Effects of Conservation Tillageon Soil Strength in

Arkansas Cotton Production Systems

Effects of Conservation Tillageon Soil Strength in

Arkansas Cotton Production Systems

USDA-Agricultural Research Service and

Arkansas State University

Research TeamCo-Investigators

Dr. Randy Raper Dr. John Snider Dr. Michele Reba Dr. Tina TeagueTechnical Support Tammy Horton Stephen Haller Staff at Judd Hill FarmGrant Funding SupportCotton, Inc.

Institution or Agency

Oklahoma State University University of Georgia USDA-ARS Arkansas State University

USDA-ARS USDA-ARS Arkansas State University

• 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.

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.

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)

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.

• 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.

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

• Irrigation applied weekly depending on rainfall.

• Total of 8-10 applications each year.

• 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.

Compaction study 1.jpg

• 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.

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).

Compaction study 5.jpg

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.

• 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

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.

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.

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.