AFM 91-19 / TM 5-629 / NAVFAC MO-314
24 May 1989
*The figures in parentheses indicate lines of this document.
**Nonproductive time includes time used in transport to and from the work site, refueling and greasing
equipment, and making repairs and adjustments. This time is subtracted from the normal 8-hour day to
derive "productive operator-hours per day."
***Computed on an hourly basis for tractormowers if they are the prime movers of the mowers to and from
the work site. The tractor-drivers' time is included in the 2 hour "nonproductive time" or in-transit time
and is therefore not included again in 4g.
Figure 6-4. Continued.
a. We will assume that prescribed application
(2) This part of the analysis should receive
procedures are followed and that the effective-
special attention because of the variations in
ness of a PGR can be expressed in terms of an
price and effectiveness of PGRs. The choice of a
effectiveness-rate and an effectiveness-period.
PGR will depend on both the PGR's cost and its
These terms provide a basic description of how
effectiveness under local conditions. A PGR
much a PGR application is expected to reduce
which may be more effective on a pound-per-
plant growth and, thus, mowing requirements,
acre basis may not be recommended because of
over a certain period of time.
its disproportionately greater cost. (Mefluidide is
b. The effectiveness-rate is simply the percent-
about equal to maleic hydrazide in terms of
age by which total growth will be reduced over a
specified period of time. The specified period of
time is the effectiveness-period. For example, if
a PGR application would reduce total growth by
Section C -- Determining Cost-Effectiveness
50 percent over an 8-week period, then the
effectiveness-rate would be 50 percent, and the
6-7. Effectiveness-Rates and Effectiveness-
effectiveness-period would be 8 weeks. We can
Periods of PGRs. It is necessary to know how
specify either the effectiveness-rate or the
much and how long a PGR is likely to suppress
effectiveness-period and then estimate the other
the growth of grass before we can estimate its
based on local experience, manufacturers' litera-
ture, or research reports.