71st SWCS International Annual Conference July 24-27, 2016 Louisville, KY

1. Effects of Conservation Tillage
on Soil Strength in
Arkansas Cotton Production Systems
Effects of Conservation Tillage
on Soil Strength in
Arkansas Cotton Production Systems
USDA-Agricultural Research Service
and
Arkansas State University

2. Research Team
Co-Investigators
 Dr. Randy Raper
 Dr. John Snider
 Dr. Michele Reba
 Dr. Tina Teague
Technical Support
 Tammy Horton
 Stephen Haller
 Staff at Judd Hill Farm
Grant Funding Support
Cotton, Inc.
Institution or Agency
 Oklahoma State University
 University of Georgia
 USDA-ARS
 Arkansas State University
 USDA-ARS
 USDA-ARS
 Arkansas State University

5. • Frequent tillage has historically been used to manage
soil compaction, but also degrades soil quality.
• To improve soil quality and prevent erosion, many
cotton farmers now use no-till systems or conservation
tillage with a cover crop.
• Because these conservation systems reduce tillage,
they have increased concerns regarding the possibility
of soil compaction problems.

6. Objective
To better understand the effect of tillage
system on soil compaction by comparing
three cotton production systems:
 Conventional tillage.
 No-till.
 Reduced tillage with a cover crop.

8. Dundee silt loam:
• fine-silty mixed, active,
thermic Typic Endoaqualfs
• Slope < 1%
• Moderately slow
permeability
• Somewhat poor drainage
• Silty clay loam texture
below the plow layer
(15-cm depth)

9. Experimental Design
• 3 tillage treatments X 3 replications =
9 experimental plots.
• Each plot: 15.5 m wide X 137 m long
with 0.97-m (38-inch) row spacing.
• Randomized complete block design.
• Treatments repeated annually for
three years.

10. • The primary crop on all experimental plots was cotton
(Gossypium hirsutum) planted in May each year.
• Plots that included a cover crop treatment were also
planted to winter wheat (Triticum aestivum L.) the
previous fall (October or November).
• Each spring , the wheat crop was terminated by
applying glyphosate approximately 30 days before
planting cotton.

12. • Sweep plows used to clear row
middles for furrow irrigation.

13. • Irrigation applied weekly
depending on rainfall.
• Total of 8-10 applications
each year.

21. • Veris P4000T soil probe.
• Provides cone index (CI)
data as recommended by
the American Society of
Agricultural Engineers
(ASAE) to measure soil
strength.
• Used in November each
year after cotton harvest.

22. Compaction study 1.jpg

23. • Base diameter of 27.8 mm on
cone-shaped tip.
• Base diameter of ASAE standard
cones: 12.8 or 20.3 mm.
• Larger cones are more precise
and yield lower CI than smaller
cones of the same shape.
• However, cones with a
prominent shoulder greatly
increase CI due to increased
sliding friction.

24. Cotton rows were spaced 96.5 cm apart and
five locations across the row were sampled:
 Trafficked row middle (-48 cm location).
 Midway between the row and trafficked row
middle (-24 cm location).
 In the row (0 cm location).
 Midway between the row and non-trafficked row
middle (24 cm location).
 Non-trafficked row middle (48 cm location).

25. Compaction study 5.jpg

26. Statistical Analyses
 For each plot x row position combination, 6 replicate
data points were obtained along the length of each plot.
 CI values were obtained in 1-mm depth intervals in the
soil profile, rounded to the nearest 0.1-m depth, and
averaged for each depth.
 Means and standard deviations were calculated for
each treatment, depth, and row position.
 Effect of tillage treatment was assessed at each depth
and row position using a mixed model ANOVA, where
block was considered a random effect and tillage
treatment was a fixed effect.

27. • Impacts CI readings.
• Characterized by 3 samples
for each CI measurement and
treatment.
• In the cotton row (in row)
and trafficked row middle
(between row).
• Two soil depths: 0-15 cm
and 15-30 cm.
Soil Moisture

29. Observations
 In the first year, CI values were often lowest in
conventional tillage plots.
 In the second year, CI was hardly affected by tillage
treatment.
 In the third year, the no-till treatment tended to decrease
CI, especially in the cotton row.
 No indication that a wheat cover crop combined with
reduced tillage helped decrease soil compaction, but
other studies have shown that it can help prevent wind
erosion while improving weed management, water
infiltration, and early-season root health.

30. Conclusions
 Results from this study support previous
observations that soil compaction can
initially increase after the conversion of
fields to conservation tillage practices,
but this is often a temporary condition.
 Conservation tillage can eventually
decrease soil compaction and produce
a somewhat softer soil condition.

31. Economic Comparison
 No-till system was the least expensive.
 Conventional tillage cost $29.00 / ha
($11.75 / acre) more than the no-till system.
 Reduced tillage with a cover crop cost
$34.57 / ha ($14.00 / acre) more than the
no-till system.