Page 18 - GreenMaster Winter 2025

u FEATURE u DR XI XIONG AND DR. STEPHEN H. ANDERSON,
UNIVERSITY OF MISSOURI, XIONGX@MISSOURI.EDU
Science
Series Part 3
The Localized Dry Spots (LDS) are confined in squares as this is
the plot area where various wetting agent treatments were applied.
The areas showing LDS are without wetting agent treatment. Photo
taken on the University of Missouri research putting green.
WHAT IS LDS?
Localized dry spot (LDS), caused by soil water
repellency, is a common phenomenon on golf course
putting greens. Although water repellency could be
an issue for all soil types, sand-based media is
especially prone to this problem, due to its small
specific surface area (surface area per unit mass)
compared to silt and clay (Larsbo et al., 2008).
To alleviate LDS, wetting agent is a common tool
used by over 98% of golf course superintendents
(Karnok, 2006). Besides preventing LDS,
superintendents also apply wetting agents for a
whole array of purposes, such as improving water
use efficiency, optimizing water distribution, and
preventing surface runoff and/or excessive leaching.
CREATING A HYDROPHOBIC STATE
Formation of water repellency is due to the
decomposition of soil organic matter, including peat
moss added to the initial sand-based rootzone and
the plant residues, which over time break down into
Localized Dry Spots (LDS) are visible in untreated sections, while other areas
highlight the contrast in turf response when a wetting agent is applied.
organic compounds such as humic substances, wax, and
fatty acids (McGhie and Posner, 1981). Those compounds are
nonpolar molecules, and when they accumulate on the
surface of soil particles, they form hydrophobic layers,
creating a water-repellent rootzone.
As this process is driven by soil microbial activities
(Feeney, etc., 2006), occurrence of soil hydrophobicity is
inevitable on sand-based greens, and it will take place within
just a few years after green construction (Lewis et al., 2010).
As wetting agents are amphiphilic molecules, i.e., their
chemical structures contain both a hydrophobic tail and a
hydrophilic head, they can function as a “bridge” between
the hydrophobic soil particles and the by-pass water, thus
creating a wettable media.
Although not all wetting agents are created equal, most
wetting agents we use in the turf market can effectively
control LDS under field conditions. Previous research
conducted at the University of Missouri (UofM) has found
that wetting agents vary substantially for their influence on
surface tension of water, and there was a negative correlation
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