Information About Different Types of Fertilizers

If you’re looking for information about the many types of fertilizers, then keep reading.

Learn the answer to ‘what is fertilizer?’

Learn what the fertilizer numbers (or fertilizer analysis) of NPK fertilizers mean.

And learn about some of the more popular sources of natural fertilizer that are being used more frequently as a garden fertilizer. 

What is Fertilizer?

Have you wondered?

It’s often referred to as plant food, and in a way, it is.

But that’s not quite an accurate description of fertilizer.

You could think of fertilizer as more of a plant food supplement. Sort of like vitamins for humans. Plants manufacture their own food through the process of photosynthesis.

But the various types of fertilizers supply them with chemicals and minerals that they can’t manufacture for themselves.

Just as our bodies require many different elements – things like iron, manganese and calcium, so do plants. They need these elements to grow and be productive, even though they are capable of producing their own food. They absorb these elements through their roots and even through their leaves.

Adding a garden fertilizer to your soil is just a convenient method of ensuring that your plants have all of the elements that they need. 

What do the ‘Fertilizer Numbers’ of NPK Fertilizers Mean?

NPK stands for nitrogen, phosporus and potassium. These are the 3 elements that plants need most (besides water, carbon dioxide and oxygen). Fertilizers are often labeled according to their relative percentage of these elements.

So if you have a fertilizer labeled 10-10-10, that means that the fertilizer contains nitrogen, phosphorus and potassium in equal quantities. (The numbers are always ordered in the sequence of nitrogen-phosphorus-potassium.)

And the numbers indicate the percentage of an element by weight. So in this example, 10% of the total weight of the fertilizer is nitrogen, 10% is phosphorus and 10% is potassium.

What’s the remaining 70% of the fertilizer’s weight? Usually it’s an inert material that’s used to stabilize and buffer the N-P-K; clay is often used for this purpose.

Some fertilizers also contain some of the other elements that plants need in much smaller amounts than N-P-K. These are called trace elements, and are noted on the fertilizer label when included. Trace elements (there are many!) are also necessary for healthy plant growth, but in much smaller quantities than N-P-K.

Many trace elements are needed in such small quantities that you can depend upon your soil to provide a sufficient amount. But some soils are deficient in certain trace elements which are needed in larger quantities, in which case you’ll need to be sure to include those in your fertilization program.

(The soil test that you perform yourself or have done for you during garden soil preparation will alert you to any trace elements your soil may need.)

When you’re choosing an N-P-K fertilizer, you’ll want to keep in mind the primary ways in which plants utilize the elements of N-P-K: Nitrogen contributes primarily toward vegetative growth; phosphorus helps to promote healthy root growth and blooming and seed-setting; potassium contributes to the general health of the plant and is also important in blooming and fruit production.

So an N-P-K blend that’s skewed heavily toward nitrogen might be great for greening up a lawn, but not so great for flowering or fruiting plants. Tomato plants, for example, do better with a fertilizer containing less nitrogen and more phosphorus and potassium.

That’s why you don’t want to buy one blend of fertilizer and use it for everything you grow. There are many different blends and types of fertilizer. Whatever you’re growing, there’s sure to be a perfect fertilizer for it. 

Some of the More Popular Types of Natural Fertilizer

In reality, the term ‘natural fertilizer’ is somewhat of a misnomer. All fertilizers are natural, even those made from petroleum. (After all, petroleum is a ‘naturally occurring’ element.).

But most of what is called natural fertilizer is derived from an organic source such as fish or seaweed, something that was recently living. (To belabor a point, petroleum based fertilizers are also derived from organic sources that were once living -- a very long time ago.)

I’ll save the discussion of organic vs. inorganic fertilizers for another page. But here’s a bit of information about some of the most popular types of fertilizers that are considered to be natural fertilizers:

  • Seaweed fertilizer or kelp fertilizer
    Tends to be higher in P than N or K, and is usually a rich source of trace elements.
  • Fish emulsion fertilizer
    High in N, and low in P and K. And yes, there is a smell to contend with!
  • Guano fertilizer
    Most often made from the droppings of bats or seabirds. Usually high in P, low in N and K.
  • Bone meal fertilizer
    Made from the ground bones of slaughtered animals. Very high in P, low in N and K.
  • Blood meal fertilizer
    Made from the dried and granulated blood of slaughtered animals. Very high in N, low in P, very low in K.
  • Worm castings
    Castings is a euphamism for poop. Makes a very fine fertilizer, though. It’s fairly balanced in N-P-K, with usually more of P than N and K.
  • Corn gluten meal
    A byproduct from the processing of corn. It’s a high N fertilizer, with negligible quantities of P and K. Be careful to use corn gluten meal only on established plants, because it’s been shown to inhibit the germination of seeds.

So there you have some facts about different types of fertilizers. Perhaps not everything you ever wanted to know about fertilizer (or maybe far more!), but hopefully a good start.  

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