This lady is the king of the soil food web, and she is in the no camp. Its hard to disagree with her.
https://www.youtube.com/watch?v=x2H60ritjag
https://www.youtube.com/watch?v=x2H60ritjag
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?
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 ...
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)
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.
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?
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?
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.