Environmental conditions significantly influence agricultural production, i.e. they are one of the main factors that affect its efficiency. Continuous monitoring of economic results makes it possible to identify the basic elements of revenues and expenditures in production of major agricultural crops, and use these data to plan future production – in other words, to choose the right enterprise for respective environmental conditions. The gross margin is a quick and efficient indicator used to analyse an enterprise when considering economic indicators of different enterprises and choosing the most efficient one in economic terms. In this paper we used the gross margin to compare the two production years with different production conditions, but on the same farms. Therefore, gross margin was used as an adequate indicator that aims to show the difference which is in function of various agro-ecological conditions, price and yield within the period of two years. The paper used the questionnaire carried out in 2011 and 2012 on a total of 69 chosen leader farms from the territory of 11 stations of the Agricultural Extension Service of Serbia. The questionnaire collected data on revenues and expenditures based on which gross margins for maize were calculated. The main indicator of this calculation is the gross margin, which is the difference between the value of production (value of the primary and the secondary product) and total variable costs that covers seed costs, fertilizer costs, costs of plant protection products, diesel fuels and contracted services (for sowing, harvest and labour). In these periods climatic conditions differed significantly. In 2012 there was considerably less precipitation with higher air temperatures, which was one of the main reason for reduced yields per area unit. In 2012, yields decreased by 28%, while price per kilogram of maize increased by about 37%, reducing total value of production by about 1%. It was estimated that total variable costs increased by 6%, while the gross margin was reduced by about 8%.