Variables Codes Levels (coded and real values)
    -2 -1 0 +1 +2
ST (X1) 0.5 1 1.5 2 2.5
LB (X2) 0.5 1 1.5 2 2.5
BB (X3) 0.5 1 1.5 2 2.5
LA (X4) 0.5 1 1.5 2 2.5
Table 1: Levels and codes of the independent variables for addition of inoculums of ST, LB, BB and LA.