[USCC] P accumulation in manured fields and P tests

[LARRY SIKORA]

Frank:
  We conducted studies in which we added Al and Fe byproducts to manures
and composted the mixture to determine the change in plant available
phosphorus by added the byproducts and/or by composting. The addition of
the byproducts almost immediately resulted in the decrease in phosphorus
availability as measured by two extractants, water and Mehlich
extraction. Composting did little to change the availability of the
phosphorus after the amendment(s) were added. Below is listed two
publications that report these findings. This result should answer your
question if the amendments added to manure really show up in the
phosphorus extraction test.  You question what test if any is the best
determinant of phosphorus tie up after treatment. Although many types of
P extractant are used to follow forms of phosphorus in the soil after
manure or organic amendment addition, the most reasonable extractant to
assess phosphorus run off from fields is water. I drew this conclusion
from polling several research scientists conducting phosphorus studies
in the field. All the other chemical extractants which indeed
'correlate' with runoff P or P plant uptake account for greater
percentages of total phosphorus, but not necessarily give a true value
of mobile phosphorus.

Dao, T. H., Sikora, L. J., Hamasaki, A., and Chaney, R. L. 2001. Manure
phosphorus extractability as affected by aluminum and Iron by-products and
aerobic composting. J. Environm Qual. 30:1693-1698.

Vadas, P. A., J. J. Meisinger, L.J. Sikora, and J. P. McMurtry. 2004.
Effect of poultry diet on phosphorus loss in runoff from soils amended
with poultry manure and compost. J. Environm. Qual..33:1845-1854.

Cheers,





Message: 1
Date: Tue, 29 Aug 2006 09:50:59 -0700
From: frank <frank at compostlab.com>
Subject: Re: [USCC] P accumulation in manured fields
To: US Composting Council Compost Discussion List
<compost at composter.com>
Message-ID: <44F47073.70101 at compostlab.com>
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Rufus,

First I wonder what type of P test should be done on compost to measure
the 'problem' phosphorus?
I suggest 'Dissolved acid-hydrolyzable phosphorus'. But first we should
know if when using this method adding Al to the compost will reduce the
measured P -as we need it to do if we use Al to solve the problem.

SM 4500 Method: filter a water extract (suggest 1:5 w/w) thru 45um pore
membrane filter / add dilute acid and boil for 90 min.

Frank








Larry Sikora
Compost Systems and Utilization
PO Box 6076
China Village, ME 04926
(207)968-2268
ljsikora at fairpoint.net