Changes in humus content in forest-steppe soils of Western Siberia

Abstract

The research is based on the results of local monitoring in 1990-2018 on reference plots of agricultural lands and archival materials of a large-scale agrochemical survey. The purpose of the research is to identify patterns of change in the humus content of arable soils of the forest-steppe in the Omsk region after prolonged use in agriculture. The objects of research were the soils of the forest-steppe zone of the Omsk Region: ordinary chernozem low-power low-humus heavy loamy soil; meadow-chernozem medium-thick medium-humus heavy loamy soil; solonetz meadow chernozemic deep low humus clay soil. The largest area on the last round of agrochemical survey of 1194.3 thousand ha (58.9%) has an average humus content (4.1-6.0%), it increased significantly from 784.5 thousand ha (38.7%). The increased and high (> 6%) humus content significantly decreased over the study period by 416.5 thousand ha from 1118.5 (55.1%) to 702.0 thousand ha (34.6% of the surveyed area). The weighted average humus content over 28 years has changed: from 6.2 to 6.0% in the northern forest-steppe, from 6.0 to 5.3% in the southern forest-steppe, on average it is by 0.5%. A tendency toward a decrease in the humus content of soils remains in the soils of the Omsk Priirtyshye region. The main reason for this is both the ongoing water and wind erosion of soils, and the very low level of organic fertilizers use. The authors revealed the gradual decrease in the content of humus in ordinary chernozems and meadow chernozem soils. There was a stable humus content in the arable horizon of the solonetzes of deep meadow-chernozem soils.