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Fertilizer NumbersWhat do those numbers on a bag of fertilizer mean? |
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Transcript: Fertilizer Numbers
You may have noticed that when you go and purchase fertilizer, there's three numbers on the fertilizer bag.Actually, the three numbers represent the three primary nutrients that plants need: nitrogen, phosphorous and potassium. They're listed as a percentage of those nutrients and always in that order.
For example, an 8- 2- 4 fertilizer contains 8 percent, by weight, nitrogen, 2 percent phosphorous and 4 percent potassium. A fertilizer that's 9-1-1 would contain 9 percent nitrogen, 1 percent phosphorous and 1 percent potassium.
These can occur in different combinations and different ratios, but they all represent how strong or how concentrated a fertilizer is. So a 16-4-8 would be twice as concentrated as an 8-2-4, for example.
What do these numbers mean and what do the nutrients do? Well, nitrogen is very important in plants having good vigor and a good dark green color. The middle number phosphorous is important for rooting and also for blooming. But in most of our Texas soils, we already have enough phosphorous. The third number, potassium, on the other hand, is important with cold hardiness and also plays a role in fruiting and blooming for our plants.
Typically in east Texas soils, potassium is low and in central and west Texas you usually find that it's present in large enough amounts.
Now, it's important to start with a soil test. If you begin with a soil test, you know what your plants potentially need in the way of a fertilizer and you can purchase a product accordingly.
With your common sense gardening tip on making sense out of those numbers on a fertilizer bag, I'm Skip Richter.
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Last Updated:
July 6, 2006