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The Importance of Soil Testing

by Guest Author on 04/04/2014
Jar Test for Soil Composition

[guest post by Cristina da Silva]

Why should we test our soils?

Nothing beats eating fresh homegrown fruit, and the best fruit comes when you start your trees off right. There is one thing that we can do  that will ensure healthy fruit trees and improve fruit quality and flavor at the same time: Soil tests!

It seems anticlimactic after that build up, but seriously, when we know what to add to our soil, we end up with healthy fruit trees with good quality fruit. Healthy fruit trees are more productive and less susceptible to pests, diseases, and winter injury.

All soils are different. Nutrient levels, which are necessary for plant growth — as well as soil pH, texture, and structure — vary from site to site. It’s hard to know what your soil needs without knowing what is there already. Soil tests are the way to find this information.

Soil Testing

Soil testing can be done either in a public (state) or private laboratory. For state labs, contact your local Cooperative Extension Services.

Nutrients analyzed will vary from lab to lab. Most professional soil tests give you an analysis of:

  • Nutrient levels — i.e. nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe) and zinc (Zn).
  • Soil pH — (low/acidic pH, neutral, or high/lime — most fruit trees prefer a neutral soil pH)
  • CEC – “cation-exchange capacity”; the nutrient-retention capacity of the soil
  • Organic matter

» Here are some tips from the University of Illinois Extension on Taking a Soil Sample (video).

Handy soil meters and easy-to-use soil kits are available for testing soil. These kits, often found at garden centers, give a rough idea of pH and major nutrients (N-P-K) in the soil. We can also roughly figure out our soil composition/texture with the “Jar Test”.

Jar Test

Collect a sample of soil — 1/4 cup will do. Remove debris like rocks and trash. Crush the remaining soil so that all parts are consistent and fine. Shake* your 1/4 cup of soil in a 1-quart jar (taller is preferable, with a lid), add just under 4 cups of water, and let everything settle. *Shake hard enough and long enough to agitate the particles into separating.

Once settled, measure the levels that compose your soil by marking lines on your jar:

  • Sand (settles after 1-2 min)
  • Silt (settles after 2 hours)
  • Clay (settles after 2-3 days)

» Colorado State Extension has good factsheet with instructions hereGreat project to try with kids!

Before adding anything to our soil, we must find out the nutrient requirements of our fruit trees. Spectrum Analytic labs website has good articles on nutrient requirements of apple trees as well as grapes, raspberries and other brambles.

Once we have the soil test results, we can add exactly what our soil and ultimately what our fruit trees need. We won’t run into the risk of adding too much fertilizer, which will pollute our groundwater and streams. Soil tests save time, money, and the environment — and we end up with tasty nutritious fruit! What more can we ask?

» Find more visually educational references on Cristina’s Pinterest Board here: Soil experiments

About the Author

Cristina da Silva (@CristinaGardens) organizes/hosts #groundchat on Twitter, which discusses soil-related topics every Friday at 2 pm ET/1 pm CT/11 am PT. Cristina is also the blogging horticulturist at The Real Gardener – a website intended to increase gardeners’ awareness of the soil.

Topics → Planting & Growing, Tips

5 Comments

  1. elisabeth permalink

    So this might be a silly question but does the time of year matter? I bought one of those tests from a local hardware store and was waiting for Spring (in Vermont) before digging through the snow. And now the snow is gone so I could do this if now makes sense.

    Thanks!

    • That’s a very good question Elisabeth! The best time is when the soil is workable (not frozen like it may be in the winter) and before you plant.

      If the ground isn’t frozen, then you are able to get an adequate sample of the soil your plants and trees’ roots will reside in. Getting a soil sample and having it tested prior to planting new things provides you with the opportunity to make any necessary amendments or reassess your planting site beforehand. :)

      • elisabeth permalink

        Thank you! Now I have an excuse to play in the dirt.

  2. Holly Heil permalink

    I would like to have some dwarf fruit trees. My concern is that we have black gumbo clay soil. I’m in Texas, and it gets really hot and dry in the summer. Are there any dwarf fruit trees would do well, if any, without a lot of special attention?

    • Hi Holly! From my understanding, Texas ‘Black Gumbo’ is an incredibly heavy clay that is difficult to work with wet or dry. A lot of folks dealing with heavy clay-type ground end up with nutrient and drainage issues with their plants and trees if things aren’t amended first. One recommendation is to bring in a lot of organic matter, like compost, aged manure, peat/sphagnum moss, etc. to add nutrients and break up the native clay to improve drainage. This happens before you plant the trees so that it has time to improve your soil (this varies by season, weather, and what you use to amend the soil). I would recommend contacting your local county cooperative extension to find out what is recommended to improve your ability to grow in (or around/over) the black gumbo there in Texas — prior to even trying to dig holes or plant trees.

      Your local county extension is also an ideal source for fruit-tree information specific to your area. I found an article about recommended fruit tree varieties for Texas here.

      The last thing you might consider is planting your fruit trees in containers so that you have more control over the soil medium surrounding the roots, the drainage, and the nutrients the trees are receiving in the container setting. We have a few articles on growing fruit trees in containers (including fig trees) and caring for fruit trees in containers that you might find useful if you decide to go this route. :)

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