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Brown Soil Isn’t Always Rich Soil

Your plants can’t tell you what they need; a soil test can

I recently received photographs of dead and dying plants along with soil test results sent by a Bay Weekly reader. The reader had sent numerous plant samples to a university for analysis only to be told that the injury was due to a fungus. As I studied the photographs, I could not identify a fungus that would cause such symptoms, so I requested a complete soil analysis.
    The soil test results told me that the plants were starving for essential nutrients. The calcium levels in all of the samples were extremely low, while the magnesium levels were medium to optimum. The phosphorus levels were extremely low, while the potassium levels were in the medium to high range. Some of the pH readings were below 4.5. Boron levels in most samples were only traces.

Plant Corn in Blocks

Four to five short rows of corn planted side by side will produce higher quality corn than one long row. Corn needs cross-pollination to produce nice full ears of kernels. Since the pollen in the tassels must drift down to the silk at the tip of each ear, planting in blocks compensates for changing winds. Pollination occurs over a relatively short period. To assure good pollination, I often walk through my block of corn early in the morning with outstretched arms to shake the pollen from the tassels.

    The low calcium levels in conjunction with high magnesium resulted in an imbalance that made the magnesium toxic. Plant nutrition demands soil with higher levels of calcium than magnesium. Calcium is as important in plants as it is in humans for strong cell wall development. What appeared to be a disease problem in the plants was actually collapsed cell walls from the lack of calcium. Magnesium is part of the chlorophyll molecule, but if the plant cannot maintain cellular structure, what value is chlorophyll?
    The low pH in the soil meant that aluminum toxicity could also be contributing to the problem. Most of our soils contain aluminum, but it is not toxic because its solubility is easily controlled by raising the pH above 4.5.
    I recommended liming with agricultural-grade limestone plus generous amounts of gypsum (calcium sulfate). The calcium in gypsum is more readily available than calcium from limestone. A very soluble form of calcium was needed to immediately correct the glaring calcium deficiency. I also recommended calcium nitrate fertilizer applications around azaleas and related species that do not require acid soils.
    The phosphorus-deficient soil was treated with superphosphate. I recommended solubor to correct the boron deficiency.
    This is one of many problems that could not have been solved without soil test results from a reputable laboratory.
    I recommend sending soil samples to A&L Eastern Laboratories, Inc., 7621 White Pine Rd., Richmond, VA 23237. Get information on taking soil samples and the types of soil testing at

Ask Dr. Gouin your questions at [email protected]. All questions will appear in Bay Weekly. Please include your name and address.