Kazakhstan black soil organic substance agrogenic transformation

Currently despite the extended study of the temporary dynamic of the cultivated soil organic substance on the global scale scientists pay much attention to the establishing the patterns of its quantitative transformation on the regional level depending on the systems of agricultural exploitation for the purpose of clarifying the worldwide estimate of humus reserve in relation to the issue of the «greenhouse effect». In this regard we have examined the modern dynamic (1990–2015) of the regular and southern black soil organic substance in the conditions of long-term stationary field experiments in the primary grain-sowing region of the Northern Kazakhstan. Based on the data from alternative time periods on the proportion of Соргand N in the upper (mainly 0–25 cm) layer of virgin and agrogenic black soil of Akmolinsk and Kostanay regions of Kazakhstan we have discovered the distinctive characteristics of changes in the content of soil organic substance. It has been demonstrated that the content of humus in the regular black soil is significantly higher than that in the southern carbonated black soil. Evaluation of transforming and inert pool of organic carbon in virgin and agrogenic variants of southern black soil has been made. It has been established that currently in the result of influence from various methods of southern black soil treatment the rate of humus percentage decrease is slowing down in comparison with that of the previous period of its agricultural exploitation, however, in practice, those methods, including the subsurface tilling, do not halt the de-humusization process. Content of humus in soil of the variants with continuous spring wheat is approaching that with continuous complete fallow. There are sufficient grounds to suggest that the reason for de-humusization of the southern black soil could reside in biochemical (mineralization), as well as physical (deflation) loss of humus. Particular danger comes from the wind erosion resulting in percentage of humus dropping even below its minimal value, i.e. due to the decrease of nearly unrecoverable inert part. In agrogenic regular black soil, during the closing period of its agricultural exploitation, there has been no humus loss detected, which is most probably related to the existence of protective anti-erosion forest belts in the studied fields area.