An ounce of prevention: plant nutrient deficiencies
Plants need 17 chemical elements to thrive, and these are called essential plant nutrients, three of which are atmospheric – carbon, hydrogen and oxygen. Essential plant nutrients are subdivided into groups based on whether plants require them in large or small quantities. Nutrients which plants need in large quantities are called ‘macro’ nutrients – examples include nitrogen, phosphorous and potassium; nutrients which plants need in smaller quantities are called ‘micro’ nutrients – examples include manganese and boron. Nutrients vary in their solubility and so some nutrients are more easily washed out (leached) through over-irrigation or during heavy rainfall periods. Potassium and magnesium are especially prone to leaching and so it is important that if fertilizer is applied to plants, nutrient leaching is avoided by using slow-release fertilizers and managing irrigation schedules to prevent over-watering.
When applying fertilizers, it is critical to apply a balanced formulation because plants need a combination of nutrients in appropriate proportions, and fertilizers which have an excess amount of one nutrient over another, can in fact trigger a nutrient deficiency. Calcium deficiency can often result from an excess amount of magnesium fertilizer. It is important to note also that soil pH has a significant effect on nutrient availability, which means that even if fertilizer is applied, plant roots may not be able to access the nutrients, resulting in a nutrient deficiency.
Excessive pruning is another source of nutrient deficiency and this is especially true in palms. As leaves naturally age, before they turn brown and fall off the plant (senescence), essential nutrients get recycled from older leaves to newer leaves. When older leaves are continually removed while they are still green and prior to the completion of the nutrient recycling process, new leaves become starved of nutrients and are susceptible to nutrient deficiencies.
Bottom line – to prevent nutrient deficiencies: (i) avoid over-irrigating plants (ii) use fertilizer spikes (slow-release) for potted plants (iii) fertilize with a blend of nutrients (complete fertilizer) versus individual nutrients unless treating specific nutrient deficiencies (iv) use slow-release fertilizers (v) avoid pruning off palm fronds before they turn brown, or removing more than 15 percent of a plant’s green foliage.
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