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cheap soil test kits?

914safbmx

Member
should i trust a cheap soil test kit from the grow shop? its just one of those little rapitest ones where you mix the soil into distilled water then crack a small capsule into it and observe the color change. according to the chart mine is testing wayyyy high in N and pretty low in P and K. plants were pretty shocked when first introduced but thats because i didnt let the mix cook for very long... i think. after about 7-10 days recovery they all look great aside from the lower growth which seemed to just never really spring back to life after the shock.
 

KIS

Active member
should i trust a cheap soil test kit from the grow shop? its just one of those little rapitest ones where you mix the soil into distilled water then crack a small capsule into it and observe the color change. according to the chart mine is testing wayyyy high in N and pretty low in P and K. plants were pretty shocked when first introduced but thats because i didnt let the mix cook for very long... i think. after about 7-10 days recovery they all look great aside from the lower growth which seemed to just never really spring back to life after the shock.
Those kits are notoriously inaccurate. As someone who owns a garden center, I refuse to sell them because I think they cause more problems then they are worth. Much better to spend $25 and send it off to a lab. I do sell the Soil savvy kits but they work more like a tissue test than a traditional soil test. Really depends on what info you’re trying to get from the test. Sorry to be the bearer of bad news...
 

914safbmx

Member
no, its great news! plants are doing well. i figured they must not be very accurate because the plants show no symptoms of excess or deficiencies. i hope to send out a sample to a real lab now that they are starting to flower. if it really is too N heavy i gotta figure something out just about.... now! guess theres not much i can do about an excess though,,,, i planted some timothy grass and clovers to see if that helps at all
 
M

moose eater

Have you tried or played with the LaMotte's soil test kits?

They don't do secondary or micro-nutes in the basic NPK kits, but I've used their ph test tray with their alcohol-based 2221 reagent, and the labs have confirmed my kit's accuracy a couple times now.

I have an N-P-K kit of theirs on-hand, unused, from last year, and have samples being sent to a lab last week, so I could do a comparison of primary nutes (NPK) in the 2 tests; something I've never done before).

The Rapid Test kits I gave up on YEARS ago.


Those kits are notoriously inaccurate. As someone who owns a garden center, I refuse to sell them because I think they cause more problems then they are worth. Much better to spend $25 and send it off to a lab. I do sell the Soil savvy kits but they work more like a tissue test than a traditional soil test. Really depends on what info you’re trying to get from the test. Sorry to be the bearer of bad news...
 

KIS

Active member
no, its great news! plants are doing well. i figured they must not be very accurate because the plants show no symptoms of excess or deficiencies. i hope to send out a sample to a real lab now that they are starting to flower. if it really is too N heavy i gotta figure something out just about.... now! guess theres not much i can do about an excess though,,,, i planted some timothy grass and clovers to see if that helps at all

Clover fixes atmospheric N, up to 200 lbs per acre according to some agronomists. You can flush out excessive N too.
 

Microbeman

The Logical Gardener
ICMag Donor
Veteran
I used a LaMotte soil test kit using Mehlich 2 extraction acids. I eventually realized it was highly inaccurate and stopped using it. The simple soil labs mostly use Mehlich 3 acids. These are much improved but in mild disparity with Tad (KIS) and my friend Jeff Lowenfels, I remain skeptical about the applicability to using them to extract and assay sequestered nutrients. As always, I can easily be off base.

http://www.ncagr.gov/agronomi/obmehlch.htm
 
Last edited:
M

moose eater

Thanks.

As stated, their alcohol-based ph test reagent has proven itself to be accurate for me over the past ~20 years, but I haven't contrasted results for NP&K with lab samples yet. Now I have the chance.

If anything, I've been most suspicious in the past of the K readings from the kit, but have used them in a pinch, in days when I never sent samples out for testing...

Now'days, I can send off 2 samples for fairly thorough analysis for about $2 more than the cost of the NPK kit.

Thanks again.
 

h.h.

Active member
Veteran
You put a plant in it, it grew. Your soil passed the test.
Repeat and compare.
 
M

moose eater

True enough, h. But there's growing, and there's G-R-O-W-I-N-G.

I like the latter when ever I can help that to happen. ;^>)

Hope you're well.
 

914safbmx

Member
True enough, h. But there's growing, and there's G-R-O-W-I-N-G.

I like the latter when ever I can help that to happen. ;^>)

Hope you're well.

exactly. they are not GROWING. in fact only about 90% of them truly bounced back. some are producing new growth but still looking droopy and shocked. the ones who have fully recovered still arent quite exploding. i'd say only about 15% percent of them are really capital lettered GROWING.

what i dont understand is that i made this exact same mix on a smaller scale when i first started these girls at the beginning of the season. very young seedlings went in and exploded on contact. im wondering if i allowed some anaerobic bacteria to develop while my giant pile of worm castings and compost sat in one place for a few weeks. my mix got put off for a little while because of weather and other stuff
 
M

moose eater

I've grown for a long time, but don't consider myself all-knowing by any stretch of the imagination. I know a lot less than there is to know, and I learn things every time I turn around, it seems.

That said, when I see 'droopy,' and there's not an absence of water, I think over-watering, or excess feed.

There can be other issues as well.

Sometimes putting plants into a fresh mix, the nutes haven't completely become active yet. The plants get a reprieve from the conditions they were in, and thank you with some vigor.

If there's excess nutes in there, and they become available soon after, AND ESPECIALLY if you're continuing to feed through that period, then you can move into a shift in your nutrient balance that causes issues for you.

I've harmed enough plants to have seen this a few times.

Can't say this is applicable to your situation. Just tossing that out there, without knowing what all is going on with your mix.

Also, amendments can change from batch to batch, even from the same companies. Seen it many times.

My local soil folks send samples out, and I pay about $40/sample for a fairly thorough analysis.

Sometimes my guesswork paid off, and sometimes it was a bit disappointing, so I decided to get to the bottom of it, as well as enlisting the help of a knowledgeable person who has their head wrapped around organics in a deeper understanding than I did..

I'm still waiting on results from a final sample after some modifications, but things are looking up for now.

Don't know what resources you have in your area, or how you feel about offering up samples of your mix to labs, but after doing this for many years, I'm glad I finally did so..

Good luck.
 

KIS

Active member
exactly. they are not GROWING. in fact only about 90% of them truly bounced back. some are producing new growth but still looking droopy and shocked. the ones who have fully recovered still arent quite exploding. i'd say only about 15% percent of them are really capital lettered GROWING.

what i dont understand is that i made this exact same mix on a smaller scale when i first started these girls at the beginning of the season. very young seedlings went in and exploded on contact. im wondering if i allowed some anaerobic bacteria to develop while my giant pile of worm castings and compost sat in one place for a few weeks. my mix got put off for a little while because of weather and other stuff

Could be difference in nitrates based on compost and leaching. But purely speculation.
 
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