Fertilizer:What the numbers mean.
The Numbers Game:
There are three main numbers on a bag of fertilizer that represent the percentage of the main nutrients used by plants,NITROGEN, PHOSPHORIC ACID and POTASH.
They may be available in different ratio's such as 21-3-6 or 8-15-30. Some may not be present at all such as in speacialty fertilizers like 22-0-20. These fertilizers, with different components, may be used to make certain nutrients more available to plants. A main consideration when choosing a fertilizer is the rate at which the fertilizer breaks down, and is absorbed by plants. The nitrogen in fertilizer is sometimes bonded to a chemical or substance, so that it is released slowly. These slow-release fertilizers have the advantage of supplying nutrients over a longer period of time (up to eight weeks) and are less likely to burn foliage. These fertilizers usually demand a premium price, but are well worth it and are commonly used in the lawn care industry.
The application rate is also provided on a bag of fertilizer, and refers to the amount of fertilizer that should be applied to an area (expressed in square meters or feet) for the proper ratio of nitrogen. Too much fertilizer may cause excessive plant growth, or may even burn and kill the grass. Fertilizer applied too thin may have little effect on plant growth. Always follow the directions on the bag carefully, and remember it is better to apply too little than too much!
What does it do?
NITROGEN: Used in plant growth, mainly in shoots and leaves. Responsible for the green up of grass in spring. Nitrogen is an important ingredient in fertilizers and is used to calculate the application rate of the product. Spring and summer fertilizers are usually high in nitrogen content.
PHOSPHORUS: The second number of a fertilizer formulation, phophorus is important for root growth, and the establishment of seedlings.
POTASSIUM: The last number in a formulation, potassium (or potash), increases winter hardiness and hardening off of plant tissues. Fall fertilizers usually contain higher amounts of Potassium, and reduced amounts of Nitrogen, as lush green growth is not required at this time.
The Big and the Small:
Plants require more than just Nitrogen, Phosphorus and Potassium for proper growth, there are in fact 9 essential macro, and 8 essential micronutrients use by plants. But most of these are available to plants without the need of fertilizers. The macronutrients include; Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Potassium, Calcium, Magnesium ans Sulfur. The micronutients include; Iron, Manganese, Molybdenum, Boron, Copper, Zinc, Chlorine and Colbalt.
The Good, The Bad and the Liquid:
There are countless varieties and manufactures of fertilizer available, but which ones are better, and why do some cost so much more than others? The main difference is in the quality of the product. A basic cheap fertilizer such as 7-7-7 is low in available nutrients, may contain no micronutrients and usually has no slow-release properties. This translates to poor overall results with a temporary green up at best, and the chance of foliage burn. Quality fertilizers, with a high percentage of slow-release nitrogen provide a more balanced, and longer-lasting supply of nutrients. There is a visible difference between the two extremes!
Becoming more popular, especially in the lawn care business, is the use of water soluble, or liquid fertilizers. These are available in slow release form and are convenient when used in conjunction with liquid herbicides. Coverage is more uniform, but more time consuming, than with granular fertilizers.
Organic or Inorganic?
There has been an increase in the amount of organic fertilizers (those obtained from sources such as blood meal or sewage) used in the lawn care industry in recent years. What these fertilizers may lack in the form of high nitrogen content, and slow release properties, they make up in their ability to improve soil structure and organic matter concentrations. Man-made fertilizers tend to be acidic, and add nothing to the make up of the soil. Soil micro-organisms which work to the benefit of grass roots, are enriched by the introduction of organic fertilizers. A good organic soil base helps improve the movement of water and air to the roots, resists compaction and reduces thatch. Consistency, availability and price of organic fertilizers may vary greatly, but are improving as more manufacturers are providing alternatives to inorganic fertilizers.
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