Soil Tests

by Stephanie Suesan Smith on July 21, 2010

You may be asking yourself why do I need a soil test?  I always put the same fertilizer down at this time of year, so why waste the money?  Well, by not spending $10 for a soil test, you may be wasting a lot of money on the wrong fertilizer.  Worse, you may be poisoning the soil and making your plants sick.

Soil tests measure the amount of nutrients in the ground.  The three most important nutrients are Nitrogen (N), Phosphorus (P), and Potassium (K).  When you buy fertilizer, the numbers on the front of the sack are the amount of these nutrients in the fertilizer.  If your soil is low on Nitrogen, but is medium or even high on Phosphorus and Potassium, you can make plants sick by adding a fertilizer with a lot of Phosphorus and Potassium in it.  In my county, we have a problem with high Phosphorus and sometimes high Potassium, depending on what crops have been grown on that land and what fertilizers have been used.

Agricultural producers test their soil every year before they buy their fertilizer.  It costs them money to put down fertilizer that is not needed.  As I mentioned, a farmer can even make his crop sick with too much of one nutrient or not enough of another nutrient.

Soil tests are easy to do.  You can get the soil bags, forms, and instructions from you county Extension Agent.  They are usually free.

Once you have your forms and bag, you get a bucket, go out into your flower bed or lawn, or whatever area you are trying to grow things, dig down two to three inches and put a shovel of dirt in the bucket.  Now sample four or five other places in your flower bed or lawn the same way.  Mix the dirt in the bucket good and put it into your soil test bag.  Fill out the accompanying form, being sure to list what types of things you will be growing in the soil that bag represents.  Keep a record of which bag is which when sending in your samples, as the results will only say “Sample 1” or “Sample 2”.  If you don’t remember what sample 1 is, you have a problem.  Send it to the soil lab on the label, and wait for the results.  In about four weeks, you will receive a print out in the mail with your soil analysis.

So far, so good.  Now, what does the soil analysis mean?  The results will indicate the amount of Nitrogen, Phosphorous, and Potassium in your soil, along with whether this is high, medium, or low for the crop you are growing.  It will also have an indication of how much of each nutrient, if any, you should put on your crop area.  You should follow these indications when you fertilize.  If you get hopelessly confused when looking at the results, call the county Extension Agent and they will explain it for you.

This year, wait to put that expensive fertilizer on your plants until you are sure they need it.  Have your soil tested and give your growing things exactly what they need to grow better.

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{ 8 comments… read them below or add one }

Richmond Movers July 21, 2010 at 2:11 pm

Interesting thoughts on soil analysis. Maybe I’ll consider this when buying fertilizer next spring!


Manhattan July 21, 2010 at 3:20 pm

Is it possible that the soil contents will be so varied across a small plot, that we’ll need two different types of fertilizer?


Stephanie Suesan Smith July 21, 2010 at 3:22 pm

If you have an area that is very different from the rest of the plot, such as a seep or hole that collects water, or a rise that doesn’t get it, a place with a streak of a different soil type, then yes, it is recommended you take two soil samples.


J. Johnson July 23, 2010 at 10:24 am

I always thought fertilizer was basically the same. I guess not. I will have to pay much more attention the rest of this year and for years to come. Thanks for the heads up.


Immersion heating elements July 24, 2010 at 1:20 am

What is salinity test? What is the purpose of doing it?
Immersion heating elements recently posted..The Heaterbands Heating Elements BlogMy Profile


Stephanie Suesan Smith July 24, 2010 at 5:46 am

The salinity test measures the amount of salt in the soil. Too much, and plants cannot grow. A lot of water has salt dissolved in it from underground and over time it can build up in your flower beds. Mixing organic matter in can help, as can rain.


Mike August 23, 2010 at 7:01 pm

This post is a great refresher for me, and a reminder of the probable reason that my garden didn’t do as well as I had hoped this year. It’s a refresher from my Horticulture class about 10 years ago in college…..most of those brain cells have come and gone!


Stephanie Suesan Smith August 24, 2010 at 10:55 am

Yes, if you do not do a soil test you do not know what nutrients to add, so the garden doesn’t do as well. More reminders for growing things are found under the gardening101 category.


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