Are these test results meaningful?

last year

I'm testing my soil for pH and NPK for the first time, and I'm not sure what to make of the results I'm getting. Suggestions are welcome.

I'm using an Environmental Concepts testing kit that I bought on Amazon a few months ago. Until today it was unopened.

I'm testing five samples:

Three from different vegetable beds.
One from a formerly grassy area that was dug up by construction workers last summer, and now is probably mostly subsoil.
One from an area on my patio that contained several years’ accumulation of leaf mold and droppings collected from my chicken coop, together with a quantity of bedding (wood shavings) that came along when I picked up the droppings. I would estimate that the volume of wood shavings was about half the volume of droppings, and of course, they were much less dense. Everything is now thoroughly rotted, and has been mixed and sifted.

The pH of all five samples came out to be 7.0 or 7.5. I don't know if those numbers are accurate, but they seem within reason. But the nitrogen content of all five samples came out to be 0. I'm suspicious of that. I just don't see how a mixture of leaf mold and chicken droppings, with a few wood shavings mixed in, can contain no nitrogen. And being suspicious of that nitrogen result makes me suspicious of the other four.

I have not performed the phosphorus and potassium tests yet. I’m waiting to read the comments on this post before I decide whether it’s worth the effort.

The kit has no expiration date, but should be reasonably new. The instructions are somewhat complex but easy to understand, and I followed them carefully. Unless I read the instructions five times and misunderstood them the same way each time, I don't see how my technique could have been at fault.

Should I accept these results as valid? Buy a better test kit (if so, what)? Or just forget about home testing and send my soil out for analysis?

Featured Answer

gardengal48 (PNW Z8/9)

last year

I'm not sure what sources you have been investigating but the costs you quote are extraordinarily high. Most labs will do a routine soil sample test - basic nutrients and pH - for around $20-25 per sample. Additional tests (nitrates, OM, soluble salts, etc.) can up this fee by $10-15 or so.

The lab does not need to be local. UMass and Texas A&M are very popular and well known/regarded. You can also check with your local extension service. They used to do soil testing for free but can no longer handle the volume or fund the costs so they now refer you to local professional labs.

Do not believe much of anything AI when it comes to gardening. The data you receive is just not very accurate,

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Comments (8)

gardengal48 (PNW Z8/9)
last year
Home soil test kits can be expected to provide a reasonably accurate soil pH reading (when using distilled water). But they are worthless for assessing nutrient levels or mineral deficiencies. For that you need a professional testing lab. Even many of those do not test for nitrogen levels, as it is difficult to generate an accurate reading for more than a moment in time. It can and will vary widely.
central_valley
Original Author
last year
That's a rather discouraging answer. I asked Google about soil analysis services for homeowners, and its AI agent told me that typical costs are $700 to $1800. I assume that's for a single sample. I found one service whose web site specifies that it's intended for homeowners (most apparently don't say), and it said $186 for a basic analysis, $286 for a more comprehensive one. The simple analysis would satisfy me, but testing my five samples would cost $930. And I intended those five to be an initial trial of the testing process. My property is hilly, and extensively graded and "improved"; it would be naive to assume that the results from any one part would tell me anything about others.

It looks like I'll have to settle for the test kit results, no matter how inaccurate they are, or just go with my gut. My gut tells me that my soil is generally short of nitrogen, and that I won't be able to tell what else is wrong until I correct the nitrogen deficiency and see how things grow.
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central_valley
Original Author
last year
The lab I found was this one. I know nothing about them except what's on their web site. I mentioned them because I searched for something like "soil analysis lab for homeowners," and they're the first match I found that actually mentioned homeowners.

Do you have a recommendation? I'm seeking one because the amount of difficulty I had finding this one, plus its high prices, suggest that my common sense is not going to be a reliable guide in this area.
gardengal48 (PNW Z8/9)
last year
https://soiltesting.tamu.edu

https://ag.umass.edu/services/soil-plant-nutrient-testing-laboratory
annpat
last year
Here's who I've used: https://umaine.edu/soiltestinglab/
central_valley
Original Author
last year
Thank you... your suggestions made it plain that this is something ag services do, so I'll check out U.C. Davis, which is actually local for me. If they don't have such a service I'll use one of the ones you suggested.
gardengal48 (PNW Z8/9)
last year
The CA extension service does not provide soil testing. But it does provide a list of independent testing labs that do.

https://ucanr.edu/sites/newinyomonomg/files/323581.pdf