Right now is the best time to test your garden soil. But which "earth exam" should you give? MOTHER EARTH NEWS evaluates the best garden soil tests for 1985. (See the soil test chart in the image gallery.)
Point number one: While the best indicator of your garden
soil's quality is how well your crops grow in it, a test of
major chemical nutrients should provide a useful check on
your plot's condition.
Point number two: The best time to test your soil is in the
fall. Not only will any organic nutrients you add in
response to the test results have time to decompose in the
soil, but you'll be a whole lot more likely to get those
results promptly. (You may have to wait six weeks or more
to get a mail-ordered kit or audit in spring!)
Point number three: The test you should use is . . . uh, is
. . . well, what is the best garden soil test? Have you
ever wondered? We often have, so to try to satisfy our
curiosity, we carefully unearthed a sample of Eco-Village
garden soil—following all the recommended guidelines,
such as taking the sample from several representative spots
and being careful not to touch it with our hands or
galvanized tools. Then we ran some of that sample through
five different tests so that we—and
you—could compare the results.
MOTHER EARTH NEWS evaluated the best garden soil tests for 2000. We used two do-it-yourself kits: the least
expensive Sudbury model ($13.04 at our local nursery) and
the LaMotte garden kit (model EL; $25.30 plus shipping from
LaMotte Chemical, Chestertown, MD). We
also sent off for three soil audits: one by our
local agricultural extension service (available—at
little or no cost—in most areas of the country) . . .
a "standard audit" by Woods End Laboratory (Orchard Hill
Rd., Temple, ME; $20.00) . . . and the
"basic soil audit" by Necessary Trading Company (New Castle, VA; $19.50). Incidentally, if you
decide to send a sample to either of the private labs, be
sure to write for a questionnaire and sampling instructions
before you do so.
And what did we find out for all our efforts?
The Best Soil Tests? That's a Good Question
The first thing we learned was that no two soil tests use
the same language! Their testing procedures and rating
systems vary, so you can't directly compare most of their
results. For instance, look at our "Test Results" chart
under potassium (K). Sudbury says we need 4% K . . .
LaMotte says our K level is "very high" . . . the county ag
service gives a free-floating "index" number, 286 ... Woods
End tells us we've got 780 pounds per acre of the nutrient
. . . and Necessary tallies our K at 500 parts per million!
Uh, run that by us again?
Backup literature (or, in the case of the extension
service, a friendly agent) tells how to interpret these
results into low-to-high terms, though, so we did finally
understand it all. We included those assessments in
parentheses in the chart so you could interpret our
The next thing we learned was a bit more troublesome: The
results don't always agree. Well, they all agree
that our garden's pH is somewhere between 6.1 and
7.0 (a good plant-growing range), and that we have high
levels of potassium and magnesium . . . but after that they
range from "medium" to "quite high" on the same nutrient!
Not surprisingly, then, the interpretations and
recommendations vary, as well.
Sp What's it All Mean?
That's another good question. If you just look at our "Test
Results" chart, you'll probably conclude that soil testers
are like the proverbial blind men who each feel different
parts of an elephant and therefore each decide it's a
different creature. But that's not really a fair
conclusion. For one thing, we weren't able to include all
the detailed backup descriptions of each test in our
five-in-one chart . . . and those often resolve some
apparent differences. For example, although Woods End
assesses our phosphorus (P) levels as "medium" and three of
the other tests say it's "high," the company's full report
states that, while our "available" level of P is on target,
our "reserve" P level is 70 pounds per acre greater than
desired. Woods End interprets the overall
phosphorus data as "medium," but someone else could look at
those same numbers and say they're high. Similarly, Woods
End reports that our calcium level of 2,300 pounds per acre
is "medium" (Necessary rates it "low"), yet also states
that the desired level is 2,900 pounds per acre.
Several other times the interpretation of the data varied
more than the data itself. Still, there were some real
differences in the five replies. You just can't reconcile
LaMotte's "medium" phosphorus rating with Necessary Trading
Company's "quite high" one, for instance. And since the
do-it-yourself kits involved assessing color variations of
liquid in test tubes, those homespun results sometimes
depended on who was reading them. Some people we
showed that LaMotte phosphorus test to thought the liquid
had a light blue tint, indicating a "medium low" level,
while others thought the same tube was a darker,
Equally interesting were the various assessments of
nitrogen. While the do-it-yourself kits quite confidently
reported nitrogen levels, the results from the three
services were much more equivocal. Both Woods End and
Necessary admitted that their nitrogen numbers were made-up
estimates based on such things as the amount and type of
organic matter in the sample, while our local ag service
didn't even pretend to be able to measure it there
isn't even an N category on its form! Steve Rioch of
Necessary explained the nitrogen problem to us: "The irony
is that the nutrient that's commonly considered to be the
most important one is also the one that's hardest to
measure. Nitrogen's so variable depending on soil
conditions and so volatile once taken from the ground that
you really can't measure it except out in the
Quit Stalling: Which Soil Test is Best?
The principal conclusion we were able to draw from the
variety of results we got may sound like a cop-out on our
part, but we think it's actually quite important: The
content of a soil test report depends on the philosophy of
the tester. The two kit makers and the extension
service apparently hold to the chemical theory of
agriculture—the idea that the soil is little more
than a medium to hold the plants' roots, so you have to add
the specific chemicals that crops take out. Sudbury even
gives its results in terms of how much of each nutrient you
need to add . . . while the ag service people told us to
add nitrogen to the soil even though they admitted complete
ignorance of our soil's nitrogen levels! "Why?" we asked.
"Because you're growing vegetables," they replied.
(Incidentally, if you read our article "Preparing the Soil"
in MOTHER N0. 93, you'll know how to substitute organic
soil amendments for any recommended chemical ones.)
The people at Woods End seem to have a much more
open-minded outlook. Like our gardeners, they clearly have
an organic bias and are great believers in the virtues of
compost (see their recommendation in the chart). Yet Robert
Parties of Woods End told us they suggested compost partly
because we told them on our audit questionnaire that the
homemade amendment is our primary fertilizer. "If a
gardener indicates that he or she always uses 10-10-10-type
fertilizers, we'll give our advice in those terms. No sense
in recommending something that won't be used." They also
seem to run a surprisingly tolerant testing
service. While noting that some of our readings were a bit
off from ideal, their report doesn't suggest that such
variations are cause for concern—a conclusion that's'
bound to please anyone who doesn't think chemical analysis
is the final word on soil assessment.
Necessary Trading Company seems to be taking a
refined organic approach. As Steve Rioch said to
us, "You have good fertility. What I'm trying to do is
fine-tune your soil to help prevent pest outbreaks and
nutritional imbalances in your crops." In our case, at
least, such fine-tuning emphasized a balanced relationship
between nutrients. Indeed, the words balance and
imbalance appeared repeatedly in our report:
e.g., "Your pH is out of balance primarily because of an
imbalance between calcium, magnesium, and potassium."
Necessary also placed special emphasis on the importance of
calcium in the soil ("it may very well be the most
important of all soil and plant elements") and on cation
exchange capacity (and its balance). The latter refers to
the number of calcium, magnesium, and potassium ions in the
soil, ions that help the soil hold nutrients.
"The Percentage of Milliequivalents of the Reserve Value Index . . ."
Another distinction between the soil tests is how easy or
difficult they are for the gardener to understand and
follow. The worst report in this category was the one from
our agricultural extension service: It was clearly geared
to the commercial chemical farmer (or the closet chemist!)
and was quite intimidating. On the other hand, our local
agent was readily available to explain the results in lay
terms (and the test was free!).
The LaMotte and Sudbury size-ups were easier to understand
than the county ag's, and both companies provided useful
explanatory booklets about soil and fertilizers. (The kits
also give you the capability of repeating your tests more
than a dozen times.) LaMotte's literature was the more
complete of the two—and its kit a good bit easier to
use. It was also more sophisticated; some of the LaMotte
tests required twice as many steps as the equivalent
The Woods End and Necessary reports were both a pleasure to
read. Woods End comes with a personal, down-to-earth
overview of the results. (Ours included the flattering
statement, "I hope you are not having problems with the
soil, because I would be hard put to offer any help.") The
full report was easy to digest and the enclosed discussion
of terms a definite help to anyone who ever slept through
part of chemistry class.
Necessary managed to provide the most thorough report of
all, while presenting its analysis in a clear and
understandable manner. Since its audit questionnaire was
also the most thorough—including questions on
predominant weeds and persistent bug problems—its
recommendation sheet covered areas the others didn't
address ("sprinkle diatomaceous earth for slugs"). The
additional three-page, detailed report explained the role
of each nutrient and the effect of any problem with our
levels. (Necessary also offers a 42 page booklet, called
"What Makes My Garden Grow," with each test.)
What We'll Do
So now that we've been blessed with an array of
agricultural assessments, just what are we going to do in
our garden? Well, if our comparisons make nothing else
clear, they certainly show that a soil test is just one
gardening tool, not the answer, so we'll combine
the data gleaned from the tests with our own experience
with the soil and the crops at the Eco-Village. And since
we're ardent organic growers who believe in cultivating
healthy soil first and foremost ("feed the soil, not the
plant," the saying goes), we'll give more weight ourselves
to the Woods End and Necessary reports. Susan Glaese, our
head gardener, says, "I figure our soil deserves about a
`three-star' rating. It's definitely not a 10-10-10
wasteland, but it's not growing Findhorn-size cabbages,
either. I agree with Necessary that our humus levels are
too low, but that's because in the past we've had to spread
our compost over 130 raised beds! I've made the garden
smaller now, so I should be able to use more compost in
each growing area. And I think I'll follow Necessary's
recommendations for increasing our calcium levels and
avoiding additional potassium it'll be interesting to watch
the garden over the next year and see if such measures make
any difference in our crops."
But What Should You Do?
One thing for sure: Don't get five soil tests!
It's a bear to sort them all out . . . and hard to deal
with their contradictions. Instead, we'd recommend
that—if you choose to test your soil at all—you
pick the approach that suits your own gardening philosophy.
If (perish the thought) you'd like to sprinkle an N-P-K
formulation on your plot and be done with it, go with one
of the first three tests we used. If the organic approaches
of the "moderate" Woods End or "balancing" Necessary audits
sound like your cup of (manure) tea, pick one of
those—both companies were impressively helpful and
Most important, whichever test you pick, don't
automatically believe everything it tells you. Heck, even
professional soil testers will admit that what we
don't know about soil is a whole lot greater than
what we do. So let your own eyes, hands, and crops be the
final authorities on the state of your soil.
Sizing Up Your Soil
Bill Wolf of Necessary Trading
Company gave us these suggestions for non-chemically
assessing the state of the soil:
 Organic matter: If your soil has a high humus
level, it should look dark and have an appealing "earthy"
 Texture: Roll a handful of medium dry soil into a ball. If it holds its shape,
you've got a substantial amount of clay
in your soil . . . and if you can further roll the ball into
a "sausage, " you've got a lot of clay.
If you can make scratches on the surface of your clod, it's got a significant sand content, but if
it feels somewhat greasy in your hand, your soil's got a
fair amount of silt. If that handful crumbles when you try
to ball it up, your soil has a nice, balanced texture.
 Root development: Dig a hole two feet deep in your
garden and examine it to see where your plants' roots are.
If they're going down the full two feet, your soil is
fairly friable. If they run lateral at some
point, though, you've got a compacted layer—plowpan
or hardpan—that needs to be broken up.
 Drainage: Now fill that hole with water. The liquid
should slowly percolate out into the surrounding soil. If
it stays pooled at any level, you have a drainage
 Soil fauna: Pick a day when your garden is somewhat
moist, dig up an exact 1 inch by 1 foot by 1 foot section of
soil, sift through this cubic foot, and count the
number of earthworms you find (they'll serve as
barometers of all kinds of
soil fauna). Ten or more is a good sign of soil life; zero is terrible.
 Nitrogen facing: Dig up the roots of some legumes—beans, peas, alfalfa,
clover—and examine them for nodules. Break a few of
those root lumps open. If they're fixing and storing
nitrogen as they should be, they'll be pink inside.
Several garden weeds can give you indications of your
Fertile soil: lamb's-quarter, chicory, purslane,
burdock, and dandelion.
Soil with low fertility: fennel, sorrel, mayweed, and
Soil with a crust or hardpan problem: horse nettle,
morning glory, quack grass, chamomile, field mustard,
pineapple weed, and pennycress.
Soil with poor drainage: hedge bindweed, smartweed,
Acid soil: dock, horsetail, hawkweed, sorrel, lady's
Salty soil: sea plantain, sea aster, Russian thistle,
"Seeing" Nutrient Deficiencies
We asked our friend Don North, an area nurseryman,
horticultural consultant, and native plant propagator, to
describe the common nutrient deficiency symptoms of garden
crops. Don told us that, in general, tomato plants are
especially good "deficiency meters" and then listed the
shortage symptoms he most often sees:
Nitrogen: Many deficiencies, including nitrogen, show
up as chlorosis, a yellowing of leaves. N
shortage, though, appears mostly in the older
leaves (the young ones hog the available nitrogen) at
the bottom of the plant. These yellow and "fire"
(get a burnt look). The entire plant may also be
Iron: The veins keep their green color in
iron-deficient plants, but the rest of the leaves
yellow or turn light green. (Don's remedy? Iron
Sulfur: In this case, the young leaves
(including veins) turn chlorotic.
Potassium: K-short crops exhibit yellow streaking,
along with curling, mottling, or spotting of older
leaves. The plants are often particularly
Phosphorus: Plants low in phosphorus are often small,
have very dark green or bluish foliage, and red or purplish
veins. Poor fruit development is another indication of P
Calcium: The classic sign of calcium deficiency in
tomatoes is blossom-end rot. Other symptoms are hard to
spot: Young leaves and terminal buds may become hooked in
appearance or die back at their tops, or the young leaves
may remain folded or look wrinkled. (Don recommends Viking
brand calcium nitrate—from Norway—for both
calcium and nitrogen shortages: "It's one of the best
fertilizers around. ")
Boron: If your broccoli and cauliflower stems
are soft and brown in the center, your soil's got a boron
Soil Test Results for Mother's Eco-Village Garden