environment in which the crop in the trial is going to be
planted normally. Likewise, paths, canals, large trees,
and other conditions which are not normally part of the
environment should be avoided. If the crop is usually
planted in these special environments, of course, it is
appropriate to locate the experimental area in them.

Experimental designs

 Conducting field trials on farms does not mean that
scientific methods can be overlooked. The same basic
methods are used as for any other research. The
experimental design or arrangement depends on the results
of the preliminary reconnaissance of the region, the
variables to be measured or controlled, environmental
variability, and the specific objectives of the trial. It
should be stressed that a good design is essential for
trials conducted on farms, as it is often the key to
helping farmers retain their beliefs and confidence in the
research institution and in the researchers themselves.
 Using specific designs simply because they were used
elsewhere in similar experiments is discouraged. Whether
or not to use blocks, how many replications to make, plot
size, and other design considerations will depend on the
particular problem in the particular location. The number
of controlled variables and the amount of data collected
should not be more than necessary for attaining trial
objectives. There is a natural tendency to record as much
information as possible, on the assumption that it might
help explain findings that may emerge upon completion of
the trials, or simply that it might be "interesting." But
experimental information, particularly at the farmer's
field level, is costly to obtain, and it is preferable to
limit data recording only to those data which are useful.
 Another consideration in planning a field trial is to
specify who will conduct it. The degree of complexity
will depend largely on who will be in charge of
implementation. Implementation may be assigned to
personnel working on an experiment station, or to a
multidisciplinary field team that planned the trials, or
perhaps to technical assistants trained for this purpose.
Extension agents or farmers may also be involved in the
management of the trials. Farmers' participation, in
particular, should be carefully defined in order to make