Crop/livestock rotations in Peru go back three thousand years to before the Incas and the Romans practiced fallows in between grain cops. But the application of Zero Tillage (ZT) to crop/livestock rotations effectively only took effect after the introduction of Glyphosate, ca. 1980. The Brazilians and later Australians and Americans applied ZT to ley farming. The literature rarely distinguishes ZT in ley farming. Today, the Brazilian and Australian literature are the most complete. The most important synergies are : (i) improved soil structure and organic matter, (ii) higher nutrient use efficiency, (iii) suppression of pests and diseases, (iv) higher yields in crops and animals and hence, (v) a better bottom line. The Australians and New Zealanders took longer than the N. & S. Americans to embrace ZT but were well ahead in tropical and sub-tropical ley farming.