[USCC] Iron Contect in Compost

[Chaney, Rufus]

Dear Brian, David et al.:

I am writing to extent the explanation offered by David Hill which is
correct but incomplete.

The reason that biosolids Fe was stressed was for surface application of
liquid biosolids with over 4% Fe on pastures because the ingestion of
high Fe biosolids stuck on pasture grasses did induce Cu deficiency in
cattle in an experiment at Beltsville in 1976. Thus, when high Fe
biosolids are surface sprayed on pasture, special care should be taken
to supply adequate Cu for the cattle.

When compost rich in Fe was surface applied as N-fertilizer, no adverse
effects of Fe were found, but the Fe was not as high as the liquid
biosolids applied.

High Fe can also interfere with Mn availability to plants, so if you are
dealing with low Mn soils, Mn should be applied along with high Fe
composts or biosolids. Composts are little different from biosolids
regarding the Fe risk to Cu availability to ruminants, or Mn
availability to plants.

Now, the good side of Fe in composts: It binds phosphate and limits P
runoff from amended fields without greatly reducing the plant
availability of the applied P. Plants change the chemistry of the
rhizosphere soils and thus release P for uptake in that microenvironment
without causing P runoff. With the increasing regulation of P in applied
organic amendments (especially manures which have low Fe and Al which
could bind P and limit runoff), having higher Fe or Al in the amendment
can justify higher one-time applications without risk of P runoff. 

Now the last comment to extend David Hill's comment is that you should
add some Fe-rich byproduct if you can find one. We find steel mill slag
can be rich in Fe and Mn and limestone equivalent, and a useful
amendment to limit P runoff when mixed with manure or composts. Adding
Fe-chelates would be far too expensive and of little value because Fe
bound by compost is a good Fe fertilizer. The Fe source should be added
before composting so that the composting process can increase the
binding of Fe to the organic matter.

Regards,

Rufus Chaney
USDA-ARS
Beltsville, MD

-----Original Message-----
From: compost-bounces at mailman.cloudnet.com
[mailto:compost-bounces at mailman.cloudnet.com] On Behalf Of
BfleuryWeCare at aol.com
Sent: Monday, September 28, 2009 4:34 PM
To: compost at mailman.cloudnet.com
Subject: [USCC] Iron Contect in Compost

Does anyone have information on acceptable ranges of iron in compost?
I 
understand that Iron is good, but....How much is too much?
 
Thank you in  advance for your responses.

Brian C. Fleury
Senior Project  Manager

WeCare Organics, LLC
PO Box  785
Hillburn, NY 10931
(O) 845 / 753 / 2314
(F) 845 / 753 / 2349
(C)  315 / 374 / 5098
bfleurywecare at aol.com
_www.wecareorganics.com_ (http://www.wecareorganics.com/) 

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