Comparison of soil organic matter content, aggregate composition and water stability of gleyic fluvisol from adjacent forest and cultivated areas

The paper includes the results of comparative investigation of soil organic matter (SOM) content, aggregate size distribution (ASD) and water-stability of structural aggregates (WSA) of humus horizon (0–30 cm) of non-carbonate silty clay gleyic fluvisol in the Kolubara river valley (West Serbia) under natural deciduous forest vegetation and the same gleyic fluvisol used for more than 100 years as arable soil. Long-term cultivation significantly (P < 0.01) decreased the SOM content in the plough horizon (0–20 cm). Due to long-term anthropogenization, the ASD and WSA in plough and sub-plough (20–30 cm) horizons of cultivated gleyic fluvisol are significantly degraded. In plough and sub-plough horizons, the content of the agronomically most valuable fraction (0.25– 10 mm) is decreased about twice (from 67.7–74.0% to 37.1–39.2%), while the content of very coarse aggregates (> 10 mm) is increased to the same degree (from 22.8–31.2 % to 48.3– 62.1%). The conversion of forest semigley to continuous cropping using conventional cultivation significantly (P < 0.05) decreased the water stability of soil aggregates in the plough horizon. The lowest water-stability is found in structure aggregates > 3 mm. Their content is 2–3 times lower in the plough horizon (12.6–15.6%) than in the same depth zone of forest gleyic fluvisol (31.9–42.3%). Due to anthropogenization, water-stability of micro-aggregates (< 0.25 mm) is decreased in the plough horizon. The content of these aggregates is about twice as high in this horizon (29.9–34.0%), as in the same depth zone of the forest gleyic fluvisol (16.7–17.2%).