necessary.
 Two multi-location examples are given to show what
types of treatments might be chosen in particular
situations and how these treatments might relate to one
another. The first example is a set of trials at ten
locations to evaluate five varieties (V1,...V5) each at
three nitrogen fertilizer rates (N1, N2, N3), as shown in
Table V-l. The major portion of these fifteen treatments
is a 5 x 3 factorial. In addition to these 15 treatment
combinations, three controls are included.

 TABLE V-l. Treatment combinations
 (5 X 3 factorial + 3 controls).


VINOCPc V4NOCPc
VINICPc V4NiCPc
VlN2CPc V4N2CPc
V2NOCPc V5NOCPc
V2NlCPc V5NICPc
V2N2CPc V5N2CPc
V3NOCPc VfNfCPf
V3NICPc VcNcCPc
V3N2CPc VrNrCPr


The controls represent:

 1) each farmer's variety (Vf), nitrogen fertilizer rate
 (Nf), and cultural practices (CPf);
 2) the variety (Vc), nitrogen rate (Nc), and cultural
 practices (CPc) typical of the area, or those
 commonly used by most farmers; and
 3) the variety (Vr), nitrogen rate (Nr), and practices
 (CPr) currently being recommended for the region.

In this trial, the variety and fertilizer treatments are
considered additive to the common technology of the area
(CPc), so those practices which constitute that technology
are used in the major portion of the treatment set.
 A second example illustrated in Fig. V-l represents a
fertilizer trial in which the intention is to measure the
response to nitrogen (N) and phosphorus (P) over a range
of rates, and to estimate a yield response surface within
this range. It is assumed that a good variety has already