Verdure: Don't reject air or sand injection

Today, various core cultivation (also referred to as aerification) practices, along with sand topdressing, are commonly used to manage soil organic matter and alleviate soil compaction.


To correct soil physical problems, farmers often plow up their fields after harvesting the crop, essentially flipping and mixing the soil. This is not possible with low-mowed, intensively managed perennial turfgrass pastures of golf course putting greens. Therefore, “forking” was perhaps the first practice used for the physical penetration of turf: “But if a green becomes badly caked, one of the best things to do is to ease the surface of the whole green with forks, and give a dressing of sharp sea-sand, which will work into the holes made by the forks” (p. 76 in “Golf Greens and Green-keeping” by H.G. Hutchinson, 1906).

Excessive organic matter — specifically those thatch-mat layers — can decrease infiltration, decrease turfgrass’s tolerance to temperature stress, increase localized dry spot/dry patch, increase compaction at the playing surface and increase disease, weed and insect pest problems. Today, various core cultivation (also referred to as aerification) practices, along with sand topdressing, are commonly used to manage soil organic matter and alleviate soil compaction.

Researchers at Oklahoma State University (Stillwater, Okla.) evaluated the short-term effects of hollow-tine cultivation (HTC; ProCore 648, The Toro Co., Bloomington, Minn.), air-injection cultivation (AIC; Air2G2, GT AirInject Inc., Jacksonville, Fla.), sand-injection cultivation (SIC; DryJect, DryJect Inc., Hatboro, Pa.), and no cultivation (untreated) on soil physical properties and playability of a Penncross creeping bentgrass putting green. The USGA-recommendation sand green was mowed at 0.153 inch (3.9 millimeters) and subjected to routine maintenance practices, including kiln-dried sand topdressing.

Cultivation treatments were replicated four times in a randomized design typical for field research plots. All treatments were applied once in fall 2017, then once in spring and summer 2018, before repeating those treatments in fall 2019 and again in spring and summer 2019. HTC tines were 0.5-inch (1.3-centimeter) diameter by 2.5-inch (6.4-centimeter) depth, at 2 inch × 2 inch (5 centimeter × 5 centimeter) spacing, with cores removed and holes filled with sand. AIC inserted air at 50 psi (345 kilopascals) pressure into a rod, 0.75-inch (1.9-centimeter) diameter by 12-inch (30.5-centimeter) depth, at 24 inch × 24 inch (61 centimeter × 61 centimeter) spacing. SIC inserted sand at 3,000 psi (20,684 kilopascals) water pressure, 0.4-inch diameter (1-centimeter) by 4-inch depth (10-centimeter), at 3 inch × 2 inch (7.6 centimeter × 5.1 centimeter) spacing. 

For each application event, various measurements were made to all plots just prior to applying those cultivation treatments, then measured again at 7, 14, 21 and 28 days later. HTC, AIC and SIC data were each compared to the untreated, not to each other.

What about those short-term effects on soil properties? HTC increased root zone infiltration rate and reduced soil compaction compared to untreated, but infiltration or compaction results with AIC or SIC were not any different versus untreated. Volumetric water content at 3-inch (7.6-centimeter) root zone depth for HTC, AIC, SIC were all similar versus untreated. HTC, AIC or SIC did not reduce soil organic matter (ranged from 2.29% to 2.44% at 2.5-inch [6.4-centimeter] depth) compared to untreated. HTC and AIC reduced soil bulk density between one to seven days after cultivation was applied.

What about short-term effects on playability? HTC reduced ball roll distance, but AIC or SIC did not. HTC reduced surface firmness (i.e., softer putting surface), but AIC and SIC did not. HTC reduced visual turfgrass quality, but AIC and SIC did not. Also of note, turf surface recovery time was longer with HTC compared to SIC, while AIC showed almost no visible injury.

So, within a 28-day period, HTC was more effective for increasing soil infiltration rate and reducing soil compaction but needed longer turf recovery time. The research also showed AIC can have small but potentially meaningful effects on soil bulk density and soil infiltration rates, and SIC offers a less injurious method to incorporate sand (or possibly other materials) into the thatch-mat layer. AIC or SIC should not be a replacement for conventional core cultivation practices; however, both have their place in a comprehensive root zone management program, and both are unique tools useful to address specific changes and needs in putting green management.

Source:  Amgain, N.R., C.H. Fontanier and D.L. Martin. 2021. Short-term effects of alternative cultivation practices on putting green infiltration rates. Crop Science 61:4425-4434.

Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 20-year member of GCSAA.