Soil Minerals and Soil Prescriptions for Organic Gardeners

Instructions for taking a soil sample, and prices for recommendations.

Updated June 2020
Why get a soil test?
Soil Test Recommendations and Soil Mineral Prescriptions
By Michael Astera

We charge $45 to make a detailed study of your laboratory soil test and make custom mineral and fertility recommendations for your soil, crops, and climate. This is not a computer-generated report; each soil report is given as much personal time and attention as needed for an accurate assessment and prescription in order to achieve maximum health, mineral balance, and fertility for your garden, farm, lawn or landscape using USDA Organic approved amendments.

Our price does not include the laboratory test; you will need to take a soil sample and send it to the lab for testing and then email the test results to us.

Instructions for taking a soil sample:

You only need to send 1 cup of soil, approximately 8 ounces (225 grams). The goal is to get a representative sample of your soil 6" (15cm) deep. This is the aerobic zone where most root growth and nutrient exchange happens. You will want to take several samples of the area and mix them together. As a rule, you would take six to ten samples of any area that you are going to treat the same, while avoiding strange or unusual areas or sampling them separately for a separate test. Clear the surface area of loose duff, rocks and organic matter before you take your sample. Dig a hole six to eight inches deep with an ordinary shovel, then take a thin slice straight down along one side of the hole. This slice is your soil sample. Use a clean shovel to do the digging.

Take as many samples as you think necessary and mix them together thoroughly in a plastic or stainless steel container, removing large roots, stones, or chunks of organic matter, then take about one cup of this mixed sample and place it in a clean plastic or heavy paper bag to send to the soil testing laboratory. If the soil is extremely wet when you take the sample, spread it out in a warm place and let it dry until it can be handled without leaving mud on your hands.

Where do I send the soil sample?

We recommend Logan Labs in Lakeview Ohio as we have worked with them for a number of years and have found them to be fast, dependable, and accurate. Logan Labs’ website address is

Soil samples should be sent to:
Logan Labs, LLC
620 North Main Street
Lakeview, OH 43331
Toll Free: 1-888-494-SOIL

You will want their Basic or Standard Mehlich 3 soil test, which costs $25 [October 2017] and includes: pH, organic matter, Total Exchange Capacity, base saturation % for Calcium, Magnesium, Potassium and Sodium, along with Mehlich III extractable Sulfur, Phosphorous, Calcium, Magnesium, Potassium, Sodium, Boron, Iron, Manganese, Copper, Zinc, and Aluminum.

You do not want or need the "paste test" as it is of no use for the Ideal Soil method.

Important when sending samples to Logan Labs:

A. Request results in parts per million ppm on the submission worksheet or you will get results in lbs/acre and they will need to be converted to ppm.

B. Do NOT list sampling depth on submission worksheet. (Normal sampling depth is 6"). Just ignore that and request results in ppm

C. You do not need to send 2 cups of soil. The lab uses less than 1 ounce of soil for the chemistry test.

Logan Labs will provide your soil test results in a PDF format. Email the results to us at along with a short description of your growing area, soil type, what you are growing, and any special problems or goals. See sample questions Here.

When we receive your soil report we will send you a PayPal invoice for $45 for each soil Rx you are requesting and begin writing your soil's custom fertility prescription.

The entire process from mailing the soil sample to the lab until getting our recommendations normally takes about two weeks. Questions? Email us at

We will be glad to answer any simple questions about your soil prescription by email.  We do not offer telephone consulting, via email only.

More Soil Testing Labs

Below is a short list of other private soil testing laboratories that we have used in the past.  There are a number of good and inexpensive soil testing labs in the USA and Canada; they tend to be scarcer, more expensive, and less reliable in the rest of the world.

If outside the USA, do a search online to find your best options. Those outside the US who wish to send a soil sample to a US Lab will need to contact the lab to check that they can receive samples from other countries. Many non-USA growers have found it cheaper and faster to send a soil sample to the US than to pay the often very high prices charged by labs outside the US.

What you want is what is commonly known as a "complete soil test" usng the Mehlich 3 method. The results of this test give an excellent overall picture of the soil's mineral balance.  A "complete" or standard soil test tests for: 11 essential nutrients: Sulfur, Phosphorus, Calcium, Magnesium, Potassium, Sodium, Boron, Iron, Manganese, Copper, and Zinc, and also for:
organic matter
total cation exchange capacity (Ca, Mg, K, and Na)
and % of base saturation of: Calcium, Magnesium, Potassium, Sodium,and exchangeable Hydrogen

Soil Testing Laboratories USA:

Logan Labs LLC:
(Logan Labs uses the same soil report format that uses in our examples on this web site and in our Ideal Soil book)

Dairy One:

Soil Testing Laboratories Canada

A&L Canada:

Please contact the soil testing lab of your choice for prices and any special instructions.

Soil Fertility Rx $45.00 US
Send Your Soil Test results to: and we will send you a PayPal invoice for $45.

We use only PayPal for all orders. 

When we get the results of your soil test we combine them with any other information that you give us and make recommendations based on what you are growing.  Unless you inform us differently, all of these recommendations will be for amendments and cultural methods that are approved under the USDA National Organic Program. Here are samples of the results and recommendations for this test.

Your results and recommendations will be sent by e-mail as a .pdf file.

Expect your recommendations in 7 to 10 working days.

Questions?  e-mail us at

Or, if you would rather do it yourself....

Another option for many growers, and one we recommend, especially for do-it-yourselfers who enjoy basic chemistry and arithmetic, is to pruchase a copy of our new book The Ideal Soil: A Handbook for the New Agriculture v2.0 You will learn to interpret your own soil test results and write your own prescription and recommendations.  The Handbook is available in both hardcopy and ebook versions.

The Ideal Soil v2.0:
A Handbook for the New Agriculture

new from

All you need to know to become your own soil minerals expert!
(Yes, really)

Featured Grower:
Tom Bigger
Kenosha Wisconsin

Tom Bigger contacted us in mid-July of 2015. He had been growing a garden in this spot since 1996, and thought that the previous owners had been gardening there since 1976. Espoma brand Tomato Tone and Garden Tone were the only fertilizers being used on the garden plot. He noted that he had been having problems growing beans, peppers and potatoes the last few years. Tom's soil test from Logan Labs was attached; you can see it here. The soil Rx we sent to him a week later is here. (Note that the minerals listed in lbs/acre on the Logan Labs report have been converted to parts per million on the Rx).

Tom ordered some of the amendments listed on his soil Rx from us in August of 2015, then we didn't hear from him again for almost a year.

In July of 2016 he emailed to say

" Hi Michael, I followed your Rx to a tee and so far the results have been great!  This years garden is shaping up to be one of the best that I've grown in a long time!  ... I've attached a few photos of the garden.  That's a 13 inch softball by the  onions!

That's a 13" softball by the  onions!

Two months later, on September 20th, we received the following email:

"Well the verdict is in for the Rx for my garden! Outstanding!! 650 lbs. of vegetables from 900 sq. ft.!! 185 lbs. of tomatoes alone from 4 plants!! All the vegetables had excellent flavor.


"185 lbs. of tomatoes from 4 plants!"

The corn patch in September

I've never seen better looking corn.

Update 28 October 2017

Tom's garden pics from 2017

Truly healthy fresh vegetables have a glow to them

Unless Tom is a midget (he's not), that sunflower is around 12 feet tall.

This is what you can expect when plants are given all they need to reach their full genetic potential. The beneficial soil organisms also thrive. Soil organic matter reaches its optimum level. The soil remains in good tilth in all weather, loose and granulated with good water infiltration and moisture holding properties.

The ongoing result is flavorul food delivering excellent nutrition.


Soil Test Services    Minerals and Fertilizers  The Ideal Soil   Home