Excess phosphorus in soils causes yellowing or bleaching of the leaves of plants, especially in species that lack deep roots. Too much phosphorus sometimes even kills plants that require acidic soil, such as azaleas. If excess garden phosphorus enters streams and lakes via runoff, it causes overgrowth of algae and weeds. Whenever soil testing shows excess phosphorus, corrective action benefits both the garden and the environment.
Things You'll Need
- Pine bark
- Blood meal
- Ammonium sulfate
- Magnesium sulfate
- Iron and zinc solution
- Soil-testing kits
Stop adding organic products that increase phosphorus levels in the soil. The worst culprits include manure and other organic composts. If you must have an organic mulch or an organic nitrogen-builder, substitute pine bark or blood meal. These products are low in phosphorus.
Stop using phosphorus-containing commercial fertilizers. Fertilizer containers normally describe the formula with three numbers -- the middle one indicates the amount of phosphorus. A fertilizer with a middle number of zero does not contain phosphorus or phosphates. For example, choose fertilizers such as ammonium sulfate or magnesium sulfate.
Add iron and zinc to help restore health to the garden. Because a high phosphorus level prevents absorption from the soil, use a sprayer to apply a solution of these minerals to plant leaves.
Test your soil regularly. Many state agricultural extension offices provide inexpensive soil-testing services. Avoid phosphorus-containing fertilizers or amendments as long as your soil remains high in phosphorus.
- The Texas A & M University System: Phosphorus -- Too Much and Plants May Suffer
- Washington State University: Soil versus Foliar Fertilizer Application
- University of Minnesota: Preventing Pollution Problems from Lawn and Garden Fertilizers
- Rutgers Cooperative Research & Extension: Fertilizing the Home Lawn
- Washington State University: The Myth of Beneficial Bone Meal
- University of Arizona Cooperative Extension: Backyard Gardener
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