Project Summaries

10-791  Project Manager: E. M. Barnes


Daniel H. Pote, Randy L. Raper and John L. Snider, USDA-ARS

Eastern Arkansas soils present specific soil management problems exacerbated by the large percentage of clay content present in these soils. Traditional management of Eastern Arkansas soils has been to use tillage systems that require large equipment and frequent field trips. Soil management systems under development include reduced tillage systems with cover crops. However, the conversion to conservation systems has been partially stymied by the excessive amounts of soil compaction found in these soils that limits root development and reduces crop yields. Frequent tillage has been used to manage soil compaction, but with reduced tillage systems these extra tillage opportunities are not possible.
An experiment has been in place at Judd Hill Plantation in Eastern Arkansas for three years that has compared three tillage systems: (1) conventional tillage system, (2) reduced-tillage system, and (3) reduced-tillage system with a cover crop. A Veris Technologies P4000T VIS-NIR-EC-Force Probe (Salina, KS) was used to obtain a full set of cone index (CI) and electrical conductivity (EC) data for this experiment. Five separate locations across the row were sampled; (1) nontrafficked row middle, (2) midway between nontrafficked row middle and row, (3) in the row, (4) midway between row and trafficked row middle, and (5) trafficked row middle. Three sets of data were obtained at each location at opposite ends of the plot. For 2012 figures, the data were combined in 10-cm depth increments to provide clearer interpretation of results.

Previous research results indicate that a CI of 2 MPa restricts root growth and reduces cotton yield. Using these criteria illustrates that the CI data obtained at the Judd Hill Plantation achieve a root-limiting condition at all five positions across the row and at relatively shallow depths. A potential fix for this condition is to conduct in-row subsoiling down to a depth where rooting is desired. The soil compaction condition indicated by the CI data obtained in 2011 did not tend to support this management practice because no clearly identifiable reduction in CI was noted at the depths sampled in this study, so excessive amounts of energy would have been required. However, those 2011 data were collected when the soil was too dry for optimum CI measurement. In contrast, the 2012 data were collected when soil moisture was near field capacity), the moisture level at which the most meaningful CI data can be obtained, and show that root-limiting conditions existed only above the 0.4-m depth.  Therefore, in-row subsoiling may be helpful for alleviating the root-limiting conditions in this case, particularly for the no-till treatment in which subsoiling would require less energy because compaction only occurred within the top 20 cm of soil. In-row subsoiling could also provide some additional benefits, including increased infiltration that may be beneficial to overall crop production.

Another possible method of reducing CI is to incorporate a cover crop which can help decrease soil compaction by increasing infiltration, increasing soil organic matter, and increasing water holding capacity of the soil. In 2011, this trend was not observed at any of the row positions because soil compaction was unaffected by the presence of a wheat cover crop. Similar results were seen in 2012, as the wheat cover crop significantly decreased soil compaction only at one depth (10-cm) and at one location (row middle).

The important conclusions that can be drawn from the analysis of these data are:

    1. Root-limiting conditions were found with the CI data at relatively shallow depths. However, in-row subsoiling for the no-till treatment may be a viable option to decrease CI, and the practice could have other benefits that should be examined.
    2. In this study, cover crops did not lessen soil compaction, increase the depth of root limiting CI levels, nor increase soil moisture content.
    3. Reduced tillage systems are gradually reducing soil compaction in the soil profile at 20-cm depths and below.

Project Year: 2012

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