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THE INFLUENCE OF BIOLOGICAL ACTIVITY ON SOIL STRUCTURE BY THE ORGANIC MATTER BIOTURBATION

Dr. Sorina Dumitru, Dr. Petru Ignat, Dr. Alexandrina Manea, Dr. Daniela Raducu, Lecturer Dr. Valerica Tudor

Abstract

The objective of the paper was to emphasize the influence of the biological activity on the structural improvement of the compacted clayey pedogenetic horizons of two Chromic Luvisols, by the organic matter bioturbation. The researches were performed on two Chromic Luvisols from Romanian Plain, where the mean annual temperature is 10.5oC and the mean annual precipitation is 548 mm. The analytical data showed that clay content increased from the top layer of both soil profiles (28.9% in P1, and 29.8% in P2), to Bt horizon (38.8% in P1, and 36.5% in P2 respectively), decreasing afterwards in the bottom of the soil profiles. In these conditions, the bulk density increased with depth, ranging from 1.44 g/cm3 to 1.58 g/cm3 in P1, and.46 g/cm3 пїЅ 1.58 g/cm3 in P2. Under the influence of the summer dry conditions, the soil compaction intensified, affecting macrofauna (earthworms) activity which proved to be tenacious in exploring the whole soil profile and marked their own passage with biological pedofeatures (tubules and coprolites) enriched in humic material. To a closer examination of P1 a very high biological activity was identified, restoring both platy and angular blocky structure. Many pedotubuls replaced the platy structural elements, while many coprolites and channels had been observed in the pedogenetic horizons, on the background of a very compacted soil. In P2 a smooth profile section formed (after digging by backhoe) and reveals a special pattern: macrofauna pedotubuls with humic material (brought from the top layer) and vertical orientation, clearly distinguished on the lighter color of the Bt horizon. In some macrofauna pedotubuls there are chambers with leaves partially consumed by the earthworms and replaced with their coprolites. The biological activity improved soil ecological characteristics by the bioturbation of both: humified organic matter (humus intimately mixed with the abiotic constituents, specific to the humic upper horizons); and fresh organic matter (leaves and other vegetal residues pulled into the burrows and deposited in the deeper horizons). Consequently, the studied soils showed a moderately-high degree of fertility, according to the C:N and H%/N% indexes.

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DOI resolver: doi.org/10.5593/sgem2017/32/s13.078

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