7.4 An experiment was performed to investigate the factors that influence the predation of seeds lying on the ground in an area on which a crop has been grown. Seeds of three species were placed on the ground in cages of four designs that excluded different types of predators, in areas on which three types of crop residue were present, and at four distances from an area of bushland. The levels of these treatment factors are given in Table 7.11. This experimental area was divided into three blocks, and each block was further divided into three strips. Each strip had a boundary with the bushland at one end. Each strip received a crop residue treatment, each treatment being applied to one randomly chosen strip in each block. In each strip, one cage of each design was placed at each distance from the edge of the bushland. At each distance, the four cages in each strip were positioned at random.

Each cage contained seeds of all three species. After 15 days, the number of seeds of each species that remained in each cage was recorded, and the percent predation was calculated.

The layout of the experiment is illustrated in Figure 7.7.

The first and last few rows of the spreadsheet holding the data are presented in Table 7.12: the full data set is held in the file ‘seed predation.xlsx’ on this book’s website

(see Preface). (Data reproduced by kind permission of Robert Gallagher.)

Distance, residue, cage_type and species are to be classified as treatment factors.