8. This is what we must
represent177
144 44
1
<1
Soil P – mg kg-1
Runoff – liters
P loss – kg P ha-1 yr-1
92
Buda et al. JEQ, 2009
Lowest field is now a CREP buffer that
continues to yield largest P loads
4620
DPDPDP
8
DPDPDP78
9. Hydrologic Routine Testing – Mahantango Creek
• Similar outlet discharge
hydrographs
• Better spatial distribution of
runoff with TopoSWAT
• Improved identification of
nutrient sources with TopoSWAT
Standard SWAT
WE38 outlet
TopoSWAT
Collick et al., 2014
19. 0 40 80 120 160 20020
Meters
0 40 80 120 160 20020
Meters
0 40 80 120 160 20020
Meters
0 40 80 120 160 20020
Meters
Figure : The delineations of the four
ditches on the 1m LiDAR (A), 3m NED
DEM (B) and 10m NED DEM (C).
Only three drainage areas are
apparent from the 10m DEM.
A. 1m DEM B. 3m DEM
C. 10m DEM
0 1 2 30.5
Kilometers
'4
0 1 2 30.5
Kilometers
HUC12 Manokin River –
Taylor Branch
10m DEM
3m DEM
UMES
Experimental Farm
D. Manokin Watershed
Ditch 5 Ditch 7
Ditch 6
Ditch 8
Ditch 5 Ditch 7
Ditch 6
Ditch 8
Ditch 5
Ditch 6 &
Ditch 7
Ditch 8
19
21. General field layout with field ditches and
a schematic of the water balance model
View from above Lateral view
The model (Collick et al., 2006) seems appropriate for
Manokin fields (the low slope gradient may still cause
problems), which are divided by field drainage ditches
that flow into larger public drainage association (PDA)
channels
27. Dissolved P
loss
Particulate P
loss
% %
Comparison of application method, same amount of P applied
Spring, 6000, surface apply 100 100
Spring, 6000, incorporation within 1 day 66 95
Spring, 6000, injection 31 85
Comparison of surface versus incorporation and injection, same N supply
Spring, 15500, surface apply 100 100
Spring, 6000, incorporation within 1 day 23 52
Spring, 6000, injection 11 47
Comparison for cover crop use
Fall, 6000, surface apply 100 100
Fall, 6000, surface apply + cover crop 110 81
Relative differences between methods
to be compared to P index coefficients
Ketterings et al., 2016 in review, JEQ
32. NY P index and TopoSWAT – 1st Run
R² = 0.29
R² = 0.57
0
5
10
15
20
25
30
35
40
45
0.0 100.0 200.0 300.0 400.0 500.0 600.0
Soluble P from TopoSWAT, kg ha‐1
Dissolved P index
Corn and alfalfa fields Grass fields
Very preliminary results from uncalibrated TopoSWAT run of Factory Brook
1st Run indicates further vetting of
results and rerunning when necessary
33. Pennsylvania P Index
Screening tool
• Special Protection Watershed
• Significant management changes
• STP > 200 ppm Mehlich 3
• Distance to Stream < 150 feet
Source factors
• Soil Test P (Mehlich 3)
• Manure P (Rate, Timing x Method, P Availability Coeff.)
• Fertilizer P (Rate, Timing x Method)
Transport factors
• Erosion (RUSLE2)
• Runoff Potential (Drainage Class)
• Subsurface drainage
• Distance to the Stream
Modified connectivity
• Riparian Buffer • Grassed waterway • Direct connection