Root Density

Aeration and Reducing Soil Compaction

Frequently compacted urban soils cause the majority of sports field problems. Reducing compaction softens the soil to allow air, water and nutrients to get in and out of the soil profile, promote deep turfgrass root systems and add shock-absorption and injury evasion for player falls. Achieving these benefits will reduce a sporting field’s overall pesticide, fertilizer and water needs.  

Aeration that opens 8 percent of the soil surface should reduce compaction by 10 to 15 percent.  The amount of surface opened depends on aeration depth, equipment and frequency.   

Aeration Depth:

1 to 6” deep→ Known as Surface Aeration, this practice grows strong root mass and microbiology diversity on the top soil layer.  Surface aerators use slicers, hollow-tines or solid tines to break the surface.  

8 to 12” deep→ Known as decompaction aeration or deep-tine aeration, this practice breaks clay, rocks and construction debris in the soil profile and cuts deep enough in the soil to improve drainage and turfgrass root depth. Most deep-tine aerators use solid tines, but can use hollow-tines.    

Aeration Equipment:

Slicing→ Slitting the soil three to four inches deep to open the surface for air.  This facilitates the lateral growth of Kentucky bluegrass. If densely lined (2” by 2” spacing or closer), can open eight percent of the surface. 

Hollow Tine Coring→ Removes soil cores, generally 3-6” deep, to increase soil porosity. The straight up and down action of most hollow tine core aerators open less than one percent of the surface. To increase the amount of surface opened, accommodate the core aeration with a slicer.       

Aeration Frequency:  

How often→ High traffic sports fields should receive 6 to 8 aerifications per year. Hollow-tine core for at least two of the aerifications.  Slicing can replace hollow tine or solid tine coring for the other aerifications. Managers should aerate fields no less than two times per year.  

Where→ To save time and costs, aerate at highly trafficked sections of sports fields as opposed to the entire field.  Aerate those sections two or more times to open more of the surface. 

When→ Aerate when grass actively grows. Cool-season grasses grow the most in May and September. Aeration greatly complements overseeding, compost topdressing and fertilization by improving seed to soil contact and germination rates. 

Improving Drainage

Well drained fields create a better environment for the grass plant by increasing pore space and reducing nutrient loss. Soil compaction and clay tend to cause low infiltration rates (< 1 inch per hour) in native soil fields that prevent turfgrass seeds from germinating and roots from taking up nutrients. Inexpensive methods to improve drainage include aeration or adding soil amendments.  Do not mix sand into clay soil as a substitute.

Poor drainage on some natural fields may warrant a complete design renovation with sand and/or drainage tiles. See Table 1 for field redesign options if your district or authority needs to keep a field in-play after heavy rain events.  

Table 1. Overview of field design options to handle heavy rain events. MGG recommends native soil fields over the other options. In the case that drainage is very poor and rain very high, however, MGG will suggest sand-based alternatives.