Evaluation of soils of agrocenoses in the forest-steppe zone of the Omsk Irtysh region by the level of cultivation and fertility

We assessed soil fertility of agricultural lands based on the relative index and the complex agrochemical index (CAI), which was calculated from the data on the content of humus, mobile forms of phosphorus and potassium, and the reaction of the environment. The reaction of the soil medium was neutral, with the exception of calcareous soils and solonetzes. The structural condition in the arable layer (0–20 cm) of the soils was assessed as good. Fractions, the most valuable from the agronomic point of view (10.0–0.25 mm), prevailed in the aggregate composition. In the soils of the Kormilovka and Lyubinsky districts, their quantity was below the optimal level and amounted to 60.9–61.9%. The content of the blocky fraction (> 10 mm) exceeded the critical level by 5.0–6.0%. The deviation from the optimal parameters indicated a low degree of physical degradation in the soils. The structural aggregates were not resistant to the destructive effects of water. The calculation of the CAI showed that the soils of the Kormilovka and Lyubinsky districts had the highest fertility, the estimated score was 66–95. The soil fertility of the Azov district was estimated at 53 points. Soils under fallow and forage lands had high CAI (71–100 points). The degree of cultivation of arable land was medium and high.