To begin the analysis, from the menus choose:

Analyze
Nonparametric Tests
2 Independent Samples...

Select Aflatoxin PPB and Centered aflatoxin level as the test variables.

Deselect Mann-Whitney U, and select Kolmogorov-Smirnov Z.

Select Corn yield as the grouping variable.

Click Define Groups.

Type 4 as the group 1 value and 8 as the group 2 value.

Click Continue.

Click OK in the Two-Independent-Samples Tests dialog box.