How to Make Sandy Loam Soil

Sandy loam soil offers plants the perfect balance of moisture-retention capabilities and good drainage. If you aren’t fortunate enough to have this type of soil on hand for your gardening projects, you can make it by combining a few basic ingredients in just the right quantities. You can use the resulting mixture to fill a raised bed or create a garden spot in front of your home.

If it is clay you will be able to roll a handful of it into a ball that holds its shape, and you can flatten it into a ribbon that will remain together even at a length of one to two inches. Silt will form a ball but will easily crumble when you press on it; it will crack when you try to form it into a ribbon. Sand crumbles easily and feels rough and gritty in your hand. Sandy loam feels gritty, but also has some of the properties of clay and silt. It won’t make a ribbon longer than an inch.

To get a more detailed idea of your soil’s composition, use the following procedure for a sediment test. (REF 4)

Shovel

Old newspapers

Jar, such as a one-quart canning jar, with tight lid

Non-foaming dishwasher detergent

Permanent marker

Measuring tape or ruler

Spread a shovelful of soil on a layer of newspapers and allow it to dry out.

Remove anything that isn’t soil from the sample, such as roots, trash and rocks.

Crush the sample so that nothing remains but fine particles. Be sure to break up any dirt clods as part of this process.

Fill a slender, tall jar such as a one-quart canning jar about 1/4 full of the soil. The jar will need to have a tightly-fitting lid.

Add water until the jar is 3/4 full.

Pour in 1 teaspoonful of liquid dishwasher detergent that is a non-foaming type.

Put the lid on the jar and shake it vigorously to separate the aggregates within. This typically takes about 10 to 15 minutes.

Set the jar in a location where it won’t be disturbed.

Wait one minute and then use a marker to make a line on the jar at the top of the first layer of sediment. This is sand.

Wait 2 hours and then make another line on the jar at the top of the next layer, which is silt.

Leave the sample alone until the water clears. This usually is a matter of no more than three days, but with some soil types it might take weeks for the particles to settle. Make a line on the jar at the top of the final layer to identify the clay layer.

Measure the layers. You’ll need to know the thickness of the individual layers as well as the total of all three. Don’t count the water.

Determine the percentage of each main component on your soil by dividing the thickness of the individual layer by the total thickness. For example, if your total thickness was 4 inches and your sand layer was 2 inches, your silt layer was 1.6 inch and your clay layer was 0.4 inches, you would divide 2 inches by 4 inches to determine the percentage of sand, 1.6 inch by 4 inches to determine the percentage of the silt and 0.4 inches by 4 inches to figure the percentage of clay. In this case your soil would be 50 percent sand, 40 percent silt and 10 percent clay.

According to the, U.S. Department of Agriculture, sandy loam soil consists of 60 to 80 percent sand, 10 to 15 percent clay and 5 to 30 percent silt. To make your soil into sandy loam, you need to bring the components within these ranges. Knowing the makeup of your existing soil will guide you as to which amendments to add and how much you’ll need of each. The USDA has a soil calculator that will help you to determine your current soil type.

To make sandy loam that is 60 percent sand, 10 percent clay and 30 percent silt, take your initial percentages as determined by the sediment test into consideration to determine what to add. Another way to think of this is that the soil should be 6 parts sand, 1 part clay and 3 parts silt. If you're measuring soil with a gallon bucket, think of it as 6 buckets of sand, 1 of clay, and 3 of silt for every 10 gallon buckets of soil. Use your soil composition as your guide for amending your soil.

For example, if you've determined that your soil is 50 percent sand, 40 percent silt and 10 percent clay, you’ll need to add enough sand to alter the balance. In this case you need to increase the amount of sand by 10 percent so for every 10 gallons of soil you should add 1 gallon of sand. In this example you won’t need to add anything else, but if your soil was lacking in silt you would need to add organic amendments such as compost to increase the level of silt. Since the components of sandy loam soil fall into a range, you have some margin for error.

Wheel barrow

1 gallon Bucket

Shovel or spade

Soil

Coarse sand

Organic amendment such as compost or rotted manure

Ammonium sulfate or ammonium nitrate

Don’t use fine sand as that will work to compact the soil, interfering with its ability to drain and let air into the roots of your plants.

Calculate the percentages of the components in your soil as detailed in the Determine Your Soil Type section of this article.

Dump 10 gallons of soil into the wheelbarrow.

Add enough sand to bring the amount of sand in your soil up to at least 60 percent. If your soil already has a lot of sand, you can skip this step.

Add enough organic amendments such as wood shavings or rotted manure, to bring the silt level of your soil into the range of 5 to 30 percent. If your soil is already in this range after adding sand you can skip this step.

Add enough clay to increase the level of clay in your soil to at least 15 percent, if necessary.

Add 1/4 pound of ammonium sulfate or ammonium nitrate for every bushel of organic material to prevent nitrogen deficiency.

Use a spade or a shovel to mix the soil, organic amendment, ammonium compound and sand together thoroughly. Continue mixing until everything is well-blended to create sandy loam.