Those of us who garden or have green thumbs know the smell of good loamy soil. You hold it in your hand, and can feel the goodness of it. Rich, fertile and ready to provide nutrients, it has a quality to it that is nearly ethereal. It is the Earth's mother's milk.
If you have moved into a new house in a suburban housing development, this writeup will help you. My house was built on former farm land, but you would never know it. Close by there was a small retaining pond that collected drainage from the fields. When the homebuilder was doing their land development, they needed to make the pond deeper, and to do this they dredged up the clay and shale from the bottom of the bottom of the pond and used it for the grade work on the field. My house now sits on top this clay and shale. In some ways its great because I have great drainage around the foundation of my home and have not problems with water seepage in my basement. But when I dig in my yard, I get down about 4-5 inches and then hit a hard layer of clay and shale that is like cement. The soil in my yard is one of the hardest types of soil textures to amend. I have my work cut out for me, what about you? Let's begin.
Why should I test my soil?
Well, the obvious answer to this is another question. How can you amend or fertilize your soil unless you know what it needs?
Adding too much of the wrong material can be harmful to plants and soil organisms. Testing your soil takes away any guesswork. Once you know what you have, you can correct any deficiencies. Further, testing your soil allows you to know your soil texture, soil pH and the mineral and organic contents of your soil. If your soil has a high nitrogen content, you would not want to put down a high nitrogen fertilizer. Doing so would kill your grass.
Ways to test your soil at home
- Supplies Needed:
- Glass Jar with a tight fitting lid
- Non-sudsing Surfactant (Calgon Water Softener or a powder dishwashing detergent)
- Soil Texture Triangle (You can find one online, your local library or garden center)
- Hammer or Meat mallet (optional)
- First, you need to get a soil sample. Select about 10 different areas in your yard. Or, if you want to test garden soil, select multiple locations from your garden. Regardless of what area you want to test, the idea is that you want to get a good representative sample of soil.
- Using a shovel pick up a scoop of soil creating a hole approximately 6 inches deep. Set this soil aside. You can use this to refill the hole you have created in your lawn or garden.
- Using the shovel, cut a 1” wide, 6” deep slice of soil. Alternately, if you have a 1 - 2” pipe available, you can use this instead, it provides a nice “core sampling”. However, if your soil is very compacted the shovel will work better for you. Put this soil into a container. Repeat this in all areas you have selected for sampling and put all of the soil into the same container.
- Next, wait. You have to let your soil dry out completely. You want the soil to be dry enough so that you can crumble it all together and mix it thoroughly. If you have heavy clay soil, you may need to use alternate means of crushing the soil. This was a problem for me. I found that using a meat mallet worked well. If you have to resort to this, I recommend spreading the soil out onto a plastic trash bag on top of cement or asphalt. Then you can crush the soil as needed. I will warn you though, do not do this indoors, it makes a dirty dusty mess, trust me.
- Take your clean glass jar and fill it half full with your crumbled soil. Add about a teaspoon of surfactant. This will help your soil become fully suspended in the water and allows the soil/water solution to mix completely. Add water to jar until there is only about an inch of space remaining unfilled. Shake the jar for at least 5 minutes. Then set it down and do not pick it up or disturb it for at least 20-24 hours.
- In the meantime, you are going to do a ribbon test which is a good preliminary assessment for your soil. Grab a handful of the remaining soil and trickle enough water into your hand to thoroughly moisten the soil without making it all drip out of your hand. You should be able to squeeze the soil together without it falling apart. Then using your thumb and forefinger, squeeze the soil through creating a small thin ribbon. Soil with high silt content will form flakes or peel instead of forming a ribbon. The longer and thinner the ribbon, the higher the percentage of clay. The ribbon test that I did on my soil ended with a ribbon about 2 ½ inches long.
- After your 20-24 hours have elapsed get a ruler and measure the the total height of your soil in glass jar using milimeters. This will be the number you use to determine the percentages of soil make-up. Write down that number and shake the jar for 3 minutes. Make sure it is completely mixed again. Then set it down for 5 minutes.
- After the five minutes have elapsed measure the amount of sand that has settled in your jar. It may be hard to distinguish, but if you look at the jar, you will see some darker particulates along the glass. Measure the distance to the top of that layer. If you cannot find a layer of sand, you will estimate it to be 5%.
- After 30 more minutes, measure the amount of silt that has deposited on top of the sand. It will appear as a slightly lighter layer. The remaining amount of soil in the jar is clay. So you can do the math. Here's an example of the soil in my yard:
Total was 73mm
Sand 20mm 27%
Clay 48mm 66%
Silt 5mm 7%
- Lastly, break out the old soil texture triangle and use the percentages to figure out your soil texture. Using the example I provided, you'll find that my soil is “clay” in texture.
Having your soil tested professionally
I highly recommend having your soil tested professionally. It will tell you pH, nutrient content and texture of your soil. I know, you’re thinking to yourself that you can simply use one of those at home soil pH test kits, they are usually wildly inaccurate. Since the difference in pH is logarithmic, a slight miscalculation can be a big deal. Before you take your soil samples, contact your county cooperative extension office to see if it performs soil tests. If they do, they probably charge a small fee. In some states, you may have to use a private soil lab. The cost of the average soil test can be anywhere from $15-$30. This is money well spent when you consider the wealth of knowledge you get from their test results.
Once you settle on the lab that you will use for this, be sure to check with them to get their sample instructions. Each lab will vary slightly in their sample directions.
Good luck and happy amending.