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Welcome to the March 2003 edition of my web site! The roses I write about are the Old Garden Roses and select shrub and miniature roses of the 20th century. For tips on rose culture, pruning, propagation and history, see the "Site Resources Guide" box in the navigation panel at left. To return to this page, click on the "thorn icon" in the margin at left. Articles from the previous months are archived and can be viewed by clicking on the listings in the left margin. Oh, and please don't write to me for a catalog or pricelist.....this is an information site only, not a commercial nursery. If you wish to buy roses, see my sponsor, The Uncommon Rose.

Soil Analysis: Just Do It!
by Anastasia Dimitriu Shupp

Getting your soil analyzed will likely be one of the best investments you ever make for your garden. Why? Armed with your soil’s exact composition, you will know—rather than having to guess—what you need to do in order to grow better roses, vegetables, flowers, plants, and trees.

Un-named Gallica seedling
This concept was graphically illustrated to me when a friend of mine who is in the landscape consulting and pest management business shook her head after examining my "virgin" soil. My backyard was comprised of what remained after the builders of my housing complex removed any topsoil that had existed so that they could build on a solid foundation. I had assumed that the reason rainwater wasn’t draining was due to a hardpan condition, but Tracey guessed it was a sodium problem…a bad one. She strongly urged me to get my soil analyzed, but for the longest time I did what many novice home gardeners do: I whined and made excuses why I couldn’t afford to have the analysis done. After all, I was having raised beds put in with brand new soil and built-in drains, so why did I have to care what my native ground was made of?

Tracey explained the concept of "horizons". Soil is made up of three distinct layers called horizons "A", "B", and "C", and is topped with a layer variously known as "duff", "detritus", and "humus". The "C" horizon is the deepest, and is generally comprised of rocks and bedrock. It is the mineral component of the soil. The "B" horizon has smaller rocks and more weathered materials such as clays, the mineral calcite, and oxides. The "A" horizon is the upper and most weathered layer. It contains the highest level of organic debris of the three layers. Humus is decomposing organic matter. The area where it and the "A" horizon meet is called "topsoil", and is the richest, most fertile part of the soil. Since most plants root in the topsoil, the humus and the "A" horizon are where the gardener must concentrate the most amount of care. Unfortunately, many of our urban soils are stripped of topsoil and sometimes the entire "A" horizon is disturbed, leaving only a mixed "A" and "B" horizon.

Un-named Gallica seedlingWhat my backyard was comprised of was essentially the "B" horizon, meaning that what I had to work with was not suitable for gardening…and wouldn’t be for some years. It needs continuous work to improve it to an "A" horizon, upon which I then have to add topsoil. In other words, just putting in raised beds was not going to solve the underlying problem. Drainage, for example, would be all right in the silt loam I had bought to fill the beds, but as soon as water hit the underlying native ground it would pool between the two layers. This means that the drainage problem wouldn’t have been solved at all: it would have just moved relatively lower.

In frustration I told her to go ahead and have my soil analyzed, but I wasn’t expecting to learn much. I mean, "everyone" knows that adding gypsum to "tight" soil will loosen it up. Tracey agreed, and while we waited for the labwork to come back she had me put down a lot of gypsum—eight pounds per 1,000 square feet—because she could tell by looking at it that my soil was bad off.

When she got the results, even she was shocked by how awful Mira Mesa soil is. In fact, the lab—based in El Segundo, California—had never seen such results. Eight pounds of gypsum per 1,000 square feet? Try just under 170 pounds of gypsum per 1,000 square feet for six inches of depth! The pH was off, too, but it seemed that the very alkaline pH was about the least of my worries. The following are the values from some selected measurements. My comments are italicized; everything else is from the report itself.

Ratio of calcium to magnesium needs to be more than 2 or 3

  • calcium: 351.40 mg/kg—moderate
  • magnesium: 563.03 mg/kg—very high

The proper ratio of calcium to magnesium is reversed in my soil (in other words, there should be at least two or three times as much calcium as there is magnesium, but my soil contains almost twice as much magnesium as calcium). This means that if I were to apply to my soilwhich is already nearly toxic with magnesiumthe popular "basal break booster" Epsom salts (magnesium sulfate), I would kill just about everything.

Sodium should be less than potassium

  • sodium: 382.35 mg/kg—very high
  • potassium: 45.92 mg/kg—low

Tracey’s hunch was right: the amount of salt in my soil is tremendous.

Increasing problems start at 4 – 6 SAR

  • SAR: 6.6—high

SAR is the Sodium Absorption Rate

pH value

  • 7.87—very high

Estimated soil texture

  • loam

Tracey had guessed that my soil was a type of loam, and had urged me to buy backfill with a similar composition to the native soil to lessen drainage problems that can arise when dissimilar layers meet. The silt loam that I purchased from Best Soils ended up being the right choice.

Relative infiltration rate

  • very slow

This is the rate at which water filters through the soil.

Estimated gypsum requirements-lbs./1000 sq. ft.

  • 168

Out of Yesteryear
The quantity of metals in my soil
aluminum, arsenic, barium, cadmium, chromium, cobalt, lead, lithium, mercury, nickel, selenium, silver, strontium, tin, and vanadiumall came back very low or not detected.

From these readings, Tracey was able to design an improvement plan tailor-made to my conditions. If I hadn’t have taken Tracey’s advise to go ahead with the soil analysis, I don’t think we would have been able to make a dent in the problems with my native soil…and my roses, vegetables, and fruit trees would have suffered or died as a result. Worse yet, I may have applied common additives—such as Epsom salts—that could have had disastrous consequences. I have heard reports from other homeowners in my complex that their bougainvilleas are dying, and that it can take as many as four times of laying sod before the grass will grow. Since I’m a board member of our homeowners association, I’m sharing what I have learned with whoever is interested in the hopes of solving some of our landscaping problems…now that I know what the problems are!

Please: Do yourself—and your garden—a favor, and get your soil analyzed. All it takes is a handful of soil in a plastic baggy and a check for the work. The peace of mind and the knowledge you will get back will be more than worth it.

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