Gardening : Here’s the Real Dirt About Ordering Topsoil : Often what’s needed are amendments to improve what’s in your garden now.

Who do you call when you need good dirt?

Maybe you are sick to death of your garden and the fact that nothing will grow, and you think this is the solution.

Well, most people look under “Topsoil” in the classified pages of the phone book, but topsoil is a much-abused word. It can mean just about anything--some horrible soil that someone else wanted to get rid of or the heavy clay excavated for a swimming pool or (the best possible scenario) a wonderful, weed-free, sandy loam that is a joy to dig in.

Soil amendments, such as peat moss, ground bark or shavings, are also called “topsoil,” and are often sold by the same outfits. Although they are anything but topsoils, these soil amendments are really what you want.

“The first thing I ask anyone who calls is, ‘Do you need to raise the level of the soil?’ ” said Jeff Van Ess of Lewis Topsoil in Los Angeles.

“When you have to make a part of the garden higher, to fill low ground or to fill planter boxes or raised beds . . . is the only time you really need topsoil. The rest of the time what the caller really wants is a soil amendment.”

Both Cost Same

What’s the difference? It’s really very simple, but a lot of homeowners don’t get it: Topsoil is just that--dirt scooped from the ground. Soil amendments are organic or chemical products that improve dirt--make it softer or help it hold water.

There is no difference price-wise if you are buying good topsoil or amendments. Both cost about $30 a cubic yard, plus a delivery charge if you are not near their point of origin.

The best true topsoil is a sandy loam and a reputable topsoil company will provide topsoil that has been ground up and pulverized in a machine so there are no chunks, and they will remove the rocks. They also make sure the soil is weed-free.

Precisely what kind of amendment or topsoil you need depends.

“We always ask what their soil is like and what they are going to plant,” said Bernie White of White Topsoil.

Hold Water, Fertilizer

If you are going to plant something woodsy, such as azaleas or ferns, you need to add lots of soil amendment because these plants like a porous soil full of organic matter, like the leaf litter found on a forest floor.

You may also want to add lots of amendment in a very sandy soil because organic amendments help hold onto water and fertilizer that otherwise would wash right through the sand.

In an average clay soil you may want to add sand to keep the surface from caking, and you certainly want to add organic amendments and gypsum, a powdery white mineral that helps keep a clay soil from getting too heavy and dense. Gypsum physically separates the soil particles.

There are lots of ways to go, given that there are so many kinds of soil, situations and plants.

Variety of Mixes

“We have over 500 different mixes, from super-lightweight mixes that can go in planters on rooftops or balconies, to special azalea mixes,” White said. They even have a special soil mix for those who want to grow cactus and succulents, which will quickly rot in a normal clay soil.

“But certainly there must be some average recommendation?” he was asked.

“Well, if you have a typical clay soil, do not need to raise the level of the garden and are just growing ordinary garden flowers and shrubs, we would probably recommend adding a 2-inch-high layer of redwood and fir shavings, which have been nitrolized, plus some gypsum. “If you needed to add a 2-inch layer over 1,000 square feet, you would need 6 yards of material, which is about one truck load” is Lewis Topsoil’s reply to this broad question.

Of course, you don’t just spread this on top and plant. You must till it into the soil with a power rotary tiller, which can be rented. That even goes for topsoil. It too must be tilled in so there is no abrupt line between old soil and new, which would repel water and roots.

Robbed of Nitrogen

What are “nitrolized” shavings? Wood byproducts such as sawdust or shavings that have not been thoroughly composted, will rob the soil of nitrogen, that all-important fertilizer element. To prevent this, the topsoil companies can add nitrogen to the product, so it is readily available to aid decomposition. Be sure to ask if amendments have been nitrolized or have had nitrogen added.

These organic amendments can also be bought by the bag at nurseries or you can bag it yourself at building or garden supply stores, but getting a truckload at a time offers considerable savings. By the truckload, it costs about half what it does by the bag.

At this time of year, the very beginning of the fall planting season--our best planting season--you may be contemplating major changes and replanting and a truck load of organic amendments will make a tremendous difference in your soil. Be sure you have a wheelbarrow to cart it around and a place to store it until you use it up. A truckload makes a very big pile.