A student of plant pathology studied the `weed suppressiveness' of
tree soils. David Maxwell examined the sensitivity of `Rutgers'
variety tomato, known to be sensitive to biological factors, to
several different soils. Three of the soils (vermix,
promix and grnhous) are in a certain sense controls, the first
two being artificial and the third coming from a controlled
environment. A fourth soil contained only grass. The
other four are of particular interest, as the scientist wants to know
whether soil from tree nm-6 is better (lower score)
than those of the other three trees. The score was the number
of germinating tomato seeds out of ten planted. In addition, the mean
height of seedlings was measured at different times.
For each type of soil, there were six soil samples
(reps(soil)). These soil samples were inoculated with pathogen.
Then these soil samples were split (acc), with one half
autoclaved (sterilized) and the other half not. Thus there were
12 half-samples (acc*reps(soil)). Each of these 12 half-samples
was placed in storage and scored on six different dates.
In addition, the mean height of seedlings was measured at three
of these times. The primary focus is on the half-samples that were
not autoclaved.