Water Quality Trade-offs When Adopting Conservation Practices - Dr. Doug Smith, USDA Agricultural Research Service (ARS), from the 2018 Conservation Tillage and Technology Conference, March 6 - 7, Ada, OH, USA. More presentations at https://www.youtube.com/channel/UCZBwPfKdlk4SB63zZy16kyA

1. Water Quality
Tradeoffs When
Adopting Conservation
Practices
D.R. SMITH

2. Background
• Conservationists
sometimes believe
practices are without
fault
• Can be difficult to
convince some that not
all conservation
practices will address all
resource concerns

3. Watershed Scale P Balance

4. Conservation Tillage Adoption

5. Cumulative Sandusky River SRP Loss
(1974-2013)

6. Sandusky River Flow and SRP Loss
70% of increased
P resulted from
increased delivery
(availability/
transmission)
30% of increased
P from increased
runoff

7. What Happened?
In the 1980’s, stop the
sediment – stop the P
Increased drainage density
Adopted conservation tillage
without considering fertility
management
Law of Unintended
Consequences

8. No-till reduced erosion from wheat 95%
Converted
to no-till
1980 1985 1990 1995
Conventional
till wheat
6
4
2
0
-
-
Total P, mg L-1
Sharpley & Smith, 1994 – El Reno, OK
1980 1985 1990 1995
20
15
10
0
-
5
-
Total N, mg L-1
Conventional
till wheat
Converted
to no-till-

9. 1980 1985 19951990
0.5
1.0
0
Infiltration increased 33%
Converted
to no-till
Runoff - Dissolved P, mg L-1
Conventional till wheat
1980 1985 19951990
Nitrate, mg L-1
30
20
10
0
Converted
to no-till
Conventional till wheat
Leached -
Sharpley & Smith, 1994 – El Reno, OK

10. Relative Change in Annual Load for
Nutrients and Sediments by Conservation Practice
NH4-N NO3-N TKN Soluble P Total P Sediment
RelativeChangeinAnnualLoad
-100
-50
0
50
100
150
200
Grassed Waterway
Blind Inlet
Conservation Crop Rotation
Tillage

11. • Ever increasing list of novel conservation practices
• Not yet able to develop model subroutines for
practices, especially new ones
• Conservation Practice Effectiveness Database
developed to provide soft-data to modelers
Background

12. Objectives
Can we use the
Conservation Practice
Effectiveness
Database to evaluate
tradeoffs related to
practice adoption?

13. Conservation Practice
Effectiveness Database
• Published international
Literature
• 13 practices
─ Bioreactors, Blind inlet,
Conservation crop
rotation, Constructed
wetlands, Cover crops,
Drainage water
management, Grassed
waterways, Vegetative
filter strips, Manure
amendments, No-tillage,
Two-stage ditch, Stream
modifications, Riparian
buffer

14. Conservation Practice
Effectiveness Database
• 119 sources
• 1,733 reported
observations
• Comparisons made on
loads (priority) or
concentration

15. Conservation Practice
Effectiveness Database
•Surface runoff + tile
drainage
•NO3-N, NH4-N, TKN, TN,
SRP, TP, Sediment,
Atrazine, glyphosate
and E. coli data input
•2,161 individual
constituent practice
efficiencies calculated

16. No-till - Surface RunoffEffectiveness(%)
-400
-300
-200
-100
0
100
NO3-N NH4-N TKN SRP TP Sediment Atrazine
n = 25
n = 19
n = 16
n = 17
n = 20
n = 12
n = 5

17. No-Till - Tile DrainsEffectiveness(%)
-400
-300
-200
-100
0
100
NO3-N NH4-N TKN SRP TP Atrazine
n = 65
n = 10
n = 5
n = 6
n = 6
n = 4

18. Bioreactor Effectiveness - Tile DrainsEffectiveness(%)
-400
-300
-200
-100
0
100
NO3-N NH4-N TKN SRP TP Sediment E. coli
n = 101
n = 16
n = 10 n = 10
n = 1
n = 1 n = 1

19. Drainage Water Management Effectiveness - Tile Drains
Effectiveness(%)
-250
-200
-150
-100
-50
0
50
100
150
NO3-N NH4-N TKN SRP TP Atrazine
n = 103
n = 9
n = 2
n = 25
n = 23 n = 4

20. Effectiveness(%)
-200
-150
-100
-50
0
50
100
NO3-N TKN TN TP Atrazine
n = 15
n = 1
n = 1
n = 1
n = 4
Drainage Water Management Effectiveness - Surface Runoff

21. Conservation Crop Rotation - Surface Runoff
Effectiveness(%)
-400
-300
-200
-100
0
100
NO3-N NH4-N TKN SRP TP Sediment
n = 7
n = 5
n = 5
n = 6
n = 8
n = 1

22. Conservation Crop Rotation - Tile Drains
Effectiveness(%)
-400
-300
-200
-100
0
100
NO3-N NH4-N SRP TPTKN
n = 52
n = 5
n = 5
n = 6 n = 6

23. Cover Crops Effectiveness - Surface RunoffEffectiveness(%)
-300
-200
-100
0
100
NO3-N NH4-N TKN SRP TP Atrazine
n = 23
n = 9 n = 0
n = 15
n = 6 n = 4

24. Cover Crop Effectiveness - Tile Drains
Effectiveness(%)
-400
-300
-200
-100
0
100
NO3-N NH4-N TKN SRP TP Atrazine
n = 70
n = 0 n = 0 n = 0 n = 0
n = 4

25. Conclusions
• Conservation adoption
across the landscape is
essential to resource
protection
• Encourage publication of
all results to provide
complete picture.
• Few, if any, practices are
going to address all
resource concerns equally
• Need to consider stacking
conservation to address
multiple resource
concerns

26. Thank You!