Unlocking the potential of conservation agriculture for soil carbon sequestration influenced by soil texture and climate: A worldwide systematic review

Conservation Agriculture (CA) systems have gained significant attention as a sustainable cropping approach that not only improves crop yields but also contributes to climate change adaptation and mitigation through enhanced soil organic carbon (SOC) sequestration. However, a comprehensive understanding of the influence of soil texture and climate conditions on SOC sequestration under CA remains limited. To address this knowledge gap, we conducted a systematic review using the PRISMA method, analyzing data from 35 peer-reviewed articles encompassing 71 field experiments and 451 observations worldwide. Our findings demonstrate the substantial positive impact of CA on SOC sequestration, with an overall increase of approximately 78%. Remarkably, only a mere 2% of observations reported neutral effects, while 20% indicated adverse outcomes. Notably, SOC sequestration rates were highest in tropical regions experiencing dry winters, reaching an impressive 2.50 Mg/ha/year in the topsoil layers. Moreover, fine and moderate textured soils, such as clay, clay loam, loam, and clay sandy, exhibited higher SOC sequestration rates (20-27%) compared to coarse-textured soils dominated by sandy proportions (9%). These findings emphasize the significance of climate conditions and soil texture in shaping the impact of CA on SOC sequestration

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

Modeling Soil Organic Carbon Changes under Alternative Climatic Scenarios and Soil Properties Using DNDC Model at a Semi-Arid Mediterranean Environment

Soil organic carbon (SOC) is one of the central issues in dealing with soil fertility as well as environmental and food safety. Due to the lack of relevant data sources and methodologies, analyzing SOC dynamics has been a challenge in Morocco. During the last two decades, processbased models have been adopted as alternative and powerful tools for modeling SOC dynamics; whereas, information and knowledge on the most sensitive model inputs under different climate, and soil conditions are still very limited. For this purpose, a sensitivity analysis was conducted in the present work, using the DeNitrification-DeComposition (DNDC) model based on the data collected at a semi-arid region (Merchouch station, Morocco). The objective is to identify the most influential factors affecting the DNDC-modeled SOC dynamics in a semi-arid region across different climatic and soil conditions. The results of sensitivity analysis highlighted air temperature as the main determinant of SOC. A decrease in air temperature of 4 C results in an almost 161 kg C ha?1 yr?1 increase in C sequestration rate. Initial SOC was also confirmed to be one of the most sensitive parameters for SOC. There was a 96 kg C ha?1 yr?1 increase in C sequestration rate under low initial SOC (0.005 kg C ha?1). In the DNDC, air temperature in climatic factors and initial SOC in variable soil properties had the largest impacts on SOC accumulation in Merchouch station. We can conclude that the sensitivity analysis conducted in this study within the DNDC can contribute to provide a scientific evidence of uncertainties of the selected inputs variables who can lead to uncertainties on the SOC in the study site. The information in this paper can be helpful for scientists and policy makers, who are dealing with regions of similar environmental conditions as Merchouch Station, by identifying alternative scenarios of soil carbon sequestration

Effet à moyen et à long terme du Semis direct sur la matière organique, la stabilité structurale et la compaction des sols argileux au Maroc

In Morocco, the effects of climate change coupled with the degradation of soil resources are major factors limiting socio-economic development. Among these factors, intensive plowing practiced by Moroccan farmers causes depletion of soil organic matter (OM) and affect their physical properties (structural stability, apparent density) which promotes their erosion. The purpose of this paper is to assess the extent to which no-till (SD) can be used to address these various challenges. The adopted methodology consists of monitoring the OM contents at different depths in two sites on soils of Central Morocco with mixed plowing practices in the medium and long term: direct seeding (SD) and conventional seeding (SC). In addition, we studied the effect of SD on two physical properties of the soil: structural stability and apparent density (Da). The results obtained showed the favorable effects of the EA system on these soil properties. Differences between the two treatments were recorded on the one hand on the soil surface after 10 and 11 years of testing (first site) and on the other hand, at depth after 32 years of testing (second site) . These differences were significant (P-value <0.05) for all parameters except Da. It is concluded that EA has improved soil quality over the medium and long term, which contributes to reducing its vulnerability to erosion. Keywords: direct sowing, organic matter, structural stability, apparent density, Central MoroccoAu Maroc, les effets des changements climatiques couplés à la dégradation des ressources en sol constituent des facteurs majeurs limitant le développement socio-économique. Parmi ces facteurs, le labour intensif pratiqué par les agriculteurs marocains provoquent l’appauvrissement des sols en matière organique (MO) et affectent leurs propriétés physiques (stabilité structurale, densité apparente) ce qui favorise leur érosion. L’objectif de ce papier est d’évaluer dans quelle mesure le semis direct (SD), peut être utilisé pour remédier à ces divers défis précités. La méthodologie adoptée consiste à suivre les teneurs en MO à différentes profondeurs dans deux sites sur des sols du Maroc Central ayant des conduites contrastées de labour sur le moyen et le long terme: semis direct (SD) et semis conventionnel (SC). En complément, nous avons étudié l’effet du SD sur deux propriétés physiques du sol à savoir : la stabilité structurale et la densité apparente (Da). Les résultats obtenus ont montré les effets favorables du système du SD sur ces propriétés du sol. Des différences entre les deux traitements ont été enregistrées, d’une part, à la surface du sol après 10 et 11 ans d’essai (premier site) et d’autre part, en profondeur après 32 ans d’essai (deuxième site). Ces différences ont été significatives (P-value <0,05) pour tous les paramètres à l’exception de la Da. On en conclut que le SD a amélioré la qualité du sol sur le moyen et le long terme, ce qui contribue à réduire sa vulnérabilité à l’érosion. Mots Clés: semis direct, matière organique, stabilité structurale, densité apparente, Maroc Centra

Étude quantitative de l’érosion hydrique des sols dans le bassin versant de Ben Ahmed (Maroc Central)

Soil erosion is a major problem in Morocco. However, few studies have addressed this phenomenon in Central Morocco. This paper presents the results of a quantitative study of water erosion in Ben Ahmed watershed (70 km Southeast from Casablanca). Several rainfall simulations using an intensity of 60mm h-1during one hour have been undertaken on the major soil types of the watershed. Results showed that soil detachability varied between 19 and 34g l-1and erosion rates ranged between 4.3 and 12.3t ha-1. Also 38 to 73% of rainfall was transformed into runoff. Laboratory analysis of soil samples has confirmed that the studied soils present low organic matter (1.2 to 3.3%) and bulk density ranges between 1.1 and 1.5 g cm-3. Keywords: Water erosion, Runoff, Detachability, Rainfall simulation, Central MoroccoL’érosion hydrique constitue une problématique majeure au Maroc. Cependant, peu d’études sur ce fléau ont concerné les bassins du Maroc Central. Cet article présente les résultats d’une étude quantitative sur l’érosion hydrique dans le bassin de Ben Ahmed (située à 70 km au sud-est de Casablanca).Une campagne de simulations de pluie avec une intensité érosive de 60mmh-1 sur les principaux sols du bassin a permis d’estimer leur détachabilité varie entre19 et 34g l-1, correspondant à des taux d’érosion oscillants entre 4,3 et 12,3 t ha-1, pour les conditions de pluie testées, et que les coefficients de ruissellement variaient entre 38 et 73 %. Les analyses des échantillons prélevés de chaque site montrent que les sols sont faiblement à moyennement pourvus en matière organique avec des teneurs variant entre 1,2 et 3,3 %, et des valeurs de la densité apparente variant entre 1,1 et 1,5 g cm-3. Mots-clés : Érosion hydrique, ruissellement, détachabilité, Simulation de pluie, Maroc centra

Crop Yields under Climate Variability and No-Tillage System in Dry Areas of Morocco

In Morocco, the intensive use of agricultural land coupled with irregular precipitation is a serious threat to the country’s food security. Conservation agriculture especially no-tillage (NT) system has shown an important result in the semi-arid regions of Morocco, but its dissemination to other, more humid, agro-ecological zones (precipita tion > 350 mm) is still low. For this purpose, a field experiment under NT system has been installed since 2004 in the Zaer Plateau (Central Morocco) to study the adaptation of this system to the irregular rainfall compared to a conventional tillage (CT). Yields (grain and biomass) of crops (wheat and lentil) under NT and CT were analyzed and compared over the years of study. The ANOVA test showed that yields over the seven years were significantly different and that both crop yields under NT system were greater than or equal to those under CT system even though lentil is more vulnerable to extreme climate events under CT and NT systems. Unlike NT, yields under CT were significantly correlated with the rainfall amount received during the crop cycle. This indicates the dependence of CT precipitation, whereas NT is more adaptable to the irregularities of the climate in the study area

Why Conservation Agriculture in rainfed drylands in Morocco

Crop yield in the rainfed Mediterranean environment in Morocco, the hot spot for climate change, is highly affected by rainfall variability, temperature extremes, and declining soil quality. Several research findings reported that Conservation agriculture (CA) has potential to minimize climatic risk, reduce soil erosion, and improve water use efficiency and soil health compared to conventionally tilled (CT) field in such climatic condition

Phytoremediation study of mining soils: case of the Mibladen and Zaida mine (High Moulouya, Morocco)

The Upper Moulouya region, including the Mibladen (M) and Zaïda (Z) mines, is one of the highest lead (Pb) deposit areas in Morocco. These mines, abandoned without any measure of rehabilitation, constitute the main source of soil pollution by Metallic Trace Elements (MTEs) accumulation in the region. In this study, two greenhouse phytoremediation experiments (for the Mibladen and Zaida sites) were set up using Italian ryegrass (Lolium multiflorum) specie to assess its capacity and ability to remediate soils contaminated by zinc (Zn), cadmium (Cd), copper (Cu), and Pb. For both experiments, various factors including (i) three substrates (waste treatment [Wt]; clay uncovering [Cun]; and unpolluted control soil [Ucs]) and (ii) three treatments (no treatment, treatment with organic matter, and treatment with chemical fertilizers) were studied. The results before planting indicated that Wt substrates had poorer physicochemical properties than those of Cun, thus they are the most exposed to the degradation phenomena. This is confirmed by pollution index (PI) results that revealed the trend of PI (Z Wt)> PI (M wt)> PI (M Cun)> PI (Z Cun)> PI (Z Ucs)> PI (M Ucs). The results of experiments indicated that ryegrass crops can grow on substrates contaminated with MTEs. Depending on the applied fertilizers, available metals, and the type of soil, the phytoremediation results showed that L. multiflorum can tolerate, hyperaccumulate, and translocate MTEs from polluted substrates. Our findings suggest that this plant can be a solution for remediating alkaline soils polluted by Cd, Pb, Zn, and Cu in Mediterranean conditions

Comparative study of the hydraulic, energy and agronomic performances of conventional and low pressure drip irrigation on citrus

In countries facing water scarcity, drip irrigation can raise crop productivity and save water compared to flood irrigation. In spite of its benefits, the adoption of drip irrigation is still low mainly due to the high cost of investment and the energy cost of operation. For this latter constraint, new types of drippers operating at low pressure are being tested. The present study aims to compare the performances of two types of drippers, represented by conventional drippers (CD) operating at nominal pressure of one bar and the new drippers (LP) operating at a pressure of 0.15 bars. The study was carried out in a citrus grove in Tadla, Morocco. Results showed that low pressure emitters reduced hydraulic energy per unit volume of water supplied by around 43% compared to conventional emitters, without significant reduction in water distribution uniformity. Low pressure drippers had uniformities of 80 to 92%, compared to 88 to 97% for conventional drippers. Citrus growth parameters, fruit yield and the fruit quality of the Maroc late variety were identical under the two types of drippers. Thus, low pressure emitters can be used as a substitute for conventional drippers which require higher energy. Key words: Drip irrigation, performance indicators, low pressure, citrus, Morocc