I think every plant I have ever purchased from a nursery had a tag that said “best when grown in sandy-loam”. Well thanks. That was really helpful. I’ll just run down to my local soil dealership and pick up a couple of yard sized loads of sandy-loam.
I’ve gardened in California (clay-loam), Arizona (rocky sand) and Colorado (clay-loam, with an emphasis on clay), and now in northeast Washington. And lo and behold, the soil here is sandy-loam. It DOES exist!
What’s the big deal with soil (and if you want to appear knowledgeable, you’ll call it soil and not dirt, as my soil science class professor reminded us EVERY time someone said dirt)? Well, turns out soil is made up of tiny particles that are classified as either sand, silt, or clay, or some combination of all three, based on size. Sand is the largest and clay is the smallest. A clay particle can be 1,000 times smaller than a sand particle. If we scaled them up for comparison, that would be 1 inch (clay) to 83 feet (sand). The difference is HUGE.
The smaller the soil particle, the better the soil will hold onto water. Smaller particles are packed so closely together that water has a difficult time draining away. This would seem like a good thing, until you remember that plants also need oxygen at their roots in order to thrive. A small addition of clay can go a long way when it comes to filling in those air spaces. And when clay soils dry out, then tend to crack. If you try to work them when they are too wet, they just stay clumped up like, well, a lump of clay waiting for the potter’s wheel.
Larger soil particles drain water so quickly that the plants have a hard time getting a drink before all the water has drained away. If you’ve ever spent time at the beach, think about how sand drains the ocean waves in seconds. But like Goldilocks with the bear beds, sandy-loam proves to be “just right” for most plants.
How do you know what type of soil you have? Well, you could ask at your local cooperative extension office. Or try to look it up online. A lot of state National Resources Conservation Service (NRCS) offices have online soil survey data available. Or, you could do a simple shake test to find out.
Soil Type Shake Test
- 1 quart or larger clear glass or plastic jar with tight-fitting lid. The straighter the sides the better. Canning jars work well.
- Sample of the soil you want to test – enough to fill the jar half way. Remove any large pieces or organic matter such as grass, bark and twigs and any rocks. Break up the soil as best you can.
- Small squirt dish soap
- Water to fill jar
Place soil in jar. Fill with water. Add small squirt dish soap. Tighten lid and shake really well for about 2 minutes (a great project for your kids). Now flip the jar right side up and start timing. After one minute, make a mark where the soil has settled. This is your sand layer. After one hour, make a second mark where the soil has settled. This is your silt layer. After 24 hours or more, make a mark where your last layer has settled. This is your clay layer. Measuring each layer and dividing by the total layer height will give you a rough approximation of your sand, silt, and clay proportions. My shake test in Colorado yielded about 80% sand, 10% silt and 10% clay, which wasn’t as bad as it could have been. It wasn’t bad to work with as long as it wasn’t too wet or dry.
My soil here in Washington is about 36% sand, 62.5% silt and 1.5% clay. It is a dream to work with. Need to dig a post hole? No problem. It goes lickety-split. Need to turn over the soil so you can get your peas planted even though it’s been raining. No problem. Want to dig out that hounds tongue by its deep tap root with one shovel full? No problem. Don’t want to have to water every day. No problem. Not to rub it in, but I am downright giddy about my sandy-loam soil.
I’ll write about the importance of adding organic matter, the great equalizer for all soil types, in another post.
Miles Away Farm Blog © 2011, where we’re miles away from having enough compost, but we definitely have sandy-loam under our fingernails.