| SOIL
AMENDMENTS
Soil amendments are sometimes beneficial to landscape plantings. If used, they should be added before planting, so plant roots are not disturbed. There are two types of soil amendments: non-chemical and chemical. Descriptions and recommended uses follow. Non-chemical Soil Amendments Examples include decomposed products (either commercially prepared or from backyard compost piles) such as compost, lawn clippings, and peat moss. These soil amendments are mixed with landscape soil to increase water-holding capacity and improve soil structure. Since they supply only small amounts of nutrients, soil amendments should not be thought of as fertilizers. While amendments are often useful, there are cases where you may be better off without them. Here are some general guidelines concerning nonchemical soil amendments: Most soils in the High Desert are sandy loams and loamy sands. As long as your soil is a consistent texture without layers or hardpan, you do not need to amend it to conserve water or achieve adequate plant growth. This is particularly true in areas to be planted with turfgrass or trees. By properly scheduling irrigations, you can avoid water waste without adding amendments. Soil amendments are useful in vegetable and flower gardens, and in shrub plantings. Amendments should be mixed thoroughly with original soil, at least 40% by volume. Amended soil should be at least 1'-deep for gardens and at least 1-1/2" deep for shrub plantings. Never add only a few inches of soil amendment. This causes layering and reduces downward movement of water. It is better to not amend a soil than to add only a shallow layer. Use only decomposed products as soil amendments. Freshly cut turfgrass, green manure and similar products should be composted first. A rule of thumb is: if it's still recognizable, it's not ready for use! Chemical Soil Amendments Gypsum (CaSO4) is useful for reclaiming soils with high levels of sodium. It will not correct problems caused by layered soils. A simple test will help determine whether your soil would benefit from gypsum: Remove the bottom of two coffee cans. Replace the bottoms with window screen, placing a paper towel filter on top of each screen. Fill each can with one pint of soil, and allow it to dry. Add one tablespoon of gypsum to one coffee can, mixing it thoroughly into the soil. Set each coffee can on an empty coffee cup; fill each can with tap water. Collect
drainage water until 1/2 pint or more is collected from the gypsum-treated
sample. If more than twice as much water has drained from the amended
soil, your soil contains excess sodium. Likely, a chemical amendment
such as gypsum will help reclaim the soil. Soil Alkalinity Most High Desert soils are alkaline, with pHs between 7.5 - 9.0. A soil test is useful to determine soil pH. Alkaline soils tie up necessary plant elements, such as phosphorus, manganese, zinc and iron. Even if these elements exist in the soil, they are not available to your plants until the soil is neutralized. A pH of 7.0 is neutral, although most plants grow well in pHs between 6.0 - 7.5. Ammonium sulfate is a popular and useful fertilizer in the High Desert. It serves a dual purpose by providing both nitrogen and sulphur. The sulphur reduces pH. A soil test is useful to determine proper rates of sulphur. It is usually necessary to apply sulphur over a relatively long time period since reducing alkalinity takes repeated sulphur applications.
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