Transformation of soil organic matter in leached chernozems under minimized treatment in the forest-steppe of West Siberia

Abstract

Changes in the contents of total organic carbon and the carbon of easily mineralizable fractions of organic matter (labile humus, detritus, and mortmass) in the layers of 0–10, 10–25, and 0–25 cm were studied in leached chernozems ((Luvic Chernozems (Loamic, Aric)) subjected to deep plowing and surface tillage for nine years. In the layer of 0–25 cm, the content of Corg did not show significant difference between these two treatments and comprised 3.68–3.92% in the case of deep plowing and 3.63–4.08% in the case of surface tillage. Tillage practices greatly affected the distribution of easily mineralizable fractions of organic matter in the layers of 0–10 and 10–25 cm, though the difference between two treatments for the entire layer (0–25 cm) was insignificant. Surface tillage resulted in the increase in the contents of mortmass (by 59%), detritus (by 32%), and labile humus (by 8%) in the layer of 0–10 cm in comparison with deep plowing. At the same time, the contents of these fractions in the layer of 10–25 cm in the surface tillage treatment decreased by 67, 46, and 3%, respectively. The estimate of the nitrogen-mineralizing capacity made according to the data on the uptake of soil nitrogen by oat plants in a special greenhouse experiment confirmed the observed regularities of the redistribution of easily mineralizable organic matter fractions by the soil layers. In case of surface tillage, it increased by 23% in the layer of 0–10 cm; for the layer of 0–25 cm, no significant differences in the uptake of nitrogen by oat plants were found for the two studied treatments.