- pH of the foliar spray solution – Nutrients must be in their soluble form in order for the plant to be able to absorb them. pH affects the solubility of nutrients and their interaction with other components in the water. Generally, acidic pH improves the penetration of nutrients through leaf surfaces.
Author: Mr. Guy Sela, agronomist, expert in plant nutrition and irrigation.
However, many open questions and uncertainty still surround this practice.
Many believe that foliar feeding is favorable over soil application and it is associated with higher yields, and better fruit quality.
In addition, pH affects foliar absorption of nutrients in three other ways:
Therefore, when a deficiency symptom shows up, a quick, but temporary fix, would be applying the deficient nutrient through foliar application.
- pH affects the charge of the cuticle (a waxy layer covering the leaves) and therefore its selectivity to ions;
- The ionic form of nutrients is pH dependent, and therefore pH can affect the penetration rate;
- pH might affect the phytotoxicity of the sprayed compounds.
We can conclude that pH of the spray solution must be adjusted according to the applied nutrient.
- Use of surfactants – Surfactants contribute to a more uniform coverage of the foliage. They increase the retention of the spray solution by reducing the surface tension of the droplets.
- Time of the day – the best time to foliar feed is early morning or late evening, when the stomata are open. Foliar feeding is not recommended when temperature exceeds 80°F ( 27° C).
- Droplet size – Smaller droplets cover a larger area and increase efficiency of foliar applications. However, when droplets are too small (less than 100 microns), a drift might occur.
- Spray volume – Spray volume has a significant effect on the nutrient absorption efficiency. Spray volume must be such that it is sufficient to fully cover the plant canopy, but not too high so it does not run off the leaves.
Limiting conditions – A foliar feeding is recommended when environmental conditions limit the uptake of nutrients by roots. Such conditions may include high or low soil pH, temperature stress, too low or too high soil moisture, root disease, presence of pests that affect nutrient uptake, nutrient imbalances in soil etc.
11 facts about foliar-sprays you must know before your next foliar application.
Don’t spray when you expect bad weather. Rain can make your foliar spray a waste of time by washing away or diluting your spray solution. The same goes for strong winds. When you spray outdoors, wait for rain and stormy weather to pass. When you spray indoors, it can be a good idea to turn off ventilation fans for an hour or two. This allows the solution to be absorbed by the plants without any major disturbances.
These pump sprayers also come with an extended spray wand which makes them especially convenient so you can spray your plants easily from all sides, including the underside of the leaves where it counts.
Take note of the recommended nutrient strengths of your solution. Most of the time, foliar feeding requires a much lower nutrient strength than feeding your plants through soil. If the product that you are spraying doesn’t specify the proper amount for foliar application, start with half the recommended dose.
Avoid spraying during flowering. Spraying the buds can be bad for a number of reasons. Depending on your spray solution, this can lead to anything from a spoilt taste to an increased chance for mouldy buds.
Not all growers may be familiar with it, but most will at some point encounter a scenario where they should apply a foliar spray to their cannabis plants. The reasons for this are various; from treating your plants with insecticides or fungicides, to addressing a nutrient deficiency in the fastest way possible.
The best time for foliar spraying is either early in the morning or late in the evening. Do not spray in direct sunlight. The sunlight can not only burn your plants through the “lens effect” from droplets on the leaves, it can also degrade active substances and nutrients contained in your solution. In the evening, the plant’s pores are fully open, which allows for a quicker intake as compared to during the day. If you grow indoors, the best time to spray is at the beginning or the end of the dark period.
There are two main types of sprayers available that you can use for foliar sprays; both types are useful depending on the circumstances.
While foliar spraying (or foliar feeding) your plants doesn’t really require any special growing skills, it can nevertheless be helpful to know how to do it right so you can get the best results. Let us take a closer look at foliar spraying; what it is and when you want to use it.
One type is a simple hand-sprayer that may take 500ml to 1l of spray solution. These small and handy sprayers are great if you only have a few plants or if you require a sprayer for some “precision work;” for instance, when you want to avoid spraying buds.
Learn about how and why to foliar feed your cannabis plants. What makes foliar spraying so effective and how do you get started?