Agriculture Reference
In-Depth Information
Figure 5.3
A technician marks off sample plots from a celery fi eld trial before harvest. Photo
by author.
the latter with the conventional chemicals usually applied to this kind of
celery crop. The idea was to compare the differences in yield and past
control between the control area and the new treatment area. If the alter-
native chemicals proved effective at controlling pests and still allowed the
same crop yield, this information may have convinced growers to use
the new treatment.
There are several different meanings for
control
here, but two are espe-
cially relevant: the advisors typically
control variables
in their experiments,
and the growers and advisors want to
control for pests
of their crops. The
diffi culty of maintaining a fi eld trial on a grower's land lies in a potential
confl ict between these two kinds of control. Field trials often bring a level
of risk to the grower's crop, depending on the research design. In some
cases this may lead the grower to become nervous as he or she eyes the
portion of the fi eld in which the experimental treatment is being tested.
For instance, in the celery trial depicted in fi gure 5.3, if by the middle of
the trial the alternative treatment appears not to be effective, the grower
might be tempted to spray a more conventional treatment on the experi-
