A data set from Oehlert (2000) \emph{A First Course in Design and
Analysis of Experiments}, New York: W. H. Freeman.

Data originally from Whiting, Kelly Reid (1990) "Host-Specific
Pathogens and the Corn/Soybean Rotation Effect", Ph. D. Dissertation,
University of Minnesota, St. Paul, MN.

The response of interest is the weight (g) of 100 random seeds from
soybean plants.  The plants are of two varieties (Hodgson 78 and
BSR191).  We observe data from the fifth year of four different
crop rotation patterns (soybeans after 4 years of corn, second
year of soybeans after 3 years of corn, final soybean in an
S-C-S-C-S pattern, and 5 consequtive years of soybeans).
This experiment was conducted twice in Waseca and twice in 
Lamberton, with 1987 and 1988 being the fifth years of the
two replicates (ie, the sequences were offset one year).
Column 1 is the response.  Column 2 indicates year/location
(1=W87, 2=W88, 3=L87, 4=L88).  Column 3 indicates rotation treatment
(1-4 in the order given above).  Column 4 indicates variety
(1=HOD, 2=BSR).