The dynamics of cereal yields on drained land are examined and the factors causing variations in yield are noted. The study is based on the taiga zones of the European part of the USSR. It is emphasised that the development and effective use of land based on soil improvement depend on an assessment of the potential productivity of the soils and a forecast of changes in the properties of the soils resulting from economic activity. Soil improvement techniques must be matched to the hydrothermal conditions and structure of the soil cover in the various regions. -P.Cooke