In Mediterranean areas, olive mill wastes pose a major environmental problem owing to their important production and their high polyphenolic compounds and organic acids concentrations. In this work, the evolution of polyphenolic compounds was studied during co-composting of olive mill wastewater sludge and poultry manure, based on qualitative (G-50 sephadex) and quantitative (Folin–Ciocalteu), as well as high pressure liquid chromatography analyses. Results showed a significant polyphenolic content decrease of 99% and a noticeable transformation of low to high molecular weight fraction during the compost maturation period. During this step, polyphenols disappearance suggested their assimilation by thermophilic bacteria as a carbon and energy source, and contributed to humic substances synthesis. Polyphenolic compounds, identified initially by high pressure liquid chromatography, disappeared by composting and only traces of caffeic, coumaric and ferulic acids were detected in the compost. In the soil, the produced compost application improved the chemical and physico–chemical soil properties, mainly fertilising elements such as calcium, magnesium, nitrogen, potassium and phosphorus. Consequently, a higher potato production was harvested in comparison with manure amendment.

Full scale composting studies were performed with stoned (SEOOPSW) and non stoned exhausted olive‐oil processing solid waste (NSEOOPSW) mixed with 20% poultry manure to reach a C/N ratio of around 30 and to improve the chemical and microbiological properties of the end products. The experiment was performed on two windrows (3 m wide, 25 m high and 10 tonne weight) to investigate the effects of stone removal and poultry manure addition on composting process efficiency and on the quality of composts. The partially stone removal operation reduced the total composting time by at least one month compared with the untreated waste. The addition of poultry manure improved the chemical quality of the end product as shown by the doubling of the nitrogen concentration after four months composting together with the increased amount of P and K. Compost from stoned exhausted olive‐oil processing solid waste had higher levels of cation exchange capacity (CEC) and humic add content with a lower [FA/HA] ratio indicating a high polymerisation level. Agronomic field test showed that both composts are not phytotoxic. When applied at the rate of 40 tonne ha^‐1 to a potato culture, they produced approximately the same yield (46 and 48.5 tonne ha^‐1) but they acted differently in terms of plant development Compost produced from the NSEOOPSW acted more positively on the stem length (84.1 against 77.6 cm) and on leaf weight (354 against 238 g), whereas compost from the SEOOPSW more positively affected tuber sizes (76% large grade compared to 55%).

There is no doubt that mining activities result in a serious threat to the environment. This study dealt with the heavy metals pollution and ecological risk assessment of the former Jebal Ressas mining site on soils and surrounding sediments. Twenty soil samples were gathered from around the mining discharges and agricultural land, and six sediment samples were collected from Wadi Hmma. Then the trace metal elements Pb, Zn, Cd, As, Ni, Cr and Cu concentrations were determined for these samples. The analyses revealed the presence of the heavy metals (Pb, Zn, Cd and As) in the soil for most of the samples, mainly those close to the mining waste. The Pb, Zn, Cd and As concentrations were remarked to exceed the respective local geo-geochemical backgrounds, indicating an anthropogenic source of pollution. However, the weak presence of Ni and Cr with Fe, not exceeding 3, in these soils reflect the natural origin of these elements. The ecological risk potential index study results unveiled that the Cd content has a significant potential ecological risk. University of Sfax, centre Régional des Oeuvre Universitaire et Scolaire Résidence Hélène BOUCHER Cité Scientifique, 59650 Lille, France

Soil organic carbon (SOC) plays an important role in the global C cycle, as well as in the maintenance and improvement of the soil quality. Over time, special attention has been paid to it in the study of the SOC reserves worldwide; however, reduced attention has been given to assessing the spatial patterns of SOC stock (SOCS) in semi-desert ecosystems. In this line, there are no conclusive studies in drylands of Africa affected by aeolian processes (semi-desert conditions) mainly due to the complexity of sample collection, and this is especially significant in some soil types such as Arenosols (AR) and Calcisols (CL). This study evaluated the spatial variability of SOC and SOCS in AR and CL with woody crops in relation to land use and management (old plantations > 100 years: centenary olive grove; new plantations < 12 years: young olive grove, almond, and pistachio) in semi-desert conditions. For this purpose, 16 soil profiles (for 0–40 and 40–100 cm depth) were selected and studied in an experimental area of Menzel Chaker-Sfax in southeastern Tunisia (North Africa). The main results indicated that the SOCS on average was higher in Old Cultivated AR (OC-AR) with 41.16 Mg ha⁻¹ compared to Newly Cultivated AR (NC-AR) with 25.13 Mg ha⁻¹. However, the SOCS decreased after a long period of cultivation in CL from 43.00 Mg ha⁻¹ (Newly Cultivated CL: NC-CL) to 32.19 Mg ha⁻¹ (Old Cultivated CL: OC-CL). This indicates that in the long term, CL has more capacity to store SOC than AR, and that in the short term, AR is more sensitive to land management than CL.