I don't do soil testing at all because I believe tinkering with the
soil can do more harm than good. I know I have acidic soil because my
Blueberries are doing well and the most aggressive weed here is a Sheep
Sorrel. Both love acidic soils. To improve my sandy soil I add as much
varied organic materials as I can. My plants, including Tomatoes are
doing well, thank you.

OP has clearly in mind laboratory soil testing to determine the level of nutrients in his soil. "In agriculture, a soil test commonly refers to the analysis of a soil sample to determine nutrient content, composition, and other characteristics such as the acidity or pH level." (Wikipedia)

The results of this kind of testing most often give an inaccurate overall picture since the soil nutrients can vary greatly from one spot to another and "... soil nutrients vary with depth and soil components change with time".

Efforts to "fix the problem" by an inexperienced, lacking sufficient knowledge gardener, based on this kind of results usually leads only to creating new ones.

The article in the link above however, talks about different, based on observation, soil testing. Testing the soil structure and tilth, compaction, workability, soil organisms (earthworms including), plant residue in the soil, observing plant vigour, root development, water infiltration and availability, all this can and should be done by the intelligent gardener. His or her efforts should be directed towards ensuring positive results of this kind of testing, and all other problems will take care of themselves.

windberry, you do both sets of tests, not one or the other.

I have never done laboratory tests and never will. I constantly observe, though, my plants performance, my soil physical properties, soil organisms. I supply my soil with organic materials, practice intercropping, green manuring, mulching and composting. As I already said above, I am convinced (based on observation of other people's gardens) that in the long run efforts to modify the soil nutrients level artificially by the use of fertilizers lead only to even more problems.

I have been gardening for years. For most of my gardening life I used commercial fertilizers and had no understanding of the soil and little knowledge of the nutritional value of food. I then became interested in growing giant vegetables and it became important to understand the nutrients in the soil if I was going to grow big. First I grew pumpkins and got to 1090 pounds. Then I switched to tomatoes and have grown some over 6 pounds. I had to understand seed varieties, how to make crosses, how to prune, how to water, how to manage my soil from the standpoint of nutrients available and the biology of what was going on in the soil. None of this could have been improved without soil testing and nutrient targets for my soil and all done in an organic manner using things like greensand, potash, alfalfa meal and so on. I have not even mentioned my compost pile. In order to improve your soil as best you can, you need to know what is in it so as to understand imbalances, both deficiencies and excesses, and then you can do what you must to make corrections so as to improve the soil. None of this is possible without soil testing. Green manuring, mulching and composting are all positive for the soil but they are only part of the story if you are wanting the "perfect soil," if there is such a thing, since it also depends on the crop you are growing. I am still trying to understand my soil and to determine the best soil for my tomatoes and how to get there with organic amendments. Sorry if I got a little windy. And I did not mean to offend anyone if I did so.

By describing your approach to gardening you are not offending anyone.

From what you write one thing is clear though: you are constantly trying to correct your soil and the process never ends. It only confirms what I already said: this kind of approach doesn't work in the long run. It is also unsustainable.

The living soil is not a pile of dirt consisting of a limited, rather small number of ingredients that can be easily adjusted to become that perfect mix. The soil is a dynamic, living ecosystem, too complex to be understood fully. Tinkering with it will not bring lasting positive results. The best approach in the long run is simply to follow Nature' ways of doing things. Nature, having 3.8 billion of years of experience, is the best gardener of all.

Following Nature's approach is called bio-mimicry, from bios - meaning life, and mimesis - meaning to imitate. In gardening, inter-cropping, green manuring or cover crops, mulching and composting are major components of this approach.

As for soil testing per se, it is a rather new invention. First tests of the chemical composition of the soil as related to crop production were performed at the beginning of the previous century, roughly one hundred years ago. It took a long time before they became more popular. But people grew plants successfully and had gardens much longer than that, since the beginning of the agrarian era 10,000 years ago.

For those who are interested, here is a link to a great article on soil biology

http://pnwsteep.wsu.edu/DirectSeed/conf2k2/dscclapperton.htm 

and here is a link to a website with comprehensive information on soil health and soil biology

https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/soils/health/biology/?cid=nrcs142p2_053868 - follow the links on the left of the entry page.

I also never test the soil. Most plants have a soil Ph preference and I know my soil is alkaline so I do soil amendments for acid loving plants like blueberries. It has been my experience that improving the fertility of the soil with grass and weed clippings and chipped tree branches, compost and urine is all that is ever needed. In fact my garden and all the trees that I put grass and weed clippings on thrive; they grow two to four times faster than otherwise.

Most all plants evolved to grow in a soil pH of 6.0 to 7.0 where most all soil nutrients are most readily available, there are a few that prefer a different soil pH because they evolved growing in an acidic, boggy soil. Plants best utilize nutrients when they are in balance, ie, Calcium and Magnesium. If not in balance problems (blossom end rot) appears. Plants need both and in the right ratio to grow up strong and healthy. Too much Nitrogen will produce lush green growth and little fruit as well as make those plants more attractive to insect pests and other plant diseases.

Many people stumble around the garden and could have better results if they followed some of these simple tests instead of disparaging them as too new to be of any use.

I think there is value in doing basic soil tests for pH and nutrients when one starts gardening in a particular plot since it gives a basic starting point. Also, doing some basic physical tests for percolation, organic matter, and particle size is helpful, especially for new gardeners. Beyond that, I don’t do soil tests or use prescriptive inorganic fertilizers. Knowing the soil and nutrient preferences of the plants I grow, rotating crops, and adding compost and mulches that will break down over time and thus releasing nutrients makes more sense to me.

I am of the philosophy that I feed the soil web and the soil feeds the plants.