Dubova L., 2020. Influence of symbiotic associations on yield formation of beans (Vicia faba L.) Latvia University of Life Scienes and Technologies: Jelgava. Legumes are widely grown crops, which symbiotically fix nitrogen from the atmosphere. Following the decline in legume production at the turn of the century, sown areas in Latvia have expanded rapidly in recent years. EU directives, which set requirements for the diversification of arable crops, are an important contributor to the growing popularity of legumes. The intensification of legume cultivation is linked to changes in cultivation technologies and to the amount of varieties available to growers. The beneficial effects of legumes on various environmental processes are possible with the interaction with symbiotic microorganisms. With the growth of bean-cultivation areas in compliance with the requirements of European directives, as well as with the changing cultivation technologies and agro-climatic conditions, the need to intensify research on the interaction of beans and microorganisms is becoming more and more important. In Latvia, rhizobia have been studied for a long period of time. However, the research has been carried out with varying intensity. There is little research done on the role of mycorrhizal fungi in agroecosystems, but the interaction between rhizobia and mycorrhizal fungi has not been studied at all in Latvia yet. The aim of this study is to evaluate the effect of symbiotic associations on the bean (Vicia faba L). The following tasks have been set: to evaluate the suitability of Rhizobium leguminosarum strains of the Rhizobia collection of the LLU Institute of Soil and Plant Science for efficient symbiosis of faba beans; to clarify the influence of environmental factors on the formation and efficiency of symbiotic associations, to assess whether it is appropriate to double seed inoculation with symbiotic microorganisms in order to increase the quality of a bean crop. The research has been carried out between 2014 – 2019. The trials were set up under controlled conditions in the vegetation pots and in field conditions. Rhizobia from the LLU Institute of Soil and Plant Science collection were used, mycorrhizal fungi preparation was obtained from the Czech company Symbiom® and contains three mycorrhizal fungal species - Glomus claroideum, G. intraradices and G. mosseae. The research was done within the framework of the European Union 7th Framework Program project EUROLEGUME (Enhancing legumes growing in Europe through sustainable cropping for protein supply for food and feed). It was concluded that bacterial strains of the LLU Rhizobia Collection has different activity and ability to form symbiosis with beans. Evaluating dehydrogenase activity and nodule formation it has been found that to reduce the inhibitory effect of environmental factors, it is useful to use rhizobia associations for inoculation. The use of rhizobia together with mycorrhizal fungi stimulated mycorrhizal intensity. It was found that supplemental mineral nitrogen fertilizers did not promote colonisation of mycorrhizal fungi in bean roots, the mean mycorrhization rate was lower than with double inoculation. Mycorrhizal fungi were presented in all soil types analyzed. There was a difference in mycorrhizal rate (F %) and arbuscular incidence (A %) in small seed and coarse seed bean. Positive effects on crop yield and quality can be observed in the double-inoculation variants. However, the positive effect varied from year to year. In most cases, only a positive trend occurred. The Ph.D. Thesis consists of 105 pages (apart from references). Thesis contains 8 tables and 54 figures.

Topicality. The events of recent years (the Covid-19 pandemic, hostilities in Ukraine) have led to a significant increase in world food prices. Thus, the FAO price index in February 2022 reached a historic high of 140.7 percentage points. One of the significant factors in this situation is a significant increase in prices for fertilizers for agriculture, which leads to their shortage. This actualizes the search for a solution to the problem of using sewage sludge as biological resource for sustainable agriculture and ensuring the implementation of sustainable development goals, including goals 2, 6, 11, 12, 15.Aim and tasks. The purpose of the article is to analyze various aspects of the use of sewage sludge in agricultural production as one of the promising ways to achieve sustainable development goals.Research results. The content of organic matter in the sludge can improve the physical, chemical, and biological properties of the soil by ensuring better soil cultivation and water retention capacity, especially when dehydrated sewage sludge is used. Biosolids reduce runoff and increase surface water retention. Organic nitrogen in sludge is much less likely to cause groundwater pollution than chemical nitrogen fertilizers. The use of sewage sludge on agricultural land is the best way to recycle the nutrients it contains. Sewage sludge can therefore be considered an important biological resource for sustainable agriculture. Physico-chemical characteristics of sewage sludge of different origin were compared. The concentration of carbon, nitrogen, and phosphorus were similar. Nevertheless, there are some site-specific factors that make each sewage sludge unique and must be taken into account to predict the outcome of sewage sludge treatment. To achieve the goal, an analysis was made of the effect of sewage sludge on the physico-chemical and microbial properties of the soil; its impact on plants and their productivity; the problems of using soil sludge in agriculture, taking into account its contamination with various substances (heavy metals, microplastics and pharmaceuticals), have been studied.Conclusions. Sewage sludge is a promising fertilizer for sustainable agriculture, taking into account the need for an effective technology for its purification from hazardous substances.