[USCC] Iron Contect in Compost

[Craig Coker]

Rufus, et.al.:

Is there a way to predict the extent of P-binding due to Fe content? 

I have a client who makes a 80% sand / 20% compost bioretention pond media.
The media contains 113 ppm Total Phosphorus, 6 ppm Water-Soluble Phosphorus
and 35 ppm Iron (lab test by A&L Great Lakes 8/17/09).  The project engineer
is rejecting this as "out-of-spec" for a rain garden job as the spec calls
for a maximum P content of "75 lbs/acre" (which, in agricultural nutrient
management terms = 37.5 ppm).  

Is there a way I can calculate how much of the Total P will remain bound in
the soil based on this iron content (I've already lost the argument that
"Only 6 ppm is soluble, the rest stays bound in the soil").

Thanks for any insight you (or anyone else) can provide.

Craig

Craig Coker | Coker Composting & Consulting
1213 Spradlin Rd.  Vinton Va 24179
Tel. (540) 890-1086; Fax. (540) 890-1087
Cell. (540) 874-5168; Email. cscoker at verizon.net
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