Evaluating DayCent and STICS in simulating the long-term impact of contrasting organic resource amendments on soil organic carbon and maize yields in sub-Saharan Africa

Problem: Low crop yields in sub-Saharan Africa mainly result from low soil fertility and insufficient nutrient inputs. A key component of Integrated Soil Fertility Management (ISFM), namely combining inputs of mineral fertilizers and organic resources, presents an opportunity to boost yields and maintain soil organic carbon (SOC) stocks in the long run. Soil-crop models help to assess the performance of ISFM under contrasting soil, climate, and management combinations. Yet, to date, most soil-crop models have been calibrated and tested in temperate conditions. Objective: Our objective was to evaluate and compare the performance of two different soil-crop models, DayCent and STICS, to represent crop yields and SOC dynamics under contrasting organic resource amendments. Methods: We used a large dataset representing 3384 cropping situations (site x season x treatment) from four long-term experiments in Kenya. Each experiment included the same treatments with the addition of two quantities of low- to high-quality organic resource amendments (high vs low C/N ratio, respectively), with (+N) and without (-N) mineral nitrogen fertilizer. Each treatment included a cropped and uncropped subplot, allowing for a unique stepwise calibration of soil and crop parameters. Results: Both models represented SOC and yield dynamics with similar accuracy across sites and treatments. They reproduced SOC dynamics well (nRMSE below 30 %) in the two clayey soils sites but not in the two sandy soils. Yet, in most sites they reproduced well SOC differences between high (Farmyard manure, Thithonia and Calliandra) and low-quality (maize stover and sawdust) organic resources. Models reproduced the average yield across sites and treatments similarly. They reproduced the positive effects of high-quality organic resources and the addition of mineral N on maize yield well. Models had similar inaccuracy in reproducing yield and yield variability under poor-quality organic resources and -N treatments. Conclusion: The stepwise calibration approach used in this study enabled highlighting the models' strengths and weaknesses in soil and plant simulations. The results suggest that the two models have similar strengths and struggle with the same problems despite having different structures. Collecting detailed plant (leaf area index, plant N uptake) and soil (water, nitrogen dynamics) in-season data from long-term experiments will be critical to exploit the full model complexity and improve their accuracy for tropical conditions

Experimental evaluation of zinc and copper terrestrial ecotoxicity prediction by life cycle assessment in agricultural recycling of livestock effluent

The agronomic benefits of organic waste application on farmland can be overshadowed by the potential health and environmental impacts associated with trace element emissions, especially copper (Cu) and zinc (Zn). This has prompted a need for life cycle assessment (LCA) models to predict their terrestrial comparative toxicity potential (CTP) and impact score. We compared the LCA (reference method) prediction ability with that obtained with an experimental data set obtained from a month-long incubation experiment (experimental method) on a soil amended or not with 31 livestock effluents mimicking agronomically relevant scenarios. The impact scores for Cu and Zn differed between the reference and experimental methods due to CTP discrepancies between the two methods. The application of 31 livestock effluents on the soil resulted in variability in the experimentally determined CTP for Zn and Cu (0.6 and 1.9 log10 units) comparable to the CTP variability estimated by the reference method for several hundred worldwide soils. These results could be explained by the inadequate prediction of the dissolved organic carbon concentration and Cu and Zn concentration and speciation in soil solution. We propose refinements to the multilinear regressions used for the CTP computation that take the soil property patterns following livestock effluent application on soils into account

Trajectoires d'innovations sur les bioproduits à base de micro-organismes une contextualisation par l'agriculture tropicale

L'utilisation des micro-organismes comme ressources constitutives de l'agriculture est historiquement ancrée dans les pratiques agricoles (compostage, lactofermentation.) des sociétés rurales depuis des siècles. La caractérisation de ces micro-organismes (virus, champignons, bactéries) par leur fonctionnalité pour restaurer la fertilité des sols, réduire l'usage de pesticides mobilise elle depuis une trentaine d'années les organisations de la société civile, entreprises, organisations professionnelles agricoles et la recherche agronomique principalement dans les pays du sud. L'augmentation, la multiplication des situations exploratoires de développement ou productives est cependant en croissance en liens par la science qui explore les conditions d'exploitation de ces ressources invisibles. Pour la recherche agronomique elles sont la promesse d'une révolution agronomique majeure qui permettra de s'affranchir des externalités négatives des intrants chimiques, mais aussi répondre à des enjeux économiques dont les couts reliés à ceux de l'énergie sont en croissance dans l'agriculture et l'alimentation. Le marché des bioproduits connaît ainsi depuis une dizaine d'année une croissance spectaculaire. Ces nouveaux intrants peuvent être différenciés en deux catégories : les produits de lutte biologique au sens large (y compris les biopesticides) et les biofertilisants (y compris les biostimulants). Ils peuvent être autoproduit par les agriculteurs et les petites entreprises à partir de ressources locales ou faire l'objet d'une production industrielle ce qui structure potentiellement deux trajectoires technologiques qui s'affirment à l'échelle mondiale. Cette communication référence l'historicité de ces trajectoires est documente par des recherches participatives situées en quoi l'autoproduction de biofertilisants est une opportunité d'intensification socio-écologique de l'agriculture ou une nouvelle "promesse" pour solidifier l'intensification industrielle et chimique mondialisée de l'agriculture

Assessing pastoral reforms through the performance of agro-pastoral community-based organizations in South Tunisia

Pastoralism is one of the most important agricultural production systems in drylands worldwide. It plays an important role in both the economy and the cycle of ecosystem goods and services. However, it is vulnerable to climatic challenges such as prolonged drought and socioeconomic pressures such as administrative shortcomings and ineffective governance. Under neoliberal influence, political and economic reforms have been implemented over the last 30 years to address these threats. These reforms have promoted local institutions for rangeland management and agro-pastoral development. In this paper, we assess the impact of these reforms on pastoral devolvement and Community-based natural resource management (CBNRM) by analyzing the performance of agro-pastoral community-based organizations CBOs in the province of Médenine (south-eastern Tunisia). We use a two-step methodology, with the first step focusing on a quantitative typology analysis of the performance of 31 CBOs. In a subsequent qualitative step, data from semi-structured interviews with 21 CBO chairpersons were used to identify the drivers of CBO performance. Results show that only 10% of the CBOs studied are able to move towards autonomy and proper integration into local and regional institutional networks and development dynamics. About 42% of the CBOs need further support and are in a precarious situation as they are dependent on public support. The remaining 48% have a low growth potential and in the early stages of consolidation. The qualitative analysis suggests that these shortcomings are mainly related to the CBOs' lack of networking skills. In addition, CBOs should improve their reputation and gain more trust from pastoral communities. Our findings suggest that well-functioning institutions do contribute to rural development; however, the design of pastoralist policy and institutional reforms should include long-term complementary support for the institutions created and consideration of the pastoralist community and regional contexts in order to achieve long-lasting transformative outcomes

Camel meat composition by species, breeds, publication year, age, and breeding system: A global systematic review and meta-analysis

Camel meat is increasingly being recognized as a sustainable and nutritious red meat source, particularly in arid and semi-arid areas where camels are thriving. However, its chemical composition and sensory attributes vary significantly owing to genetic, management, and environmental factors. This study conducted a systematic review and a meta-analysis to quantify the nutritional and sensory properties of camel meat and identify the key factors influencing these characteristics. A systematic review of peer-reviewed studies was conducted using Springer, PubMed/MEDLINE, Scopus, and ScienceDirect databases. This review comprised 57 papers published in English from 12 countries, covering the period between January 1991 and August 2024, including 377 analyses focusing on camel species, breeds, and breeding systems. Statistical analyses were performed to determine the effect sizes, heterogeneity, and impact of the moderating factors. The findings from our meta-regression and subgroup analyses revealed that variations in camel meat profiles are influenced by multiple factors, including breeding system, camel species, breeds, and age, but not by sex. Subgroup analysis revealed that higher final body weight (FBW) was reported for meat from Camelus bactrianus camels raised under the extensive system. Camels slaughtered at ≤6 years of age were characterized by higher dry matter, ash, and fat contents, but lower sarcomere length, lightness, redness, and cobalt content. The Najdi, Baladi Saudi, and Pakistani breeds were characterized as tender meat breeds. This study emphasizes the need for improved breeding strategies, meat processing techniques, and market awareness to enhance the appeal of camel meat. These findings provide valuable insights for livestock producers, policymakers, and the food industry, supporting the promotion of camel meat as a viable substitute for traditional red meat in regions affected by climate change and food insecurity