Lake-dredged material (LDM) in pedotechnique for the restoration of Mediterranean soils affected by erosion/entisolization processes

Purpose: Anthropic-accelerated erosion processes have led to an increase in reported loss of soil surface horizons worldwide. Lake-dredged materials (LDMs) have often been considered suitable for upland disposal. This study aimed to assess the potential beneficial use of LDMs in soil rebuilding strategies for Mediterranean soils affected by the loss of surface horizons with consequent erosion/entisolization processes.

Materials and methods: Different model proto-horizons (MPHs) were assembled by means of the co-utilization of LDMs, other mineral matrices, organic amendment, and mineral fertilizer for the growth of a pasture grass under controlled (pot) conditions. The evolution of nine different MPHs was monitored by means of an evaluation/comparison of several physical–chemical parameters (texture, pH, electrical conductivity, N, P, K, and cation-exchange capacity) and the stability-modification of organic matter (OM) quality in relation to plant development (dry matter production, agronomic efficiency, and plant cover).

Results and discussion: The addition of LDM resulted in statistically significant (p < 0.05) improvement to both plant performance and several soil physical–chemical properties. Compared with the reference soil (degraded soil without any additional treatment), the model proto-horizons treated with the highest LDM content (50 % w LDM without any additional treatment) showed the largest total dry matter production, the highest agronomic efficiency, and a quali-quantitative increase in plant cover. A more balanced texture (loamy) and a generalized increase in total organic carbon, cation-exchange capacity, N, and K were also detected with particular reference to models treated with the higher LDM content. Humic substances greatly increased in the treatment with the higher LDM amounts showing a generalized soil organic matter equilibrium, i.e., no mineralization or humification process prevalence.

Conclusions: This study showed that there is indeed the possibility of turning what is currently an awkward refuse material into a commodity that can be properly and advantageously used in pedotechniques for soil rebuilding and land recovery and protection. From this standpoint, LDM would appear to be apt for inclusion on a possible list of useful pedotechnomaterials.