The necessity of carrying out functional zoning of agricultural lands to regulate the legal regime of their use for a certain type of permitted use of land plots is substantiated. The zones of functional use are types of agricultural land and elements of the transport and ecological framework of the territory. A balanced ecological and economic justification for solving the problem of establishing the boundaries of arable land, which meets modern economic conditions for conducting agricultural production, is proposed to be carried out according to the criterion of ensuring reproduction processes, the numerical indicator of which is a positive value of the standard rental income. This takes into account not only uncontrollable natural factors, but also the economic parameters of reproduction processes in the form of the ratio of prices for agricultural products and production resources, the amount of subsidies. On the example of the Engels municipal district of the Saratov region, the influence of economic factors on the criterion values (soil fertility, transport accessibility) and the total arable area of the district, which meets the conditions of profitable production, is shown.