While much lower levels of micronutrients are needed to satisfy growth and boost yield, all play a role, particularly in supporting key tissue growth.
How to influence almond quality
Almond quality is greatly influenced by crop nutrition.
Calcium and potassium help to improve good fill and tolerance to disease, reducing molds and storage rots. Nitrogen – in excess – can have a detrimental effect on almond quality. Correct quantity and application regime of nitrogen fertilizers are important. Boron reduces water stage fruit split.
Macronutrients
A large amount of nutrients are taken up to build the frame and the canopy of the tree and retained as reserves. For example, as much as 178 lb N/ac is found in almond tree roots and a similar quantity in the rest of the tree’s vegetative components.
Some of this nitrogen is remobilized after winter to promote early leaf production, tree growth, flower bud and fruit formation, and fill. Alongside nitrogen, significant amounts of other nutrients are also needed. Calcium is particularly important in supporting the tree’s structure.
Potassium nutrition influences almond quality, leading to higher kernel weights, more split shells and fewer blank nuts. K also plays a role in improving tree health, improving resistance to disease. Potassium source is important. Potassium nitrate and potassium sulfate applied to the leaf were particularly effective.
Almonds are particularly sensitive to K-source and salinity. Potassium chloride – which has a high salt index - may lead to leaf burn and loss of yield when it is foliar applied and also leads to injury of roots, especially in dry years. As a result, potassium sulfate is a more common potassium source in dry regions such as California than potassium chloride.
Micronutrients
The micronutrient taken up in greatest quantities is iron, however supplies are rarely limiting in most groves unless soil pH levels are highly alkaline.
Boron and zinc – are both required for strong tissue growth, pollination and fruiting, and need to be readily available before flowering.
Timing of boron and zinc is best prior to nitrogen application in the spring or in the autumn. Zinc is commonly used as a defoliant after harvest and its use at this time will also encourage good bud development in the following season.
