Set-aside and changes in utilization of agricultural land are, in general, connected with insufficient profitability of agricultural production, urbanization of rural areas or a loss of soil productivity. The Set-aside Land Option (SLO) introduced in the European Union countries at the end of the eighties as part of Common Agricultural Policy (CAP) resulted from surplus in agricultural production. Its main purpose were equal prices on the world food market. In Poland set-aside is mainly due to a decrease in the production productivity. At the end of the nineties the area of arable land excluded from production was over 2 m ha. The present review presents the main research problems. The results of studies conducted recently in Western Europe and the United States confirm the positive effect of taking land out of production on the soil environment, surface waters, animal and plant species diversity and on the physical and chemical processes within agroecosystems.

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