Research

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Research

• Water-extractable P in poultry and dairy manures
  and in manure-amended soils over time

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Runoff P Particulate P and dissolved P
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P dissolves into saturated soil solution prior
to runoff
lt 5 cm

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Water-extractable P is indicative of relative
susceptibility of P to dissolution in
runoff.Pote et al., 1999Hooda et al.,
2000Kleinman et al., 2002 a and b
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Water extractable P
Protocol 110 dilution for 1 hour Filtered lt
0.45 µm
WE-RP Water extractable reactive P H2PO4- or
HPO4-2
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Experiments

• Water-extractions of raw poultry litter and dairy
  manures.
• Electron microscopy of particulate P in manures.
• Incubations of Plano silt loam soil with
  different original Bray-1 P concentrations
  amended with poultry litter or dairy manure.

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Manures
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P concentrations in five poultry litters
Total P ranged from 17 to 18 g kg-1 dry matter.
Dissolved
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Poultry litter particle on 5-µm filter
2200

C


O
P

counts

Mg
K
Na

Si


Ca
Ca

0
keV

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Another poultry litter particle on 5-µm filter
5000
21 of 25 particles examined in the 35 5 µm
class were primarily Ca-Mg-P
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Cluster of bacteria from dairy manure on 5-µm
filter
4000
C
Counts
O
Mg
P
0
keV
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Proportion of total P in dairy manures that is
water-extractable increases with increasing
dilution
For a liquid manure, the percent of total P that
was water soluble ranged from 4 to 108 with
increasing dilution (M. Kalbasi, UW-Madison,
unpublished data).
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Water-extractable P in raw dairy manures
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For 1100 extractions, WE-RP is positively
linearly related to water-extractable ammonia (R2
0.60).Dairy manures may contain ammonium
phosphates like struviteFor 11000 extractions
WE-RP positively linearly related to total P in
manure dry matter (R2 0.73).
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Manure-amended soil
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• Incubation 1
• Plano silt loam surface soil
• Low P soil 12 ppm
• High P soil 30 ppm
• Total P application 162 lb P205 per acre

Dairy manure 0.6 P Applied 25 wet T per acre
Poultry litter 1.7 P Applied 3 wet T per acre

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Six treatments x six replicates 36 boxes
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Dairy manure contained more than twice as much
water-extractable P as poultry litter
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Water-extractable P in incubated amended and
unamended soils
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Soil mixed with dairy manure
Soil no manure
Soil mixed with poultry litter
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Second incubation

• Used soil with higher Bray1 P concentrations
• Was dynamic allowed for regular P removal by
  water under conditions simulating runoff from
  aggregated soil

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Incubation 2 Treatments

• Soils Plano silty clay loam surface soil
• NoM No previous manure, 32 ppm
• 2yrM 40 tons/acre/yr dairy manure 1994 and 1997,
  
• 76 ppm
• AnM 40 tons/acre/yr dairy manure 1994 - 1999, 85
  ppm
• Amendments
• DM Dairy manure 110 lb P2O5/acre
• PL Poultry litter 110 lb P2O5/acre
• CaP Calcium phosphate mineral P 55 lb
  P2O5/acre
• Twelve treatments, four replications per
  treatment.

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Minimal Disturbance Water Extraction
Four sets of 48 incubation units 192 units
Destructively sampled one set on days 0, 14, 84
and 168.
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Water-extractable reactive P in incubated soils,
all treatments
WE-RP (mg P L-1)
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Incubation 1 and Incubation 2 WE-RP results
similar for similar treatments
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Water-extractable P in dairy manure amended soils
with a previous manure history is not higher in
the soil with the higher soil test P
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Following dairy manure applications,
water-extractable P concentrations were elevated
within a narrow concentration range for years
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Minimal disturbance water extract P
concentrations from incubated unamended soils
Sewage discharge limit
EPA criteria for streams and rivers
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Minimal disturbance extract P from incubated
amended and unamended soil with no previous
manure history
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Minimal disturbance water extract P from
incubated amended and unamended soils with
previous manure history
2.50
2.00
1.50
-1
mg P L
1.00
0.50
0.00
0
35
70
105
140
Time (days)
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Cumulative P Removal in MDWE over 168 Days
13
10
8
6
2
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Why?
Dispersion dairy manure amended soils had
increased water stable aggregation compared to
other treatments at 14 days but reverse was true
at 168 days. Moisture differences dairy manure
amended soils retained moisture over time while
other treatments lost moisture.
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Summary

• Poultry litter contained sparingly soluble
  mineral phosphates.
• Most of the P in raw dairy manure could be
  dissolved in water with increasing dilution.
• When initially applied to soil, water-extractable
  P in manure-amended soil reflected the relative
  amount of water-extractable P in the manures.

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Summary (more)

• Following manure applications to soil, the P
  potentially extractable by precipitation and
  runoff may remain unacceptably high for years.
• Relationship between original soil test P and
  water-extractable P following manure applications
  was not consistent.

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Relationship between water-extractable P and
antecedent soil test P
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Implications for Management of Manure P
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Potential management implications for poultry
litter
Applications to cropland Incorporate to reduce
losses to water of easily suspended
particles. Interventions to reduce P
solubility Adjust poultry diet, litter
conditions to encourage formation of
Ca-Mg-phosphates.
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Potential management implications for dairy manure
Applications to cropland Consider dairy manure
P to be mostly available at time of
application. Promote infiltration as the
solution to reducing P in runoff from dairy
manure amended soils.
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How do our findings relate to the Phosphorus
Index?
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Phosphorus IndexPI Particulate P Soluble P
Leached P
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• Impact on both particulate and soluble P losses
• Dairy manure greatly increases soluble P for long
  periods after manure amendment
• Poultry litter contains discrete P-rich minerals
  that can be lost in dissolved and particulate form

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The relationship between particulate P and
soluble P in runoff is dynamic and is always
approaching chemical equilibrium
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P Index considerations (contd)
Animal manure amendments change soil
physical/chemical properties in ways that
influence the P extraction efficiency of
runoff.
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Research Needs

• Develop research-based guidelines for assessing P
  water-availability from different animal manures
• Assess differences in P solubilities among dairy
  manures based on storage (liquid vs. daily haul)
  and how these differences affect potential runoff
  P losses.
• Assess effects of cumulative manure amendments on
  water soluble P in a range of Wisconsin soils.

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Thank you
Funders U.W. Graduate School, U.S.D.A. National
Research Initiative, Wisconsin Fertilizer
Research Council, Wisconsin Department of Natural
Resources Special thanks to Wes Jarrell, Larry
Bundy, Bill Bland, Erik Nordheim. Mark Lawton,
Kris Niemann, Adena Rissman, Chris Newman, Dorith
Rotenberg