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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63
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.
 

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