Seasonal sequestration capacity of chernozem under different agrotechnological impacts in agrocenosis

V. Bulgakov¹, I. Gadzalo², S. Pascuzzi³, O. Demydenko⁴, I. Holovach¹, Ye. Ihnatiev⁵⁶ and J. Olt⁵*

¹National University of Life and Environmental Sciences of Ukraine, 15 Heroyiv Oborony Str., UA 03041 Kyiv, Ukraine
²National Academy of Agrarian Sciences of Ukraine, 9 Mykhailo Omelyanovych-Pavlenko Str., UA 01010 Kyiv, Ukraine
³Department of Soil, Plant and Food Science, University of Bari Aldo Moro, Via Amendola 165/A, IT70126 Bari, Italy
⁴Cherkasy State Agricultural Experimental Station National Scientific Centre, Institute of Agriculture of NAAS of Ukraine, 2B Mashinobudivniki Str., UA08163 Chabany, Kiev region Ukraine
⁵Estonian University of Life Sciences, Institute of Forestry and Engineering, 56 Kreutzwaldi Str., EE 51006 Tartu, Estonia
⁶Dmytro Motornyi Tavria State Agrotechnological University, 66 Zhukovsky Str., UA 69600 Zaporizhzhia, Ukraine
*Correspondence: jyri.olt@emu.ee

Abstract:

The soil’s sequestration capacity is primarily determined by the fine-dispersed fraction of the soil and strongly influences the properties and fertility level of the soil. To assess the sequestration capacity of C-CO₂ humus in soil formation and fertility of typical chornozem (black soil), to identify the causes, rates, existing limits of the sequestration capacity decrease, it is important to study the seasonal dynamics of qualitative and quantitative indicators of humus state in time depending on the method of tillage and fertilization in agrocenoses of short rotation crop rotations in the central part of the Forest-Steppe region of Ukraine. During the research, a stationary field experiment was conducted to study the influence of methods of soil cultivation and fertilizer application on the sequestering capacity of chornozem. Laboratory studies were conducted to determine the content of humus and to calculate the seasonal reserves of absorbed carbon and phosphorus and to model the absorption capacity of chernozem. When processing with chisel plows and applying fertilizers, the increase in the C-CO₂ reserve during the April-July period was +21 t ha^-1 (0–0.2 m) and +36 t ha^-1a (0–0.3 m). Under moldboard plowing, the growth tended to increase by 1.52 times (0–0.2 m) and 1.25 times (0–0.3 m), but occurred at a lower quantitative level, and in the period July-September, the change in the humus C-CO₂ stock was insignificant, indicating the predominance of C-CO₂ sequestration processes in the summer-autumn period with chisel plowing. With chisel plowing, the reserve of labile organic substances (LOS) in April exceeded the stock for plowing in the thickness of 0–0.3 m by 4.34–7.67 times (without fertilizers), 1.5–2.76 times (with fertilizers); in July – by 4.59–8.90 times (without fertilizers) and 1.32–3.16 times (with fertilizers); in September – by 4.52–4.04 times (without fertilizers) and by 1.11–1.93 times (with fertilizers), and the C-CO₂ stock of the LOS compared to fallow land under chisel plowing without fertilizers in April, July, and September was
1.59–1.78 times, 2.31–3.29 times, and 1.4–1.78 times higher, and under fertilization – by 1.99–2.0, 1.86–4.50, and 1.7–2.6 times, respectively, depending on the seasons. Under fallow land maintenance, the seasonal dynamics of the C-CO₂ stock of the LOS is subject to the seasonal dynamics of P_org(LOS). A direct strong correlation was found at the level of R = +0.89 ± 0.02; R² = 79. In the period April-July, the decrease of P_org(LOS) stock in the thickness of 0–0.2 m was found to be 1.15 times, and in the thickness of 0–0.3 m – 1.1 times. From summer to autumn, the stock of P_org(LOS) was restored, and the stock in the thickness of 0–0.3 m increased by 1.10 times. Conclusions. Trends in C-CO₂ stocks of humus and LOS indicate that in the series plowing-chiseling-fallow land, the cyclicality index under chisel plowing was closer to the value of the seasonal cyclicality of fallow land than the seasonal cyclicality under plowing, which indicates the restoration of the CI. Trends in C-CO₂ stocks of humus and LOS indicate that in the series plowing-chiseling-fallow, the index of cyclicality under chisel plowing was closer to the value of the seasonal cyclicality of fallow land than the seasonal cyclicality of plowing, which indicates the restoration of the I_SC. However, the timing of changes in the P_org(LOS) stock indicates that in the series plowing-chiseling-fallow, chisel plowing is directed to fallow land by its seasonal cyclicality. The general regularity of seasonal cyclicality for all parameters of humus condition lies in the fact that a decrease in the values of I_SC, as in fallow land or under moldboardless tillage, indicates the ordering of I_SC, and an increase in the index of cyclicality to destruction, as under plowing.

Key words:

chisel plowing, light-hydrolyzable organic matter, organic carbon and phosphorus stocks, plowing, trends in stock changes