2019 SWCS International Annual Conference July 28-31, 2019 Pittsburgh, Pennsylvania

1. Effects of a Precision Agriculture
System on Soil and Water Quality in
the Central Mississippi River Basin
Successive management systems in response to
economic, social, and environmental pressures
Claire Baffaut, Fessehaie Ghidey, Robert N. Lerch, Kristen S. Veum,
E. John Sadler, Kenneth A. Sudduth, Newell R. Kitchen
Soil and Water Conservation Society International Annual Conference Pittsburgh, PA. Jul. 28-31, 2019.

2. The Claypan Area
Tucker Prairie, July 2018
Soil and Water Conservation Society International Annual Conference Pittsburgh, PA. Jul. 28-31, 2019.

3. • 72% crop land, distributed as (2006):
• Soybean (56%)
• Corn (26%)
• Wheat (8%)
• Others (10%)
• Pasture and hay (16%)
• Woodland (8%)
• Urban (4%)
Goodwater Creek Experimental Watershed, now
Crop production
Soil and Water Conservation Society International Annual Conference Pittsburgh, PA. Jul. 28-31, 2019.

4. Experimental setup in the early 1990’s.
• Replicated plots to compare
production and transport of
dissolved constituents from
different grain cropping systems
• Research field to monitor
production and water quality at
field scale.

5. Field 1 from 1990 -2003
• Corn – soybean rotation, sorghum in
1995 because of delayed planting
• Pre-planting N and P
• Pre-planting atrazine when in corn
years
• Spring tillage (cultivation, seedbed
preparation, and inputs incorporation)
• Weir for flow and water quality
monitoring at the north end:
• Sediment
• Atrazine
• Dissolved N and P

6. 2004: Transition to management zones based
on profitability
m

7. 2004-2014: Precision Agriculture System
Fall 2004
• Wheat - Soybean
• No-till
• Winter and summer cover crops
• No atrazine
• N on wheat
• 20-50 kg N ha-1 in October
• 50-110 kg N ha-1 in late March or early
April, top-dress, variable rate
• P as needed (soil test P), variable timing
• Corn – soybean
• No-till
• Winter and summer cover crops
• Split application of atrazine in corn
• N on corn
• 20-60 kg N ha-1 in April – May
• 100-150 kg N ha-1 early June to mid-July, top-
dress, variable rate
• P as needed (soil test P), variable timing

8. Objectives and Methods
• Did the Precision Agriculture System make a difference in edge-of-field
losses?
• How did we do this?
• Compare 1993-2003 and 2004-2014.
• Average annual total expressed as a fraction of applied amounts
• Flow and load duration curves and Kolmogorov-Smirnov test
• Regression slope of Quantile-Quantile plots of daily flow and loads for the two
systems.

9. Rainfall was similar over the two periods
0
200
400
600
800
1000
1200
1400
1993-2003 2004-2014
Rainfall (mm)
Daily precipitation exceeds 10 mm
(0.4”) 7.5% of the time.

10. Runoff was very similar as well
0
200
400
600
1993-2003 2004-2014
Runoff (mm)

11. No-till and cover crops reduce sediment loss
One order of magnitude reduction
Soil and Water Conservation Society International Annual Conference Pittsburgh, PA. Jul. 28-31, 2019.
0
2000
4000
6000
8000
10000
1993-2003 2004-2014
Sediment loss (kg ha-1)
87% reduction

12. Smaller atrazine loss? Not so simple but
better than expected!
Soil and Water Conservation Society International Annual Conference Pittsburgh, PA. Jul. 28-31, 2019.
0
1
2
Atrazine loss (kg)
0
2
4
6
1993-2003 2004-2014
Atrazine loss as a % of applied
No significant difference

13. Nutrient loss
0
100
200
300
400
500
Dissolved N Dissolved P
Dissolved nutrient loss (kg ha-1)
1993-2003 2004-2014
0
2
4
6
8
10
12
Dissolved N Dissolved P
Loss as a percentage of applied
(%)
1993-2003 2004-2014

14. In Summary
• The no-till precision agriculture system did not affect surface runoff
volumes but improved its water quality, as shown by:
• A large reduction in soil erosion and sediment transport
• A significant reduction in surface runoff dissolved nitrogen. However,
leaching, denitrification, and volatilization may have increased.
• No significant increase in surface runoff dissolved phosphorus.
• Lower runoff atrazine losses than expected.
• It appears than cover crops have in part mitigated the effect of no-till
losses on the loss of surface applied atrazine and phosphorus.

15. The challenge with this system!
• Weeds in the wheat-soybean area.
• Timing of field operations on the odd year: preparing the field and
planting corn conflicts with harvesting wheat.
• No-till Corn-soybean-wheat + cover crops on the whole field.
• But that might not be enough…
• Increased challenges with planting corn after wheat and cover crops during a
wet spring. A win-win may not be feasible and compromises may be needed.
Adaptive management never ends…