| Good agronomic practices necessitate aerification of the soil profile to maintain a high level of macro-pores in the root zone. A well-aerated soil is cooler in the summer since air is a better insulator to heat than water. In contrast however, water is an excellent conductor of heat.
Temperature moderation
If the soils are saturated during extreme weather, the roots are further subjected to high temperatures and will cease to function. This is a primary reason that roots are generally lost during the heat of the summer. A vigorous venting program during the summer months will help maintain high levels of air in the profile and therefore a cooler root zone and healthier roots. A deep, functioning root system allows the plant to transport water through its tissue in the transpiration process, which enhances self-cooling. Similar conditions are desirable for the growth and development of an active microbial population in the profile.
Compaction relief
Turfs that are heavily trafficked such as golf course fairways, tee boxes, and greens are subject to physical impacts that can alter the bulk density of the soils. In most cases we think about this as compaction or appropriately identified as the compression of the soil profile. This increase in bulk density is generally at the expense of macro pore space. A well-maintained soil profile will have between 35 – 50% of its total volume as micro- and macro-pores. Occasionally the site must be aerated to maintain or reestablish the balance in pore space. Numerous types of aerifiers have been developed by the iron manufactures supporting the turf industry. These include coring devices that are designed to extract a portion of the existing root zone leaving behind an opening for water and air to flow. Coring devices include open-back tines, spoons, tube tines, and drills. Core aeration is also an extraction process in which part of the soil profile is physically removed. This removal can relieve compaction as well as reduce the amount of organic material which has been accumulating in the root zone area. During the spring and fall periods core aeration is generally followed by moderate to heavy top dressing to replace or dilute the root zone mixture replacing the extracted organic material with sand or a sand/peat mixture. There is no substitute for periodic core aeration to maintain a balance in soil organic levels.
Possibly one of the most important cultural practices for maintaining a strong deep root system is to maintain the maximum level of macro pore space possible in the root zone throughout the season. Short of constant core aeration which may be highly desirable for plant growth and development, but antagonistic to the consumer is to institute a good venting program which will allow for frequent deep penetration into the soil profile with minimal surface disturbance. This slicing or penetration of the root zone results in a downward and/or sideward movement (compression) of the soil leaves a puncture hole or slit. The star-tine (3.5”) and VENTINE tm (6.0”) tines (pictured) are good example of puncture type tines, which readily fit on self-propelled aerifiers. These puncture type tines are designed to provide a vertical shaft (macro-pores) in order to promote infiltration of water, and to provide a vent for excessive water to escape (drying channel) and allow air to be exchanged throughout the root system. Rooting depth is more often determined by the depth of aeration not water penetration. Root depth is more often determined by the depth of aeration, and restricted by degree of water penetration.
The venting tines also have the added advantage of reduced cost over water injectors, fit on existing equipment, and do not cause soil particle separation nor inject additional water into a root zone that may be severely saturated and in need of drying.
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I use the terminology of venting verses aeration or aerification as we often associate aerification with the removal of cores from the soil profile, a presence of cores on the playing surface, and a loss of playing quality for an extended period of time. Venting is accomplished with instruments like the newly developed venting tines that result in minimal surface disturbance with maximum penetration into the root zone. In most cases aerification equipment has been designed to penetrate to a depth of 2-3.5 inches and no more. Newer equipment on the market has been designed with a 6" or longer stroke rather than a 3.5" stroke and will therefore make a deeper shaft. The venting tine is a flat bladed tine that when oriented in the direction of travel will create a slice in the turf with narrow sides, but longer slot. This rectangular slot will remain open for 10-14 days permitting a continuous exchange of excessive water with atmospheric gases. Venting should be done primarily during the hot seasons of the year to permit maximum infiltration of water during rain, irrigation or flushing and provide maximum evaporation of excessive water following irrigation or a rain event.
A vigorous venting program during the summer months will help maintain high levels of air in the profile and therefore a cooler root zone and healthier roots. Similar conditions are desirable for the growth and development of an active microbial population in the profile. Not to be overlooked is the importance of this living - breathing microbial population which is essential to decomposition of organic material and the recycle and release of nutrients back into the soil profile.
The primary goal is to maintain an upper root zone that is well balanced in moisture, nutrition and soil air. During heavy rains, the bulk of the water will be removed by surface flow. A significant portion of water will enter into the root zone however, and it is desirable to have this water move away from the surface as quickly as possible.
To reestablish a high permeable surface, it will be necessary to use shallow-tine aerifiers equipped with hollow tines or open back tines to remove a plug of root zone-organic matter layer. Frequently this may be combined with the deep tine aerifiers to provide penetration throughout the profile and reduce compaction below the normal aerification range. The created channels need to be back-filled with material of good porosity and preferably similar to the construction root zone material. Star tines and venting tines are the primary means of summer aerification to maintain positive atmospheric gas and water movement. We will grow roots to the depth that we can put oxygen. Deep plump, white roots growing down aerification channels and through cup changes dramatically communicate what “enhancing profile porosity means”.
It therefore becomes important to have the air at the canopy surface under continuous flow, i.e., moving the moisture away from the plant. Further when creating VENTING holes during the summer, the airflow across theses vents behave as a Ventura and aid in extracting excessive moisture from the soil. This obviously requires adequate airflow across the surface of the green.
If the plant has a well-maintained roots system, an adequate supply of soil moisture, nutrients and air and a microclimate in which to expend energy, the plant will effectively and continuously cool itself, create a healthier turf, experience less disease incidence and more competitive against weed invasion.
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