Lawn fertility is one of the most important aspects of lawn maintenance, so knowing what is in a bag of lawn fertilizer and how it will affect your lawn is important. Each lawn fertilizer should be clearly labeled to indicate the amount of elemental nutrients in the product. The standard convention for naming these quantities is a percentage ratio. The three main numbers in the fertilizer label stand for the percentage of nitrogen (N), phosphorus (P) or potassium (K). For example, if a 50 pound bag of manure is labeled 20-20-20, it means it has 10 pounds each of nitrogen, phosphorus, and potassium (20 percent of 50 pounds).
The selection of the appropriate fertilizer mix should be based on the type of soil, soil test results and other factors such as:
If you get a soil test from a university advisory service or a professional test laboratory, the results will give specific recommendations on how to improve or fertilize the soil to create optimal growing conditions. This information includes a recommendation on how much potassium your soil needs for good grass growth.
Potassium in nature
Potassium (chemical symbol K) is one of the three most important elements for plant nutrition, along with nitrogen (chemical symbol N) and phosphorus (chemical symbol P). Potassium is broken down and in the form of Potash which refers to salts containing potassium in water soluble form. It is most often used for fertilizers in its inorganic versions – potassium chloride (Potassium chloride) and potassium sulfate (Potassium sulfate).
Potash is abundant in many different soils, but not all is available to the plant. Soils with a high clay content provide hiding places for potassium to bind it, making it unavailable. Of course, potassium is also found in organic fertilizer and compost sources, such as algae products, wood ash, and animal feed and bedding material.
How grass uses potassium
Along with nitrogen and phosphorus, potassium is one of the essential macronutrients that plants need in large quantities for growth and vitality. Potassium is important in the synthesis of some plant components and the regulation of processes, including the more efficient use of nitrogen by the plant. Addition of soluble potash (K2O) to the ground helps the grass withstand stress, drought and disease. Potassium in particular helps with maintenance Turgor pressure in the cells of the plant, which has a positive influence on drought tolerance, cold hardness and disease resistance. As a result, a lack of potassium in the lawn can make it more susceptible to drought, winter injuries and disease.
Potassium is mobile in plants and can be absorbed in larger quantities than are needed for optimal growth. It can be difficult to tell if excessive consumption is a problem as little is known about the optimal levels of potassium in the lawn. While soil surveys are the best way to determine the nutritional needs of the lawn, in some cases it can be difficult to identify more than a potassium deficiency. The plant-available potassium in the soil is constantly changing and depends on many interrelated factors. An overall healthy soil should be the goal and aim for potassium levels that are naturally balanced – or by adding fertilizers.
Fertilizer mixtures with a high K (potassium) content are often sold as winter fertilizers due to the effect of potassium on the cold hardness of grass. Consumers need to be aware that terms like winterproof or Summer fertilizer are more marketing terms than actual statements about the benefits of a fertilizer.
Risk of expiration
Since potassium salts are water-soluble, they are easily washed out into the groundwater and, if overused, can also be present in the rainwater runoff. However, potash is not a known pollutant and rarely occurs in concentrations that are toxic to humans and animals. Potassium does not deprive water of the available oxygen, as it does with some of the other elements found in fertilizers.
Excess potassium is relatively harmless to the lawn and the environment, but too much potassium likely means excess nitrogen and / or phosphorus, both of which can be harmful. And overuse of nitrogen fertilizers can damage the lawn itself – either from too much tip growth or possibly from burning the grass plants.