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High Organic Matter Levels and the Squeeze Test, USGA Central Region Update

Published on 8/5/2022
Zach Nicoludis, agronomist, Central Region

Being able to squeeze water out of the thatch-mat layer after just a normal irrigation cycle or light rain is an indication organic matter levels are too high.

Superintendents are always focused on preserving turf health, especially during the heat of summer! However, additional factors like high organic matter levels, can compound turf health issues during periods of stressful weather.

Deferring cultural practices and other maintenance has led to excessive organic matter accumulation at many golf courses, especially on fairways and tees. Whether it’s a lack of resources, trying to avoid disruptions or a busy golf schedule, addressing this issue cannot be kicked down the road any farther. If organic matter levels are a concern, it’s important to begin planning cultural practices for the spring or fall to make up for lost time.

An easy way to determine if organic matter levels are excessive is to collect a sample from the playing surface in question after an irrigation cycle or light rainfall. If water can be squeezed from the top of the profile like it’s a sponge, organic matter levels are too high. From a visual standpoint, if the top few inches of the soil profile resemble a layered chocolate cake, this further confirms that organic matter levels are too high. If the squeeze test indicates an issue, sending out samples regularly for testing will confirm your suspicions and help you track what impact cultural practices and inputs are having on percent organic matter over time.

Core aeration or vertical mowing are usually good starting points for rectifying this issue. For more input on what changes can be made to the cultural management program to reduce organic matter levels, reach out to your USGA regional agronomist to set up a Course Consulting Service visit prior to performing aeration or vertical mowing.

Central Region Agronomists:
Paul Jacobs, agronomist –

Zach Nicoludis, agronomist –

Information on the USGA’s Course Consulting Service

Contact the Green Section Staff

(616) 834-0450