Here’s some thoughts relating to Cashew.
First – remember one absolutely important issue. Each tree will grow for many years. That means if it is poor quality in its first 5 years, well, the next 25 are going to get no better! So, start with the very best trees. One way of achieving that is to air layer from really good trees. Failing that, obtain seeds from the very best sources, then plant those seeds that sink when placed in water. There’s more info at the link below.
Note also that the seeds are often planted, three to a well prepared planting hole and thinned to one – that means their roots are not disturbed/damaged by transplanting out of planting bags.
A link to an FAO report/training manual worth a visit.
They state – relating to air layering
A strip of bark about 0.5 cm wide is removed from either a year-old branch or a pencil-thick shoot (about 1 cm diameter) of the current season, at about 20-30 cm from the growing point. The exposed wood is wrapped with twine to prevent the bark from growing over it during the healing process and covered thickly with moist moss, wood shavings or sand. It is then wrapped securely in a sheet of 100-150-gauge plastic and the ends are tied tightly to the branch with twine- refer picture-
After 20-30 days, callus is formed at the foot of the layer and 40-50 days later, small roots emerge from the callus tissue. After approximately 75 days, there should be adequate root formation (five or more well formed roots measuring 1.0-1.5 cm long) to separate the twig from the tree. The part of the twig below the layer is cut about halfway through. One week later, the cut is deepened and a few days later the layer can be removed and transplanted into plastic bags or other containers and hardened off before planting. If the layer is separated from the tree in one cut, the shock will be too great for it to survive.
The whole process takes about two and a half months, although the time varies depending upon the period of the year when the layer is being prepared. Layers that are produced early in the rainy season have time to establish themselves and develop a large enough root system to survive the dry season.
Air-layering has been one of the most successful methods of vegetative propagation in cashew. The method is rather laborious and the cost is relatively high, but the advantages of obtaining a plantation from high yielding, uniform material make these costs extremely worthwhile. A large disadvantage of this method, as with all methods of layering, is the relatively small number of layers that can be produced by one tree per year. It is estimated that from one tree, 80 to 120 successful layers can be obtained. In order to obtain sufficient material for a fairly large plantation, the first generation of air layers should be grown to maturity, and only then, from many trees of the same quality, could sufficient material be obtained for later plantings.
With regard to fertiliser, FAO recommendations are given below
Cashew is often grown as a casual crop by smallholder farmers and as a result its fertilizer requirements are overlooked. Also the trees are long standing and are frequently grown in soils that are of poor quality. As each season passes, the soils become more depleted and productivity gradually declines. Yields of trees grown in this way are very much lower than the potential that could be gained if fertilizer was applied.
Experiments have demonstrated that regular application of the major plant nutrients (nitrogen, potassium and phosphorus) is beneficial for healthy trees and increased cashew yields. In addition, application of magnesium to cashew is beneficial (Fernandopulle, 2000). Two separate mixtures of fertilizer, based on the combination of nitrogen (N), phosphorus (P) and potassium (K), have been recommended according to the growth stage of the plant.