Cashew Latest Planting Techniques and Methods Tutorial

Cashew, also known as the cashew tree, chicken cashew, and Jieshou fruit. An evergreen tree with an upright trunk, reaching up to 10 m tall. The cashew is a kidney-shaped nut in the order Sapindales, family Anacardiaceae, genus Anacardium. Cashew is rich in nutritional value, can be used in stir-fried dishes, and can also be used medicinally; it is one of the world's four famous dried fruits. It is native to northeastern Brazil, within 10° south latitude. It was introduced to Asia and Africa in the 16th century and has now spread throughout East Africa and South Asian countries. The countries with relatively large cashew planting areas in the world include India, Brazil, Vietnam, Mozambique, and Tanzania. In China, cashew is mainly distributed in Hainan and Yunnan, and has also been introduced in Guangxi, Guangdong, Fujian, and Taiwan.

Growth Habits of Cashew

Cashew has extremely strong adaptability and is a warmth-loving, strongly heliophilous tree species. It is tolerant of drought and poor soil and has a certain wind resistance. It is suitable for growth below 400 m altitude. It has low soil requirements; aside from poor development on heavy clay and limestone, it can grow on red soil, sandy loam, or rocky mountain soil with organic matter content of less than 1%.

Cashew is not cold-tolerant and requires very high temperatures during the growing period. With a monthly average temperature of 23-30°C, flowering and fruiting are normal; at 20°C growth is slow; below 17°C it is susceptible to cold damage; below 15°C it suffers severe damage and dies. It requires annual sunshine of more than 2000 hours, and annual precipitation of 1000-1600 mm is preferable. It should not be planted in areas where the groundwater level is too high or where water accumulates in the rainy season. Rainy weather is taboo during the flowering period.

The peak growth period is generally in the early rainy season. The taproot of a 4-5-year-old tree reaches 5 m deep, and the lateral roots are well developed; the lateral roots of a 6-year-old tree reach about 7 m long. After planting, it flowers in 2 years, fruits in 3 years, and enters the full fruiting period after 8 years; the full fruiting period lasts 15-25 years.

Propagation Techniques of Cashew

Due to the instability in yield characteristics of cashew seedling progeny, vegetative propagation is mostly used. Cashew vegetative propagation techniques include layering, cuttings, epicotyl grafting, veneer grafting, approach grafting, budding, cleft grafting, cut grafting, softwood grafting, tissue culture, and others.

1. Seed propagation

Soaking seeds with 30 mg/100 g of indolebutyric acid (ITT) for 24 hours can increase the seedling formation rate by 61.11%; soaking seeds in warm water at room temperature of 55°C for 24 hours can increase the seedling formation rate by 50%. In addition, soaking seeds with 60 mg/100 g of ITT for 24 hours, or with 1/2 strength of ADNK (ADNK) for 24 hours, can also promote the germination of cashew seeds. Soaking seeds with 90 mg/100 g of naphthaleneacetic acid (NAA) for 24 hours has the best effect on promoting seedling height growth.

2. Layering propagation

Air layering for cashew seedling cultivation should be carried out from February to April or from October to November each year, when the survival rate is highest, at more than 93%. The age of the stock plant for layering is best below 10 years; after layering, roots can develop in 35 days, and it can be separated from the mother tree in 45 days. If the stock plant is more than 20 years old, it is very difficult to root after layering. Peat, moss, and wood shavings are good materials for layering. Before layering propagation, first treat the mother tree with 0.00025 g/mL of ethephon or 0.001 g/mL of chlormequat, then treat its air layers with 0.003-0.005 g/mL of ITT and 0.0002 g/mL of para-carboxybenzyl, which can promote branch rooting and increase the number and length of roots.

3. Tissue culture

Cotyledon explants cultured on a medium supplemented with 0.5 mg/L of IAA and 0.5 mg/L of kinetin can directly form organs, and after about 5 weeks directly form complete plants without further culturing and induction of plant rooting.

Cultivation Techniques of Cashew

1. Shaping and pruning

Shaping and pruning can regulate the canopy structure and improve ventilation and light penetration in the tree body, thereby increasing the fruit-setting rate and yield. The principle for pruning young cashew trees is to prune lightly rather than heavily, and early rather than late, using a method of pruning in stages, batches, and multiple times; pyramid-shaped pruning and shaping gives good results.

2. Fertilization management

Although cashew trees are tolerant of poor soil and resistant to drought, cultivation practice has proven that naturally growing cashew trees that are left to grow on their own have almost no yield. The yield of mature fruit trees will increase several times after fertilization. From the perspective of fertilizer type, mixed application of N, P, and K has the best yield-increasing effect; next is P alone, followed by mixed application of N and P. Relatively high levels of N can prolong the flowering period, while relatively high levels of P and K shorten the flowering period. Applying 600 g of N, 200 g of P, and 200 g of K per tree each year can significantly increase the number of nuts per tree and improve the total yield and kernel outturn rate.

Pest and Disease Control of Cashew

At different stages of its growth, cashew is harmed by more than 60 kinds of pests and diseases. Among them, the main cashew diseases include inflorescence blight, damping-off, gummosis, branch rot and leaf fall disease, leaf rot, yellow leaf spot, and little leaf disease; the main pests include the cashew tea mosquito bug, cashew leaf miner, cashew stem borer, and scarab beetles.

The cashew stem borer is a pest of the cashew tree trunk, and the best control is carried out during the egg-laying period from July to August. Generally, 0.15% carbaryl or 0.05% monocrotophos can be used to treat the exposed roots of cashew trees.

Scarab larvae mainly harm cashew tree roots. The chemical control method is applying lime sulfur mixture at 1 kg of effective ingredient per hectare, which gives the best effect; 15 days after application, the pest population decreases by 74.4%.