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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.

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Residuals and manure management for environmental and agronomic benefits

Residuals and Manure Management for Environmental and Agronomic Benefits

Olawale O. Oladeji

Soil and Water Science Department

University of Florida


Residual application rates
Residual Application Rates Agronomic Benefits

  • 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
Phosphorus Loss Agronomic Benefits

  • Sandy soils of Florida sorb P poorly and surround P sensitive water bodies


Water treatment residuals wtrs
Water Treatment Residuals Agronomic Benefits (WTRs)

  • Generated with Al and Fe coagulants

  • Mostly Al and Fe hydroxides

  • High affinity for phosphorus !!!


Wtr rates
WTR Rates Agronomic Benefits

  • 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

Inadequate WTR

Excess WTR

Deficiency

(P loss)

Deficiency

(Excessive immobilization)


Soil test methods
Soil Test Methods Agronomic Benefits

  • 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
Hypotheses Agronomic Benefits

  • There exist suitable soil test methods for P bioavailability in soil receiving organic sources of P and WTRs.

  • (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.

  • Amendment rates selected in (II) that optimize P uptake also minimize leaching and runoff P.


Objectives
Objectives Agronomic Benefits

  • 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: Agronomic Benefits

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 (Paspalumnotatum Fluggae) follow by Fescue grass (Festucaovina “Glauca”)

Experiment I: Glasshouse Study


Glasshouse experiment
Glasshouse Experiment Agronomic Benefits

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
Experiment II: Rainfall Simulation Agronomic Benefits

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
Rainfall Simulation Agronomic Benefits

  • 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 simulation1
Rainfall Simulation Agronomic Benefits

Data to be collected:

  • Quantity of runoff and leachate

  • Total runoff and leaching P

  • Runoff and leaching dissolved P


Expected results
Expected Results Agronomic Benefits

  • 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

Agronomic threshold

RDP (mgL-1)

Change point

A

E = ~3A

Soil test P


Experiment iii field experiment
Experiment III: Field Experiment Agronomic Benefits

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
Field Experiment Agronomic Benefits

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
Preliminary Results Agronomic Benefits

  • 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.


Preliminary results1
Preliminary Results Agronomic Benefits

  • Potential P loss (readily desorbable P) is lower in WTR treated soil as indicated by the WEP and ISP

With WTR

Without WTR


Preliminary results2
Preliminary Results Agronomic Benefits

  • DPSox = (Ox-P) X 100

  • α(Ox-Fe + Ox-Al)


Preliminary results3
Preliminary Results Agronomic Benefits

Nair et al., 2004

  • 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.

35

30

20

25

15

With WTR

WEP (mg/kg)

10

Control

5

Without WTR

0

0

20

40

60

80

100

120

%DSP(OX)


Impact of wtr on soil and plants
Impact of WTR on Soil and Plants Agronomic Benefits

  • WTR addition lowers DPSox without significantly impacting the plant


Thanks
THANKS Agronomic Benefits


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