S. Todorova, N. Simeonova, K. Trendafilov, V. Valcheva
Abstract. In our research we are studying changes of some common chemical properties (pH, salt concentration, total carbonates, and humus content) during long-term organic-mineral fertilization and after its cessation. The object of our study is alluvial-meadow soil (Mollic fluvisol) in the region of Plovdiv (Bulgaria), on which in 1959 was set a trial with different variants of fertilization. Since 2006 the fertilization was stopped. Forty years of fertilization leads to increase in humus content, compared with unfertilized variant, and this is best expressed in variant with combined organic-mineral fertilization. After cessation of fertilization, soil organic matter content decrease in all variants. In other physicochemical parameters of the studied soil, there are no significant changes during the fertilization and after its cessation.