The work presents the formation of a system for assessing soil fertility and plant development using test monitoring polygons. Monitoring polygons became the basis for the introduction of modern technologies to increase plant productivity and soil fertility. The monitoring sites were located in the main agro-climatic regions of the Leningrad Region on soil types typical for the respective region. Analysis of the dynamics of the main parameters of soil fertility in test plots shows a tendency towards a decrease in the content of mobile forms of potassium and acidification of soils, as well as other signs of degradation. A decrease in soil fertility is associated with a decrease in the proportion of applied fertilizers and a decrease in soil liming. This process develops on all types of soils, with the exception of those areas that are located in suburban farms. The data for the test sites are consistent with the overall results of the agrochemical surveys. For industrial practice, test sites and information collected on them can serve as “information keys” for decoding space and aerial photographs in order to assess the state of agroecosystems, monitor changes in soil fertility and plant development. On the example of the cultivation of spring wheat, the way of precision assessment of the management of the productivity of cultivated crops and the increase of soil fertility is shown. The mechanism for the implementation of the plant productivity management system was carried out with the introduction of elements of precision farming.