A research article recommended two spring and one autumn hollow-tine aerification, supplemented by solid-tine aerification during summer, for creeping bentgrass putting greens in the transition zone.

I discussed this, and include links to the article, in this post: https://www.asianturfgrass.com/post/coring-three-times-a-year-is-recommended-when/

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More about ATC soil tests at https://www.asianturfgrass.com/project/soil-tests/