Power and machinery is a single largest cost component, constituting about 60% of the total investment cost on mechanized farm. The profit of a farm depends, to a great extent, on the appropriate mechanization planning of the farm. Selection of proper size of power source(s) and its matching equipment is of paramount importance for an efficient mechanization planning.The bottleneck in the farm mechanization planning has been due to complexity of available machinery systems and their diversity with respect to type, size, number and operational characteristics. The process is further complicated in multiple cropping farms. Several models have been developed for the selection of agricultural machinery system using different techniques, like, linear programming, heuristic models, dynamic programming, and least cost approach. All those models were crop and location specific. This book describes the development of computer based mathematical models using least cost technique and a software for the selection of optimum power and machinery system. The developed models were validated for paddy-wheat crop rotation of Northern India.