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Soil Tests? Yay or Nay?

bigbadbiddy

Active member
I think a soil test can never hurt (unless you run wild with misinterpreting the results), I personally feel like they only make sense once you reach a certain size.


Maybe to be clearer:
I doubt a soil test will give you much of a benefit if you are running a small closet grow with 10 plants. Simply because it is probably cheaper to scrap your soil batch and mix a new one than "fixing" the existing soil batch (and paying for a proper soil analysis which doesn't cost 5 bucks either...).


At a certain size, certainly the latest when you move outdoors and get to greenhouse/farm size operations, a soil test is basically mandatory. If for no other reason then simply because you can't start a new soil batch for your entire greenhouse all nilly-willy.
You gotta fix the soil you have and that only goes through a soil test.
 

MJPassion

Observer
ICMag Donor
Veteran
Soil testing can be as beneficial as you want it to be as long as you understand HOW to add back the recommended minerals. Not understanding how to add back minerals can be detrimental to your crops. I know... I've funked up a garden with my misunderstandings. hehe
 

PaulieWaulie

Member
Veteran
I think a soil test can never hurt (unless you run wild with misinterpreting the results), I personally feel like they only make sense once you reach a certain size.


Maybe to be clearer:
I doubt a soil test will give you much of a benefit if you are running a small closet grow with 10 plants. Simply because it is probably cheaper to scrap your soil batch and mix a new one than "fixing" the existing soil batch (and paying for a proper soil analysis which doesn't cost 5 bucks either...).


At a certain size, certainly the latest when you move outdoors and get to greenhouse/farm size operations, a soil test is basically mandatory. If for no other reason then simply because you can't start a new soil batch for your entire greenhouse all nilly-willy.
You gotta fix the soil you have and that only goes through a soil test.


If they were cheaper it would make sense, but I guess Im hesitant because its close to $50 bucks here, and I doubt the results will be very accurate, enough for me to make any concrete adjustments.

But I guess I will give it a go, and post up my results here,

side note, I love my soil, I have been working on it for a year, making it as microbially alive as possible, I would never toss it and start fresh, that doesn't even make sense to me at this point. I have 48 plants at a time under 3K HPS lights so not closet size.

Would it make sense to do a test before growing plants so like a month after ammending, and then one after harvest, to see the difference and learn what they use up roughly during one run? I mean Im going to have to do a test at either one of those points, so wouldn't it make sense to do both and see what the beginning and end looked like?
 

theJointedOne

Active member
Veteran
She lives down the hill from me. Lots of growers have heeded her expertise. I am still learning about her approach, interesting regardless.

Nice post
 
Would you dig a hole in your back yard and fill your cannabis pots, or would you go and buy quality potting soil? Why?

The reason is, not all soils are equal. Best way to improve your soil is testing, amending then bringing in the microbes. IME.
 

bigbadbiddy

Active member
If they were cheaper it would make sense, but I guess Im hesitant because its close to $50 bucks here, and I doubt the results will be very accurate, enough for me to make any concrete adjustments.

But I guess I will give it a go, and post up my results here,

side note, I love my soil, I have been working on it for a year, making it as microbially alive as possible, I would never toss it and start fresh, that doesn't even make sense to me at this point. I have 48 plants at a time under 3K HPS lights so not closet size.

Would it make sense to do a test before growing plants so like a month after ammending, and then one after harvest, to see the difference and learn what they use up roughly during one run? I mean Im going to have to do a test at either one of those points, so wouldn't it make sense to do both and see what the beginning and end looked like?




Like I said, it wouldn't hurt, wouldn't it? Only if you misinterpreted the results could it hurt.


The drawback is what you mentioned. Soil tests aren't cheap (50 bucks is already on the lower end of the price spectrum afaik).




If soil tests were cheap or free, you would ideally get your soil tested in 3 or more labs. Compare the findings.


Then, as you mentioned, run your show and afterwards, test it again. Reammend it based on the test results.
Let it cook/rest a bit after reammending.
Test it again before you plant the next round.


Rinse and repeat.


Do that for say 3 rounds and the only remaining unknown variable going forward would be changes in the composition of your amendments when you have to rebuy them (e.g.if the worm-farm you buy your EWC from changes the foodsource of the worms or the kelp is harvested from somewhere else or processing methods change etc. etc.).




But this is wishful thinking as we would run at least a grand in soil analysis fees alone to get to this point.


Now I think we would all agree that this might be a feasible expense for a farm/greenhouse operation but not for a small indoor op. Even if it is 3k w and 50 plants (although I would say this is starting to become the point where it is debatable and depends on the situation/person).


Now let's step back and work with something that isn't the ideal (as above) but work in the real world, where a soil analysis costs 50 bucks and the willingness to spend is limited.


Do a soil analysis from 1 lab, 50 bucks.
Do a soil analysis after running the show from 1 lab, again 50 bucks.


You are out 100 and potentially have some good but potentially also some misleading info on your soil.
Depends on the quality of the soil analysis really. And you have no way of confirming anything, unless you go for at least a second lab.


But let's say you stay with the 1 lab because we stay realistic here.


So you reamend based on your soil analysis before and after running a crop.


Then you run the next crop, do you do another soil analysis before/after? Basically you have to, at least 1 more round, right? Because you need to see what your reammendmends actually resulted in.


Then you adjust these reammendmends based on the second soil analysis after the first run. Basically you would have to do it again, after, no?




My point is, the end result is the same. Either you go big from the start and get 3 separate labs to do an analysis and then you do that two or three times (after each cycle) until you have honed in on the "perfect" values, OR you stick with one lab, meaning you just have to do it over a longer period most likely (probably more like 5 or 6 rounds), until you get to the "perfect" values and you end up paying the same amount (or close to it) if you had gone with 3 labs from the start.


Plus you always have the insecurity of it only being from 1 lab and their readings/measurements might just be a bit off, you have no real way of knowing.




Now if you adopt a "close enough"-attitude, I guess it is sensible to go that route with just 1 lab and still just do a test once a year or after every round and maybe only do it 3 times.


But there will be several unknown variables remaining when you do this and that sort of defeats the purpose of the whole ordeal, doesn't it?




So to summarize:
Purpose of soil analysis is to remove unknown variables and go all science on this.
To do so, imho, you gotta go hard or go home. Meaning you gotta pay good money for several (I would say at least 3) soil analysis from independent lab in order to be able to eliminate unknown variables from the start. Then need to continue those 3 analysis over a longer period of time.
Imho this isn't feasible for anything but a farm or upwards and if you go with some halfway solution (e.g. just 1 soil analysis from 1 lab), you might as well go with trial and error.






Hope I made myself clear, think I mentioned some stuff twice and rambled on a bit, oh well ... :D
 

St. Phatty

Active member
Soil testing is bad ?

How could talking with a soil enthusiast be bad - especially if he only charges $20 for his soil tests ?!
 

MJPassion

Observer
ICMag Donor
Veteran
Like I said, it wouldn't hurt, wouldn't it? Only if you misinterpreted the results could it hurt.


The drawback is what you mentioned. Soil tests aren't cheap (50 bucks is already on the lower end of the price spectrum afaik).




If soil tests were cheap or free, you would ideally get your soil tested in 3 or more labs. Compare the findings.


Then, as you mentioned, run your show and afterwards, test it again. Reammend it based on the test results.
Let it cook/rest a bit after reammending.
Test it again before you plant the next round.


Rinse and repeat.


Do that for say 3 rounds and the only remaining unknown variable going forward would be changes in the composition of your amendments when you have to rebuy them (e.g.if the worm-farm you buy your EWC from changes the foodsource of the worms or the kelp is harvested from somewhere else or processing methods change etc. etc.).




But this is wishful thinking as we would run at least a grand in soil analysis fees alone to get to this point.


Now I think we would all agree that this might be a feasible expense for a farm/greenhouse operation but not for a small indoor op. Even if it is 3k w and 50 plants (although I would say this is starting to become the point where it is debatable and depends on the situation/person).


Now let's step back and work with something that isn't the ideal (as above) but work in the real world, where a soil analysis costs 50 bucks and the willingness to spend is limited.


Do a soil analysis from 1 lab, 50 bucks.
Do a soil analysis after running the show from 1 lab, again 50 bucks.


You are out 100 and potentially have some good but potentially also some misleading info on your soil.
Depends on the quality of the soil analysis really. And you have no way of confirming anything, unless you go for at least a second lab.


But let's say you stay with the 1 lab because we stay realistic here.


So you reamend based on your soil analysis before and after running a crop.


Then you run the next crop, do you do another soil analysis before/after? Basically you have to, at least 1 more round, right? Because you need to see what your reammendmends actually resulted in.


Then you adjust these reammendmends based on the second soil analysis after the first run. Basically you would have to do it again, after, no?




My point is, the end result is the same. Either you go big from the start and get 3 separate labs to do an analysis and then you do that two or three times (after each cycle) until you have honed in on the "perfect" values, OR you stick with one lab, meaning you just have to do it over a longer period most likely (probably more like 5 or 6 rounds), until you get to the "perfect" values and you end up paying the same amount (or close to it) if you had gone with 3 labs from the start.


Plus you always have the insecurity of it only being from 1 lab and their readings/measurements might just be a bit off, you have no real way of knowing.




Now if you adopt a "close enough"-attitude, I guess it is sensible to go that route with just 1 lab and still just do a test once a year or after every round and maybe only do it 3 times.


But there will be several unknown variables remaining when you do this and that sort of defeats the purpose of the whole ordeal, doesn't it?




So to summarize:
Purpose of soil analysis is to remove unknown variables and go all science on this.
To do so, imho, you gotta go hard or go home. Meaning you gotta pay good money for several (I would say at least 3) soil analysis from independent lab in order to be able to eliminate unknown variables from the start. Then need to continue those 3 analysis over a longer period of time.
Imho this isn't feasible for anything but a farm or upwards and if you go with some halfway solution (e.g. just 1 soil analysis from 1 lab), you might as well go with trial and error.






Hope I made myself clear, think I mentioned some stuff twice and rambled on a bit, oh well ... :D

Clear as MUD yo!
This is about as useful as looking at 3 different pH pens that all display different numbers in the same water!
Which one do you adjust to?
Or do you attempt to adjust to all 3 to get all three tests to read the exact same numbers?




IMO... You find a GOOD QUALITY lab to do the testing that you can trust the results from.


It's not like soil testing is a new technology. Testing has been going on for damn near a century now, if not longer! Labs KNOW what they are doing and WHY they are doing it when it comes to soil testing.

If I recall correctly, I paid $25 for a soil analysis and $20 for a recommendation on inputs from Logan Labs. If you know how to do molar math (chemistry) you do not need the recommendation.

And YES, it is recommended that you do an initial test to get a baseline then another test after amending then another test after a season then another test after the subsequent season then the same for as long as you feel it's necessary.

If you are using Jacks nutrients they can do the testing and give you specific recommendations for cannabis. They've been studying cannabis growing for a little over a decade now, according to their website.

If you are working with native soils you can get testing done at your local AG department.
If you've got any universities near by you can check them for soil testing services. Sometimes they're more affordable as are the AG departments.

Hope this helps those that ARE interested in testing.

Nutrition Matters
 

troutman

Seed Whore
If you think how much money and time you spend on growing.

A soil test is wise thing to get done at least once in an outdoor garden's life.

I got one done last year from laboratory and I'm glad I know my soil issues now.
 

PaulieWaulie

Member
Veteran
I guess a more simple approach is to do a soil test lets say once a year, just to see if anything is extremely low - then it is fair to assume that it has been under amended on every run almost, and if something is way too high - then it is fair to see that it has been over amended all most every run. Then just adjust your amendment recipe, and a year down the road do another test.

This is what I will do, gonna get a soil test, and add a second aspect to this thread, where everyone can chime in and interpret the reading of my analysis, just to see how each of you would interpret the data and act on it.

To be honest, I have put in a lot of effort to make a perfect soil, and im really curious to see some data on it. I can't see me having to add anything more. if anything it could be dangerously high in some numbers.

heres my mix, I re amend with this on every new run, re using some of the old mix, thus my overall soil is slowly growing.

NPK MACRO MEALS
[]1 Cup Kelp (1-0-2)
[]1/2 Cup Bone (4-10-0)
[]1/2 Cup Fishbone (4-18-0)
[]1/2 Cup Neem (4-3-2)
[]1/2 Cup Insect Frass (3-1-3)
[]1/3 Cup Alfalfa (3-1-2)
[]1/3 Cup Soymeal (7-2-2)

MINERAL
[]2 Cup Granite Grit (0-0-3)
[]1 Cup Diatomaceous Earth
[]1 Cup Glacial Rock Dust (0-0-1)
[]1/8 Cup Basalt (0-0-1)
[]1/8 Cup Azomite

CALCIUM
[]1/2 Cup Gypsum
[]1/4 Cup Dolomite

OTHER
[]1 Cup Dehydrated Molasses

BASE
1 CF = 8 LOOSE FILLED GALLON

5 Gallon Recycled Soil Mix
(33% Peat, 33% Organic Matter, 33% Perlite)

+
1 Gallon EWC
1/4 Gallon BioChar
1/2 Gallon Guinea/Horse Manure
1/2 Gallon Vermiculite
1/2 Gallon Expanded Clay
 

St. Phatty

Active member
NPK MACRO MEALS
[]1 Cup Kelp (1-0-2)
[]1/2 Cup Bone (4-10-0)
[]1/2 Cup Fishbone (4-18-0)
[]1/2 Cup Neem (4-3-2)
[]1/2 Cup Insect Frass (3-1-3)
[]1/3 Cup Alfalfa (3-1-2)
[]1/3 Cup Soymeal (7-2-2)

If I was your neighbor I'd want to buy your used soil.

I'm sure the earthworms have a good time with it !
 

KIS

Active member
Here’s my take. Soil testing definitely matters! If you think soil companies and nutrient companies are doing proper testing and have “balanced” soil and recipes then you’re giving them way too much credit. I recently was helping a guy get setup in Oklahoma as they are about to go legal. My first question was for him to get a soil test and the results were shocking. Na and K were crazy high to the point where neither of us felt comfortable planting into the soil. Long story short, I contacted the company that sold the soil and they didn’t have a soil test for comparison they were willing to share nor seemed to have a basic grasp of CEC and why having Na and K so high and a pH of 7.4 could be a problem.

Now if you’re a small grower, sure it may not be cost efficient to test your soil. If you’re growing commercially though then I think it’s a requirement. It’s just another tool to make better decisions moving forward. How do you know what to fertilize with if you don’t have a starting point?!?

Lastly, while I have a lot of respect for Dr Ingram for promoting the soil foodweb and importance of microbes in soil and plant health, I don’t believe you can claim that proper biology can fix everything. At the end of the day the minerals still need to be present and by having them there in the right ratios and pH it will make it easier for the Microbe-Plant interactions to occur, improving plant health and yield.
 

CannaRed

Cannabinerd
Lastly, while I have a lot of respect for Dr Ingram for promoting the soil foodweb and importance of microbes in soil and plant health, I don’t believe you can claim that proper biology can fix everything. At the end of the day the minerals still need to be present and by having them there in the right ratios and pH it will make it easier for the Microbe-Plant interactions to occur, improving plant health and yield.

For a small timer, growing in a dozen or so 4 and 5 gals how do you recommend testing?
I want to test my ph
I know outdoors when getting samples you collect from several collection sites. Is this necessary in pots? In my pots where I have been topdressing layer after layer of organic matter- how deep in the pot should I go down?
What about (just as an example) lava rock. If I collect a sample that doesn't have lava rock does that skew ph results?
 

bigbadbiddy

Active member
Clear as MUD yo!
This is about as useful as looking at 3 different pH pens that all display different numbers in the same water!
Which one do you adjust to?
Or do you attempt to adjust to all 3 to get all three tests to read the exact same numbers?




Well you could continuously measure with all 3, also after each adjustment.


If you have three starting readings of PH 6.1; 6.3; and 6.7, then you know your actual PH is likely somewhere in between as well as having a min/max value.


Now you adjust your PH with some PH down or up and then comes the interesting, second reading.


If all three PH meters read a PH reduction of say 0.2, then it is fair to assume that all 3 PH meters work correctly and just their base calibration is off. In that case you ideally would have to get another 10 or 20 PH meters and find a base average and then calibrate them all to it, or something like that.

If one reads a reduction of 0.2 and the other of 0.5 then the PH meters are likely just crap or at least one of them is faulty etc.




Same idea with the soil analysis. You can just compare the base values, which almost guaranteed will be at least marginally different, and then compare the values after amending the soil and see how far they differ in changes. Is it really just the base value that is different due to different analysis methods? Or are the reductions/increases in values also varying? If so, then at least one of the soil analysis is faulty and I would move on to test with another lab until I am confident my ACTUAL base values (and the values after amending) are correct.


I would be confident in this, when I would have say 3 soil analysis that vary very slightly in both base values and values after amending and would be satisfied to know my actual values are within a small range as given by the 3 soil tests (like in the PH example, I would be confident if all 3 PH pens I use show me my PH is in a range of say 6.1 to 6.3 so I would have a 0.2 variance which I would deem acceptable in that scenario and would be confident in my readings).




Aside from that, I just want to state I fully agree with KIS:
If you grow commercial, a soil test is a must.
If you grow as a hobbyist, it is a luxury and might not be "worth" it but it might be as well. Either way, if you can afford it, it will never be a net negative unless you wildly misinterpret the results.

But how valuable a single soil test is, is debatable, even if it never hurts to have it.
For myself, I decided it only makes sense if you go big. Which doesn't matter if you are commercial but might break the bank or be unfeasible if you are a hobbyist.
 
For a small timer, growing in a dozen or so 4 and 5 gals how do you recommend testing?
I want to test my ph
I know outdoors when getting samples you collect from several collection sites. Is this necessary in pots? In my pots where I have been topdressing layer after layer of organic matter- how deep in the pot should I go down?
What about (just as an example) lava rock. If I collect a sample that doesn't have lava rock does that skew ph results?

I would recommend testing any size crop.

I always take out any lava rock or perlite before sending in for testing.
 

Microbeman

The Logical Gardener
ICMag Donor
Veteran
I think soil testing can be valuable IF you are working with a reliable lab. They must clearly state their protocols and parameters (benchmarks) and reasons for using these. The same lab should also do leaf tissue analysis and should be recommending this to you.

In my opinion, they should be using HPLC and ICP where applicable

If this is not the case, you could be dealing with a substandard non-accredited lab and end up wasting money. Worse, you could be chasing your tail.

In the instance where one is growing commercially AND buying soil, I think testing is essential and I would compare results from 2 similar labs. However one would expect a commercial grower to be mixing their own soil.

When growing commercially using living soil, we did not test our soil but did test raw materials used for mineral inputs. Prior to this we did get soil testing and did chase our tail with the recommendations of; add this or that, without seeing improvement and sometimes worse results.

Another point is that no matter the testing technique used, not everything is known and not all sequestered nutrients can be tested for. Just look at the SNAFU around the plant uptake of boron.
 

MJPassion

Observer
ICMag Donor
Veteran
Well you could continuously measure with all 3, also after each adjustment.


If you have three starting readings of PH 6.1; 6.3; and 6.7, then you know your actual PH is likely somewhere in between as well as having a min/max value.


Now you adjust your PH with some PH down or up and then comes the interesting, second reading.


If all three PH meters read a PH reduction of say 0.2, then it is fair to assume that all 3 PH meters work correctly and just their base calibration is off. In that case you ideally would have to get another 10 or 20 PH meters and find a base average and then calibrate them all to it, or something like that.

If one reads a reduction of 0.2 and the other of 0.5 then the PH meters are likely just crap or at least one of them is faulty etc.




Same idea with the soil analysis. You can just compare the base values, which almost guaranteed will be at least marginally different, and then compare the values after amending the soil and see how far they differ in changes. Is it really just the base value that is different due to different analysis methods? Or are the reductions/increases in values also varying? If so, then at least one of the soil analysis is faulty and I would move on to test with another lab until I am confident my ACTUAL base values (and the values after amending) are correct.


I would be confident in this, when I would have say 3 soil analysis that vary very slightly in both base values and values after amending and would be satisfied to know my actual values are within a small range as given by the 3 soil tests (like in the PH example, I would be confident if all 3 PH pens I use show me my PH is in a range of say 6.1 to 6.3 so I would have a 0.2 variance which I would deem acceptable in that scenario and would be confident in my readings).




Aside from that, I just want to state I fully agree with KIS:
If you grow commercial, a soil test is a must.
If you grow as a hobbyist, it is a luxury and might not be "worth" it but it might be as well. Either way, if you can afford it, it will never be a net negative unless you wildly misinterpret the results.

But how valuable a single soil test is, is debatable, even if it never hurts to have it.
For myself, I decided it only makes sense if you go big. Which doesn't matter if you are commercial but might break the bank or be unfeasible if you are a hobbyist.


This sounds more like your testing the various labs until you get the numbers you expect rather than simple soil analysis.


Most labs use Melich III(sp?) testing sequences so are using known and verified protocols that have been proven to work for many decades. There is zero reason to use multiple labs unless you want to just blindly spend your money. Ratios shouln't differ between labs that use the same testing methods so pick one and stick with it rather than getting testing done by different labs all the time.
 

Microbeman

The Logical Gardener
ICMag Donor
Veteran
It seems that Mehlich 3 became accepted and popular in many soil laboratories in the 1990s after the failure of Mehlich 2. As has been stated it has become quite relied upon and most find it reliable.
There are some exceptions;
https://aglabs.com/accuracy-of-a-soil-test.html

As I've stated before, I was one of the unfortunates duped by Mehlich 2 (reigning pre 80s through early 2000s) both by the local Ag lab and through using this extraction technique in an on farm lab. The taste in my mouth and skepticism remains.
 
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