The following are the crop details for Cashew Nuts
Cashew is an evergreen tree with deep tap roots, grown for its edible fruits (nuts). The cashew tree has a branching main trunk and characteristic domed crown. The thin foliage of the tree is limited to the ends of the branches and is made up of oval-oblong leathery, shiny dark green leaves.
The leaves are smooth with pronounced veins and midrib and possess petioles that are swollen at their base. The tree produces numerous pinkish-white flowers on drooping panicles and a kidney-shaped true fruit (nut) which is approximately 3 cm (1.2 in) long with a grey-brown shell and develops from a fleshy accessory fruit, sometimes referred to as the 'cashew apple'. The cashew apple is pear-shaped and red to yellow.
Cashew trees can reach a height of 12 m (39.4 ft) and have an economic lifespan of 25 years after which time they are replaced in commercial plantations.
Cashew originates from Brazil. The Portuguese introduced cashew to Mozambique in the 16th century where it flourished, forming extensive forests; eventually, it also became dispersed in East Africa along the coastal plains of Kenya and Tanzania.
Recommended varieties of cashew nuts by KALRO are A75/83, A100, A81, and A82.
Cashew trees are usually grown at altitudes of between 0-500 m above sea level (asl) but can grow up to 1000 m asl. They can be very drought resistant provided their roots penetrate deeply into the soil and draw water from the subsoil. For mature trees 500 mm of rainfall per year is adequate, but seedlings should be watered until properly established. If rainfall is below 900 mm per year plant at the widest spacing indicated. Cashew nut trees tolerate a wide range of soils provided they are deep and well-drained. They can grow quite well on infertile soils but do not do well on coral outcrops at the coast.
The kernels or nuts have a high nutritional as well as commercial value and are used for human consumption either raw or roasted. The cashew nut apple is rich in Vitamin C (about 5 times higher than the orange) and is used for the production of juice, wines, spirits, jam, pickles, and chutneys. The liquid of the shell is used for brake linings, heatproof and waterproof paints, and protective varnishes. Cashew nut wood is of poor quality but can be used as firewood if mixed with other types of wood.
Cashew nuts should be planted at the beginning of the rainy season. In the Coastal lowlands, the best time for planting is between April to June.
Cashew nuts are usually propagated through seed or grafted seedlings. In propagation by direct seeding 3 seeds are planted in the planting hole and two months after germination the weak seedlings are uprooted leaving the strong ones to grow.
The holes should be 60 cm by 60cm so that they can be able to collect water during the rainy season which will be used during the dry season.
Cashew trees are generally planted with a spacing of 7.5 m X 7.5 m (175 plants/ ha) or 8 m X 8 m (156 plants/ ha) is recommended. High-density planting of cashew at a closer spacing of 4 m X 4 m (625 plants/ ha) in the beginning and thinning out in stages to maintain a final spacing of 8 m X 8 m in the tenth year is also recommended.
Proper seed selection from healthy, high-yielding trees is important, and it can be done by sorting out seeds by the water density method:
Intercropping can be done before the canopies close. Most annual crops can be used apart from cotton and sweet potatoes, which are host plants for Helopeltis bugs, major pests of cashew. Do not interplant young trees with pasture because of the high competition for water during the dry season.
Planting using grafted seedlings
Propagation through grafting starts by raising rootstock propagated from local cashew nut varieties. The first step is a visual selection of seeds to remove diseased or deformed seeds. The selected seeds are taken through a flotation test in water. Seeds that sink are planted in pre-germination beds.
The pre-germinated seeds are transplanted into potting bags when the radicals (tap root) are 2.5 –3cm after 7-10 days. The recommended soil media for cashew nut seedlings is in the ratio of 2:1:150 where: 2 is two buckets of soil, 1 is one bucket of well-decomposed farmyard manure, and 150gms of DAP. The seedlings are transplanted in potting bags (6" x 9"). This composition can sustain the plant for an average of three months after transplanting the pre-germinated seeds in them.
Seedlings are ready for grafting when they attain more than two functional leaves and the cotyledons are still attached to the young stem. Grafting is done 3-4 weeks after transplanting into potting bags.
Scions for grafting are harvested from select mother plants. The following procedure for
grafting is recommended:
a. Cut and remove the actively growing part of the rootstock, leaving two functional leaves.
b. Vertically cut down the stock between the two leaves to a depth of 2.5 – 3.0cm.
c. Make a wedge cut of the scion of a similar length of 2.5-3.0 cm and sharpen it.
d. Insert the scion into the rootstock and tie them together.
e. Cover the scion and the rootstock by wrapping them with grafting tape.
f. Wait for 2-3 weeks and unwrap the scion.
No fertilizer is required, but well-rotted manure at planting is beneficial. The area around the tree should be 1 ½ times the size of the canopy and should be kept clean of weeds for the first 2 years to avoid competition.
If planted on a slope the tree should have a U-shaped mound of soil below it to collect rainwater for improved growth. Seeds germinate within 2-4 weeks. Thin after 3-4 months leaving only the strongest plant at each site.
Mulching with black polythene is beneficial to increase the growth and yield of cashew. However, locally available materials like green or dry grass or weeds can be utilized for mulching the basins. Small pebbles or stones can also be used for mulching the basin.
Plastic or stone mulch does not improve soil health but ensures better moisture retention in the soil and also prevents the attack of soil-borne insects and pests.
The topsoil and sub-soil are kept separately and allowed to wither under the sun. It helps in the migration of termites and ants(this is in the planting process).
Weeding with light digging should preferably be done before the end of the rainy season. Hoeing, cutting the weeds off underground is more effective than slashing.
Cashew plants start bearing after three years of planting and reach full bearing during the tenth year and continue giving remunerative yields for another 20 years(so they can yield up to 45 years after being planted).
Protect seedlings from monkeys, rodents, and bucks by placing wire cages or thorns around the seedlings. Support plants with a stick and trim off side shoots up to 60-90 cm from ground level. When trees are mature, prune dead wood or any borer-damaged or intergrowing branches to give the canopy air and light.
Cashew nuts planted using seeds begin bearing 3 to 4 years after transplanting the seedlings. The nuts should be harvested as soon as possible, especially under wet conditions, and should be dried before storage.
Grafted seedlings begin bearing within 2 years of transplanting. Depending on the age and maturity of the plant, a tree yields between 10 to 100 kilograms of unshelled nuts per year. One hectare can thus produce between 2,000 to 5,000 kilograms of unshelled nuts per year. Although trees are produced for 40 to 50 years, commercial harvesting is for 35 years.
The cashew nuts do not mature at the same time. The duration of harvest extends from 45-75 days and the nuts should be collected daily during this period. November to May is the harvesting period, with the peak harvest period from November to January. The nuts are collected at weekly intervals from the farm during the harvesting season. During that period the land should be clean to facilitate the collection of cashew. To get good quality nuts, clear the area beneath the tree, collect fallen fruits, detach the nut from the apple, and dry the nuts under the sun for about 2 hours.
The nuts can be graded into Fair Average Quality (FAQ) and Under Grade (UG). FAQ are well-matured nuts and they should be full and well-dried (12% moisture content). The color should be grey or pale brown. They should neither be wrinkled nor spotted.
UG are well-dried and mature nuts. They can be spotted but not wrinkled.