Effets de l’apport en Bois Raméal Fragmenté (BRF) sur les caractéristiques physico-chimiques du sol oasien du Sud Tunisien

L’amendement du sol avec des branches, notamment avec des bois rameaux fragmentes (BRF), suscite un intérêt croissant chez les agriculteurs et les services de vulgarisation, Cet article présente les résultats concernant l’effet d’apports enfouis de BRF sur le sol oasien de la zone de Tozeur dans deux sites différentes oasis El Manachie et oasis de CRAAO. L’apport de BRF a généralement un effet positif sur les propriétés physico-hydriques du sol (humidité, porosité structure), enrichit le sol en matière organique, stimule l’activité biologique, et accroit la disponibilité des nutriments à moyen terme. Les effets des BRF sont modules par plusieurs facteurs, comme la dose, la périodicité, la dimension des fragments, etc. Mais à long terme le BRF peut causer des effets néfastes sur la salinité du sol s’il est utilisé d’une manière non contrôlé

Green waste biochar effects on sandy soil physicochemical properties

The organic amendment of degraded soil in South East of Tunisia was used to restore the chemical, and physical properties of soil quality investigated in this study. Biochar derived from pyrolyzed green waste at 360°C was used like organic amendment.  Nines randomized plots with one square meter of the area of each plot in three replicates have been installed in the Institute of Arid Area in Mednine South East of Tunisia, with two rates of biochar 20 and 40 t/ha were investigated: 20 tons/ha (B20) (2 kg/m²) and 40 tons/ha (B40) (4 kg/m²). The results showed that biochar had a positive effect on soil's physical and chemical properties compared to non-amended soil (Untreated soil). Biochar supply at rates of 20 and 40 tons/ha, causes a decrease in electrical conductivity to achieve 2.66 mS/cm for the B40 dose after 1 year of amendment, also a decrease in the bulk density at the surface layer (0-20 cm) has been registered, the total porosity which was decreased with depth. The hydraulic conductivity is favored by the incorporation of biochar in the soil which increases the volume of voids and tends to create preferential flow paths

Effects of land use management, landscape forms and soil types on soil organic carbon in the watershed of Wadi Beja in Northwest of Tunisia

Understanding changes in soil quality resulting from land management changes, landscape forms and soil types is crucial to design sustainable land management plans and interventions. This study evaluated the influence of land use/management, landscape forms (slope/aspect) and soil types on soil organic carbon (SOC) which is a key soil quality indicator within a watershed of Wadi Beja in the northwest of Tunisia. Factor analysis based on Multiple Correspondence analysis (MCA) was used to visualize relativities between the selected factors. Surface (0–20 cm) soil samples were collected from four main LU/management types in the watershed (i.e., field crops, Permanent crops, plantation forest, grazing land) and at two aspects classes (north and south), 3 slope classes (flat, moderate and steep) and 7 different type of soils (Vertisols, Pedosols, brown calcareous, Isohumic, regosols and rendzinas). A soil spectral library was developed and used to assess the variation of the SOC across all the selected variables. A factorial analysis of variance ANOVA showed that all the variables significantly affected the soil organic carbon (SOC) levels. Under the grazing land use, the aspect, slope and soil types together affected significantly the SOC levels. Under the permanent crops land use, only the slope and the soil type affected significantly the SOC levels. Under the field crops, only the slope has a significant effect as well. However, in the forest, there is no significant effects of any of the selected variables on the SOC. The afforestation of the field crops with olive trees can significantly increase the SOC at different levels of slopes especially in vertisols and brown calcareous soils. Since 71 % of the area is field crops land use system includes 64 % of steep terrain under intensive monoculture, SOC level appear better in flat area compared to others. Regarding grazing lands, level of SOC was increased significantly in the flat and north facing areas particularly in brown calcareous soils. Soil fertility decline on sloping agricultural land poses a serious problem for the environment as well as for soil quality and productivity. In areas with highly erodible soils, such as those in steep slopes and south facing zones, application of soil and water conservation measures is crucial to sustain agricultural fields and to prevent or reduce soil degradation. There is strong indications that agroforestry have been successful in retaining soil fertility

Assessment of the physio-biochemical performance of Tunisian barley landraces under deficit saline-irrigation during grain filling stage

Salinity is one of the main and important abiotic stresses that adversely affects crop growth, development and production. In this study, two barley (Hordeum vulgare L.) landraces were subjected to three treatments of deficit saline-irrigation (12 dS/cm) (T0 = 100%ETc, T1 = 75%ETc, and T2 = 50%ETc) during grain filling stage. Carbon isotope discrimination (Δ13C) was associated with some physio-biochemical parameters to evaluate barley response to saline conditions. Results of this study showed that deficit saline-irrigation significantly (p < 0.05) decreases Δ13C in both barley landraces. Moreover, photosynthetic rate (A), transpiration (E), stomatal conductance (gs), and instantaneous water use efficiency (iWUE) were significantly affected by treatments. Relative water content (RWC), chlorophyll a, and chlorophyll (SPAD) value were significantly (p < 0.01 and p < 0.001) were affected by deficit saline-irrigation. In addition, phenolic compounds were affected by treatments and landraces (except syringic and p-coumaric acids), and their interactions (except syringic acid). Moreover, high correlations were noticed between Δ13C and physio-biochemical parameters. Results suggested that both barley landraces make a higher iWUE, and a weak variation in phenolic compounds. Moreover, Δ13C associated with physio-biochemical traits can also be good criteria for screening of salt-tolerance of barley during grain filling stage. Taken together, our study suggests that the response to deficit saline-irrigation in barley landraces involves an interplay between various physiological and biochemical mechanisms mainly related to Δ13C

Impact de la dégradation des oasis de Nefzaoua sur les moyens de subsistance et la sécurité alimentaire auprès des agriculteurs de la région

Les agrosystèmes oasiens ont joué un rôle important dans le développement des zones arides et dans l'établissement de bien être  humain dans ces zones. Cependant, ces agrosystèmes sont sous plusieurs menaces naturelles et anthropiques de dégradation. L'adoption de pratiques durables pour atténuer les impacts de la dégradation est liée aux perceptions des agriculteurs. Cette recherche vise à identifier les perceptions des agriculteurs sur la dégradation des agrosystèmes oasiens et  sur les moyens de subsistance des agriculteurs et les facteurs qui peuvent entraver les décisions des agriculteurs d'adopter des pratiques de gestion durables. L'étude de cas a été réalisée dans les 'oasis de Nefzaoua au sud de la Tunisie. 179 enquêtes semi-structurées chez 286 agriculteurs  ont été menées, d’une manière aléatoire et simple en raison des caractéristiques heterogene des agriculteurs. Les résultats ont indiqué que 100% des agriculteurs sont conscients du processus de dégradation dans leurs oasis; ils ont reconnu la rareté de l'eau, la salinité du sol, suivie de la perte de la biodiversité comme les signes les plus visibles de la dégradation. La dégradation de l'oasis a entraîné une réduction de la productivité et une détérioration des moyens de subsistance des agriculteurs. Les pratiques agricoles adoptées par les agriculteurs se limitaient à l'utilisation d'amendements sableux. Cela explique, l'intervention de l'Etat à travers des programmes de renforcement des capacités pour les agriculteurs et des politiques qui encouragent le développement durable de l'oasis et renforcer l'engagement actif des agriculteurs dans le processus de prise de décisions concernant la gestion des oasis

Effets de l’apport en Bois Raméal Fragmenté (BRF) sur les caractéristiques physico-chimiques du sol oasien du Sud Tunisien

L’amendement du sol avec des branches, notamment avec des bois rameaux fragmentes (BRF), suscite un intérêt croissant chez les agriculteurs et les services de vulgarisation, Cet article présente les résultats concernant l’effet d’apports enfouis de BRF sur le sol oasien de la zone de Tozeur dans deux sites différentes oasis El Manachie et oasis de CRAAO. L’apport de BRF a généralement un effet positif sur les propriétés physico-hydriques du sol (humidité, porosité structure), enrichit le sol en matière organique, stimule l’activité biologique, et accroit la disponibilité des nutriments à moyen terme. Les effets des BRF sont modules par plusieurs facteurs, comme la dose, la périodicité, la dimension des fragments, etc. Mais à long terme le BRF peut causer des effets néfastes sur la salinité du sol s’il est utilisé d’une manière non contrôlé

Global Landscape of Organic Carbon and Total Nitrogen in the Soils of Oasis Ecosystems in Southern Tunisia

The oasis soils of Tunisia face several climatic and soil constraints. Trying to have cultures that are profitable and beneficial in terms of soil C and N sequestration in such environments is already a challenge. To conduct this, we tested under identical conditions four types of occupation in sub-plots adjacent to the crops; barley alone, alfalfa alone, intercropping barley/alfalfa, and a control fallow in a saline gypseous desert soil poor in organic matter. Field experimentation was carried out in the oasis of Degache, which is very representative of other Tunisian oases. The stocks of C and N of the plot were calculated from the start in September 2019 before the installation of the different crops. After 21 months, the control plot shows a decrease of −41% in its stock of C and −25% in its stock N. However, the best result is that of the barley/alfalfa intercropping with an increase of +126.46% in the C stock and +178.67% in the N stock. After almost two years of experience, the beneficial effect of the intercropping system in the oasis is clear. These results are very motivating and seem to be a solution to the rapid decline in soil organic stocks

Green waste biochar effects on sandy soil physicochemical properties

The organic amendment of degraded soil in South East of Tunisia was used to restore the chemical, and physical properties of soil quality investigated in this study. Biochar derived from pyrolyzed green waste at 360°C was used like organic amendment.  Nines randomized plots with one square meter of the area of each plot in three replicates have been installed in the Institute of Arid Area in Mednine South East of Tunisia, with two rates of biochar 20 and 40 t/ha were investigated: 20 tons/ha (B20) (2 kg/m²) and 40 tons/ha (B40) (4 kg/m²). The results showed that biochar had a positive effect on soil's physical and chemical properties compared to non-amended soil (Untreated soil). Biochar supply at rates of 20 and 40 tons/ha, causes a decrease in electrical conductivity to achieve 2.66 mS/cm for the B40 dose after 1 year of amendment, also a decrease in the bulk density at the surface layer (0-20 cm) has been registered, the total porosity which was decreased with depth. The hydraulic conductivity is favored by the incorporation of biochar in the soil which increases the volume of voids and tends to create preferential flow paths

Mixed organic and bentonite based amendments improve soil hydrological conditions and irrigation efficiency in oasis soils

The major constraint for sustainable agriculture in arid regions of the world is the availability of (suitable irrigation) water. The quantity and quality of irrigation water, as well as the application technique and intervals between irrigation are important due to the useful amount of water brought to the soil and their direct influence on crop production. The oasis systems in southern Tunisia also suffer from scarcity of irrigation water resources because of low precipitation and limited available ground water. Organic matter (OM) application to improve soil fertility and enhance water holding capacity (WHC) is the traditional method in Tunisian oasis systems, but because of regional climatic conditions (dry and hot weather) the degradation of applied OM in the soils is very fast and consequently the WHC decreases too. The objective of this study was to examine the WHC of new alternative soil amendments in the oasis systems in a state of degradation. The soil studied is a gypsum soil. We compared these sandy soils amended either with (i) manure (MS), (ii) compost (CS), (iii) manure and bentonite (MBS) and (iv) compost and bentonite (CBS). The treatments were compared with untreated original oasis sandy soil (U). These five treatments were compared with the most degraded regional soil, i.e. that of the salt plain Chott Djerid (CD). To estimate the soil hydraulic parameters (including WHC) retention curves were measured and van Genuchten parameters fitted to the data. The results of soil water retention curves revealed that the untreated soil (U) retained less water at any matric potential compared to the amended soils. The soil hydraulic conductivity decreased with the use of bentonite combined with organic matter. The saturated hydraulic conductivity for untreated soil was higher than the amended soil with CBS and MBS by 11 and 18 times, respectively. These results suggested that the soil amendments significantly improved the soil water retention. Therefore these soil mixed amendments are appropriate for their potential wider use in sandy (oasis) soils to improve irrigation efficiency amounts and to reduce irrigation frequency