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Most hydroponic information you read regarding nutrient uptake refers to root feeding, that is applying the nutrient solution directly to the root zone. However, it is also possible to feed plants by applying nutrients to their leaves or foliage, a technique known as foliar feeding. This technique was developed in the 1950s by Dr. H. B. Tukey and S.H. Wittwer at the Michigan State University department of agriculture. Their research debunked the conventional belief that it was damaging to get a plant’s leaves wet.
Why Foliar Feed?
Hydroponics offers a great deal of control to the average grower, which has the fantastic potential to increase yield, but the increased number of factors also decreases the margin for error. A nutrient solution must contain a very delicate balance of nutrients, correct temperature, and correct pH levels for the plant to be sufficiently supplied with nutrients. Sometimes, even when it appears that all of the conditions are optimized, the plants may not receive all of the nutrients they need. In these instances, many growers choose to foliar feed to ensure that their plants get all of the nutrients they need to grow to their potential.
In other instances a plant’s roots may become damaged either through overwatering, underwatering, or disease. As it recovers from this damage, your plants will likely struggle to get sufficient nutrients because of the loss of root mass. Again, foliar feeding offers gardeners an opportunity to give their crops nutrients that they are not able to get otherwise.
How to Foliar Feed
How quickly your plant is able to absorb the nutrients through their leaves will depend upon a number of factors. Like with the nutrient solution you use on your roots, the one you will apply to your leaves should have a pH of 5.6 and should not be too cold or too hot.
The nutrient solution should be applied using a finely atomized drifting mist. This can be accomplished by using something as small as a hand pump sprayer, or something as large as a backpack leaf blower with a liquid attachment, depending upon the size of your operation. The fine mist should be thoroughly applied until it begins to “run off” of the leaves. Make certain that it applied to both sides of each leaf. To get the nutrients to stick to the leaves, and thus increase uptake, you should include a non-ionic wetting or sticking agent.
Your plant’s leaves will receive the nutrient solution through “stomata,” or pores mostly used for gas exchange. For this reason, you should only foliar feed in slightly cooler conditions. If the environment is too hot the stomata will be closed, and your plants will receive very little of the solution, or perhaps none at all.
Even if your plants appear to be receiving adequate nutrients, it is still possible your plants can benefit form foliar feeding. As always, experiment with one plant and collect as much hydroponic information as possible on foliar feeding before you try it on your entire crop. It is entirely possible to give a plant too many nutrients, and it may then suffer some of the ailments that a under fertilized plant can experience.
