Section 6: Soil, Other Growing Media, and Fertilizer

Glossary

Lesson 3: Fertilizers


In order for a plant to grow and thrive, it needs carbon, hydrogen, and oxygen. These are readily available from air and water, and thus are in plentiful supply. In Section 5 of this course, you learned about additional plant nutrient requirements. You learned that the additional requirements consist of the following:
Nitrogen, phosphorus, and potassium.
Sulphur, calcium, and magnesium.
Boron, cobalt, copper, iron, manganese, molybdenum, and zinc are the essential seven.

Without nitrogen, phosphorus, and potassium, the primary macronutrients, a plant simply cannot grow because it cannot make new cells without them. It would be just like a car factory running out of steel, or a road paving crew running out of asphalt.
In nature, the macronutrients come from the decay of plants that have died. If any of them are hard to obtain from the soil, it will limit the growth rate for the plant.

The Purpose and Use of Fertilizer

To make plants grow faster, you must supply the primary macronutrients that are needed, in readily-available form. That's the goal of fertilizer!


Most fertilizers supply just nitrogen, phosphorus, and potassium because the other chemicals are needed in much lower quantities and are generally available in most soils. Remember that it is these three elements that are necessary for growth.

Bags or containers of fertilizers usually have three numbers on them that tell you the percentages of available nitrogen, phosphorus, and potassium. This is know as the fertilizer's NPK analysis (N = nitrogen, P = phosphorus, K = kalium, neo-latin for potassium).
For example, a 16-8-6 fertilizer has 16% nitrogen, 8% phosphorus, and 6% potassium. The rest of the fertilizer, 70% for this example, is known as ballast and has no value to the plant.

Sometimes an NPKS analysis is used; the fourth number then gives the percentage of sulphur content (S = sulphur).

Fertilizer called "Lawn Starter" works because of its high phosphorus content, which helps the root growth of a new lawn.
Source: http://www.learn2grow.com

The Different Forms of Fertilizer

Fertilizers are broadly divided into two types:

Organic fertilizers are composed of enriched organic matter, either plant or animal. The composting of dead plant and animal material is a rich source of organic fertilizer.
Inorganic fertilizers are sometimes referred to as synthetic or artificial fertilizers, because they are artificially synthesized. Most commonly, it is in granulated or powdered form, but it can also be in liquid form.
Liquid fertilizers have the advantage of immediate effect.



Bonemeal, a mixture of crushed and coarsely ground bones, is an organic fertilizer high in phosphorous content.

The use of synthetic inorganic fertilizers has increased steadily in the last 50 years. In that period of time the use of artificial nitrogen fertilizer has increased almost twenty-fold.
However, more recently, the use of organic fertilizer is on the rise again as people are resorting to "green" or environmentally friendly products. Although organic fertilizers usually contain fewer nutrients, some people still prefer organic because of the natural ingredients.


A Compost Pile


Kitchen waste, garden refuse, lawn clippings, and leaves from trees are added to a compost pile.

What appears to be a heap of junk will soon be on its way to decomposition. The result will be a rich, moisture-retaining organic fertilizer that will serve to feed plants and
re-condition the soil.

The decomposition is caused by the many microorganisms which live naturally in soil.