Nearly all lawn fertilizers contain large amounts of nitrogen and small amounts of phosphorus, potassium and other elements. This is because nitrogen is the element missing from most soils and its the stuff that grass uses the most.
While nitrogen may be the top nutrient, its not the only one required. Actually there are 17 nutrients that are essential to lawns. All 17 are equally important and must be present for a lawn to survive. They vary only in how much the grass uses. Macro-nutrients, such as carbon, hydrogen, magnesium, and calcium, are picked up by the plants in the largest quantities. Micro-nutrients, such as nickel, manganese, molybdenum, chlorine, boron, copper, zinc, and iron, are used in small amounts. Most come from the soil, but some are obtained from the atmosphere.
Because yellowing and poor color are common symptoms among most nutrient deficiencies, its difficult to identify which element is missing from the lawn.
The Big Three
A key component of many chemicals within a plant, nitrogen takes part in nearly every plant function. It is critical to chlorophyll, the chemical that gives plants their green color and allows them to manufacture their own food. When nitrogen is low, lawns turn pale to yellow and grow slowly.
Most soils contain plenty of phosphorus, which is a mineral. However, it may not be readily available to plants. The main role of phosphorus is in shoot and root growth. Deficiencies are rare. If grasses do need phosphorus, they first turn unusually dark green, then purple, and they may be susceptible to disease.
The main time you might see problems is when starting a lawn. Phosphorus is immobile in soil and a small developing root system may be unable to tap the supply. Once the roots grow, they are better able to obtain phosphorus.
Potassium is in involved in overall plant health, resistance to stresses such as excessively high and low temps, disease resistance, wear tolerance, and cold hardiness. No easily recognized color changes occur, so it’s hard to identify a deficiency.
Other Important Nutrients
Iron is the most likely micro-nutrient to be deficient, particularly in high pH soils. It is involved in chlorophyll production, so a deficiency turns the grass yellow. Many high quality lawn fertilizers contain iron.
Calcium and magnesium
Because of its involvement in cell wall development, cell division, and growth of young shoots and roots, calcium is important to plant vigor. The main symptom is slow growth.
Magnesium is a constituent of chlorophyll, so the primary symptom of a deficiency is yellowing. Lime, used to raise soil pH, supplies both calcium and magnesium.
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