 Dry fibres are machine combed and sorted into various grades, largely on the basis of the previous in-field separation of leaves into size groups.Sisal farming initially caused environmental degradation, because sisal plantations replaced native forests, but is still considered less damaging than many types of farming.No chemical fertilizers are used in sisal production, and although herbicides are occasionally used, even this impact may be eliminated, since most weeding is done by hand.