When it comes to turf aeration, professionals define quality by quantity, depth and pattern. Aeration, the process of penetrating the turf, thatch and soil to reduce soil compaction, is vital to the life-cycle of turf grass and improves water retention, air circulation and nutrient absorption to the grass root system to promote new or deepening root growth.
Mechanisms Used to Penetrate Soil
There are several types of mechanisms used to penetrate the soil. Vertical slicers or slit aerators utilize thin blades to reduce surface area compaction. Spike tine aerators utilize solid shaft tines to relieve the compaction found in transplanted grasses like sod that have a relatively shallow layer of grass root and soil applied over sandy or porous basins. Core tine aerators utilize hollow shaft tines that remove a plug or core of turf, thatch and soil to instantly relieve soil compaction.
In a national survey of more than 5,000 landscape contractors, turf care professionals and golf and sport field superintendents in the United States conducted in the fall of 2015, 91% of the respondents said they use core tine aeration over all other methods. There are numerous core tine aerators on the market to consider. The right aerator makes all the difference in core quality.
Defining Quality of Core
Professionals surveyed determined quality of core to be a combination of three factors: Core quantity, Core depth, and Core pattern. While all three factors were considered statistically significant in the final survey results, landscape contractors put more emphasis on core quantity as a productivity factor, where turf care professionals and superintendents put more emphasis on depth and core pattern.
Core quantity is determined by the number of tines, tine spacing, rate of operation and (to some extent) the tine drive mechanism. There are two tine drive mechanisms most commonly used in powered core aerators: tine wheels that rely on weight to penetrate the soil and reciprocating tine rods that rely on force to penetrate the soil.
Tine wheels are circular disks spaced along a rod (or shaft) that have numerous core tines mounted or welded to them fanned out around the wheel. The tine shaft is lowered to place the tines on the soil surface. Proper depth is achieved as the unit is propelled forward. The speed at which the unit travels does not affect the quantity of holes it is able to produce. The number of tines and distance between the tines on the wheel and the number of wheels and distance between them along the shaft determines the quantity of holes the unit can produce in a single swath.
Tine rods are mechanically or hydraulically driven in and out of the ground. The quantity of holes produced on tine rod units depends on the rate of reciprocation and the speed at which the unit is being propelled. While some tine rod units are capable of hundreds of tine reciprocations per minute, the distance between each tine rod along the shaft is set. If the unit only has four tine rods set six inches apart, you will still need to do a couple of passes to produce a proper core pattern. Core quantity is just one productivity factor to consider.
Proper core depth is vital in alleviating soil compaction. Achieving a depth of two to three inches is sufficient to relieve most soil compaction and give the root system new room to grow. The compaction area in turf grass soil runs about an inch and a half deep.
Accounting for an average half-inch thatch layer, you will need to aerate at a depth of at least two inches to relieve soil compaction. And you should allow an additional half inch or so to create a growth pocket to promote deeper existing root growth. Heavy traffic areas with deep rooting systems may require deeper aeration from time to time, while other areas may only tolerate shallow aeration. Using an aerator that allows for easy depth adjustment provides flexibility. The key is in knowing the turf conditions and terrain before you start aerating.
It is important to utilize an aerator that allows you to set a maintained depth or at least to lock in a maximum depth. Inconsistent core depth can be a problem with aerators that maintain tine depth hydraulically. Stand-on aerators, for example, utilize hydraulic pressure to drive and maintain tine depth. However, there is no way of knowing from the pressure gauge exactly how deep the tines are penetrating. Some newer units now offer depth-stop settings to ensure the tines do not exceed a set depth.
Regardless of the unit you choose to use- walk-behind, stand-on, or tow-behind-core depth is something you’ll want to monitor. Make a first pass and pick up a few cores to make sure you are achieving the depth needed and that you are maintaining consistent depth. A good rule of thumb is to simply use your thumb to measure the length of the core pulled. The average adult thumb length is 2. inches (female) to 2. inches (male) from the first knuckle to the tip. That measures up nicely with the two- to three-inch depth professionals recommend.
Core pattern is considered by many turf care professionals to be the most important factor. The proximity of the tines to one another, not just in the distance between the tines along the shaft but also in the distance from one tine tip to the next on the wheel, or the distance traveled before the tine rod once again punctures the ground, is the core pattern.
In core aeration, there are two primary core patterns: straight line and staggered. Both patterns will aerate the turf grass effectively so long as the holes are spaced evenly apart in any direction. Professionals suggest a two‐ to three‐inch tine pattern. When in doubt, test a small area in a crisscross pattern and measure the distance between the holes with a ruler or your thumb. In general, quality of core is a combination of quantity, depth and proximity. Using aeration equipment designed with these three key attributes in mind will provide the best quality of core result for the turf.