What is the purpose of fertilizer? Plants need sixteen essential
nutrients in order to grow. These are:
Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorus, Potassium,
Calcium, Iron, Magnesium, Boron, Manganese, Copper, Zinc,
Molybdenum, and Chlorine.
These elements are needed in different amounts and are used up at
different rates by the soil. The idea of fertilization is to add
back to the soil what the plants have taken out.
What fertilizer you add will depend on what nutrients you need to
add to the soil. This will depend on what type of plants you are
growing (different plants have different nutrient needs), the
type, and the soil condition. Something to keep in mind is that
adding too much of one nutrient can cause some serious problems.
There could be the potential of runoff into ground water, damage
the crop, and a total waste of money. As you might begin to see,
soil fertilization is a very "situation dependent" process.
(For anyone considering any serious gardening or farming, a good
place to start might be a soil test. Your local extension agent
should be able to help you out here. This will indicate what the
soil needs and what it has enough of so you know what problems
The fertilizer should not contain anything you don't want to add
the soil such as heavy metals, weed seeds, or plant diseases.
is a common sense way of avoiding trouble in the future.
Two main fertilization strategies come to mind. First is "Feed
Plant". This is the idea used my most farmers in the United
today. They apply a readily available non-organic fertilizer to
the soil with the idea that the plant will take up what it needs.
Pick up any bag or bottle of fertilizer at your local store and
odds are this is the type of fertilizer you have. The fertilizer
will contain chemicals like Calcium nitrate and Potassium
phosphate. Inorganic fertilizers are a very well researched
Coming up with some new mix would be difficult and obtaining the
minerals needed might be difficult.
On the other hand, organic growers "Feed the soil". The idea
is to add organic material back to the soil and let the
microorganisms break these down into a form the plants can use.
This method prevents the nutrients from being washed out of the
soil by the first good rain, but it may take weeks or months for
the nutrients to become available to the plants. Examples of
things organic growers might add include composted plant
kelp, and bat guano. Because so many gardeners and organic
compost their plant waste, they have a good source of compost to
add back to the soil. They might add a bit of another fertilizer
to balance out what the soil needs. Many add manure from a local
farm to their compost to provide more nitrogen.
So what does that leave us with? Inventing something new with
fertilizers might be a bit difficult. As I said before, what you
use really depends on what the soil needs. I wish I could offer
you something new or original, but I am afraid that I will be
repeating what has been done for years.
Concerning some new ideas for a project, you might check around
Library. There are some really good links for science fairs
there. In addition, I might have a few suggestions for you if
happen to be interested in hydroponic plant systems. Feel free
Well, that about does it. If you have any more questions, please
e-mail me! Keep asking those questions!
Eric J. Biddinger
Grad Student - Department of Horticulture
Penn State University firstname.lastname@example.org