Organic soil dry amendment EC targets

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bigbagofbuds

bigbagofbuds

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Hey growers!

I have been growing organically for a few years now and have decent success but not many perfect runs. I am looking to improve my consistency and so I purchased a soil EC meter to get another data point.

My main problem tends to be calcium and magnesium deficiencies, growing under LED.

I believe I may be under feeding them because I take a half assed approach to fertilizing so sometimes plants get a bit more, sometimes a bit less, and sometimes Im late to the party and top dress half the plants but forget to do the other half (due to offset watering days).

My idea here was that having a soil EC meter I could check medium EC to better inform me on fertilzer applications.

I grow in a peat based soilless mix, usually ProMix BX with added perlite or Sunshine mix #4. I top dress approximately a half cup per 3 gallon pot every 3 to 4 weeks of 4-4-4 and 2-8-4 mixed.

My question is that after recieving the new meter I went to testing. What I found was the readings were significant lower than I expected ranging from 0.3 to 0.65 EC. I understand that with organics the nutrients are more gradually released via microorganisms so I know that I shouldn't expect 1 to 2 EC. However these numbers are so low I wonder if I am still underfeeding?

What are typical EC readings for organic soil (not run off but the medium itself via direct measure or slurry test)?

How should I improve the conversion of organic matter to nutrient salts? I am currently using fulvic acid, amino acids, carbohydrates, and recharge to try and get the medium working.

I know pot sizes can affect things too, are 3 gallon pots too small for organic growing plants ~ 3 to 4' tall?
 
PrimoClonesCanada

PrimoClonesCanada

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Man amazing thread, unfortunately I have no answers for you. I am super curious for the answer though. And that meter sounds cool I never knew you could get a soil ec tester. Is it a quality meter?

Like you said organics break down slowly, so the top dress probably isn't going to register much if any right after top dressing. And your pots are small for organics, I think I run close to the same regime as you but I use blumats.
Would be interesting to see what the readings from a big bed would be
 
bigbagofbuds

bigbagofbuds

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This is the meter I bought, this is my first time with the Hanna instruments brand but I have read they are of good quality. I typically use BlueLabs meters but their medium EC meter was more than twice the cost.


I do think that my pot size might be the issue, my better runs were in 5 gallon pots and even thoughs are still small for organics.

I am going to get the meter recalibrated ASAP to see if maybe that's causing the confusion. I'm really curious because I have your Apple Fritter clone reading at 0.3 EC but the plant is green and healthy. Then I have some autoflowers reading at 0.65 EC and 0.04 EC with both showing calcium and magnesium deficiencies. Usually my deficiencies start around week 2 of flower.
 
Aqua Man

Aqua Man

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Any recommendations on EC when feeding with amendments? I'll be using some next round so i'm just curious.
Nope organics imo should not use EC and rather are usually dosed by volume or weight. There are to many other things that add to the ppm in organics that are not nutrients. In many cases you see someone using organics getting 3000 ppm run off and the plants are happy and healthy. But as i say EC is just not a good option and imo a soil analysis is what should be done
 
bigbagofbuds

bigbagofbuds

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Nope organics imo should not use EC and rather are usually dosed by volume or weight. There are to many other things that add to the ppm in organics that are not nutrients. In many cases you see someone using organics getting 3000 ppm run off and the plants are happy and healthy. But as i say EC is just not a good option and imo a soil analysis is what should be done
Soil analysis just isnt realistic at my scale unfortunately. For what its worth im not trying to compare organic dry ammendment EC with mineral based nutrient EC.

Im mostly just looking for a way to know when I should be applying more fertilizer for the case when I forget or when my haphazard handful isnt quite enough (or too much).

At the end of the day the organics are broken down into minerals which we can measure, it should be possible to find the reading at which the plants are happy and then aim for that reading. I do know it wont be nearly as precise due to variable breakdown (problem could be not enough fertilizer, inactive medium caused by other issues, or inactive medium caused by too much fertilizer) but there must be a more scientific method than simply saying 2 tbsp a gallon is sufficient for a top dress every 4 weeks. Organics are hard and I dont want to make it easy, but I do want a way to know I have too much or too little organic matter to break down.

For what its worth my plants are always beautiful at 500 ppfd (~30 DLI) and they usually start showing deficiencies when lights start increasing in intensity to (750-1000ppfd, ~45-60 DLI). I know it should be possible to push the plants to the higher DLI even in my suboptimal 76f 50rh environment (Ive done so with mineral based fertilizer), the CO2 usually sits between 1000ppm and 1500ppm.
 
Aqua Man

Aqua Man

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Soil analysis just isnt realistic at my scale unfortunately. For what its worth im not trying to compare organic dry ammendment EC with mineral based nutrient EC.

Im mostly just looking for a way to know when I should be applying more fertilizer for the case when I forget or when my haphazard handful isnt quite enough (or too much).

At the end of the day the organics are broken down into minerals which we can measure, it should be possible to find the reading at which the plants are happy and then aim for that reading. I do know it wont be nearly as precise due to variable breakdown (problem could be not enough fertilizer, inactive medium caused by other issues, or inactive medium caused by too much fertilizer) but there must be a more scientific method than simply saying 2 tbsp a gallon is sufficient for a top dress every 4 weeks. Organics are hard and I dont want to make it easy, but I do want a way to know I have too much or too little organic matter to break down.

For what its worth my plants are always beautiful at 500 ppfd (~30 DLI) and they usually start showing deficiencies when lights start increasing in intensity to (750-1000ppfd, ~45-60 DLI). I know it should be possible to push the plants to the higher DLI even in my suboptimal 76f 50rh environment (Ive done so with mineral based fertilizer), the CO2 usually sits between 1000ppm and 1500ppm.
Base that on response to nitrogen. If your looking for a definitive answer without a soil analysis there isnt as far as i know… growing organic is a by feel and experience thing.
 
Shaded_One

Shaded_One

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My main problem tends to be calcium and magnesium deficiencies, growing under LED.

I believe I may be under feeding them because I take a half assed approach to fertilizing so sometimes plants get a bit more, sometimes a bit less, and sometimes Im late to the party and top dress half the plants but forget to do the other half (due to offset watering days).

Check out the thread in my signature if you haven't - there's detailed breakdown of how much nutrients to use. @Aqua Man has given you some great pointers here and I don't even bother checking my soil either. It's all based off feel and just using the same nutrients over and over and over.

So majority of Cal & Mag issues come from people who use RO or Distilled water. If you have decent tap water that should already contain a base level of these micronutrients. If you are feeding your plants enough general nutrients it should also provide a decent level of these micronutrients. But as we all know LED makes plants hungry so that's why I add the Gypsum, Epsom Salts, and Rock Dust Blend bi-weekly.

Gypsum - Calcium Sulfate
Epsom Salts - Magnesium Sulfate
Rock Dust Blend - micronutrient mix (iron, silicon, humics, calcium, copper, magnesium, manganese, potassium, sulfur, and zinc)
 
bigbagofbuds

bigbagofbuds

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Base that on response to nitrogen. If your looking for a definitive answer without a soil analysis there isnt as far as i know… growing organic is a by feel and experience thing.
Interestingly enough this may make my haphazard handful here and there more suitable to this growing method if I can get the right touch.
Check out the thread in my signature if you haven't - there's detailed breakdown of how much nutrients to use. @Aqua Man has given you some great pointers here and I don't even bother checking my soil either. It's all based off feel and just using the same nutrients over and over and over.

So majority of Cal & Mag issues come from people who use RO or Distilled water. If you have decent tap water that should already contain a base level of these micronutrients. If you are feeding your plants enough general nutrients it should also provide a decent level of these micronutrients. But as we all know LED makes plants hungry so that's why I add the Gypsum, Epsom Salts, and Rock Dust Blend bi-weekly.

Gypsum - Calcium Sulfate
Epsom Salts - Magnesium Sulfate
Rock Dust Blend - micronutrient mix (iron, silicon, humics, calcium, copper, magnesium, manganese, potassium, sulfur, and zinc)
I have been feeding with additional magnesium sulfate in the water every other watering since noticing the interveinal chlorosis which seems to be helping some. I just recently received some magnesium nitrate to see if I can get things on the right track just in case.

My tap water usually runs around 100ppm with 30ppm calcium and 8.5ppm magnesium. My research says I should be around 80-200ppm calcium and 30-70ppm magnesium. My goal was to not have to add things to my water.

I was hoping my use of rock dust and dolomite lime combined with fish bone meal and bone meal for calcium would be enough. I think I'm not applying enough of the magnesium fertilizers and need to get some gypsum in the mix to avoid PH problems. Does that sound right? I have read that dolomite lime works slowly, but Im assuming that as it adjusts PH its also releasing nutrients so I dont want to mess with the PH too much by over applying.

Thank you!
 
bigbagofbuds

bigbagofbuds

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I calibrated the meter and now my readings range from 1 EC to 0.25 EC still very low but getting closer to expected values.

Im going to keep monitoring the EC and noting how it changes over time with the top dressings and what it looks like when the plants are looking happiest.
 
bigbagofbuds

bigbagofbuds

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Good news everyone! My purchase of a soil EC meter was not a waste and I am here to share what I have observed and learned.

My conclusions on EC readings:
<6" plant height in a 4" pot will be happy vegging at 0.7 EC
>6" plant height in 0.5 gallon to 2 gallon pots will be happy vegging at >= 1 EC
Plants flowering in 3 gallon pots are happy at 1.5 - 4 EC
0.5 EC and lower always shows deficiencies

My conclusions on top dressing:
If EC is > 1 then you don't need to top dress but monitor as you will need top dress soon
If EC is < 1 top dress ASAP if larger plants, small plants are OK until 0.7 EC
Other water based supplements (enzymes, beneficial microbes, fulvics, humics, etc...) will affect how often you have to top dress, these additives seem to increase the speed at which organics are consumed which can cause deficiencies if you follow a more rigid top dress schedule.

Im going to now implement a top dress schedule based on these findings which I hope will let me consistently keep healthy plants at higher light intensities. Ill be back in a few months to let you know how that goes.
 
Week4Bytch

Week4Bytch

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Good news everyone! My purchase of a soil EC meter was not a waste and I am here to share what I have observed and learned.

My conclusions on EC readings:
<6" plant height in a 4" pot will be happy vegging at 0.7 EC
>6" plant height in 0.5 gallon to 2 gallon pots will be happy vegging at >= 1 EC
Plants flowering in 3 gallon pots are happy at 1.5 - 4 EC
0.5 EC and lower always shows deficiencies

My conclusions on top dressing:
If EC is > 1 then you don't need to top dress but monitor as you will need top dress soon
If EC is < 1 top dress ASAP if larger plants, small plants are OK until 0.7 EC
Other water based supplements (enzymes, beneficial microbes, fulvics, humics, etc...) will affect how often you have to top dress, these additives seem to increase the speed at which organics are consumed which can cause deficiencies if you follow a more rigid top dress schedule.

Im going to now implement a top dress schedule based on these findings which I hope will let me consistently keep healthy plants at higher light intensities. Ill be back in a few months to let you know how that goes.
My EC readings are at about .8 and I'm having deficiencies (7 weeks into flower). Thanks for the update on your input, guess I'll up my feed a bit.
 
Week4Bytch

Week4Bytch

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I read it somewhere (was it here?) else that keeping a record of your soils EC can help determine if your plants are eating or not. I checked my EC last night and kept a mental note of the readings, kinda wished I just wrote it down, think I will tonight. From memory one flower did measure out 1.4 EC and the rest were around .5 on average, the funny thing is the super healthy one with no signs of self preservation has the lowest EC of the group at .2, so not sure what to make of that finding yet.
2022 12 14 203537
 
bigbagofbuds

bigbagofbuds

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What you are probably seeing is either different salt build up levels or just that the one plant that is green but low EC is just a light feeder but running low on food.

Ive continued to take observations and what I have found is Aqua Man is right that with organics you can see higher EC and it could just be other salt build up. This can be an issue or not an issue depending on how much build up there is.

In fresh medium with no build up the soil EC meter can help you learn when plants want food. Once you reuse your medium the EC meter is less handy because of that salt build up so you need you to know how to feed by feel.
 
Week4Bytch

Week4Bytch

The Cannabis Karen (I'm a Bytch)
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What you are probably seeing is either different salt build up levels or just that the one plant that is green but low EC is just a light feeder but running low on food.

Ive continued to take observations and what I have found is Aqua Man is right that with organics you can see higher EC and it could just be other salt build up. This can be an issue or not an issue depending on how much build up there is.

In fresh medium with no build up the soil EC meter can help you learn when plants want food. Once you reuse your medium the EC meter is less handy because of that salt build up so you need you to know how to feed by feel.
Thanks for the quick response, it's kind of tricky for me right now because I'm mixing it up with "organic" bottled nutes and dry amendments. I feel like this EC tool can help me out. Like you I'm learning or studying how I might be able to use this to my advantage. I might be going through some kind of lockout too, that's the other equation to this story.

So far my history has been everything goes well till week 4 of flower, then it all goes to hell. Hence my profile name. And everyone's been telling me calcium, calcium, and calcium. I didn't get it till 2 years later (just last week) after reading an article (Cal Mag) on Maximum Yield (January issue). It turns out in Veg, cannabis can tolerate any amounts of calcium. It's when the biology of the plant changes, when it goes to flower, that the tolerance of calcium is interrupted. Some strains differ, but for the most part, the tolerance changes.

My hard water has a ppm of 350, and most of it is calcium carbonate. And now I'm understanding my dry amendments (Craft Blend from Build A Soil) is high in calcium too, and my side additives of Kelp has calcium, and my cal mag has CALCIUM.... see where I'm going with this...

I'm in the middle of a fix right now with RO filtering and discarding amendments with calcium in it.

I'm hoping I can figure out what I can do with my EC meter. For now I'm planning on feeding the pots that are low on EC and just using plain water on that one pot that is at the 1.4 EC, I will right down the readings and study the plants on their reaction of the said readings. It might take me a couple of grows to figure out a rhyme and reason but I am happy we can compare some notes here.
 
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