69th SWCS International Annual Conference “Making Waves in Conservation: Our Life on Land and Its Impact on Water” July 27-30, 2014 Lombard, IL

1. 1
Rain, Runoff, and Sediment Loss in
Normal and Abnormal Weather Years
in an Agricultural Landscape
in Southeastern U.S.
A 10-yr Dataset
69th SWCS International Annual Conference
Lombard-IL
July 27-30,2014

2. 2
69th SWCS International Annual Conference
Lombard-IL
July 27-30,2014
Dinku Endale
David Bosch
Tom Potter
Tim Strickland
USDA-ARS-SEWRL Tifton-GA

3. 3
THE SOUTHEAST
136
153
152
134
135
133
Tifton
Background
MLRAs, NRCS
Cropland in the Southeast
USDA-NRCS, 2006
MLRA Name Km
2
% MLRA
133 Southern Coastal Plain 46885 17
134 Southern Mississippi Valley Loess 24727 36
135 AL and MS Blackland Prairie 2640 16
136 Southern Piedmont 15010 9
152 Eastern Gulf Coast Flatwoods 332 1.3
153 Atlantic Coast Flatwoods 11158 15
Total 100,753 km
2
(10 million ha)
GA, AL, SC, NC, TN, MS 7.2 million ha planted (CTIC 2008 CRMS)
40% no-till; 41% conventional tillage
US harvested cropland 127.5 million ha (2012 Census of Agriculture)
31% no-till;24 conservation tillage other than no-till; 34% conventional tillage

4. 4
Background
Benefits of conservation tillage:
• Reduce runoff, erosion and soil loss
(Credited for 43% reduction in soil loss from U.S.
cropland 1982-2007; NRCS-2010)
• Improve soil health and water quality
• Improve soil water availability

5. 5
In the Southeast, benefits of conservation
tillage being threatened by:
• Shifts in weather
• Shifts in cropping practices
o Removal of crop residue from fields
o Increased herbicide resistance of weeds
Background

6. 6
Background
Fig. 2.11
Ingram, K., K. Dow, L. Carter, J. Anderson, eds. 2013. Climate of the
Southeast United States: Variability, change, impacts, and vulnerability.
Washington D.C.: Island Press.
Fig. 2.8

7. 7
Background
Shifts in cropping practices that could
increase soil erosion:
• Removal of crop residues from croplands in
response to renewable energy initiatives.
• Challenges with herbicide-resistance weeds
(pigweed; glyphosate-resistant Palmer amaranth) as
some growers choose to revert to conventional
tillage methods in response.

8. 8
Challenge
Long-term research and data are critical in
generating scientifically-based information on
environmental risks associated with cropping
practices in response to shifting weather, national
initiatives, weed pressure, market forces, etc.
Society needs to make wise management decisions
to sustain the natural resource base.

9. 9
Objective
Present summarized runoff and sediment loss
data from three fields managed under
conventional tillage, and three under strip
tillage, in a Southern Coastal Plain landscape,
during ten years (2000-2009) of rotational
cotton-peanut cropping with rye as a winter
cover crop.

10. 10
Methods
SITE
• Six 0.2-ha fields near
Tifton, GA
• CT – conventional tillage,
block 1, fields 1, 3, 5
• ST –strip tillage, block 2,
fields 2, 4,6
• 1.5 ft H-flumes per field
to measure & sample
runoff
Slope 3 to 4%

11. 11
Methods
SITE - soil
• Upper landscape position:
Carnegie sandy loam
(... Plinthic Kandiudult)
Ap sandy loam; Bt sandy clay
loam / sandy clay
• Middle: Tifton loamy sand
(…Plinthic Kandiudult)
Ap loamy sand; Bt sandy clay
loam
• Lower: Fuquay loamy sand
(…Arenic Plinthic Kandiudult)
Ap sand Bt sandy loam / sandy
clay loam

12. 12
Methods
Cropping
Cotton Peanuts
2000 2002
2001 2004
2003 2006
2005 2008
2007
2009
Management per UGA
Extension recommendations
Irrigation
when needed

13. 13
Methods
Monthly rain + irrigation versus long‐term monthly mean rainfall
# of months rain + irrigation is percent of year
YEAR < Normal Normal > Normal < Normal Normal > Normal
2000 7 2 3 58 17 25
2001 6 2 4 50 17 33
2002 3 5 4 25 42 33
2003 5 3 4 42 25 33
2004 6 1 5 50 8 42
2005 4 2 6 33 17 50
2006 5 2 5 42 17 42
2007 7 1 4 58 8 33
2008 4 3 5 33 25 42
2009 4 2 6 33 17 50
Total 51 23 46 43 19 38
120
Monthly rainfall < (Long-term mean < 95% Confidence Level)
Monthly rainfall = (Long-term mean +- 95% Confidence Level)
Monthly rainfall > (Long-term mean + 95% Confidence Level)

14. 14
Result Highlights
RESULT SUMMARY
Parameter Stat Unit CT ST CT/ST
Runoff 10-yr total mm 8,059 4,731 1.7
10-yr total mean mm/field 2,686 1,577 1.7
Year total range mm/yr 43 (2007) 6 (2007)
(tillage mean) 507 (2003) 315 (2002)
Normailized Mean annual % 20.5 12.0 1.7
runoff Range % 4 (2007) 1 (2007)
40 (2003) 24 (2002)
CT - conventinal tillage ST - strip tillage

15. 15
Result Highlights
Monthly runoff amount by status of monthly rain+irrigation input
CT Field 1 ST Field 6
% of % of
Status mm 10-yr total mm 10-yr total
Below normal 252 7 60 5
Normal 441 13 204 16
Above normal 2712 80 983 79
SUM 3405 100 1247 100
Below normal: Monthly rainfall+irrigation < (long-term monthly mean runoff - 95% confidence limit)
Normal: Monthly rainfall+irrigation = (long-term monthly mean runoff +- 95% confidence limit 0
Above normal: Monthly rainfall+irrigation > (long-term monthly mean runoff + 95% confidence limit)

16. 16
Result Highlights
RESULT SUMMARY
Parameter Stat Unit CT ST CT/ST
Sediment 10-yr total kg/ha 54,682 7,116 7.7
Normalized kg/ha/
mm runoff 6.8 1.5 4.5
10-yr total mean kg/ha/field 18,227 2,372 7.7
Year total range kg/ha/yr 161 (2007) 3 (2007)
(tillage mean) 5914 (2009) 696 (2002)
Tvalue surpassed 2002 None
2240 kg/ha/yr year 2003
2009
CT - conventinal tillage ST - strip tillage

17. 17
Result Highlights
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70 80
Monthly runoff coefficient (%)
Exceedance probabaility (%)
Monthly Runoff Coefficicent
CT ST
Y = a + bX + cX1.5
+ dX0.5
Y is runoff coeff. and X is exceedance
CT ST
R2
0.996 0.991
a 82.45 94.034
b 0.376 2.931
c 0.024 ‐0.094
d ‐14.48 ‐29.28

18. 18
Result Highlights
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70
Monthly sediment loss coefficient
(kg/ha/mm runoff)
Exceedance probabaility (%)
Sediment loss coefficient
CT ST
Y = a + bX2
+ c/X0.5
+ de‐X
Y is sediment coeff. and X is exceedance
CT ST
R2
0.982 0.969
a ‐9.788 ‐2.921
b 0.0002 0.0001
c 75.449 19.032
d ‐80.648 42.469

19. 19
Result Highlights
Mean sediment loss coefficient by landscape position
kg/ha/mm runoff
Period CT ST CT ST CT ST
Monthly 6.0 2.8 4.2 0.8 4.0 0.9
*** *** ***
Annual 6.9 2.1 5.7 1.5 5.8 1.6
* ** *
*, **, *** Significant difference CT vs ST at 0.05, 0.01, 0.001
probability levels, respectively
10-Yr total 24,160 2,167 14,727 2,676 15,795 2,273
kg/ha
Upper Middle Lower

20. 20
Result Highlights
Mean sediment loss coefficient by landscape position
kg/ha/mm runoff
Upper Middle Lower
Season CT ST CT ST CT ST
Fall 2.6 2.7 1.7 0.3 0.7 0.5
NS ** NS
Winter 3.3 2.8 3.3 0.7 3.1 1.1
* *** ***
Spring 8.8 0.6 3.8 0.8 3.2 1.0
*** ** NS
Summer 9.3 5.1 8.1 1.3 8.9 1.1
* *** ***
*, **, *** Significant difference CT vs ST at 0.05, 0.01, 0.001
probability levels, respectively. NS - not significant.

21. 21
Result Highlights
Mean sediment loss coefficient by landscape position
kg/ha/mm runoff
Upper Middle Lower
Crop CT ST CT ST CT ST
Cotton 6.5 5.1 5.4 1.1 6.7 0.8
NS *** ***
Peanuts 5.1 0.8 4.9 0.5 3.5 0.6
** ** *
Rye 4.1 3.4 3.5 1.1 2.6 1.1
** *** ***
Fallow 8.7 0.6 3.7 0.4 3.4 0.9
*** *** NS
*, **, *** Significant difference CT vs ST at 0.05, 0.01, 0.001
probability levels, respectively. NS - not significant.

22. 22
Result Highlights
Extreme events => 90th pecentile
CT ST
Plot 1 Plot 3 Plot 5 Sum Plot 2 Plot 4 Plot 6 Sum
Stat Daily runoff mm
Sum- all 3405 2352 2302 8,059 1781 1703 1247 4,731
Sum- extreme 1979 1323 1273 4,575 1275 1139 832 3,246
% extreme 58 56 55 57 72 67 67 69
Daily Sediment Loss kg/ha
Sum- all 24,160 14,726 15,795 54,682 2,167 2,676 2,273 7,116
Sum- extreme 14,330 7,603 9,495 31,428 926 1,872 1,437 4,235
% extreme 59 52 60 57 43 70 63 60
Percent extreme same for monthly summary
All occurring for > normal rainfall (+irrigation) months

23. 23
Conclusions
• Runoff and sediment loss will increase in the
Coastal Plain if the projected shifts in weather and
tillage practices materialize.
In the ten years of research we reported:
o Mean normalized runoff was 70% greater
from CT than ST
o Mean sediment loss was 7.7 time greater
from CT than ST
o 80% of the runoff amount occurred during
above normal water input months

24. 24
Conclusions
• Runoff and sediment loss will increase in the
Coastal Plain if the projected shifts in weather and
tillage practices materialize.
• We used cover crop in both CT & ST but the typical CT
in the SE does not; so the risk is greater.
• In a 1951-1958 study of continuous conventional tillage
peanuts with no cover crop, researchers found soil loss
of 2758 kg/ha/yr (18 plots,8-m wide and 25-m long
close by). There was severe drought in the 1950s.
• In current study loss during 4 yr of Peanuts averaged
1461 kg/ha/yr from CT with cover crop.

25. 25
Conclusions
• To consistently reduce soil loss below tolerance levels
in the Coastal Plain, producers need to consider
combination of best management practices that include
cover crops, strip tillage, contour cultivation and
reduced slope length.
• Higher landscape positions, where clay rich sub-soils
might be near the surface, pose greater risk for runoff
and soil loss than those in lower positions that have less
clay near the surface. Summer and cotton cropping pose
most risk for soil loss at all landscape positions.
Producers need to use these facts in designing best
management practices.

26. 26
Conclusions
• Such long-term research and data are critical in
generating scientifically-based information needed to
make wise management decisions that sustain the
integrity of natural resources.
Many thanks for your attention !!
Research
Fields
Google
earth
3/26/2013
Cover
crop
fall
2012