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  10-15-20, what do the numbers stand for?

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CarolineC blog photos
Joined: 7/14/2007
Location: SE Pennsylvania zone 6b
Posts: 393
Posted: Sep/02/2007 11:07 AM PST

I'm trying to figure out, once and for all, what these numbers on the fertilizer bags mean. The first number stands for nitrogen?? What about the others? Also, what are the general properties and effects of each of the numbers? Like high nitrogen produces leafy, not fruity veggie plants? Do the various numbers make the soil more acidic? More alkaline? Thanks for any insight you have to offer.
EvonneStoryteller photos
Joined: 7/02/2007
Location: Connecticut
Posts: 769
Posted: Sep/02/2007 11:55 AM PST

http://www.ehow.com/how_110528_buy-fertilizer.html
http://www.wikihow.com/Read-a-Fertilizer-Label
http://www.clarkssecretgarden.com/Maine%20Stream%2 0Organics.htm
http://www.compostguide.com/

[I cut and pasted a lot of these lines from the above links.]

nitrogen(N) phosphorus (P) potassium or potash (K)

...percentages of the three main nutrients--N, P and K--are listed, often in an abbreviated form, such as 6-2-4

In the example of 30-10-10...it means that if you had 100 pounds of that fertilizer there would be 30 pounds of available nitrogen, 10 pounds of available phosphorus and 10 pounds of available potassium (or pot ash). The remaining 50 pounds is inert or inactive ingredients.

Know what each ingredient is used for. Nitrogen is for green and growth, Phosphorus and Potassium for fruit, flower and roots.

All-purpose fertilizer (5-5-5 or 10-10-10) is good for general garden use, including flower and vegetable gardens.

High-nitrogen lawn food (29-3-4, for instance) is designed to encourage quick green growth.

Switch the formula at the right time. For most fruits and flowers, you'll want to change the fertilizer formula about two weeks before you want the plant to slow down on the growing phase and switch to the flowering phase. That is when you switch to 0-10-10.

EvonneStoryteller photos
Joined: 7/02/2007
Location: Connecticut
Posts: 769
Posted: Sep/02/2007 11:56 AM PST

con't. I don't know why it is eating this part of my writing! I had to leave the bracket out.

Speaking of timing, I put the third link up about organic fertilization. That article speaks about speed vs. health and long term benefits for plants, people and grazing animals. Thriving soil micro-organisms are important.

As far as alkaline vs. acidic, in many cases you would consider where your soil is to start with and add other ingredients besides the usual fertilizer. Examples of this are lime to boost in the direction of alkaline. Also take into consideration the plants requirements. An azalea likes an acid boosting fertilizer. The fertilizers that are formulated to boost acid or alkaline levels state this as far as I know. I always guessed that these products simply had the key chemical to boost already added to the mix.

When you are using organic sources for fertilizing, acid or alkaline can be a consideration. Pine needles can acidify your soils. That is why you find certain plants really thriving by pines. Wood ashes or results from burn piles can add alkalinity. A lot of alkaline materials may suppress your composting pile though!]
CarolineC blog photos
Joined: 7/14/2007
Location: SE Pennsylvania zone 6b
Posts: 393
Posted: Sep/03/2007 6:05 AM PST

Thanks Evonne! Looks like I have some reading to do.
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