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Understanding the Basics of Fertilizer for the Garden

So you want to grow organically, which means chemical fertilizer isn’t an option. Well, that eliminates about 90% of fertilizers on the garden center shelf, doesn’t it? By understanding the basics of fertilizer for the garden, you can read labels to make the best decision for your garden and the environment.

What do the Numbers Mean?

Today we will just cover what the numbers on fertilizer bags mean. They are formatted in numbers that look like 10-10-10. In order, these numbers represent (to memorize it, keep in mind that it’s in alphabetical order):


This is where that handy, dandy soil test comes in. You’ll want to know your current levels in these nutrients before buying or adding fertilizer because adding too much of a certain nutrient when you already have an abundance of that nutrient can cause a problem. So, if your soil test shows that your nitrogen levels are too high, and you add more nitrogen, you will end up with large, bushy, green plants, but little fruit. This is how we remember what nutrient serves which part of the plant (it’s in reverse alphabetical order, if you want to memorize it):

Nitrogen (SHOOTS)- Phosphorus (ROOTS)- Potassium (FRUITS)

Reading Labels

Organic fertilizers use the same number system as chemical fertilizers to determine nutrient levels, they just don't have perfectly equal amounts of each nutrient. For example, the standard chemical fertilizer is 10-10-10. Feather meal, a natural fertilizer made from ground chicken feathers, is 14-0-0. These are numbers I would look or if I needed nitrogen but my phosphorus and potassium levels were already too high or if I wanted to use a different fertilization product to increase phosphorus and potassium.

How Soil Tests Help

What we are looking for here is balance. Don’t think that you can pour potassium rich fertilizer on the soil and get copious amounts of fruits while ignoring the other elements. You still won’t get fruits from a plant without a good, healthy root system. The most confusing part of reading that soil test is knowing what your numbers should be, so the UofA Department of Agriculture put together this pamphlet to help you understand your numbers.  To learn how to get a soil test in Arkansas, read my post about how to get yours for FREE (for residents).

There are over 60 nutrients necessary for healthy plants and it takes some time to understand what the garden requires. Knowing the basics of the "Big Three" is key to understanding the basics of fertilizer for the garden. Sufficient levels of many of the other nutrients are maintained in soil by simply making and applying compost to your garden yearly, so we don't have to worry about getting all of them perfectly balanced!
What is your biggest question about fertilizing the garden?


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