MadSci Network: Agricultural Sciences

Re: What could I use to make my own fertilizer?

Date: Sat Feb 21 16:59:58 1998
Posted By: Eric Biddinger, Grad Student, Horticulture, Penn State University
Area of science: Agricultural Sciences
ID: 887663364.Ag

MadSci Network: Agricultural Sciences


This is a really interesting problem!

What is the purpose of fertilizer? Plants need sixteen essential nutrients in order to grow. These are:
Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorus, Potassium, Sulfur, 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 soil 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 to 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 you might encounter.)

The fertilizer should not contain anything you don't want to add to the soil such as heavy metals, weed seeds, or plant diseases. This is a common sense way of avoiding trouble in the future.

Two main fertilization strategies come to mind. First is "Feed the Plant". This is the idea used my most farmers in the United States 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 area. 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 here 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 material, kelp, and bat guano. Because so many gardeners and organic growers 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 the Mad Scientist Library. There are some really good links for science fairs there. In addition, I might have a few suggestions for you if you happen to be interested in hydroponic plant systems. Feel free to e-mail me.

Here is a link from the University of Florida with some more information about fertilizer:
Plant Nutrients and Fertilizers for the Non-farmer

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

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