Some aspects of carbon sequestration capacity of arable soils

Abstract

The article analyzes the possibilities of arable soils for atmospheric CO₂ sequestration by using modern agricultural technologies. Such possibilities are concluded to be very limited, as they increase the content of organic matter (OM) in the topsoil up to 0.1% С use until an OM equilibrium level is reached. For chernozems (Phaeozems) in the forest-steppe region this value accounts for not more than 10% of the soil organic carbon, lost since the soils started to be used for agricultural production till they reached equilibrium in carbon content. The reasons for the poor atmospheric carbon sequestration capacity of agricultural soils are explained, firstly, by a sharp, three-fold or more, decrease in the plant residues input to soils in comparison with undisturbed soils and, secondly, by the inability to firmly fix freshly formed humus substances: firm fixation of humus substances makes them inaccessible to soil microorganisms. It was shown that with the annual application of ¹⁴C labeled plant residues, soil carbon content stopped increasing already by the fifth year of the experiment, which indicated the establishment of a balance between carbon mineralization and fixation of ¹⁴C labeled compounds in soil. A preliminary conclusion was made that the ability to firmly fix freshly formed humus substances is ​​an exclusive feature of undisturbed or abandoned arable soils. Arable land can play a significant role in atmospheric carbon sequestration only if abandoned after use. Such approach can be employed to a very limited extent on the lands that are not suitable any more for agricultural production.