Seasonal sequestration capacity of chornozem under different agrotechnological influences in agrocenose

Abstract

Goal. To study the seasonal dynamics of qualitative and quantitative indicators of the humus state over time depending on the method of cultivation and fertilization in short-rotation agrocenoses of the central part of the Forest Steppe of Ukraine. Methods. Field — setting up and conducting a stationary field experiment to study the influence of tillage and fertilization methods on the sequestration capacity of typical chornozem; laboratory — determination of humus content; calculation-statistical — for calculating seasonal stocks of sequestered carbon and phosphorus and for modeling the sequestration capacity of chornozem. Results. In the case of no-till cultivation with the application of fertilizers, the growth of C–CO2 stock in the period April–July was: +21 t/ha (0–20 cm), and +36 t/ha (0–30 cm). During plowing, growth had a tendency to increase by 1.52 times (0–20 cm), and 1.25 times (0–30 cm), but it occurred more at a low quantitative level, and in the period July–September, the change in the C–CO2 stock of humus was insignificant, which indicated the predominance of C–CO2 sequestration processes in the summer–autumn period under tillage. Under no-till cultivation, the stock of labile organic substances (LOS) in April exceeded the stock for plowing in a layer of 0–30 cm by 4.34–7.67 times without fertilizers, and by 1.5–2.76 times with fertilizers; in July — 4.59–8.90 times without fertilizers, and 1.32–3.16 times with fertilizers; in September — 4.52–4.04 times without fertilizers, and 1.11–1.93 times with fertilizers. A direct strong correlation was established at the level of R=+0.89±0.02; R2=79. In the period from April to July, a decrease in Rorg (LOS) reserves was established by 1.15 times in the 0–20 cm layer, and by 1.1 times in the 0–30 cm layer. From summer to autumn, the Rorg (LOS) stock recovered, and the stock in the 0–30 cm layer increased by 1.10 times. Conclusions. The trends of changes in C–CO2 reserves of humus and LOS indicated that in the series of plowing — tillage — fallow, the index of cyclicity under tillage was closer to the seasonal cyclicity of fallow than the seasonal cyclicity under plowing, which indicated the recovery of Ic. The trends of changes in the stock of Rorg LOS indicated that in the row of plowing — tillage — fallow, tillage with its seasonal cycle was directed towards fallow.