SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: http://read.dmtmag.com/i/517437
www.stma.org June 2015 | SportsTurf 19 air into the rootzone through injection tines. It uses similar principles to the water injection systems. Currently, there is limited research done on air injection systems; particularly, with regard to impacts on soil physical properties. The goal of this study was to determine the ability of an air injection machine to reduce surface hardness and soil bulk density as well as increase the total porosity of two compacted silt loam athletic fields. The hypothesis was that an air injection machine can decrease surface hardness and soil bulk density, thereby increasing total porosity. The Air2G2 was the air injection system used during this study. It was manufactured by GT Airinject. The system uses a self-contained air compressor to build up the needed pres- sure to inject air below the soil surface. The air injection system (Air2G2) is a three-wheeled machine that can be easily maneu- vered across a desired area (Figure 1). The unit contains three tines that are simultaneously injected into the ground. Once in the ground compressed bursts of air are released at the desired depth. The unit has tine lengths ranging from 8 to 12 inches. Thicker tines can be used to penetrate into more compacted soils. The three injection tines are spaced 18-inches apart. The unit has adjustable pressure that ranges from 0 to 150 psi. There are also two adjustable pressure settings for using the machine. The first setting is for injecting the tine, and the second setting is for releasing the air into the soil. The ability to adjust these pres- sures enables the unit to be used on all soil types. The company has different recommendations for sand versus native soil fields to maximize the impact on the rootzone. Research was conducted at the University of Tennessee from July 1 through August 30, 2014. Studies were conducted on two compacted native soil (silt loam) bermudagrass athletic fields. Two application frequencies were compared: once every 15 days and once every 30 days were compared to a non-treated con- trol. Data collected for the study included surface hardness, soil moisture, soil bulk density, total soil porosity, and digital image analysis for percent green cover. Soil cores were extracted every 30 days to run physical analysis to determine soil bulk density and total soil porosities. A Clegg impact surface hammer with a 5-pound missile was used to record surface hardness mea- surements. Surface hardness was collected before and after the application of air injection. Soil moisture was collected using a Time Domain Reflectometry probe (Spectrum Technologies). The experiment was set up as a randomized complete block design with three replications of each treatment. ANOVA's were conducted in SAS 9.3 using Fisher's protected LSD. No differ- ences were detected between locations; therefore the results are pooled for location. The surface hardness was found to be reduced immediately after air injection treatments were applied. Both locations saw a 21% reduction in surface hardness immediately after applica- tions (Figure 2). Soil moisture content values at location two were on average 20% higher than at location one on all dates (data not shown). Soil bulk density was reduced for both air injection application timings by an average of 15% in the top two inches of soil (Figure 3). Total soil porosity increased by an average of 17% in the top 2 inches of soil for both air injec- tion treatments, while the untreated control saw no differences (data not shown). The results of this study demonstrate that the air injection system decreases soil bulk density, while increasing total soil porosity on silt loam athletic fields. A reduction in surface hardness was found immediately after each air injection treat- ment application. No differences were found in percent green cover for this study. With minimal surface disruption, play could take place immediately after air injection applications. While this study shows the potential of the unit, future studies are warranted to determine long term effects of air injection aeration equipment on fields during periods of traffic. See www.sportsturfonline.com for literature cited listing. ■ ST Figure 2. Surface hardness (Gmax) values taken with the Clegg hammer for both locations immediately after air injection applications on hybrid ber- mudagrass. Data was collected from 1 July – 15 August 2014 in Knoxville, TN. Errors bars represent Fisher's LSD values at P < 0.05. Figure 3. Soil bulk density of hybrid bermudagrass subjected to air injec- tion treatments for two locations at the conclusion of the study on 15 August 2014, Knoxville, TN. Errors bars represent Fisher's LSD values at P < 0.05.