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I've read the posts on soil testing, and I realize it's cheap and widely available through local universities, etc.

Question: Is it possible to do my own soil testing? Are there some compounds that it's very difficult to test for without a big fancy lab like at the university? Can the same chemistry be used to test for compounds in things like compost, manure, etc?

In other words, if I invest in a little chemistry lab and follow instructions, can I test any mulch, compost, whatever that comes my way for chemical quantities, and make use of those numbers in deciding how to mix them and how long to let it age?

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to be more specific in response to the first 2 answers: I'm interested in doing my own testing 1. so I can test soil from many different sites, combine them, test manure, compost, synthetic ammendments, etc, combine them, test again. and 2. for the fun of learning about soil more "hands-on" by actually watching the chemicals produce the readings and being able to play around. –  themirror May 8 '12 at 20:06
If that's the case, you might be better served by asking how you can do that testing at home, what you should be looking for in a kit, etc. It is possible, I think it will be a matter of how much precision you want and how much you're willing to invest in a kit. –  bstpierre May 15 '12 at 15:00
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3 Answers

The easiest test to do is also perhaps the most important: organic matter content. You do this with what is commonly called a "soil shake test."

Find an area clear of weeds and growth where you can get about ¼ quart jar of screened soil (no rocks or huge lumps). Add water to the quart jar until it is perhaps ¾ full. Attach lid and shake vigorously for some minutes until the slurry is a consistent suspension -- no big lumps of anything.

Let it settle for a day or so. You should now observe four distinct "horizons" in the jar, each corresponding to the four basic physical soil ingredients (bottom to top): sand, silt, clay, and organic matter.

Measure the depth of each layer, and divide that by the total depth of the stratified sample, and you'll have the percentage of each constituent.

The major goal of soil building is to increase the amount of organic material, which increases oxygenation, water storage, and nutrient availability. Land that is industrially-farmed year after year may only have a few percent. Good content will be 10% or more.

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+1 good lofi test... I like it. –  Grady Player May 12 '12 at 20:37
Percent by weight? Percent by volume? Do you have a reference? How can this information be used? –  David May 15 '12 at 3:53
The shake test will produce a percentage by volume. The three basic constituents (sand, silt, and clay) all have similar specific gravity, and so a percentage by volume is essentially a percentage by weight. But organic material will tend to be much lighter, and so. –  Jan Steinman May 15 '12 at 18:12
As for references, look at the link I posted, please. The shake test results are useful for tracking progress in building soil tilth. As I had mentioned, compare your results against industrial farming numbers (a few percent -- bad) with 10% or more (good). –  Jan Steinman May 15 '12 at 18:25
A picture would be really awesome. –  ashes999 May 24 '13 at 16:40
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Yes, you can do your own testing. I've been told by different people whose opinion I trust that the consumer-grade kits that are available sometimes have problems with accuracy. It isn't clear if this is due to low quality in the kits, or problems that consumers have following directions, or both.

For me, the point of soil testing is to make sure my soil isn't too low or too high on any nutrient. Levels don't change radically from year to year; my extension service recommends testing every couple of years. For my time and money, I'd rather get a high quality test every couple of years.

Lastly, I'm not sure that you can do organic matter content (%) testing easily at home.

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Home kits definitely have low precision; accuracy is fine if you can match the color of the indicator to the key - I find that this step is what limits accuracy. But accuracy is sufficient for management decisions required in the garden. –  David May 15 '12 at 3:55
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Short answer: yes you can find them for 3-20 usd depending on features.

Long answer: When I was young my biology teaching father brought home a suitcase full of colorful vials and reagents, each set represented a test for an aspect of the soil, phosphate, nitrate, pH, etc... I remember running every test available on the garden soil... When I was done I had a little card with all of the results... And as a result we did what we did every year, add more manure (we had horses).

So the moral of the story is, sure you can buy these tests and amend you soil and retest in the fall or next spring, but only bother if you have a plan an ideal target for something in particular.

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