Soil tests are back, and Houston we have a problem.

[SNEAKYp]

Hey there RIU Organics!

I’ve been building my soil this month and had a soil test done by my states’ ag extension. I’ve gotten the results back and wheew there were some shockers. This initial test was done to get a baseline of the inputs I have locally. This is Pre-amendment and building, half compost half leaf mulch for one sample and then another with kelp meal at ~2% and bio char at 10%. Both uncooked.

The results came back as follows:
C/LM:
PH- 7.1
P Index-114
K Index-423
MN Index-501
ZN Index-345
Cu Index-115
S Index-29
CEC- 16.1

C/LM/BC/KM:
PH- 7.5
P Index -113
K Index-554
MN Index-601
ZN Index-374
Cu Index-106
S Index-99
CEC -19.0

Me, being the impatient dummy I am, went ahead and built the soil before these results were in. (I know I know). I made 8 cu.f and added the following:
4 cups kelp meal
12 cups azomite
8 cups Dolomite lime
10% by volume bio char

Sooo am I fucked with my PH being in the 7’s and adding 8 cups of lime? Also my Nitrogen levels are apparently really low with the report suggesting I add 5 lbs of 21-0-0 per 1000 sq ft.

Any and all recommendations/observations would be helpful, and much appreciated!

Stay cool RIU,
SneakyP

 

[Northwood]

I wonder about those results. With an Mn index that high, lowering your pH too much might bring toxicity issues. It looks like all of your index values are extremely high, especially P/K. Assuming these test results are near accurate, where did you get soil like that? If it's for outside use, at least it will get leached into the ground water if you have heavy rains or over irrigate. Keep in mind these index values mean very little to organic growers, because availability isn't so much of a thing when we have a biological system that converts unavailable nutrients locked in organic matter to available throughout your grow(s) in a JIT way.

In my municipality in Canada, our agricultural extension caters to conventional farmers who depend more on immediate availability. It's typically better for organic growers to send samples to a specialty testing facility for that purpose. Your local organic certification body will have contacts for this in your area. It will cost a bit more, but they include recommendations using amendments found in your locale and can even visit your property.

I would only worry about pH if you can't bring this soil back to life (provided your index levels are down to ideal ranges). Otherwise, lots of biological activity will eventually buffer and stabilize the pH to more ideal levels. It's the least I would worry about in your soil test. If your tests are accurate, I wouldn't even think of using that soil for an indoor no-till however because of those high index values. I worry about potassium accumulation just from adding more fresh organic material to my pots than I harvest each cycle. Need... balance... lol

If I were growing outdoors with your soil, I'd let it age for a season growing edible legumes. This would give it time for those index values to drop by leaching, bacteria and fungi to multiply, and allow the legumes to supplement your N. Think of it as a "test" grow. Plus you may get to eat free beans. lentils, or peas. And by Spring 2021, I bet the pH would drop considerably too. It would be pretty hard to supplement your N now without increasing the issues with your other index values by organic means.

Also be careful with the kelp. I would not add kelp unless I gathered the seaweed and leached the salt out of it myself. And that's even too much work! Kelp meal pellets sold in small amounts on Amazon are often just repackaged kelp from big feed bags destined for horse feed supplement use, (sold in every seed/farm store). Sodium levels in these meals are very high - often over 8% (seriously). While there are liquid formulations meant for horticulture use, it's not exactly "organic". I avoid the use of it, or anything else that can contain a lot of sodium chloride or free salts.

But I'm also no-till indoor, so avoiding accumulation of anything is a major objective when I reuse my soil 3 cycles a year, for years and years.

 

[Bignutes]

Take a couple of bottles of lemon juice and grab some water, get ph down below 4 and give that soil a soak with it. Retest ph using distilled water and a cheap ph pen with run thru water. It will lower it. I had to do this, I took ph 3.4 water and soaked ph 7.6 soil, in a week the ph dropped to 6.9 and stayed that way. Repeat but not as low ph to drift it into 6.5 range. Don't use the cheap prong style ph probe, use the $20 rectangular ones off amazon.

 

[Bignutes]

Dilute the soil with more inert media to reduce nutrient levels. Also can use low nutrient soil like sand.

 

[toomp]

I wonder about those results. With an Mn index that high, lowering your pH too much might bring toxicity issues. It looks like all of your index values are extremely high, especially P/K. Assuming these test results are near accurate, where did you get soil like that? If it's for outside use, at least it will get leached into the ground water if you have heavy rains or over irrigate. Keep in mind these index values mean very little to organic growers, because availability isn't so much of a thing when we have a biological system that converts unavailable nutrients locked in organic matter to available throughout your grow(s) in a JIT way.

In my municipality in Canada, our agricultural extension caters to conventional farmers who depend more on immediate availability. It's typically better for organic growers to send samples to a specialty testing facility for that purpose. Your local organic certification body will have contacts for this in your area. It will cost a bit more, but they include recommendations using amendments found in your locale and can even visit your property.

I would only worry about pH if you can't bring this soil back to life (provided your index levels are down to ideal ranges). Otherwise, lots of biological activity will eventually buffer and stabilize the pH to more ideal levels. It's the least I would worry about in your soil test. If your tests are accurate, I wouldn't even think of using that soil for an indoor no-till however because of those high index values. I worry about potassium accumulation just from adding more fresh organic material to my pots than I harvest each cycle. Need... balance... lol

If I were growing outdoors with your soil, I'd let it age for a season growing edible legumes. This would give it time for those index values to drop by leaching, bacteria and fungi to multiply, and allow the legumes to supplement your N. Think of it as a "test" grow. Plus you may get to eat free beans. lentils, or peas. And by Spring 2021, I bet the pH would drop considerably too. It would be pretty hard to supplement your N now without increasing the issues with your other index values by organic means.

Also be careful with the kelp. I would not add kelp unless I gathered the seaweed and leached the salt out of it myself. And that's even too much work! Kelp meal pellets sold in small amounts on Amazon are often just repackaged kelp from big feed bags destined for horse feed supplement use, (sold in every seed/farm store). Sodium levels in these meals are very high - often over 8% (seriously). While there are liquid formulations meant for horticulture use, it's not exactly "organic". I avoid the use of it, or anything else that can contain a lot of sodium chloride or free salts.

But I'm also no-till indoor, so avoiding accumulation of anything is a major objective when I reuse my soil 3 cycles a year, for years and years.

just cut it with peat

 

[Gardenator]

I agree cut the soil with peat and retest the medium. Also bignutes is right to about the pH issue, soaking that soil with lemon juice and water will work too... id cut it first as you could achieve lower more ideal P and K values along with reducing the pH down into a more acceptable range before having to treat the soil, you may also have an easier time after cutting it with Peat reducing these values as there will be less concentration by volume to deal with in the soil.

 

[Bignutes]

I agree , use peat - sunshine mix #1 as its straight peat. Top out at about 1/3 peat otherwise your soil becomes to block like and you may have root issues. 1/3 is just a general guideline as other amendments will vary that to certain degrees

 

[getogrow]

Take a couple of bottles of lemon juice and grab some water, get ph down below 4 and give that soil a soak with it. Retest ph using distilled water and a cheap ph pen with run thru water. It will lower it. I had to do this, I took ph 3.4 water and soaked ph 7.6 soil, in a week the ph dropped to 6.9 and stayed that way. Repeat but not as low ph to drift it into 6.5 range. Don't use the cheap prong style ph probe, use the $20 rectangular ones off amazon.

This is absolutely not how soil works. That may trick the ph meter but not the soil. You cannot permanently lower ph with liquid anything. Lemon juice is just like ph down ..... it only lasts long enough to read a meter. As soon as the soil fixes itself it will go back to normal. (a day or two? prolly a few hours)
Peat will actually lower the ph of the whole mix.

 

[Bignutes]

This is absolutely not how soil works. That may trick the ph meter but not the soil. You cannot permanently lower ph with liquid anything. Lemon juice is just like ph down ..... it only lasts long enough to read a meter. As soon as the soil fixes itself it will go back to normal. (a day or two? prolly a few hours)
Peat will actually lower the ph of the whole mix.

Try it, just don't be timid about adding a lot of lemon juice. Soil is well buffered so to counter that you need to really buffer the water. Renfro and doubleAron do this and they are pretty established growers as you can see by their grow journals.

 

[getogrow]

Try it, just don't be timid about adding a lot of lemon juice. Soil is well buffered so to counter that you need to really buffer the water. Renfro and doubleAron do this and they are pretty established growers as you can see by their grow journals.

I dont see how the lemon juice can stay active for so long? Once its broken down and used , how will it continue to buffer ? I dont agree but i'll be dammed if i try to argue 3 of the better growers on the internet but i'll debate to learn all day.

 

[Bignutes]

I'll say they don't use lemon juice, I do. It doesn't remain active because it's been chemically reacted to neutralize the calcium. When I use just a little lemon juice in hard tap water it drifts back up, use more and it sticks, use a lot and it stays like glue, hence the words well buffered. I always undershoot my target ph by 0.1-0.2 because it's not strongly buffered on normal waterings. I take it from 7.5 to 8.2( it ranges) down to 5.6 and settles back up to 5.7 to 5.8. If i want to hard correct a high ph soil then i drop it down to 3.5 or less. Use enough lemon juice in hard tap water and test it over the course of a week and youll see what i mean. An acid is an acid regardless of what type it is.

 

[getogrow]

I'll say they don't use lemon juice, I do. It doesn't remain active because it's been chemically reacted to neutralize the calcium. When I use just a little lemon juice in hard tap water it drifts back up, use more and it sticks, use a lot and it stays like glue, hence the words well buffered. I always undershoot my target ph by 0.1-0.2 because it's not strongly buffered on normal waterings. I take it from 7.5 to 8.2( it ranges) down to 5.6 and settles back up to 5.7 to 5.8. If i want to hard correct a high ph soil then i drop it down to 3.5 or less. Use enough lemon juice in hard tap water and test it over the course of a week and youll see what i mean. An acid is an acid regardless of what type it is.

I got what your saying and i would have to agree. Where im lost at is how does the soil react to the lemon juice? Can enough lemon juice permanently change your ph in your container ?

 

[Bignutes]

It will, give it one or two strongarms it will bring it down. I've done this mid grow at a ph of 3.3-3.5, and the soil's ph gets adjusted down by 0.5-0.6 from 7.6. plants for the short term didn't mind.

 

[Dryxi]

I got what your saying and i would have to agree. Where im lost at is how does the soil react to the lemon juice? Can enough lemon juice permanently change your ph in your container ?

Lemon juice will acidify the soil water. Maybe it will acidify the actual soil slightly, until more regular water washes it out. It is not going to work the same as elemental sulfur or the such.

"The bioactive compounds contained in lemon (Citrus limon) each have an antibacterial [13]. Lemon (Citrus aurantifolia) juice besides being used as an antibacterial, it is also useful as an antioxidant." - iopscience.iop.org

I would assume if your goal is reusing the soil and cultivating microbes within it, soaking it with lemon may be going backwards. You need those microbes to break down the material you added to your soil.

 

[Bignutes]

It's meant to correct a soil's ph if out of whack, I'd rather have the right ph and nutrient uptake than limp along. You dont understand that it doesnt wash out, it reacts. In the quantities for regular watering it does fine. Scott's ph down has citric acid in in and guess what it's used for, yup, plants.

 

[PadawanWarrior]

It's meant to correct a soil's ph if out of whack, I'd rather have the right ph and nutrient uptake than limp along. You dont understand that it doesnt wash out, it reacts. In the quantities for regular watering it does fine. Scott's ph down has citric acid in in and guess what it's used for, yup, plants.

I've used citric acid and it helped lower my soil pH. Here's a little study from Humboldt University.

https://digitalcommons.humboldt.edu/cgi/viewcontent.cgi?article=1040&context=ideafest

 

[Bignutes]

It doesn't load for me

I've used citric acid and it helped lower my soil pH. Here's a little study from Humboldt University.

https://digitalcommons.humboldt.edu/cgi/viewcontent.cgi?article=1040&context=ideafest

 

[Dryxi]

I've used citric acid and it helped lower my soil pH. Here's a little study from Humboldt University.

https://digitalcommons.humboldt.edu/cgi/viewcontent.cgi?article=1040&context=ideafest

That's a good article! Thanks! Something it did mention was that citric acid is a chelating agent for heavy metals, and cannabis is an accumulator plant. The article was largely about chelating heavy metals for plants to uptake for contaminated soil remediation.

 

[PadawanWarrior]

That's a good article! Thanks! Something it did mention was that citric acid is a chelating agent for heavy metals, and cannabis is an accumulator plant. The article was largely about chelating heavy metals for plants to uptake for contaminated soil remediation.

Ya, I noticed that the citric acid water would bind up with some of the extra calcium carbonate and help flush it out of the soil. I can't explain it better than that link though.

 

[getogrow]

Of course you will lose some microbes but those are easy to get going again. im going to guess that it would do some decent damage to the soil food web BUT the web is easier to put back together then the ph. I dont have very many plants that stay in a pot for more then a couple months so everything has to be fast.
I was looking for real world answers and science , i got both ,. thanks guys!
Science is always up for debate for some reason, so i get some real world answers to go with the science and boom i feel smarter.

Same with leds....real world guys are getting great product off very low ppfd numbers while others on here and science is saying that light has to be no more then 18" from the canopy. In the real world i see the same light 36" from the canopy with super weak numbers but the buds look like they are under hid.