|
|
|
Posted 1 April 2009. Crop Management. Spring is Often Best Time to Assess Soil Compaction Kansas State University. www.ag.ksu.edu Manhattan, Kansas (March 27, 2009)--Spring is often the perfect time to examine soils for evidence of compaction, said DeAnn Presley, K-State Research and Extension soil management specialist. It also happens to be a time when soils are often vulnerable to compaction.
“Fields should be assessed when the soil is at or near field capacity, the point at which the entire soil profile is moist, but not saturated. These conditions typically occur in the spring, although topsoils in much of Kansas are very dry so far this spring,” she said. Compaction occurs when soil particles are pressed together, limiting the space for air and water. The amount of soil water present is a critical factor in soil compaction potential. If compaction is suspected, it can be confirmed by using a shovel or soil probe, Presley said. “With a shovel, look for either a surface crust, or for platy soil structure (soil structure that resembles a stack of dinner plates). With a soil probe, push the probe into the soil slowly, and feel for a layer of increased resistance. Quite often, if a compacted subsurface layer is present, you can punch through the tillage pan, and the soil beneath it will have less resistance,” the soil scientist said. Cone penetrometers may also be used to locate compaction, Presley added. “Penetrometers need to be used in combination with some device to assess soil moisture and texture, like a soil probe. Readings should be taken when the whole profile is at or near field capacity, approximately 24 hours after a soaking rain. If the soil is too wet, compaction could be underestimated because the soil water acts as a lubricant. If the soil is too dry, compaction could be overestimated because roots will be able to penetrate the soil when it re-wets,” she said. The idea behind using the penetrometer at field capacity is that this is the best-case scenario to mimic the penetration power of roots, she said. “If using a penetrometer, push or drive it into the soil at a rate of 1 inch per second. Record the penetration resistance at each depth increment. Note the depths at which the penetration resistance exceeds 250-300 pounds per square inch (psi), a range that is root-limiting when the soil is moist,” Presley said. Preventing the Different Types of Soil Compaction The best cure for soil compaction is by not working or driving on soils that are too wet, said DeAnn Presley, K-State Research and Extension soil management specialist. “Crop fields also can be at risk of compaction from grazing animals or manure spreaders just as much as when using any other farm equipment, especially in conditions near field capacity. Fall-planted cover crops could provide physical support for livestock and/or manure spreaders, while spring-planted cover crops might be a good option for soils with excess moisture at planting time,” she said. There are three potential types of soil compaction, and each requires different preventive measures, Presley said. • Shallow, surface compaction is related to the pressure applied to the surface of the soil, and can be controlled by distributing a load, either by using a larger tire or more tires. Global Positioning System-based auto-steering systems are a tremendous aid for establishing and maintaining a controlled traffic system. Shallow compaction is normally removed with subsequent tillage operations and to some extent, by freeze-thaw and wet-dry cycles. Surface compaction should be avoided at planting time in conventional or reduced tillage, and at all times in no-till. • Sub-surface compaction is related to the maximum axle load, and is not reduced by distributing the weight across more tires or larger tires. The only way to avoid sub-surface compaction is to limit the amount of traffic with heavy axle loads. • Sidewall compaction occurs if the crop is planted when the soil is too wet and the planter openers push on the side of the soil furrow, creating a compacted zone. Sidewall compaction is preventable by delaying planting until soils are sufficiently dry. The use of spoke wheel seed slot closers can also be helpful. If you can mold the soil into a ball in your hand and the soil ball will not easily crumble apart, it is too wet to plant. Contact: |
