We use foliar spray for nutrient deficiency issues sometimes, but to be honest, I am not sure how effective it is and I tend to believe it is not. I would love to hear what other growers think. We also have applied foliar spray of potassium silicate some times.
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I am strongly against foliar nutritional sprays they are not part of my IPM plan. I add some nematodes that require a foliar spray for thrips prevention. But, it is on a schedule. I think it was monthly. Orius was front line trips control, but the are photo period sensitive. So with the long day lighting used in cannabis, would be perfect of Orius. Might use nematodes as a preflower cycle application for thrips prevention.
CO2 is potentially the only thing that goes into my leaves but as gaseous air supplement. I want my leaves dry. I just can’t make the chemistry work for adding CO2 as an aquius foliar supplement. Until someone gives me a good paper, I am going to keep my leaves dry.
“Roots are for nutrition. Leaves are for gathering light. Leaves make bad roots.” by L H Bailey.
If I have a nutritional deficiency, I have a problem in my grow that needs to be corrected. From my experience, it is either a bad medium pH or the total salts concentration in the CLF got out of wack. Clear water on a schedule did not happen. This has been true for me 99 times out of a hundred. There is always an odd ball. That has something strange.
A true nutritional problem in an inside grow just should just not happen. It is a production issue. Example, in poinsettias Molybdenum is alway a limitation in the grow. So molybdenum goes into the CFL program on rinse day at 5 ppm. Rinse day happens once a week. And we calculate the rinse duration as calculation of time based on the salinity of soil with a good old fashioned connectivity tool. Irrigation runs longer on rinse day. If normal water time for container x is 10 minutes, the rinse time can be calculate based on the salt in the first affluent test. So the rinse time for x would probably be in the thirty minute range. My meter is so old they don’t even make it any more. I got it from a grower way older than me as a welcome to your new grow operation and our community. Still works after 40 years.
A pH meter is only good for about a year before they should be replaced. No one has made one I don’t like. Because they have a life span, I buy the least expensive one that will do what I want. Remember to buy calibration solution and have plenty of distilled water on hand for cleaning. A dirty pH pen is about as useful as a condom with a hole.
But, all of these things are in my IPM plan.
From the voices in my head
Ethan.
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Beautifully said! That is why I do not like foliar spray. Nature has built roots for that purpose.
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Let me see the paper Tom 
If you need a cal mag feed. Uses your roots, that’s what they are designed for.
Magnesium will go through the leaves epsom salt. Magnesium Sulfate. I find it works better in my feed. Magnesium is availability is a function of soil pH. pH to high no magnesium, pH to low magnesium toxicity and calcium, phosphorus deficiency.
The pH of the growth substrate or water in hydroponics is key. There are so many papers on optimal pH for your growth substrate.
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The paper is pdf form. message me your email ill send it to you.
As for calmag in foliar spray. From my experience growing with LED i notice about once in the plants life (some strains dont show this) The plant requires a little extra calmag. So we dose the roots. and do a light spray of calmag under the leaves. Within 24 hours all calmag issues disappear completly. I have been working on preloading my soil. It seems around third or fourth week of veg they need a little more. Just my experience.
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Plants also naturally take up dew every morning through the leaves and is the only way some of the plants in my area get water in the summer. It is a high desert and very dry and hot in the summers. It is natural for them to take up water other than by the roots. Not saying that is the way to feed but, if you have proper airflow and SOP there is no worry of molds and mildew and can be very beneficial to the garden.
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I get the same results when just adjusting my feed. Epson salts are really really cheep. But used as a drench. You see results in less than 24 hours. The uptake happens in the dark.
Calcium is a different problem, because how plants transport calcium. Tomato growers with blossoms end rot know calcium management a pure nutritional issue. Adjustments to the base CLF schedule solves the problem.
The issue is are you see a calcium issue or a magnesium issue or a pH issue in your growth medium.
Calcium is a know limitation in hemp. Lots of work in calcium in hemp. Calcium is need for good dry weight. So I change my fertilizer to be a N-K-P-Ca. I need to pay as close attention to all 4. Not just Nitrogen.
Magnesium is used in other organic metabolism paths. I generally see chlorophyll reabsorption from older leaves long before I see magnesium deficiency in the new leaves. It is an easy correction. If you see it in one plant of a species, the rest of the plants have the same problem but just not showing it yet. Some plants are great indicators for magnesium availability. We used petunia as an indicator plant. It shows magnesium problems before everything.
For me and experience, if magnesium is a limitation we have a pH problem and not a magnesium problem.
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Heavy 16 Foliar. Plants love it, and it inhibits pm sporulation.
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Have a look at First Horticulture, math exercise aka bucket chemistry I think you have found the most expensive form of N K P on the market.
This is an interesting way to control powdery mildew. Old time grows use to volitalize nitric acid as a PM control. Heavy 16 is a modern take on PM control.
Do you live in a state that allows volitalize Sulfer? It is better at PM control than nitric acid and a lot less expensive. It is the acid that forms when the PM spore trys to grow. I will find a citation. Nice paper if I recall correctly.
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Yeah I saw that, other than heavy, I’m blending my own salts, I’m under $.03/gal. This is the only preblended fert I use, and I use it mainly as a pm preventative because here in MA we can only use 25bs. Anyone know whats in iHeavy 16? Its like a calcium…vit b… surfactant mix I think, smells slightly fermented.
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May I ask the question “Why would you foliar feed?” The risk of wet leaves just scares me as a grower.
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Ethan is right on point… you want health plants?? feed them wisely, from the roots.
Healthy soil, clean water and proper nutrients.
Tom
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This is a subsection of plants that actively use Stomotic transfer. And store CO2 for at night for use during the day. @hunter (This is why CO2 in water should not work in cannabis, except at an early stage) Cannabis does not fall into one of these families. Stomotic density in cannabis is on the low end for all cultivated plants. I would have to look up the ranges of numbers, but it is surprisingly low for a plant that can get as big as these can.
If you can give me good literature citations, I will take a second look. But, if your SOP calls for wet leaves, I see a problem. This is strictly my opinion.
“ Roots are for nutrition. Leaves are for gathering light. Leaves make bad roots. ” by L H Bailey.
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I like to spray calcium, potassium, kelp, Sea Crop, Pacific Gro, and micro nutrients. Has provided nothing but great results for me as long as the concentrations aren’t too high. Especially helpful when soil concentrations of the particular nutrient are low or if it has low mobility.
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We have a new Foliar called Foliar Science. It is a high Nitrogen 29-9-9 and great for early veg through second week of flower. Helps with lock out issues and any kind of starving plant turns around quickly. I have lots of samples that I am sending out and not one bad review. If anyone would like to see a sample for trials, PM me you contact info to get some to you. Dakine420-1000g-Foliar-OTHER-STATES-2018-OUT2.pdf (4.2 MB)
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What’s the coverage like with the auto foiler ? I have been super interested in installing sprayers for ipm and foliar spray for a long time now.
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We spray twice a week and add maxicrop to what ever is in my IPM rotation that spray.
Ive not had any PM or adverse effects unless one of my guys messes up the mix. does not properly clean sprayer, does not agitate sprayer while spraying, ect. Since Ive used Maxicrop( going on 6 years now) The leaves are healthier, vibrant, and seemingly more resistant to pathogens.
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Vapor pressure density is important. I tend to keep the rooms around 80 degrees F. and humidity around 35% with C02. Last 3 weeks I drop the temp to around 72, but we don’t usually spray past week 5 in an 8 week bloom cycle.
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I was really just using protable units. would like to build a full system. But a warm mist foliar feed worked well in my testing.
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