risk of p movement from soils of the suwannee river basin
DESCRIPTION
Risk of P Movement from Soils of the Suwannee River Basin. Willie Harris, Vimala Nair, and Dean Rhue. W.G. Harris 1 , V.D. Nair 1 , R.D. Rhue 1 , D.A. Graetz 1 , R.S. Mylavarapu 1 C.C. Truman 2. USDA-Initiative for Future Agriculture and Food Systems. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/1.jpg)
Risk of P Movement from Soils of the Suwannee River Basin
W.G. Harris1, V.D. Nair1, R.D. Rhue1, D.A. Graetz1, R.S. Mylavarapu1
C.C. Truman2
1 Soil and Water Science Department, University of Florida2 USDA-ARS, Tifton, Georgia
USDA-Initiative for Future Agriculture and Food Systems
Willie Harris, Vimala Nair, and Dean Rhue
![Page 2: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/2.jpg)
Topics
• Hydrology – Soils –P (& N) Transport
• Predicting Vertical P Movement in Soils
![Page 3: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/3.jpg)
30 km
Drainage: Surface vs. SubsurfaceLower Suwannee Basin
Important factor inpotential P transport
![Page 4: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/4.jpg)
Surface Drainage of “Flatwoods” (“Surface” entails some shallow subsurface flow in E
horizon, which is minimally retentive of P)
E
Bh
Spodosol
Aquitard
2 m
Runoff: HighErosion: LowLeaching: LowDenitrification: High
P loss risk: High
![Page 5: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/5.jpg)
Subsurface Drainage (Karst)(Flow in soil zone mainly vertical)
E E
Bt
Entisol Ultisol
10 m
Runoff: LowErosion: LowLeaching: VariableDenitrification: Low
P loss risk: Variable
![Page 6: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/6.jpg)
Sand grain coatings,
their presence or absence,
makes a big difference in
P retention capacity
![Page 7: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/7.jpg)
Toward a More Quantitative Site Specific Assessment of Leaching Potential
• Capacity Approach– What is the remaining capacity?
• Retardation Approach– How many “pore volumes” before
“breakthrough” of elevated P concentrations at a given depth.
![Page 8: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/8.jpg)
Calculated Remaining P Sorption Capacity vs. P Concentrations in Porewater
y = -958.09x + 196.97
R2 = 0.8412
-4000
-3500
-3000
-2500
-2000
-1500
-1000
-500
0
500
1000
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
P concentration, mg L-1
Ca
pa
cit
y f
or
sa
tura
tio
n r
ati
o 0
.15
, k
g P
/ha
/cm
Remaining “Safe P Storage Capacity” for sandy soils- SPSC
(PSR0 – Soil PSR)(Oxalate Fe + Al)
![Page 9: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/9.jpg)
0-20 -20 0 2020 40 60 -40-60
Minimally-impacted dairy Heavily-impacted dairy
2 m
“Safe” P Storage Capacity (mg kg-1)
![Page 10: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/10.jpg)
Modeling P Retardation:RPA = “Relative P Adsorption Capacity”
![Page 11: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/11.jpg)
CapacityApproach
RetardationApproach
Captures previous loading effect?
Captures time factor?
Works for naturally phosphatic soils?
Yes Not well
Yes
Yes
Indirectly
No
Leaching Assessment Approaches are Complementary
![Page 12: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/12.jpg)
Summary of Findings, to Date
1. Predicted vs. observed P movement - reasonably close.
2. Typical “safe lifespan” of application site - a few years*.3. Phosphate effects realized later than nitrate effects. (BUT …)4. Phosphate effects realized longer than nitrate effects.
*A loamy horizon (Bt) could extend this greatly, barring preferential flow.
![Page 13: Risk of P Movement from Soils of the Suwannee River Basin](https://reader036.vdocument.in/reader036/viewer/2022062314/56814295550346895daec25e/html5/thumbnails/13.jpg)
Acknowledgements• Technical staff: Bill Reve, Greg Means, Dawn Lucas, Keith Hollien • Members of the Florida P-Index Committee.• Graduate student: Myrlene Chrystostome, Omar Harvey, Daniel
Herrera, Rav Ramnarine, Leighton Walker