Hayes and Garber - Cucurbit Breeding

FIELD PLOT TECHNIC 65
SUMMARY OF FIELD PLOT TECHNIC
Following is a brief summary of the more important factors
which assist in obtaining reliable plot results.
1. Soil heterogeneity exists in varying degrees, hence uniform
plots should be selected for the field experiments. To aid in
determining the comparative uniformity of different fields,
Harris' method or the check plot method may be used.
2. If the field varies uniformly from one side to the other,
check plots may be used to correct yields. In general, the use of
checks to correct yields is undesirable.
3. The yield of check plots may be used to determine the probable
error of the method of work. They should be placed systematically
throughout the experimental plots and the number should
be sufficiently large to approach a normal frequency distribution.
4. Probable errors may be used to determine whether the obtained
differences between strains are significant and thus aid in
eliminating the significantly lower yielders.
5. The probable error of an experiment may be determined
by the pairing method suggested by Wood and Stratton. It is
comparable to the one based on the checks and may be used in
the same way.
6. The probable error of an experiment may be reduced most
effectively by plot replication. Replication up to a certain
number rapidly reduces the probable error, beyond that number
additional replications do not proportionately decrease it. The
number of replications will depend considerably on the character
of the soil and somewhat on the size of the plots. On fairly uniform
land three replications have been found satisfactory for
general breeding studies.
7. Oblong plots sown with an ordinary grain drill give reliable
results when their area is approximately %o acre each.
8. Plants growing on the border of a plot adjacent to an alley
or roadway are usually superior to those growing within the plot,
hence, if it is desired to secure yields comparable with those which
would be secured under field conditions, the border plants must
be discarded. The border should be removed to a depth of at
least a foot. Different varieties and strains may have unequal
ability to utilize the free space along the pathways between plots
and consequently a second reason arises for discarding the border.
9. Cpmpetition exists between nearby varieties and strains.