THE LEVEL OF AGROCHEMICALS APPLICATION AND PHOSPHATE REGIME OF ARABLE SOIL OF VOLGA REGION OF THE REPUBLIC OF TATARSTAN

The aim of the study was to assess the dynamics of the phosphate regime of soil and to establish its dependence on the level of application of fertilizers and chemical ameliorants. The object of the study was arable soils of Volga region of the Republic of Tatarstan (RT), located on the right bank of the Volga River. This region occupies the north-eastern part of the Volga Upland and makes up about 15% of the republic’s area. Situated in the transition zone between the taiga-forest and steppe zones, Volga region of the republic is characterized by a wide distribution of gray forest soils and forest-steppe chernozems. The materials of the agrochemical service of the Republic of Tatarstan (FSBI CAS “Tatar”) for 1965-2022 are analyzed. Mobile phosphorus forms were determined by standard methods depending on typical soil characteristics: according to Kirsanov in the modification of TsINAO (GOST R 54650-2011), Chirikov (GOST 26204-91), Machigin (GOST 26205-91). It was found that according to the cycles of agrochemical survey, the content of phosphorus mobile forms in the arable soils of Volga region fluctuated significantly: if during the first period (1965-2000) there was a confident increase in mobile forms of phosphorus (from 93 to 161 mg / kg), then later (2000-2022) there was a decrease (from 161 to 137 mg/kg). All agrochemical techniques - the introduction of mineral and organic fertilizers, phosphoritization and liming had a positive effect on the accumulation of mobile forms of phosphorus. In terms of the significance of the positive impact on the average weighted content of mobile forms of phosphorus in the soils of Volga region, the studied agrochemical methods were arranged in the following descending order: application of mineral fertilizers, then liming, then phosphoritization, and finally application of organic fertilizers.