Residuals and manure management for environmental and agronomic benefits
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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

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

Inadequate WTR

Excess WTR

Deficiency

(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

  • 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

  • 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.


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

Experiment I: Glasshouse Study


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 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

Environmental threshold

Agronomic threshold

RDP (mgL-1)

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 better correlated with P uptake than Mehlich-1

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


Preliminary Results

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

With WTR

Without WTR


Preliminary Results

  • DPSox = (Ox-P) X 100

  • α(Ox-Fe + Ox-Al)


Preliminary Results

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

  • WTR addition lowers DPSox without significantly impacting the plant


THANKS


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