Potential risk of soil irrigation with treated wastewater over 40 years:a field experiment under semi-arid conditions in northeastern Tunisia

In Tunisia,water scarcity is only adding pressure on water demand in agriculture.In the context of sustainable development goals,Tunisia has been reusing treated wastewater(TWW)as a renewable and inexpensive source for soil fertigation and groundwater(GW)recharge.However,major risks can be expected when the irrigation water is of poor quality.This study aims for evaluating the potential risk of TWW and GW irrigation on soil parameters.Accordingly,we evaluated the suitability of water quality through the analysis of major and minor cations and anions,metallic trace elements(MTEs),and the sodium hazard by using the sodium adsorption ratio(SAR)and the soluble sodium percentage(SSP).The risk of soil sodicity was further assessed by SAR and the exchangeable sodium percentage(ESP).The degree of soil pollution caused by MTEs accumulation was evaluated using geoaccumulation index(Igeo)and pollution load index(PLI).Soil maps were generated using inverse spline interpolation in ArcGIS software.The results show that both water samples(i.e.,TWW and GW)are suitable for soil irrigation in terms of salinity(electrical conductivity<7000μS/cm)and sodicity(SAR<10.00;SSP<60.00%).However,the contents of PO_(4)^(3-),Cu^(2+),and Cd^(2+)exceed the maximum threshold values set by the national and other standards.Concerning the soil samples,the average levels of SAR and ESP are within the standards(SAR<13.00;ESP<15.00%).On the other hand,PLI results reveal moderate pollution in the plot irrigated with TWW and no to moderate pollution in the plot irrigated with GW.Igeo results indicate that Cu^(2+)is the metallic trace element(MTE)with the highest risk of soil pollution in both plots(Igeo>5.00),followed by Ni^(2+)and Pb^(2+).Nevertheless,Cd^(2+)presents the lowest risk of soil pollution(Igeo<0.00).Statistical data indicates that Ca^(2+),Na+,Ni^(2+),and Pb^(2+)are highly distributed in both plots(coefficient of variation>50.0%).This study shows that the use of imagery tools,such as ArcGIS,can provide important information for evaluating the current status of soil fertility or pollution and for better managing soil irrigation with TWW.

Impact Assessment of Technology Change on Durum Wheat Productivity： A Cross Sectional Analysis in Central Semi-arid Tunisia

The enhancement of wheat yield in Tunisia becomes a must for policy makers who need to reduce the importations of this commodity. In this context, the ＂Food Security in Arab Countries＂ project has been established in order to transfer technological innovations that improve irrigated wheat productivity. As a pilot area, this project is being implemented in Chebika （Central Tunisia） region, where in the last two years a new technological package of durum wheat production has been tested by many farmers of the region. The objective of this study is to identify the sources of output gains between farmers participating in the project trials and farmer＇s using conventional techniques. Tornqvist-Thiel index was used for the identification of the output gains generated by the technology package. Data used for the analysis were collected from 60 participating farmers during 2011-2012 cropping season, and 110 non-participating farmers. Results show that average production value differential between participating and non-participating farmers is 48.4%. This value is composed of 9.3% gain generated from global factor productivity and 39.1% from the increase of the inputs use. It also indicates the relative importance of inputs contributing to the global factor productivity difference between enhanced technological package and conventional practices in the region. These results are valuable for policy makers since they can be used to focus on main factors affecting the improvement of irrigated wheat productivity in Central Tunisia. Encouraging the adoption of the new technological package is then highly recommended.

Using Clove Essential Oil to Increase the Nutritional Potential of Industrial Fresh Double Cream Cheese

The present study was a potential application of Clove Essential Oil (CEO) in industrial fresh double cream cheese in order to lengthen its conservation and to improve its antioxidant potential. In this work, CEO was extracted by hydro distillation, and then analyzed by GC-MS;24 components of clove essential oil were identified. Eugenol was the major component (57.66%). Its antimicrobial properties against E. coli, Salmonella enteritidis and Staphylococcus aureus, were evaluated by disc diffusion method and minimal inhibitory concentration (MIC). As for, the antioxidant activity of CEO was evaluated by DPPH assay method. An optimum content of CEO (0.37%) was calculated by mixing plan carried out by Expert design software and then added to studied cheese. The responses, fixed from the beginning, for this mixing plan were: minimum inhibitory concentration (MIC), antioxidant activity (IC50), taste and odor intensity and global appreciation. The results found on the cheese supplemented with the optimum content of CEO showed antioxidant activity (IC50 = 0.146) was relatively important compared to conventional cheese (IC50 = 0.477). In fact, the incorporation of CEO in cheese may strongly improve its oxidative stability. Cheese antioxidant activity was not affected during the storage period for 13 days. Results showed also that the fresh double cream cheese could be stored at refrigerated temperature with good taste and odor during the period of 13 days due to antimicrobial properties given by CEO, that suggest lengthening its shelf life.

Monitoring the variation of soil quality with sewage sludge application rates in absence of rhizosphere effect

Agricultural soils in semi-arid regions have frequently been degraded due to adverse climatic conditions,organic matter depletion,and poor farming practices.To enhance soil quality,this study examines the reuse of sewage sludge(SS)as an available source of organic matter in a typical Mediterranean sandy-loam soil.Accordingly,we studied the cumulative effect of two annual applications of 40,80 and 120 tons of sludge per ha on soil quality in absence of vegetation.The dose-dependent improvement of organic matter content was the most significant event that reflected sludge application rates,and consequently influenced other soil properties.Accordingly,soil structural stability increased by 13.3%,28.8%and 59.4%for treatments SS-40,SS-80 and SS-120 respectively as compared to unamended control.Structural stability improvement was also confirmed by the dose-dependent variation of other edaphic factors including calcium content,the microbial quotient as well as Welt and C:N ratios.These param-eters are involved in cementing soil aggregates by cation bridging,the formation of microbial mucilage,and clay-humic complexes.Soil magnetic susceptibility(SMS)was measured in situ as a possible rapid tool to evaluate soil condition.SMS showed significant correlation with sludge dose and stability amelioration testifying to the aggregation role that can play Al2O3 and particularly Fe2O3 minerals added by the hematite-rich sludge.Besides,analytical results and field observations revealed no trends of soil salinization or acidification by excessive sludge amounts.By avoiding the rhizosphere effect,outcomes could reflect the resilience and intrinsic capacity of the soil to cope with excessive sludge loads.