Preliminary Response of Soils to Decompaction with Rotary Aeration

Soil compaction, the hardening of soil due to compressing soil particles closer together, negatively affects nearly all the properties and functions of soils whether they are physical, chemical, or biological in nature (Batey 2009). Compaction affects soil health in agriculture and horticulture as it inhibits root growth, hinders water infiltration, and increases stormwater runoff. Any restoration work that involves seeding or planting vegetation should consider determining and/or managing soil compaction to ensure project success, and work to reduce compaction during and after efforts.

Many techniques are available to reduce the negative effects of compaction, such as not using heavy machinery on wet soils, mechanically breaking up compacted soils, replacing topsoil, or planting vegetation prior to the formation of soil compaction. The goal of these management practices is to restore natural function to the soil. In New Jersey, USA in particular, improving soil health has been a goal of many educational institutions, government entities, and not-for-profit organizations during their ecological restoration efforts. Recent programs have moved forward in New Jersey to promote sustainable management of turfgrass or the reduction of turfgrass areas in the home landscape, replacing these areas with native plants (Jersey-Friendly Yards 2016). Traditional turfgrass management is viewed as lowering biodiversity and decreasing ecological function (Aronson et al. 2017). Native plants are seen as a boon to biodiversity and increasing ecological function (Hostetler and Main 2010).

Our project examined one technique currently implemented to alleviate soil compaction and restore soil function at Georgian Court University's (GCU) campus (Lake-wood, NJ): the use of rotary aeration. Over the last few years, GCU has been working to address ongoing problems created by soil compaction on campus athletic fields and lawns by investing in a Verti-Quake®, (Valley Park, MO, USA) a tractor-drawn implement with multiple rotating blades that cut 25–30 centimeters (cm) into the soil while leaving virtually no mark on the turf surface. This process adds void spaces to alleviate soil compaction. Reduced compaction resulting from effective use of rotary aeration improves drainage from lawns and athletic fields, which reduces the need for fertilizer and irrigation while reducing runoff and associated flooding. Despite the widespread use of Verti-Quake® and similar equipment for soil management, very little data is available on their effectiveness, other than proprietary data from the manufacturer and one study at Michigan State University (Pavely 2012).

Figure 1.

Georgian Court University campus showing location of three pairs of sampling plots.

We wanted to determine the extent to which soil decompaction strategies provided improvements to soil function. This was accomplished through measurement of soil resistance with a static cone penetrometer and soil water content for turf areas that are undergoing soil decompaction and comparing this to the same measurements in comparable locations not undergoing soil compaction management. Our goal was to observe any immediate changes to soil function of lands undergoing soil compaction management and to compare them to soil systems with no compaction management.

During the fall of 2015, we studied three sites with paired plots (one plot at each site underwent rotary aeration, the other plot did not, as a control) on GCU's campus (Figure 1). All six plots consisted of mowed turf and were 10 meters by 10 meters to provide enough room for the Verti-Quake® to pass over them twice during each treatment. One pass in the north-south direction and a second in an east-west direction was performed on one plot in each pair (the treatment plot). This was to mimic how the device was used on other areas of campus. None of the sites underwent irrigation during the course of the study. We selected sites with similar compaction and drainage problems, similar soil characteristics (sandy loam), and similar landscaping effort for comparison.

Table 1.

Mean depth to soil compaction (a) and soil water content (b) for all plots during the study. Plots at sites that underwent aeration showed an increase in depth to compaction, indicating a reduction in compaction (a).