Nowadays, tractor is still the basic power unit in almost all production processes in agriculture, including tillage. The structure of tractor-machinery systems depends on many parameters: seeding system, soil conditions, farm area etc. These relevant parameters are defined in this paper, as well as the energy inputs introduced in the tillage through the consumed fuel. Altogether, they simultaneously represent the input variables in the selection criteria of tractor-machinery systems. A method of selecting the optimal tractor for different tillage technologies is presented in this paper. The results obtained show that fuel energy consumption for all tractors in the conditions of conventional tillage is in range from 412 to 740 MJ/ha. In the case of mulch technology the energy consumption varied from 183 to 266 MJ/ha and in the case of zero tillage the energy consumption varied from 80 to 284 MJ/ha. These results show obvious differences in energy inputs regarding the applied production technology. (C) 2009 Elsevier Ltd. All rights reserved.