Small tines stimulate turf and cultivate the root zone without significant visible disruption to greens because they do not penetrate deeply or pull out a core of soil.

Needle tines, solid tines, drills, hollow tines. There are so many different aerification tools on the market. I'm tired of players' complaints about cores on the green. Which tools let me maintain good playing conditions year-round without neglecting aerification?

That, of course, depends on many things. Here are a few key considerations.

Turf stimulation. Aerification or cultivation is, among other things, a pruning process. Though perhaps not as effective as verticutting, all cultivation tools slice stolons, rhizomes and tillers, which is likely to produce more stolons, rhizomes and tillers where the cuts occur. Predictably, the cultivation tools that are most likely to cut through the thatch or mat are more likely to stimulate growth by pruning. These include hollow tines and slicers (blades that produce elongated slits in the turf surface). The best results occur when turf is growing vigorously: spring and fall for cool-season turf, early summer for warm-season turf.

Compaction. If your greens receive heavy play and the "soil" compacts near the surface, the remedy will depend on whether the problem occurs in summer or during a cooler season. Core cultivation with hollow tines is the traditional remedy for compaction, but it's messy, and it's too stressful to do in summer on cool-season grasses. Because it actually removes soil, the process leaves space where topdressed sand can fill in. Generally, cores are removed to reduce the amount of organic matter that can contribute to thatch build up.

Solid tines or water-injection cultivation may be less stressful to turf in summer than hollow-tine cultivation. Because less living tissue is removed, the turf recovers more quickly.

Soil layers and subsurface compaction. These are tough problems to remedy with cultivation. It'll take years of rather aggressive penetrations from the surface down through the layers, followed by topdressings with a consistently uniform sand, to fill in the holes, break up the layers and replace the inconsistent materials that formed the layers to begin with. If the layers are deep, longer tines are required. Also, a consistent source of topdressing sand is needed -- one that produces sand with the same specifications year after year. Hollow tines create holes that are relatively easy to fill, although some vertical-operating solid-tine cultivators "shatter" the subsurface soil to break up layers. Both leave visible surface scars for several days.

Drill tines can be rigged to go deep and deposit sand in the holes. Obviously, it's a slow process, but it aids in replacing bad soil or sand.

Seeding, fertilizing, amending. Several companies offer tiny tines that barely penetrate the thatch and turf cover to open small holes for seed, solid fertilizers or amendments. Depending on the vigor of the existing turf, such minimal cultivation may not be adequate to allow seedlings to compete, although they reduce the likelihood of competition from new Poa annua seedlings.

If your only objective is to cultivate without pulling cores, look closely at water-injection cultivators, small solid tines and slicers.

-- Mark Kind, GCM science editor

Contact Turf Talk, c/o Ed Hiscock, 1421 Research Park Drive, Lawrence, KS 66049-3859, or mention Turf Talk in an e-mail message to ehiscock@gcsaa.org. Questions are also taken from the members' discussion forum on GCSAA's Web site or generated by GCM editors.