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Re: CULT: 6-10-10?


Your explanation of the interpretation of a standard chemical fertilizer
analysis is basically correct, but not quite exact. While the first number
in the analysis refers to the percent by weight of elemental Nitrogen (N)
in the fertilizer, the following two numbers express the oxide equivalent
of Phosphorus (P) and Potassium (K) in the fertilizer.

The oxide of Phosphorus is phosphate (P2O5). It contains 44% elemental
Phosphorus by weight. Therefore, you have to multiply the middle number of
the analysis by .44 to get the actual percent of Phosphorus in the

The oxide of Potassium is potash (K2O). It is 83% elemental Potassium by
weight. Therefore, you have to multiply the last number of the analysis by
83 to get the actual percent of Potassium in the fertilizer.

I do not know how this rather baroque system of expressing fertilizer
analysis became established, but it is still the standard used in labeling
chemical fertilizers.

Jeff Walters in northern Utah  (USDA Zone 4/5, Sunset Zone 2, AHS Zone 7)
> From: Birdwoman424@aol.com
> To: iris@hort.net
> Subject: Re: [iris] CULT: 6-10-10?
> Date: Thursday, May 01, 2003 9:17 PM
> In a message dated 5/1/2003 10:15:56 PM Eastern Daylight Time, 
> corgilover@wi.rr.com writes:
> > Maybe it would be easier for my if I knew what the last two numbers 
> > stood for.  I know the first is nitrogen . . . . .
> > -- 
> > Pat Mitchell
> > 
> nitrogen, phosphorus and potassium (also known as potash).
> example: 5-10-5 is 5% nitrogen, 10% phosphorus and 5% potassium (potash).
> The remaining 80% is filler.
> Nitogen - for rapid growth and green leaves
> Phosphorus - for root growth and develop strudy plants and flowering
> Potassium - for new cell growth, roots and buds

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