Study on the Impact of Alternative Organic Fertilizers on the Dynamics of Mineral Nitrogen and the Mobile Forms of Phosphorus and Potassium under Increasing Application Rates

¹ Nikola Poushkarov Institute of Soil Science, Agrotechnologies and Plant Protection, Agricultural Academy, Department of Agricultural Mechanization and Hydromelorative Systems, Sofia, Bulgaria
² Nikola Poushkarov Institute of Soil Science, Agrotechnologies and Plant Protection, Agricultural Academy, Department of Agricultural Chemistry, Agri-environment and Farming Systems, Sofia, Bulgaria
³ Odesa State Agrarian University, Department of Plant Protection, Genetics and Breeding, Odesa, Ukraine

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

The effects of alternative organic fertilizers – Humipromoter, Biopromoter, and farmyard manure – on the dynamics of mineral nitrogen and the available forms of phosphorus and potassium under increasing application rates were investigated. Humification and mineralization processes were studied in Leached smolnitsa and alluvial-meadow soils after the application of these organic amendments. Fertilization trials with farmyard manure and alternative organic fertilizers enabled a comparative assessment of their impact on mineralization and humification processes in both soil types. The rate of mineralization was established depending on the applied fertilizer rate, relative to the control in Leached smolnitsa. A clear pattern of organic carbon changes with increasing fertilizer rates was identified. The mineralization rate depends on the applied fertilizer rate. An increase in mineral nitrogen content in Leached smolnica was observed compared to the control within the first 45 days. This effect is stronger with high rates of Humipromoter and Biopromoter, where the highest increase in mineral nitrogen was recorded – 166.50 mg·1000 g^–1 and 133.00 mg·1000 g^–1, respectively. Mineral nitrogen content rises with higher organic fertilizer rates. By day 90, high mineral nitrogen levels are recorded in high-rate Humipromoter (160.10 mg·1000 g^–1) and Biopromoter (107.70 mg·1000 g^–1) variants, despite plant uptake. Thus, high rates of organic fertilizers accelerate mineralization in Leached smolnitsa. In Alluvial-meadow soil, after 45 days, the highest mineral nitrogen content is observed in medium-rate Biopromoter (72 mg·kg^–1 soil) and Humipromoter (53 mg·kg^–1 soil) variants. By day 90, mineral nitrogen decreases in all variants except for the high-rate Biopromoter, which reaches 59 mg·kg^–1 soil. Mineralization proceeds more slowly in Alluvial-meadow soil, especially at high rates during the first 45 days.