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 plantsPotential 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 !!!

P adsorption isotherms

02000400060008000

1000012000

0 20 40 60 80 100

Time (Days)

BradentonLowellHollandTampaPanamaCocoa

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

Excess WTR

Inadequate WTRDeficiency

(P loss)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 StudyObjectives: 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 (Festuca ovina “Glauca”)

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 SimulationObjectives: 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 of runoff and leachate

Total 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

Agronomic threshold

Environmental threshold

Change point

Soil test PA E = ~3A

RD

P (

mgL

-1)

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 better

correlated with P uptake than Mehlich-1

WEP and ISP are potential soil tests for P in WTR treated soils.

A plot of P uptake against soil Mehlich 1 P

y = 0.0176x + 12.558

r2 = 0.0128

0

5

10

15

20

25

25 50 75 100 125

Mehlich 1 P (mg/kg)

P u

pta

ke (k

g/h

a)

A plot of P uptake against WEP

y = 0.1862x + 10.73

r2 = 0.346

0

5

10

15

20

25

0 10 20 30 40WEP (mg/kg)

P up

take (

kg/ha

)

A plot of P uptake against Iron strip P

y = 0.2065x + 9.0545

r2 = 0.3863

0

5

10

15

20

25

0 20 40 60

Fe strip P (mg/kg)

P u

pta

ke

(k

g/h

a)

Preliminary Results Potential P loss (readily

desorbable P) is lower in WTR treated soil as indicated by the WEP and ISP

A plot of Plant P uptakes against soil Mehlich 1 P

0

5

10

15

20

25

20 40 60 80 100 120

Soil Mehlich 1 P (mg/kg)

P u

ptak

e (k

g/ha

)

A plot of P uptake against WEP

0

5

10

15

20

25

0 10 20 30 40

WEP (mg/kg)

P up

take

(kg/

ha)

A plot of P uptake against Iron strip P

0

5

10

15

20

25

0 10 20 30 40 50

Fe strip P (mg/kg)

P u

pta

ke

(kg

/ha

)

With WTR

Without WTR

Preliminary Results

Amendments

 

Rates

DPS (%)

∆ DPS with WTR Without WTR

Manure N-based 18 73 55

Boca 14 54 40

Pompano 7 93 86

TSP 12 87 75

Manure P-based 9 49 40

Boca 4 28 24

Pompano 9 45 36

TSP 13 61 48

DPSox = (Ox-P) X 100α(Ox-Fe + Ox-Al)

Preliminary Results

Treatments without WTR have %DPSox above the change point.

Treatment with WTR have %DPSox below the change point (environmental threshold).

calculated using oxalate extraction (DPSox) for soil receiving different P sources with and without WTR.

0

5

10

15

20 25

30

35

0 20 40 60 80 100 120

%DSP(OX)

WE

P (

mg

/kg

)

With WTR

Without WTRControl

Nair et al., 2004

05

101520253035

0 20 40 60 80 100DPSox, %

WS

P (

mg

kg

-1)

With WTRWithout WRRControl

Impact of WTR on Soil and Plants

WTR addition lowers DPSox without significantly impacting the plant

0

20

40

60

80

100

Treatments

Plant P uptake

Soil %DPSox

THANKS