Testing Your Garden Soil

Not having great soil is really a problem here in Northern New Mexico and makes growing anything a challenge. Having good soil where you want to plant veggies is the most important thing you can do. People ask me all the time how do I grow such great veggies and the secret is-it’s all about the soil!  So the more we learn about how to improve our soil the better our growing results will be. So read on.

Here is an excerpt from Payne’s Nurseries site here in Santa Fe on ‘How to Build Your Northern New Mexico Soil’ which is worth reading in it’s entirety.”We have three basic types of soil here in Northern New Mexico: caliche, adobe and sand. All are alkaline, with a pH often over 7.0, and tend to contain abundant quantities of sodium, calcium and potassium. Caliche, adobe, and sand all lack organic matter, the nutrients and organisms of which are essential for sustaining high quality plant growth and production. Caliche is made up of sand, gravel and clay. Adobe is essentially fine clay. Neither soil type is easily penetrated by water. Sand, on the other hand, allows water through but has a limited ability to hold nutrients or moisture.” Check out the article. Most of us have some combination of these 3 types.  Fertilitzers feed the plant but not the soil which also needs to be fertile and more and more people are just learning that.

One of the things I mentioned in an earlier post is I’m getting a soil test specifically for growing my giant pumpkins and I will get one for my veggie garden where I grow tomatoes also. I researched where other pumpkin growers are getting their soil analysis done and I will use A & L Western Laboratories in Modesto, Ca for mine as they can test for any crop I specify versus a general soil test. My fellow pumpkin nuts tell me to get the  S3C COMPLETE Analysis package from A & L and to get the recommendations as well. The soil sample collected should be a composite from 10 to 20 locations within a selected area; a sufficient number to “average out” variations. You can learn how to properly take soil samples from them here. Other soil testing companies may have other protocol so check with whoever you use as to how they want you to collect soil samples.

There is nothing wrong with getting a general soil test (instead of for a particular crop) and that is what I would get if I didn’t grow competitively but I want to get the most out of my soil for my pumpkins.

You can also get a general soil analysis from a NMSU laboratory here and you can go to NMSU Soil Test Interpretations site to learn what your test means. Reading the tests isn’t easy but once you get one done you’ll be better able to understand what needs to be added to your garden for next year’s growing season so you can have a wonderful lush, productive garden next year. I’ll post what the results are as soon as I get them back.

4 comments on “Testing Your Garden Soil

  1. Hello,
    I have just been informed about this site and it is significant to me. I have taken the Master Gardener classes in both Seattle and Santa Fe ( after retiring here) and though only gardening for a short time, and really hooked. I have an NMSU hoop house greenhouse on my property south of Las Vegas and this particlar article is totally significant to me.

    The soil in th greenhouse was native soil here, basically clay with hardpan. I thoroughly tilled four areas to be raised beds, before the structure was built. When constructed, I added 4 raised beds and used 4 year old horse manure for planting, plus drip irrigation. Things grew well here and I harvested pole beans on a ladder since they grew to the ceiling. Harvesting root vegetables was a killer! The greenhouse got as hot as 116 during the day and most veggies seemed to just eat it up since the ground temp stayed around the 80’s. Extracting my onions, carrots and Dahlias was unberlievably difficult since that heat, combined witht the water I used turned the soil to concrete.

    With Linda’s heart attack and learning that she had diabetis, I have just finished raising the beds 8 and 10 inches. I had access to a dry creek bed and the raised beds are now filled with that sand and also the horse manure which is black and very friable.

    I am extremely interested in fertile soil since our veggies will be coming from our 16 x 32 GH and we have to adopt a new healthier lifestyle. My soil tests come from the state and using the soil combination I have referred to outside I was told the only things needed were 50 pds. of both nitrogen and also calcium per acre. Every nutrient needed seemed “off the charts” with this combination.

    Thus, this article can potentially save me years in learning how to make really healthy soil in my greenhouse and elsewhere on our property. I am interested i finding out what you will be adding to the soil to make it richer, and the resulting veggies to grow bigger.

    Thank you very much for creating this site

    Gene So


    • Hi Gene-
      Welcome aboard the blog! I was wondering in your comment, you report you had said that you were nitrogen and calcuim deficient and should put 50 pds per acre. Is that correct or a typo? Usually soil tests either say ppm (parts per million) or lbs (pounds) per acre.
      In NM we must be very careful in what form we add calcium as our ph is already so high and lime (also a source of calcium) will raise the ph even more. I always add it in the form of gypsum which is a great source of calcium but doesn’t raise the ph like lime. Also never add ashes as they will also raise the ph out here (good back east where the soil is acidic but not out here). Here is a good site on calcium deficiency. I always add gypsum in the fall (now it will be in winter as I’m late!) but as long as the soil isn’t frozen we should be in good shape by spring. 2 places you can get gypsum in Santa Fe is Newman’s nursery (comes in 10 lb bags of powder) and Paynes Nursery (50 lb bag of pelletized gypsum which is cheaper than the powder) but in your case you don’t need too much (in raised beds) so maybe the powder would be better as it takes all winter for the pelletized version to break down).
      I will research what 50 lbs breaks down to say 100 sq ft and let everyone and you know. 🙂


    • Also on the nitrogen deficency-I would wait till I planted next season to add more nitrogen product. Your test just shows your ‘crops’ just used up what nitrogen was available and if you add more now it will probably break down anyways over winter. Also if your soil is cold the amount of available nitrogen will not be as high. As soil warms up, more nitrogen is released to plants (assuming you give them an extra source of nitrogen next spring. Here is an interesting forum about organic nitrogen sources and applications.


      • Hello Jannine,

        I shall try to keep this response concentrated. I know about soil tests from U of Mass ( Amherst) they are 4.00 from the MG program in Seattle. I have had a soil test from NMSU here. They informed me that my initial amended soil was missing nitrogen and calcium and suggested I apply 50 pounds per acre. Thats very little in the 240 square feet of raised beds in my newer greenhouse from Al Calde.
        Following your, and two others advice who have greenhouses in this area I have now added these components to my recently raised beds: mainly dried creek sand,a lot of aged horse manure, some clay and lesser amounts of: humic acids, gypsum, and wood chips ( think thick sawdust) in finite layers. One of my 3 x 24 beds is now covered by cloches with row cover for a top and I shall start gardening Feb. 15 in that portion of the GH.
        Your site is almost overwhelming in terms of all it covers and I shall start from the beginning and slowly work through it taking notes all the way!
        Last year, my first here, I was troubled by both excess heat and also insects in my new GH. I believe I shall have those problems under control this year. If you have the choice between growing tomatoes outside, under a row cover or in a greenhouse, which choice would you make?


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