Soil and Plant Problems.
Sometimes a gardener runs into this special problem: some plants do poorly regardless of care, or the whole garden grows too slowly, looks stunted, and has a high mortality rate. If this happens to you, examine the seven special soil problems and solutions listed below. If none of them provide an answer to your situation, read our article on drainage.
Alkaline soil, common in light-rainfall areas of the Southwest, is soil that is high in calcium carbonate (lime) and certain other minerals. Many plants will grow well in a moderately alkaline soil, although camellias and other acid-loving plants will not. Areas with softened water are quite likely to have alkaline soil. The sodium in soft water is good for household use hut poor for plants. Hard water, on the other hand, is ideal for garden watering.
Large scale chemical treatment of extremely alkaline soils is expensive and complex. A better bet is to plant in raised beds and containers using a good soil mix.
Acid soil is at the other end of the scale from alkaline soil. It is most common in areas of heavy rainfall and is often associated with sandy soil (but ocean beaches are rarely or never acid). Mildly acid soils cause little trouble, but an intense acid condition is highly undesirable for most plants.
Ground limestone will help to neutralize an acid-reacting soil, since all acid soils are low in calcium (lime). Your choice of fertilizers can be another very important factor in controlling acidity; some fertilizers can actually increase soil acidity. Some plants—azaleas, rhododendrons, and camellias to name a few—prefer soil that is moderately acid.
SALTS IN THE SOIL
An excess of salt in the soil is a widespread problem in arid and semi-arid regions. It can prevent germination, or, if plants are already growing, it stunts them and in advanced cases burns the foliage and finally kills them. Its presence can usually be detected by a white deposit of salt on the surface of the soil. Salts in your water and fertilizer can remain in the soil. Periodic slow, deep watering will help wash the salts beyond plant roots.
Most soils, left to themselves, yield the three major plant nutrients—nitrogen, phosphorus, and potassium—only very slowly. Even the richest soil cannot continue to provide an ample amount of these vital elements year after year.
Fertilizers—either chemical or organic—are the quickest and easiest answer to a nutrient deficiency. Many balanced fertilizers containing all three major elements are available.
There are also formulations of nitrogen, phosphorus, or potassium compounds that provide these nutrients separately. Manure and well rotted compost are also beneficial in varying degrees to nutrient-shy soils, but are more effective in their ability to build up the soil’s humus supply.
CHLOROSIS—LACK OF IRON
If the leaves of some plants turn yellow, but veins stay green, it may be caused by an iron deficiency. Chelating (pronounced key-lating) agents or iron sulfate can help to control chlorosis. Buy either one at a nursery or garden store and follow label directions.
When you build on filled land, the soil has been compacted purposely to certain standards. Also any trucks and bulldozers used in the construction of your home may have caused accidental packing of soil. Little will grow in compacted soil. To counteract the effect, grow a crop of deep-rooted grass such as annual rye, then plow it under before adding amendments. If you’re planting trees, have a well digger dig some 3-foot-deep holes, then improve the removed soil with amendments and refill around the root ball.
If there is a layer of hardpan within the top 18 inches, plant roots won’t grow and water won’t penetrate. There are two possible solutions: either drill through shallow hardpan to make a vertical gravel drain, or get advice from an engineer on how to install drain tile horizontally.
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Tim Lundie, Editor