Residuals and Manure Management for Environmental
and Agronomic Benefits
Olawale O. Oladeji
Soil and Water Science Department
University of Florida
Residual Application Rates
 Meet
N needs of plants (N-based) and avoid
excessive N that can pollute the ground
water.
 N-based
rates often provide and load soils
with excessive P
 Excess
P:
 Not harmful to plants
 Potential environmental impact
Phosphorus Loss

Sandy soils of Florida sorb P poorly and surround P
sensitive water bodies
Water Treatment Residuals
(WTRs)
 Generated
with Al and Fe coagulants
 Mostly Al and Fe hydroxides
 High affinity for phosphorus !!!
WTR Rates

Land application of WTRs could lead to
excessive immobilization of soil P and Al toxicity

Negative impact of WTRs calls for best
management for environmental and agronomic
benefits
Deficiency
(P loss)
Inadequate
WTR
Excess
WTR
Deficiency
(Excessive immobilization)
Soil Test Methods

A good soil test could be a tool to identify
environmental and agronomic thresholds to
arrive at optimum rates of WTRs and P
sources.

Conflicting results from the use of conventional
soil test methods (e.g., Mehlich 1) in studying
soils receiving WTR call for identifying suitable
soil test methods.
Hypotheses
I.
There exist suitable soil test methods for P bioavailability in
soil receiving organic sources of P and WTRs.
II.
(1)
P-based rates of different organic sources of P
without WTR optimize P uptake.
(2)
N-based rates of different organic sources of P with
WTR optimize P uptakes.
III.
Amendment rates selected in (II) that optimize P uptake also
minimize leaching and runoff P.
Objectives

Determine suitable soil test methods for P bioavailability in soils
amended with different P sources and WTR.

Determine the rates of WTR and organic P sources that
optimize plant P uptake while minimizing environmental P
hazards.

Evaluate the impacts of selected amendments rates (WTR and
organic P sources) on leaching and runoff P.

Validate the expected impacts of selected amendment (WTR
and organic P sources) rates on P uptake and P loss in field
settings.
Experiment I: Glasshouse Study
Objectives:


Determine suitable soil test methods for P bioavailability in soil treated
with different organic sources of P in the presence and absence of
WTR
Determine the rates of organic sources of P (amendments), with and
without WTR, that optimize P uptake
Design:

4X2X3 factorial experiment plus 1 control in randomized complete
block with 3 replicates
Factors:



4 P Sources (Poultry manure, Boca Raton Biosolids, Pompano
Biosolids, TSP)
2 P Sources rates (N- and P-based)
3 WTRs rates (0, 1.0 and 2.5% oven dry basis)
Test plants:
Bahiagrass (Paspalum notatum Fluggae) follow by Fescue grass
Glasshouse Experiment
Data to be collected:
Total P and soil test P
(using selected extraction methods: Mehlich-1, Water
extractable P, Fe strip P)
Plant dry matter yield.
Plant P content and uptake.
Experiment II: Rainfall Simulation
Objectives:

Evaluate impact of organic sources of P on leaching and runoff P

Determine the effect of WTR placement on leaching and runoff P

Determine the environmental threshold for P
Design:
4X2X2X2 factorial experiment plus 1 control in randomized complete
block with 3 replicates
Factors:




4 P Sources: Poultry manure, Boca Biosolids, Pompano Biosolids, TSP
2 P Sources rates :N- and P-based
2 WTRs rates : 0, and 1.0%
2 placement methods: Surface and Mixed
Rainfall Simulation

Runoff boxes (100cm*20cm*7.5cm)

Surface slope (3 degree)

Simulated rain 7.1cm hr-1

Three rain events at 2-days interval

Runoff collected for 30 minutes
(Leachate also collected)
Rainfall Simulator
Rainfall Simulation
Data to be collected:
 Quantity
 Total
of runoff and leachate
runoff and leaching P
 Runoff
and leaching dissolved P
Expected Results
N based rates with WTR and P
based rates expected to give soil
test P (STP) below the change
point (environmental
threshold)

N based rate without WTR is
expected to give STP and RDP
above the change point

Environmental threshold STP
is expected to be about three
times agronomic optimum
Environmental
threshold
RDP (mgL-1)

Agronomic
threshold
Change
point
A
E = ~3A
Soil test P
Experiment III: Field Experiment
Field validation of impacts of selected rates and sources
of P and WTR on P loss and uptake
Design: 4X2X3 factorial experiment plus 1 control in
randomized complete block with 3 replicates
Factors:
 4 P Sources: Poultry manure, Boca Biosolids, Pompano
Biosolids, TSP
 2 P Sources rates :N- and P-based
 2 WTRs rates (0, and 1.0%)
Test plant: Bahiagrass
Field Experiment
Data to be collected:
Runoff and leaching P
 Plant dry matter yield
 Plant P uptake
 Total P and soil test P using selected extraction
methods (Mehlich-1, Water extractable P, Fe strip P);
oxalate extractable P, Al, Fe,).

Preliminary Results
 WEP and ISP are potential soil
tests for P in WTR treated soils.
A plot of P uptake against Iron strip P
P uptake (kg/ha)
 WEP and ISP are better
correlated with P uptake than
Mehlich-1
25
20
15
10
0
0
15
y = 0.0176x + 12.558
r 2 = 0.0128
0
50
75
Mehlich 1 P (mg/kg)
100
40
60
Fe strip P (mg/kg)
125
P uptake (kg/ha)
P uptake (kg/ha)
20
25
20
A plot of P uptake against WEP
25
5
r2 = 0.3863
5
A plot of P uptake against soil Mehlich 1 P
10
y = 0.2065x + 9.0545
25
20
15
10
y = 0.1862x + 10.73
5
r2 = 0.346
0
0
10
20
WEP (mg/kg)
30
40
Preliminary Results
Potential P loss (readily
desorbable P) is lower in WTR
treated soil as indicated by the
WEP and ISP
A plot of P uptake against Iron strip P
25
P uptake (kg/ha)

20
15
10
5
0
With WTR
0
10
20
Without WTR
P uptake (kg/ha)
P uptake (kg/ha)
50
A plot of P uptake against WEP
25
20
15
10
5
0
40
40
Fe strip P (mg/kg)
A plot of Plant P uptakes against soil Mehlich 1 P
20
30
60
80
Soil Mehlich 1 P (mg/kg)
100
120
25
20
15
10
5
0
0
10
20
WEP (mg/kg)
30
40
Preliminary Results
DPSox = (Ox-P) X 100
α(Ox-Fe + Ox-Al)
DPS (%)
Amendments
Rates
Manure
N-based
with WTR Without WTR ∆ DPS
18
73
55
Boca
14
54
40
Pompano
7
93
86
TSP
12
87
75
9
49
40
Boca
4
28
24
Pompano
9
45
36
TSP
13
61
48
Manure
P-based
Preliminary Results
Nair et al., 2004
 Treatments without WTR
have %DPSox above the
change point.
calculated using oxalate extraction (DPSox) for soil receiving
different P sources with and without WTR.
kg-1)
35
30
WEP (mg/kg)
WSP (mg
 Treatment with WTR have
%DPSox below the change
point (environmental
threshold).
20
15
10
5
0
0
35
30
25
20
25
15
10
5
0
0
With WTR
With WTR
Without WRR
Control Control
Without WTR
20
20
40
40
60
60
DPSox, %
80
%DSP(OX)
80
100
100
120
Impact of WTR on Soil and Plants

WTR addition lowers
DPSox without
significantly impacting
the plant
THANKS