The aim of this paper was to assess the joint productivity of groups of agricultural holdings specializing in field cultivation, taking into account modifications being the result of optimisation analysis and the DEA method. The results achieved by agricultural holdings operating in the Pomerania and Masuria region in the years 2004-2008 were researched based on data collected by Polish FADN (Farm Accountancy Data Network). Productivity function was measured using the three-factor Cobbs-Douglas production function, whereas changes in productivity were analysed using mathematical optimisation models, that is Lagrange’s method of undetermined multipliers, linear programming method and DEA non-parameter method. The results were compared with respect to farms’ productivity. The analysis indicates that the highest increase in productivity was achieved after implementation of changes suggested by Lagrange’s method of undetermined multipliers.