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momdino

Soil Test Kits

momdino
16 years ago

How accurate are they? A little background: We bought our house in summer of 2006 from an environmental engineer who was very much into organic gardening. There was a vegetable plot about 50' x 20' in the back that he constructed about 5 or 6 years before he sold us the house. He told us he never used any chemicals, always organic. In spring of 2007, we converted the plot to 6 raised beds, using the existing soil, which looked fairly good although had a lot of clay, and adding bagged compost from Lowes and pine bark fines as amendments. At that time we did not think to do a soil test. We grew tomatoes, cukes, squash, potatoes, peas, beans, sweet potatoes, and herbs. The garden produced, but not particularly well.

This year, after turning the soil, I bought one of those Ferry-Morse kits and followed the directions completely. Bottom line: my soil is slightly on the alkaline side, okay in potassium, but "very low" in nitrogen and phosphorus. I was pretty surprised at this, but guess it may help explain the not so great production. So I know I need to add sulphur to get the pH down some, but what else should I add and still stay organic? Sorry for the long post, but thanks in advance for any imput from you experts.

Comments (7)

  • jean001
    16 years ago

    If the kit is fresh, it will give you a ballpark figure as to pH.

    But if you put the kit away and test a year later, the result is anyone's guess.

    That said, if you want to test P and K etc., spring for a professional lab test. But realize that labs seldom, if ever, test for nitrogen because it's too mobile in the soil.

    One of the reasons your results weren't terrific is likely due to using the pine bark fines as an amendment. To do so, you should also add nitrogen to help it break down in the soil.

    I suggest that you only mix compost into the soil. But even then, you have to add enough to get results. For your veggies, mix in at least two inches each year.

    Oh yes. I need to add that clay is good. As long as you mix in the 2 inches of compost every year.

  • denno
    16 years ago

    From your user name, I'm going to assume you're from NC. If you can find your local Cooperative Extension office, they will give you some cartons to put samples of your soil into. Also, a sheet with instructions on where to send them. I send in some samples every two or three years, usually two samples at a time. One from the north end of the garden, and one from the south end. The only cost to you is the postal rate, and in about six weeks they will send back a report to you with the results.

  • Kimmsr
    16 years ago

    I have not found these soil test kits to be very reliable, and the information you get is only very general. Your available Nitrogen is highly dependant on soil temperatures so a reading now of "very low" may or may not be of any significant. The other nutrients are in the same category. The soil pH test more often than not will give you the same reading if you test soil, vinegar (acid), or baking soda (alkaline).
    If you have a good amount of organic matter in that soil those results are way off. Contact your local office of the North Carolina State University USDA Cooperative Extension Service about having a good, reliable soil test done and dig in with these simple soil tests to see what you do have,
    1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

    2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

    3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

    4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer you soil will smell.

    5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

    If you have a goodly amount of organic matter in your soil those test results should not have been that far off.

    Here is a link that might be useful: NCSU CES

  • Lloyd
    16 years ago

    kimmsr: You say (pay attention to the "fewer than 5" statement):

    5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

    The USDA Natural Resources Conservation Service Soil Quality  Agronomy Technical Note No. 11 says (pay attention to the last statement):

    "Many people consider earthworms to be an indicator of soil quality because they respond to and contribute to healthy soil. For earthworms to be abundant, a field must meet several conditions that are also associated with soil quality and agricultural sustainability: moderate pH, surface residue for food and protection, and soil that is not waterlogged, compacted, droughty, or excessively sandy. Not all healthy soils will have earthworms."

    Maybe there is another link where you read that supports what you state or maybe there are two Natural Resources Conservation Services.

    In any event it seems to be contradictory.

    Lloyd

    Here is a link that might be useful: Link to USDA

  • momdino
    Original Author
    16 years ago

    Thanks to everyone... I definitely will have the Extension service do a soil test for me. I did do the structure test, and the components of my soil was fairly representative of sandy loam. However, to the earthworm test [ : ) ] my soil fails miserably! Only saw two earthworms while turning the beds, but perhaps that can be attributed at least partly to the drought we have been experiencing as of late.

  • jeannie7
    16 years ago

    Quote: I have not found these soil test kits to be very reliable, and the information you get is only very general.

    For such findings, we must believe then Kimm, you have used such test kits. Now why did you buy them if you don't trust them.

    They're not supposed to be first-line, top of the market, professional used instruments, they are for the average gardener to give a reasonable level of test results.

    Steph, be careful about the level of nitrogen you give your vegetable garden; vegetables do not need high levels of nitrogen, in fact the resulting harvest can show exactly what you say the vegetables came out as...good, but not great.
    Watch how much compost you give your beds...vegetable gardens appreciate loose, sandy soil toward clay and add some peat moss with the compost. Any sand you add should be coarse builder's sand to help in obtaining good drainage.

  • annpat
    16 years ago

    Actually there are lots of vegetables that love nitrogen----spinach, lettuce, chard, and kale comes to mind---pretty much all "greens" do.