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Landscape and Turf Maintenance By Dr. Beth Guertal and Dr. Dave Han Aeration and Soil Compaction in Turf he effects of traffic and compaction in turf are usually easy to see — thin turf, worn paths, areas of bare ground that do not respond to applications of fertilizer or water. Turfgrass growing in compacted areas has shallow rooting, causing greater susceptibility to drought and other stress. The soils in compacted areas have low air porosity and reduced infiltration. Such compaction is most likely to occur in fine-textured soils (those with a higher clay content), but, over time, all soils are susceptible to compaction. One key to correcting soil compaction in turf is aeration, also known as aerification. Aerification is performed using a wide range of equipment that drills, slices, spikes, punches or water-injects the turf and its underlying soil to various depths. Sometimes the equipment removes a plug of turf, and sometimes it only cuts a slit or punches a hole. With some equipment there is the additional benefit of a small amount of thatch control, as the slicing or core removal also removes some thatch. T Photo provided by John Deere 16 Landscape and Irrigation January 2013 Factors affecting the effectiveness of aerification include soil wetness, tine size, depth of aerification, soil texture, aerification frequency, and equipment type. Turf aerification research is somewhat difficult to do. Studying soil compaction requires large plots, uniform areas of compacted (and non-compacted) turf, and possibly many different pieces of equipment. Additionally, collecting the data required to show treatment differences requires intensive sampling and a lot of labor. Typical data collected from compaction studies may include soil bulk density, soil penetrometer resistance, surface hardness, water infiltration, shoot density, and root length or weight. The objectives of this article are to provide explanations of the type of data collected in turf compaction experiments, and to discuss some past and current turfgrass compaction research. Research Our previous work at Auburn University found that aerification was less likely to have an effect in non-compacted soils as compared to compacted. We looked at the effects of using a deep, hollow-tine aerifier (8 inch deep, 3/4 inch diameter) at two locations: a heavily trafficked and compacted marching band practice field, and a lightly trafficked field at the Auburn University Turfgrass Research Unit. At the heavily trafficked site, every additional core aerification in a given year decreased soil resistance. This was not the case at the lightly compacted site. Only one aerification was needed in a given year to produce a significant reduction in soil resistance. At the heavily trafficked site, the effects of deep-tine aerification usually lasted about 3 weeks. This supports the conclusions of previous workers that frequent aerification might be needed on compacted sites. However we did not evaluate the effects of different equipment (e.g., tine depth, solid vs. hollow tine) on compaction in trafficked turf. We also wondered if continuous aerification would allow a compacted layer of soil to form at the bottom of the tine working depth. These "aerification pans" can form over time from the effect of tines pressing down on the soil below the level where they actually penetrate and remove soil. This research looked used three different pieces of equipment (a pull-behind aerifier, a GA-60 standard tine aerifier and a Soil Reliever deep-tine aerifier) using both solid and hollow tines. Plots were aerified four times per year, and traffic was artificially applied with a heavy roller to induce compaction. Compaction was evaluated by measuring soil resistance to a soil penetrometer at depths down to 12 inches. The equipment used has a large effect on the amount of compaction relief and where it occurs. The deep-tine aerifier (8 inches deep) reduced soil resistance when either solid or hollow tines (5/8-inch diameter) were used. The standard-tine aerifier (4 inches deep) often produced a significant reduction in resistance when hollow tines (5/8-inch diameter) were used. www.landscapeirrigation.com