Ways to Treat High Potassium in Soil
Of the three nutrients that all plants need in the largest amounts, potassium is the least understood. Unlike nitrogen and phosphorous, it does not form any part of the plant, but exists in the soil, where it acts as a catalyst to enzyme reactions necessary for plant growth But as with all beneficial soil components, too much potassium can be detrimental to plant growth, as it interferes with the uptake of other substances. There are ways to combat this, however, to assure that your plants get all the nutrients they need and in the right amounts.
The primary purpose of fertilizer is not to feed the plant but to enable it to more readily absorb the nutrients present in the soil. A soil test is the only accurate and definitive way to determine how much of any substance is present in your soil. You can send samples to your local county extension or to a testing lab, or you can use a test kit purchased from a nursery or garden center. If the test shows a high concentration of potassium, it could indicate dense clay soil, which traps the mineral and allows it to build to highly concentrated levels. The results could also mean that the fertilizer you are using contains too much of it.
Establishing the right balance between potassium and other soil components is more about controlling how much goes into the soil than trying to reduce it once it’s there. If a soil test indicates a high level of potassium, literally start from the ground up by not adding more to it in the form of a multipurpose fertilizer. Typical fertilizer blends are generally composed of the three most important substances — nitrogen, phosphorus and potassium — which are indicated on the packaging by the letters N, P and K. Selecting a blend that is low in potassium, or K, or contains none at all, is a first step in assuring that it doesn’t build up to unsuitable levels in the soil.
Plant Distress Signals
Too much potassium disrupts the uptake of other important nutrients, such as calcium, nitrogen and magnesium, creating deficiencies that usually produce visible effects. A calcium deficiency produces irregularly shaped new leaves and blossom end rot on plants, such as tomatoes (Lycopersicon esculentum ), that produce fruit. As frost-tender plants, tomatoes can be grown in U.S. Department of Agriculture plant hardiness zones 2 to 10 if set out into the garden once the soil has warmed to at least 60 degrees Fahrenheit. A nitrogen deficiency is suspected when older lower leaves on plants turn yellow while the rest remain a light green. Plants lacking magnesium will exhibit yellowing of the edges of older leaves that may also develop an arrowhead shape in their centers. While adding more of these substances to correct the imbalance may help, the excess potassium will most likely impact their long-term effectiveness.
A Healthy Balance
When present in the soil in proper amounts, potassium helps with photosynthesis, the process by which plants manufacture their own food using the sun’s energy; helps plants absorb other nutrients more efficiently; creates a favorable environment for microbacterial action; and provides turgor, or the ability of plants to stay upright. Distribute excess potassium more evenly by thoroughly working dense soil until it is loose and friable. Dilute and flush out large amounts of potassium by watering the soil any time it appears dry to a depth of one inch. Schedule any fertilizing within several weeks before planting, so that the potassium doesn’t have time to accumulate during the off-season. To minimize long-term potassium buildup, consider using aged or composted animal manure as a substitute for commercial fertilizers, as its components break down more slowly to keep up with plant demand. If using manure, apply it at a rate of 40 pounds for every 100 feet, and work it into the soil to a depth of 6 to 9 inches.
Ways to Treat High Potassium in Soil. Of the three nutrients that all plants need in the largest amounts, potassium is the least understood. Unlike nitrogen and phosphorous, it does not form any part of the plant, but exists in the soil, where it acts as a catalyst to enzyme reactions necessary for plant growth But …