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Figure 1. Corn-on-corn production has a greater potential for compaction in the fall due to the high level of traffic required to remove the volume of corn bushels compared to soybean bushels.
Susceptible soils are vulnerable to compaction when they are at or near field capacity with moisture. Field capacity is the point at which the pore space surrounding soil particles is completely occupied with water. Water in the soil acts as a lubricant between soil aggregates, allowing them to become tightly packed together.
Soil compaction typically refers to either sidewall compaction or compaction from mechanical traffic (Figure 1). Sidewall compaction can occur during planting when too much downpressure is applied by the press wheels to soils at field capacity (Figure 2).1 Compaction due to mechanical traffic occurs when any equipment enters the field at or near field capacity. Both types of compaction create a difficult environment for roots to penetrate through the soil.
Figure 2. Symptoms of sidewall compaction.
Coarse-textured soils and those with high levels of incorporated organic matter are less prone to compaction. Medium- and fine-textured soils are more susceptible to soil compaction due to increased water holding capacity and the amount of time the soils require to dry down.
Water and nutrients are provided to the plant through the root system. If the soil is compacted, the roots may be unable to capture the necessary water or nutrients, leading to nutrient deficiency. Initially, this may be difficult to diagnose because of the difficulty to observe soil and root structure compared to plant tissue above ground.
Figure 3. Increased amounts of crop residue can result in corn-on-corn fields staying wetter longer in the spring. If tillage is performed before the field is fit, then a cloddy seedbed and uneven emergence may result.
Tillage plays an important role in soil structure and nutrient availability. In a continuous corn system, where soil compaction may be an issue, tillage becomes a major management decision. Every pass through the field increases the chance of compaction. However, thorough incorporation of the previous corn crop residue is recommended to not only reduce soil drying time in the spring (Figure 3), but to also reduce the chance of the decomposing residue tying up nitrogen during warmer weather.2
Figure 4. Effect of crop rotation and tillage system on corn root growth and ear development. Monmouth, IL, 2011. Roots in the conventional tillage, continuous corn system were shallower than other treatments.
Continuous corn and a corn-soybean rotation were compared in both conventional and strip-till management systems at the Monsanto Learning Center at Monmouth, IL. Root pits were dug late in the summer to illustrate the effect of the treatments on root growth and ear development (Figure 4). Roots in the conventional tillage, continuous corn were shallower than those in other treatments. This may have been a result of poor root penetration due to soil compaction.
Rotating corn with soybean can increase soil pore space and reduce the chance of soil compaction problems. In addition, soybean rotation helps to reduce residue levels, manage corn rootworm populations, and reduce inoculum levels of diseases by interrupting pathogen lifecycles.
Soil compaction increases the potential for nutrient and water-stressed crops. This stress can reduce yield potential by up to 50 percent.3 As shown in the Monmouth demonstration, managing field operations and addressing drainage issues can help reduce or prevent soil compaction problems. Compaction can be managed by staying out of saturated fields, limiting vehicle load, using proper weight during tillage operations, and managing traffic within fields.
1 Jasa, P. 2010. Avoid sidewall compaction with planter and planting adjustments. University of Nebraska-Lincoln. UNL CropWatch. http://cropwatch.unl.edu/. 2 Nafziger, E. 2010. What ailed corn following corn in 2010?. University of Illinois Extension. The Bulletin. Issue 23. Article 8. http://news.aces.illiinois.edu/. 3 Johnson, J.W. 1999. Most asked agronomic questions. Ohio State University Extension. Bulletin 760-88. http://agcrops.osu.edu/. 4 Wolkowski, R. and Lowri, B. 2008. Soil compaction: causes, concerns, and cures. University of Wisconsin Extension. A3367. http://www.soils.wisc.edu/. Abendroth, L.J., Elmore, R.W., Boyer, M.J., and Marlay, S.K. 2011. Corn growth and development. PMR 1009. Iowa State University Extension. Ames, Iowa. 760-88. Steinhardt, G.C. and Griffith, D.R. 1992. Soil compaction in Indiana. Purdue University Cooperative Extension Service. AY-221. https://www.extension.purdue.edu/. Web sources verified 09/07/16. 130301807013