We usually think of plants feeding through their roots. But when supplements are needed or a deficiency makes itself apparent, foliar feeding can be useful. There are five key points to remember about this technique:
1 Foliar applications mean precise targeting, with the nutrients entering through the stomata or through the cuticle.
2 Since environmental conditions affect the opening and closing of stomata, applications are best made during periods of high humidity and not when sunlight levels and temperatures
3 Penetration through the cuticle is affected by the nature of the leaf surface. Some leaves have an upper surface that is waxy, making it difficult for the nutrients to enter the leaf. However, research has shown that the use of adjuvants helps by spreading the fertiliser across the whole leaf rather than leaving it in droplets. Increasing the drying time can also increase penetration rates.
4 Most soluble nutrients can be absorbed through the leaves but macronutrients are generally required in substantial quantities and uptake through the leaves is likely to be insufficient. If the root system is under-functioning, foliar applications are a good way of ensuring that the plants get the nutrients they need.
5 Soluble NPK fertilisers applied to foliage may result in residues on the leaves in hard-water areas.
Note The following table includes many of the products suitable for foliar application to a wide range of ornamental crops, including nursery stock, bedding and pot plants as well as flower production. Omission of any company or product does not imply criticism.
Solufeed has introduced K-LEAF to raise potassium levels — useful for overwintering nursery stock and to optimise spring growth. Also new from Solufeed is Kalium 25, a high-K feed that comes with the added benefit of trace elements.
Omex Horticulture has just published a 70-page catalogue with a wider range of products covering ornamentals, fruit and protected vegetable crops.
Compo Expert is adding KamaSol to its portfolio. With an analysis of 10-4-7 + Mg + S + chelated trace elements, the product is described as a convenient way of feeding.