17),K-22-1,Kanaka (H-1598),Madakkathara -1 (BLA-39-4),Madakkathara-2(NDR-2-1),Priyanka (H-1591),Sulabha (K-10-2)
Andhra Pradesh Varieties : BPP-1,BPP-2,BPP-3,BPP-4,BPP-5,BPP-6,BPP-8(H2/16)
Karnataka Varieties : Chintamani-1,NRCC-1,NRCC-2,Ullal-1,Ullal-2,Ullal-3,Ullal-4,UN-50
Maharastra : Vengurla-1,Vengurla-2,Vengurla-3,Vengurla-4,Vengurla-5,Vengurla-6,Vengurla-7
Goa : Goa-1
Orissa : Bhubaneswar-1
West Bengal : Jhargram-1
Climatic requirements
- Cashew trees are genuinely tropical and very frost sensitive.
- The trees grow in a wide spectrum of climatic regions between the 25 °N and S latitudes.
- Although the cashew can withstand high temperatures, a monthly mean of 25 °C is regarded as optimal.
- Yearly rainfall of 1 000 mm is sufficient for production but 1 500 to 2 000 mm can be regarded as optimal.
- The cashew tree has a well-developed root system and can tolerate drought conditions. Rain during the flowering season causes flower abortion due to anthracnose and mildew.
- During harvesting, while nuts are on the ground, rain and overcast weather causes the nuts to rot or start germinating.
- Nuts germinate within 4 days when lying on wet soil.
Soil requirements
The cashew is a strong plant that is renowned for growing in soils, especially sandy soils, that are generally unsuitable for other fruit trees. For the best production deep, well-drained sandy or sandy-loam soil is recommended. Cashew trees will not grow in poorly-drained soils.
Manure and Fetilizer
The application of nitrogen and phosphate are important. Approximately 75 g LAN and 200 g superphosphate per year age of the tree is applied annually with a maximum of 750 g LAN and 2 kg superphosphate. Cashew trees are subject to zinc deficiency that can be treated with 200 g zinc oxide/100 l water applied as a leaf spray
Irrigation
Irrigation is important during establishment of young trees because it doubles the growth tempo of young trees in a dry season. Due to the deep root system the trees can survive several months without irrigation. Mature trees should receive 1 800 l of water per tree every 2 weeks.
Weed control
Grass strips in the inter-rows between the tree lines are ideal to prevent erosion and should be cut regularly.
Plant protection
Pests
Stem borer
1. Collection and destruction of affected shoots
2. Swabbing the bark of exposed roots and shoots with Carbaryl 50 WP 2 g/lit. Twice a year before the onset of South West Monsoon (March – April) and after cessation of monsoon (November) painting of coal tar + kerosene mixture (1:2) or swabbing with a suspension of Carbaryl 50 WP (4 g/lit) can be done up to one metre length in the exposed trunk region after shaving the bark or swab the tree trunk with neem oil 5% thrice during JanuaryFebruary, May-June, and September-October..
3. Root feeding with Monocrotophos 36 WSC 10 ml + 10 ml of water kept in a polythene bag on one side of the tree and keep the same amount on the other side of the tree (Total 20 ml/tree) divided into two equal halves will give protection when there is moderate incidence.
4. Remove grubs from early stage infested trees and drench the damage portion with Chlorpyriphos 0.2% @ 10 ml/lit or Neem Oil 5%.
Tea mosquito bug
- Spray application of phosalone 35 EC@ 2.0 ml, followed by carbaryl 50WP @ 2g/l and monocrotophos @ 2ml/l at vegetative flush stage, panicle initiation stage and nut formation stage respectively are recommended for the management of tea mosquito bug.
- Spray schedule involving three rounds of spray viz., first spraying with Profenophos (0.05%) at flushing stage, second spraying with Chlorpyriphos (0.05%) at flowering and third spraying with Carbaryl (0.1%) at fruit set stage is most effective.
Shoot caterpillars
Shoot caterpillar can be controlled by spraying Profemophos 50 EC @ 2 ml/lit.
Root borer
Root borer can be controlled by pouring Monocrotophos 10 ml/tree in the bore holes (Insecticide 5 ml + 5 ml water).
Leaf miner
1. Collect and destroy the damaged plant parts
2. Spray NSKE 5% two rounds, first at new flush formation, second at flower formation
Diseases
Die back or Pink disease
Prune the affected shoots just below the affected portion and apply Bordeaux paste. Spray 1 % Bordeaux mixture or any copper fungicide like Blitox or Fytolan 0.25 % twice i.e. in May – June and again in October as a prophylactic measure.
Anthracnose
1. Remove the affected portions of plant/branches
2. Spray 1 % of Bordeaux mixture + Ferrous sulphate at the time of flush initiation
Harvest
The plant starts yielding 3rd year onwards. The peak picking months are March and May. Good nuts are grey green, smooth and well filled. After picking, the nuts are separated from the apple and dried in the sun for two to three days to bring down the moisture content to 10 to 12 %. Properly dried nuts are packed in alkathene bags. This will keep for 6 months.
Yield
About 3 – 4 kg/tree/year can be obtained.
Processing
The objective of cashew processing is to extract the healthy, tasty kernel from the raw nut in the shell. Most modern factories are designed to obtain the maximum number of whole nuts and as much shell oil as possible. Processing can be subdivided into a series of steps.
Drying
Harvested nuts are dried in the sun for a few days. Properly dried nuts can be stored for 2 years before being shelled. Nuts are roasted to discharge the caustic shell oil and acrid fumes. Hand shelling is impossible if the shell oil has not been removed previously. Kernels must be protected from contamination by the shell oil because it would cause blisters in the mouth and throat when eaten. Before the nuts are roasted they must be soaked in water—the moisture in the shell facilitates the rupturing of the cells containing shell oil and retaining it in the shell. Moisture makes the kernel slightly rubbery and limits breakage of the kernels. The easiest method to wet the shells is to heap the nuts into big piles and to use sprinklers intermittently. Steam may also be used.
The simplest roasting method is to heat the nuts for about a minute in an open pan with holes. Acid fumes are released and if the nuts should catch fire the flames can be doused with water. A more efficient method is to use a slanting perforated cylinder that is rotated above a fire. The shell oil flows through the holes in the cylinder and is collected in a catch through. After the roasting process the nuts are dumped into ash or sawdust to remove the excess shell oil still clinging to the shells.
Shelling
This is the most difficult operation in cashew processing. In India shelling is mostly done by cheap female labour. Shelling is carried out by using special wooden mallets and pieces of bent wire, at a rate of about 200 nuts per hour.
Mechanical shelling methods are difficult to design because of the irregular shape of the nut, hardness of the shell and brittleness of the kernel. In some mechanical processing plants compressed air is used to crack the nuts. The latest Windmer and Ernst method is to cut a groove around the shell and to place the shells in a modified centrifuge fitted with metal plates. The nuts are thrown against the plates and cracked by centrifugal forces when the machine spins. It is possible to obtain 85 % whole kernels with this method.
Removal of the testa
Before the thin, papery seed coat (testa) can be removed, the kernels must be dried. Nuts are dried on big racks in an oven at 70 °c. The testa becomes dry and brittle and is easily removed. The remaining traces of membrane are removed with bamboo knives. Modern factories use electronic machines to detect nuts with pieces of remaining testa which are then sorted and cleaned by hand.
Grading
Kernels, whole and broken, are sorted into 6 grading schedules. There is only a small demand for broken or dark and unevenly roasted kernels.
Packaging
- Kernels are dried to 3 % moisture content before they are packed.
- Drying is necessary to extend shelf life and prevent fungal and other infections.
- Dried kernels do not become rancid.
- Nut kernels of export quality are vacuum packed in tins.
By-products
Shell oil represents about a quarter of the mass of an unshelled nut and approximately equal to that of the kernel. This fluid, that is not an oil as the term “shell oil” indicates, but a mixture of anacardic acid and cardol is the main by-product.
There are more than 200 registered patents of different uses of shell oil. One of the most important uses is in the manufacture of brake linings. Shell oil is used in the manufacture of numerous materials that have to be resistant to heat, friction, acids and caustic products, for example clutch plates, special isolators, varnish and plastic materials. The wood is insect repellent and used in making book cases and packing crates. The gum is a replacement for gum arabic and used as insect repellent glue in book bindings. In the nut and the apple, a compound has been found that combats tooth decay.
The apple is highly perishable but very healthy. It can be eaten fresh or juiced. Syrup, wine, brandy, gin, preserved fruit, pickles and glazed fruit are also made from the cashew apple. In Brazil, fresh cashew-apples are packed in trays and marketed in retail fresh produce outlets.
The indigenous people in cashew-producing regions use different parts of the plant such as the leaves, bark, gum, wood, juice and roots for the preparation of local medicines or insect-repellent mixtures. The bark is rich in tannins and is used in leather tanning. The papery seed coat around the kernel can serve as cattle feed.
