A note on the construction of phase-confounded designs

Extract

In experiments comparing the effects of different crop rotations it sometimes happens that blocks of reasonably small size can only be achieved by not letting all sequences of each rotation occur in each block. If one of the rotations carries the test crop more than once such a restriction usually leads to the confounding of some phase contrasts. Stevens (1956) and Patterson (1964) provided two classes of phase-confounded designs. The two designs, however, lack the desirable property that if, in a particular block, some of the rotations carry the test crop in a given year, other rotations also do. Furthermore, the designs do not involve equal block sizes in the sense that, in any year, in any block, the number of plots carrying the test crop is the same.