Conservation Practice Impacts on Nutrient Loads from the Maryland CEAP Choptank Watershed using AnnAGNPS

• Ronald L. Bingner, USDA-ARS, Oxford, MS• Ali Sadeghi, USDA-ARS, Beltsville, MD• Henrique Momm, Middle TN State Univ.,

Murfreesboro, TN• Greg McCarty, USDA-ARS, Beltsville, MD• Dean Hively, USGS-EGSC, Reston, VA• Yongping Yuan, USEPA, Las Vegas, NV• Eugenie Kamgue, Middle TN State Univ.,

Murfreesboro, TN

Objective

To evaluate conservation practice effects on sediment and nutrient loads within the ARS Conservation Effects and Assessment Project (CEAP) Choptank, Maryland Benchmark Watershed.

Choptank Watershed, MD

German Branch

4960 ha

Landuse

#

CropForestUrbanFarms

Crop Distribution

cornwheatbarleysoybean

ManagementRotation 1 (reduced tillage): Corn, commodity wheat, double crop soybeans.

April 12th poultry manure application; 2 T/A

April 30th plant corn; no-till

June 15th sidedress 30% UAN; 100 lbs/acre

October 15th harvest corn

October 25th disk

October 30th poultry manure application; 1 T/A

November 5th plant winter wheat; drill

March 5th 30% UAN applic; 60 lbs N/A

June 10th harvest wheat

June 15th plant double crop soybean; no till

November 10th harvest soybeanWinter fallow

Rotation 2 (conventional tillage): Corn, commodity wheat, double crop soybeans

April 18th poultry manure application; 2 T/A

April 19th subsurface chisel

April 27th plant corn; conventional tillage

June 19th sidedress; 30% UAN; 100 lbs/A

September 30th harvest corn

October 6th disk

October 9th poultry manure application; 1T/A

October 12th plant wheat

March 10th 30% UAN applic.; 60 lbs/A

June 12th harvest wheat

June 15th plant soybean; conv.till

November 10th harvest soybeanWinter fallow

Reduced Tillage70% of cropland

Conventional Tillage30% of cropland

Ephemeral Gully Locations

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1607 Actual Gullies

Identified

NRCS Photo Gallery: Ephemeral Gully (?)

Where does sheet & rill end & ephemeral gullies begin?

NRCS Photo Gallery: GullyGully forming in a corn field in Pennsylvania

Narrow & Deep Gullies

German Branch

AGBUFAGNPS‐GIS Buffer Utility Feature

Provides buffer characterization for AnnAGNPS input parameters

AGBUFRiparian Buffer GIS representation

AnnAGNPS cells & reaches Buffer

AGBUF (continued)TE Estimation in AnnAGNPS Cells includes the effect of concentrated flow paths through buffers (short‐circuits)

A

0

0

0

1 2

3 4

5 6 TE = 97%

Potential short‐circuits

TE = 90%

TE = 47%

Varying widths & lengths

Runoff

0

20

40

60

80

100

120

140

Jan_

91

May

Sep

Jan_

92

May

Sep

Jan_

93

May

Sep

Jan_

94

May

Sep

Jan_

95

May

Sep

Flo

w (

mm

)

Observed Simulated

NSE = 0.71

Total Nitrogen

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Jan_

91

May

Sep

Jan_

92

May

Sep

Jan_

93

May

Sep

Jan_

94

May

Sep

Jan_

95

May

Sep

N L

oss

es

(kg/h

a)

Observed Simulated

NSE = 0.51

Buffer/Gully Comparisons

Sediment Load Sheet & Rill (% Change from Base)

Sediment Load Ephemeral Gully (% Change from Base)

Nitrogen Load (% Change from Base)

No gullies/No buffers

216 - -2

Gullies/No buffers 214 191 1

Buffer/No gullies 2 - -3

Buffers and Gullies (BASE)

- - -

Since most N load is dissolved from poultry litter, buffers do not have much impact on controlling N

Average Annual Runoff

Runoff0.098 - 3.658

3.658 - 8.874

8.874 - 13.206

13.206 - 16.441

16.441 - 45.583

tn/ac/yr

Average Annual Sediment Load

Sediment0 - 0.017

0.017 - 0.069

0.069 - 0.19

0.19 - 0.579

0.579 - 1.25

tn/ac/yr

Average Annual Nitrogen Load

Nitrogen0

0 - 36.592

36.592 - 44.342

44.342 - 84.071

84.071 - 165.311

lb/ac/yr

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100

Con

trib

uted

Loa

d (%

)

Contributing Drainage Area (%)

TOTAL CELL NITROGEN FROM ALL SOURCES

OUTLET

Areas of 50% Nitrogen Load

Nitrogen0

0 - 36.592

36.592 - 44.342

44.342 - 84.071

84.071 - 165.311

lb/ac/yr

Summary

AnnAGNPS adequately simulated runoff and nitrogen loads in the watershed.

Ephemeral gullies impacted sediment and nitrogen loads, while buffers mainly only had an impact on sediment. Since most N is transported as dissolved N from poultry litter applications.