Soil Types and Testing

Characteristics of Different Soil Types

It can be argued that no two soils are ever exactly alike. Although this is true, it is useful to group soils into categories. Three major categories of soil dominate our area. These are:

Sandy soil

Loam soil, and

Clay soil

To figure out what type of soil you have, there are several easy methods. The first, called the rope test, requires that you squeeze a moist, but not muddy, one inch ball of soil in your hand. Then rub the soil between your fingers. Sandy soil feels gritty and loose. It won’t form a ball and falls apart when rubbed between your fingers. Loam soil is smooth, slick, partially gritty and sticky and forms a ball that crumbles easily. It is a combination of sand and clay particles. Clay soil is smooth, sticky and somewhat plastic feeling. It forms ribbons when pressed between fingers. Clay soil requires more pressure to form a ball than loam soil, but does not crumble apart as easily.

A second test is called a jar test and is very easy to do. Here’s what you’ll need:

1 clean quart jar and tight fitting lid

clean water

soil sample

First, find an empty, clean quart jar (an old mayonnaise jar works very well for this test.) Fill the jar about 2/3 full with clean water.

quart jar with water.gif (8016 bytes)

quart jar with water and dirt.gif (7979 bytes) Next, take a sample of soil (break the large clods apart so it will fit through the jar opening) and fill the jar and water until the jar is nearly full, leaving about �” of air space at the top. Screw on the lid and shake it vigorously for a minute or two, until all the soil particles are broken down into suspension in the water.

Now, allow the suspended soil to settle for about a minute, and place a mark on the side of the jar at the top of the layer that has settled out. This is the sand layer is comprised primarily of sand and larger particles. Set the jar aside, being careful not to mix the sand layer that has already settled and wait approximately an hour. Now, place a mark on the side of the jar at the top of the next layer to settle out. This is the silt layer. Again, place the jar aside for a full day, being careful not to shake or mix the layers that have settled out. After 24 hours, or when the water is once again clear (more or less), place a mark on the side of the jar at the top of the final layer. This is the clay layer. The percentage of each layer tells you what kind of soil you have.

Type of Soil Example of Test Jar

Sandy soils are found throughout Southern California, but are very common near the mountain foothills, along rivers and streams and certain coastal areas. Sandy soils are typically comprised of approximately 80 – 100% sand, 0 – 10% silt and 0 – 10% clay by volume. Sandy soils are light and typically very free draining, usually holding water very poorly due to very low organic content.

quart jar with sandy soil.gif (26180 bytes)

Loam soils are also common in Southern California, particularly in the valleys and flat areas (flood plains) surrounding rivers and streams. Loam soils are typically comprised of approximately 25 – 50% sand, 30 – 50% silt and 10 – 30% clay by volume. Loam soils are somewhat heavier than sandy soils, but also tend to be fairly free draining, again, due to typically low organic content.

quart jar with loam soil.gif (25539 bytes)

Clay soils are very common in certain areas, particularly around urban areas where fill soils have been used to establish grade in subdivisions and developments. Clay soils are typically comprised of approximately 0 – 45% sand, 0 – 45% silt and 50 – 100% clay by volume. Clay soils are not typically free draining, and water tends to take a long time to infiltrate. When wet, such soils tend to allow virtually all water to run-off. Clay soils tend to be heavy and difficult to work when dry.

quart jar with clay soil.gif (25169 bytes)

via Soil Types and Testing.


Another version

Really want to try something with the soil? Take a quart jar and put normal soil (no top soil, or organic matter) in the bottom third.
Next fill with water to within 1 inch of the top and put the lid on and shake it and set it down and write down the measured amount
that falls out in the first 10 seconds–gravel, then 10 minutes–sand, then the next morning–clay