Cultivation Effects on Soil Carbon and Nitrogen Contents at Depth in the Russian Chernozem

Abstract

Little is known about changes in soil organic C (SOC) and total N with depth and with land use. We conducted this study to determine the depth of changes in SOC and total N under different management regimes in the chernozem soil. Four sites were sampled: a native grassland field (not cultivated for at least 300 yr), an adjacent 50‐yr continuous‐fallow field, a yearly cut hay field in the V.V. Alekhin Central‐Chernozem Biosphere State Reserve in the Kursk region of Russia, and a continuously cropped field in the Experimental Station of the Kursk Institute of Agronomy and Soil Erosion Control. All sampled soils were classified as fine‐silty, mixed, frigid Pachic Hapludolls. Soil organic C, total N contents, and bulk densities with depth were compared. Significant reductions in SOC and total N concentrations were detected to a depth of 120 to 130 cm in the 50‐yr continuous‐fallow field and to a depth of 80 cm in the continuously cropped field. Highest reductions were observed in the top 10 cm of soil, where reduction in SOC ranged from 38 to 43% and reduction in total N ranged from 45 to 53%. Significant losses of SOC and total N per equivalent soil mass on an area basis were observed to a depth of 60 cm in the continuously cropped field and to a depth of 100 cm in the 50‐yr continuous‐fallow field.