Effect of tillage practices on the soil carbon dioxide flux during fall and spring seasons in a Mediterranean Vertisol

In this study, we assessed the effect of conventional tillage (CT), reduced (RT) and no tillage (NT) practices on the soil CO2 flux of a Mediterranean Vertisol in semi-arid Morocco. The measurements focused on the short term (0 to 96 h) soil CO2 fluxes measured directly after tillage during the fall and spring period. Soil temperature, moisture and soil strength were measured congruently to study their effect on the soil CO2 flux magnitude. Immediately after fall tillage, the CT showed the highest CO2 flux (4.9 g m-2 h-1); RT exhibited an intermediate value (2.1 g m-2 h-1) whereas the lowest flux (0.7 g m-2 h-1) was reported under NT. After spring tillage, similar but smaller impacts of the tillage practices on soil CO2 flux were reported with fluxes ranging from 1.8 g CO2 m-2 h-1 (CT) to less than 0.1 g CO2 m-2 h-1 (NT). Soil strength was significantly correlated with soil CO2 emission; whereas surface soil temperature and moisture were low correlated to the soil CO2 flux. The intensity of rainfall events before fall and spring tillage practices could explain the seasonal CO2 flux trends. The findings promote conservation tillage and more specifically no tillage practices to reduce CO2 losses within these Mediterranean agroecosystems. (Résumé d'auteur

On the stability, boundedness, and square integrability of solutions of third order neutral delay differential equations

In this paper, sufficient conditions are established for the stability, boundedness and square integrability of solutions for some non-linear neutral delay differential equations of third order. Lyapunov’s direct method is used to obtain the results

On stability, boundedness, and square integrability of solutions of certain third order neutral differential equations

summary:The authors establish some new sufficient conditions under which all solutions of a certain class of nonlinear neutral delay differential equations of the third order are stable, bounded, and square integrable. Illustrative examples are given to demonstrate the main results

Tillage system affects soil organic carbon storage and quality in Central Morocco

Stabilizing or improving soil organic carbon content is essential for sustainable crop production under changing climate conditions. Therefore, soil organic carbon research is gaining momentum in the Mediterranean basin. Our objective is to quantify effects of no tillage (NT) and conventional tillage (CT) on soil organic carbon stock (SOCs) in three soil types (Vertisol, Cambisol, and Luvisol) within Central Morocco. Chemical analyses were used to determine how tillage affected various humic substances. Our results showed that, after 5 years, surface horizon (0–30 cm) SOC stocks varied between tillage systems and with soil type. The SOCs was significantly higher in NT compared to CT (10% more in Vertisol and 8% more in Cambisol), but no significant difference was observed in the Luvisol. Average SOCs within the 0–30 cm depth was 29.35 and 27.36 Mg ha−1 under NT and CT, respectively. The highest SOCs (31.89 Mg ha−1) was found in Vertisols under NT. A comparison of humic substances showed that humic acids and humin were significantly higher under NT compared to CT, but fulvic acid concentrations were significantly lower. These studies confirm that NT does have beneficial effects on SOCs and quality in these soils

On the stability, boundedness, and square integrability of solutions of third order neutral delay differential equations

In this paper, sufficient conditions are established for the stability, boundedness and square integrability of solutions for some non-linear neutral delay differential equations of third order. Lyapunov’s direct method is used to obtain the results

Cartographie numérique des sols: cas d’étude de la zone de Khouribga - Kasbat Tadla au Maroc Central

This work deals with the digital soil mapping as a time and cost effective alternative for soil type characterization. The e-Soter (Soil and terrain) approach was used and validated for in the Khouribga-Kasbat Tadla semi-arid rainfed agricultural area of Central Morocco, covering 217.000 ha. The GIS processing included physiography and parent material as two soil genesis factors, added to field data from 90 soil profiles. A subset of the ASTER-GDEM 30m spatial resolution digital elevation model (DEM) was used to map three physiographic indicators that are slope gradient, relief index and potential drainage density. The parent material classification was derived from 1/100.000 geological map. The e-Soter hierarchical classification was then used to derive e-Soter homogenous units that were spatially joined to soil profile data in order to define the most representative soil type and delineate soil homogenous units at the 100.000 scale. The resulting soil map was validated in the field using a transect approach, with three transects in areas that were not included in the initial field data collection. Statistical significance for similarity between the map outputs and the field observations was confirmed using four statistical indices (Chi square, Cramér’s V, Fisher’s exact and Kappa reliability test), which confirms the validation of the e-Soter approach as a digital soil mapping tool in the study area.Ce travail traite d’une étude de cas de cartographie numérique des sols et son efficience dans la caractérisation des types sols. L’approche e-Soter (Soil and Terrain) a été utilisée et validée dans la zone semi-aride de Khouribga-Kasbat Tadla, sur une superficie de 217.000ha. Une analyse spatiale sous SIG a intégré la physiographie et le matériel parental comme facteurs de pédogenèse, en plus de données de terrain sur les types de sol de 90 sites. Le modèle numérique de terrain (MNT) ASTER-GDEM de 30m de résolution spatiale a été utilisé pour dériver trois indices physiographiques que sont le gradient de pente, l’indice de relief et la densité de drainage potentiel. La classification du matériel parental a été dérivée de la carte géologique au 1/100.000. La classification hiérarchique e-Soter a été ensuite utilisée pour dériver les unités homogènes de terrain qui ont été jointes spatialement aux données de terrain pour délimiter les unités homogènes de sol à échelle 1/100.00. La carte des sols résultante a été validée au terrain par l’approche de transect, avec trois transects passant par des sites non utilisés dans la collection de données de terrain initiales. Une similarité statistiquement significative a été observée entre les résultats de cartographie numérique et les observations de terrain, à travers quatre indices statistiques (Chi carré, V de Cramér, test exact de Fisher et coefficient Kappa), ce qui a confirmé l’adaptation de l’approche e-Soter comme méthode de cartographie numérique des sols dans la zone d’étude

Application du modèle FAO-AquaCrop à l'évaluation de l’impact des changements climatiques sur la productivité du blé dans la zone pluviale de Zaer

Accurate crop development modelling is important in planning rational use of water resources and crop management, along with evaluating the effects of climate change on crop productivity and predicting yields. This study aims at modelling winter wheat productivity under different climatic scenarios and models, in a Moroccan rainfed agriculture site using the FAO AquaCrop model. The study site was a one-hectare experiment plot located in the Marchouch plateau in the North-western Morocco. The model was calibrated using field parameters of the crop growing cycle, the soil characteristics, the crop management and the observed yield for a period covering three cropping cycles (from 2014/2015 to 2016/2017) using daily rainfall and temperature data. The calibrated model was then used to simulate wheat productivity in the study site for short-term (2020-2030) and medium-term periods (2040-2050) compared to a reference (1985-2005). Two Representative Concentration Pathway scenarios (RCP 4.5 and RCP 8.5) were considered for three General circulation models (CNRM, EC-EARTH, and GFDL) to derive the average model outputs with focus on the crop yield, crop growing cycle and evapotranspiration. The results showed a good model calibration, with coefficient of determination R2 of 0.84, Nash-Sutcliffe indicator of 0.71 and Willmott index of 0.94. Simulations showed that under RCP 4.5 a short-term yield drop of 5.94%, a medium-term crop cycle decrease of 15 days and evapotranspiration reduction of 20mm. Meanwhile, the model predicted under RCP 8.5 a medium-term yield drop of 12.9%, a crop cycle decrease of 13 days and evapotranspiration reduction of 46mm. Overall, simulation results showed that AquaCrop model is suitable for simulating the effects of water and climatic stress on crop productivity in rainfed agricultural areas, which could help decision making in terms of water productivity and crop adaptation under future climate trends in the semiarid conditions.Une modélisation précise de la croissance et du développement des cultures s’avère importante en vue de planifier l'utilisation rationnelle des ressources en eau et la gestion des cultures, ainsi que pour évaluer et prévenir les effets du changement climatique sur la productivité des cultures. Cette étude porte sur la modélisation de la productivité du blé tendre sous différents scénarios et modèles climatiques en agriculture pluviale à l'aide du modèle AquaCrop de FAO. Le site d'étude est une parcelle expérimentale d'un hectare située sur le plateau de Marchouch au nord-ouest du Maroc. Le modèle a été calibré en utilisant les données météorologiques, pédologiques, phénologiques et le rendement observé pour une période couvrant trois cycles allant de 2014/2015 à 2016/2017. Le modèle a été paramétré, calibré et validé pour la prévision des rendements en grain de blé et a été ensuite utilisé pour simuler la productivité du blé dans le site d'étude pour une période à court terme (2020-2030) et à moyen terme (2040-2050) par rapport à une période de référence (1985-2005). Trois modèles de circulation générale (CNRM, EC-EARTH et GFDL) ont été considérés pour les deux scénarios d’évolution de concentration de CO2 (le scénario moyen RCP 4.5 et le scénario pessimiste RCP 8.5) pour dériver les sorties du logiciel en mettant l'accent sur le rendement des cultures, le cycle des cultures et l'évapotranspiration. Les résultats de calibration affichent un coefficient de corrélation R2 de 0,84, un indicateur de Nash-Sutcliffe de 0,71 et un indice de Willmott de 0,94. Pour le scénario RCP 4.5, la simulation a montré une baisse de rendement à court terme de 5,94 %, et une diminution à moyen terme du cycle de culture de 15 jours et de l'évapotranspiration de 20 mm. Quant au scénario RCP 8.5, le modèle a prédit une baisse de rendement de 12,9%, une diminution à moyen terme du cycle de culture de 13 jours et une réduction de l'évapotranspiration de 46 mm. En général, les résultats de la simulation ont montré que le modèle AquaCrop est adapté pour simuler les effets du stress hydrique et climatique sur la productivité des cultures dans les zones agricoles pluviales, ce qui pourrait aider à la prise de décision en termes de productivité de l'eau et d'adaptation des cultures aux futures tendances climatiques sous les conditions semi-arides