Less record keeping than pedigree method. Easy to handle more crosses. More useful than pedigree method with lower heritable traits. Large number of genotypes can be maintained. Can be carried on for many years with little effort by the breeder.
Environment changes from season to season so adaptive advantage shifts.
Most grow bulks in area of adaptation for the crop and variety. Final genotyes are bulk may be able to withstand environmental stress, they may not be the highest yielding genotypes. If utilized in cross-pollinated species, inbreeding depression may be a problem. 1. hybridization 2. The best method here is to continue to use the bulking method and pull out desirable material along the way.