THE CENTER FOR URBAN HORTICULTURE

University of Washington

Volume 2, Number 2

April 1984

MOWER BLADES SHARPNESS EFFECTS ON TURF

by Thomas B. Turner, Extension Turf Specialist.
University of Maryland in "The Agronomist,"
September 1983 (condensed).

A factor in mowing often ignored is mower
blade sharpness. In a recent issue of
Agronomy Journal , an interesting study re-
lated to this topic was presented. The effects
of a dull versus sharp rotary mower on turf-
grass and gasoline use were measured. Two
types of turf were studied, a 'Park' Kentucky
bluegrass monostand, and a ' Baron-Gl ade-
Adelphi1 Kentucky bluegrass blend. Some of
the results were as follows:

turf quality t^as reduced in both stands
9 when the dull mower was used;

2) leaf spot incidence was increased on
the 'Park1 turf with the dull mower

(the blend contained resistant cultivars);

3) thatch accumulation was not affected by
blade sharpness;

4) water use was lower when the dull mower
was used, but this was due to reduced
shoot density and verdure; and

5) gasoline use was 22% greater when the
dull mower was used.

spray solutions so the spray droplets spread
out and absorb onto a greater surface area.
This helps hold the pesticide on the sprayed
surface.

Sticker. A sticking agent gives an adhesive
effect after the spray has dried to protect
spray residues from wash-off by rain, heavy
dew, or irrigation and loss by wind erosion,
leaf abrasion, etc.

- Spreader-sti cker . A product combining the
effects of a spreader and a sticker. NOTE:
The greatest area of mi srepresentation and
misunderstanding in the whole subject of
spray adjuvants is the promiscuous use of
the term ' spreader-sti cker . ' Many products
labeled as 1 spreader-sti cker ' are nothing
more than a simple spreader, having no ad-
hesive quality whatsoever.

Extender. A sticking agent with an addi-
tional quality to prolong the life of the
pesticides, over and beyond just sticking
them in place and keeping them there longer.
NU-FILM-17, for instance, is an ulta-violet
radiation screener that protects spray resi-
dues against heat and ultra-violet radiation
which degrade many pesticides.

As the authors of this article conclude, the
study certainly "substantiates the detrimen-
tal effects of continuous mowing with a dull
blade on turfgrass quality and disease sus-
ceptibility," as well as significantly adding
to fuel costs. It thus certainly behooves
not only the homeowner but also the turf-
grass professional to maintain a sharp mower.

Reference: Steinegger, D. H., R. C. Shearman,
T. P. Riordan, and E. J. Kimbacher. 1983.
Mower blade sharpness effects on turf. Agron-
omy Journal 75:479-480.

^ S PM Y~XD JTTV A NT S : WHAT ARTTHeW

Spray adjuvants are valuable tools if used
roperly, but they can be a waste of money,
or even cause severe damage, if misused. Un-
fortunately, few people really understand
spray adjuvants and product labels may be
confusing or downright misleading. Landscape
managers must understand the various classes
of spray adjuvants available in order to
make wi se choi ces .

The following definitions are from an article
by T. E. Whitmore, "Spray Adjuvants are
Management Tools," which appeared in the
Journal of Arbori cul ture (November 1983):

Spreader, wetting agent, and surfactant .

These are synonymous terms referring to a
broad group of surface active agents; chem-
icals that reduce the surface tension of

Activator. An adjuvant which increases the
effectiveness of other chemicals such as
contact herbicides or systemics. To increase
the contact with the plant surface and to
facilitate the pentration of the chemicals
into small openings and directly through
the cuticular surfaces.

Compatibility agent. A product that facili-
tates the mixing of chemicals that do not
mix smoothly in the spray tank.

Acidifying agent or ocidifier or buffer .

An adjuvant to lower the pH of spray water.

Defoamer . Adjuvants to break foam or to
prevent its formation in the spray tank.

Dri ft control agents . Sometimes called
elast'icizers , these adjuvants reduce the
breakup of spray into fine droplets that
drift out of the spray area and may contam-
inate adjacent properties or crops.

Deposition aids. Not only do drift control
agents keep sprays from breaking up into
fine droplets that float away, but they
also increase the amount of spray actually
deposited onto the spray target. Runoff
is also reduced and pesticide deposit in-
creases of 25% to 35% are not uncommon.

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EDUCATIONAL OPPORTUNITIES
EDMONDS COMMUNITY COLLEGE

The following horticulture courses will be
offered for credit during summer quarter:
Summer Plant Propagation, Greenhouse
Studies, Woody Plant Review, Landscape
Design, Advanced Landscape Design, Soils
and Plant Nutrition, Layering.

Call 771-1545 for Retails.

ANNUAL TURF FIELD DAY

When: Wednesday, June 13; 10:00 a.m. to
12:00 Noon.

Where: Farm #5, WSU - Western Washington
Research and Extension Center.
Information: 593-8504, Puyallup.

BOOKS

Ortho's Complete Guide to Successful

Gardening . 1983. Ortho Books, 504 pp .
Including index, $29.95

For several years Ortho has been publishing
excellent garden books on special topics.
Now they have combined much of that inform-
ation into a large, comprehensive garden
book. This book is well organized and
liberally illustrated with color photo-
graphs. There are chapters on the follow-
ing subjects: color and design; climate,
microclimate, and shade; annuals; peren-
nials; bulbs; roses; shrubs; trees; lawns
and ground covers; herbs; vegetables;
fruits and berries; houseplants; and
garden care. The final section of the
book is an encyclopedia of plants which
describes the physical characteristics and
cultural requirements of cultivated plant
species .

ORNAMENTALS NORTHWEST NEWSLETTER

Ornamentals Northwest is a newsletter that
is published quarterly by the Cooperative
Extension Services of Oregon, Washington
and Idaho and the British Columbia
Ministry of Agriculture. It is available,
free of charge, to professional horticul-
turists. To be added to the mailing list,
send your name, address and zip code to
Ornamentals Northwest, c/o Jim Green, OSU,
Horticulture Department, Corvallis, OR,
97331.

(A) TREE STAKING - LESS IS BETTER

During his recent speaking engagement in
Seattle, Dr. Richard W. Harris, Professor of
Landscape Horticulture, Univ. of California
at Davis, questioned common tree staking
practices. His research and observation has
shown that staked trees will grow taller than
unstaked trees, but they will also have weaker
trunks which are often unable to stand without
support. A practical rule to follow seems- t<^k
be the less staking the better. Do not stake^^
unless it is really necessary. If you have to
stake, do it in a manner which will allow the
trunk to flex, since this movement strengthens
the trunk. Avoid rigid, single stake methods
such as those commonly used in nursery
product ion .

(B) EFFECT OF MULCHES

From: GROWING POINTS, Oct., 1982, Coop. Ext.
Service, University of California.

Data indicate that if soil is protected such as
under mulch or forest conditions, many small
roots grow upward and as many as 80% of the
feeder roots are in the top 6-12" of soil. (An
examination of the surface soil under landscape
trees may indicate similar findings. Research
in Michigan and Japan indicates that even though
there are more roots near the surface of mulched
than of bare soil, there are also more deep
roots under mulched than bare soil.)

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