Currently, less than 33% of arable land is used in Meshchovskoye Opolye. Optimizing technology elements of resource-saving development of synanthropic fallow phytocenoses with complex invasion is relevant. The article is devoted to analysis of development of self-organizing phytocenoses with varying invasion degrees and their use on lands temporarily withdrawn from active agricultural use. Field experiments were carried out on postagrogenic gray forest loamy soils in Kaluga Research Institute of Agriculture in 2006-2018. Influence of mineral fertilizers as an optimization element of technology of fallow development was studied using transects and permanent survey sites on the area of 12.0 ha. The reasons for change in productivity and its determining elements in hayfields in autogenous - allogenic phytocenoses were analysed. We established that economic value of plant communities was determined by potential of constituent species and variability of their productivity in years with various environmental conditions. 12 years later phytocenoses become homogeneous and consist of 10-12 main plant species, determining green mass productivity by 75%. Compared to native species invasive plant species have 1.4-2.0 fold higher productivity which accounts for 60% and more productivity of phytocenoses. Transforming role of Erigeron canadensis L., Lupinus polyphyllus Lindl. and Solidago gigantea Ait. on their expansion into aboriginal herb (share in mowed mass - 40% or more) communities was shown; their high adaptive potential for ecological-soil conditions of Meshchovskoye Opolye (center of Nonchernozem Zone of Russia) was established. Application of mineral fertilizers (P40K90) in the secondary Trifolium medium phytocenoses (more than 40%) contributed to 2.4-fold increase in its productivity (from 1.38 to 3.29 kg/m2) and increased productivity stability by 60%, reducing low-value species in crop structure by 1.6 times. The total area of cenopopulations increased by 10.4-21.5%, yields - from 2.31 to 4.41 kg/m2.