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In November 2018, ITAB (Institute of Agriculture and Organic Food) and INRA (National Institute for Agronomic Research) organized a transdisciplinary seminar to bring together stakeholders to: i) share issues associated with soil management in Organic Farming (OF) systems, ii) collectively define the main research questions to be addressed; and iii) facilitate the construction of networks or projects. More than 150 participants attended the seminar, which was designed using the method of citizen facilitation of the community forum type (Town Hall Meeting) allowing all parties to express themselves and a live summary by experts. The seminar identified important knowledge gaps on soils in OF systems and research needs. The 20 questions resulting from these exchanges relate to: i) the overall functioning of soils, more particularly the major biogeochemical cycles Carbon, Nitrogen, Phosphorus (CNP) and biological interactions; ii) the long-term effects of agricultural practices more or less specific to OF systems; (iii) soil protection; and iv) soil diagnostic and management tools. Most of the issues identified are generic and require multidisciplinary research, especially when responding to systemic issues. The seminar identified needs in terms of device and research observatory that provide the references necessary to validate or adapt to OF systems the tools and methods of evaluation and soil management available for conventional systems. The main questions identified during the seminar are discussed and confronted with recent dynamics in terms of soil research and development., En noviembre de 2018, el ITAB (Instituto de Agricultura y Alimentos Orgánicos) y el INRA (Instituto Nacional de Investigaciones Agronómicas) organizaron un seminario transdisciplinario para reunir a las partes interesadas para: i) compartir problemas asociados con el manejo del suelo en Agricultura Orgánica (AO) sistemas, ii) definir colectivamente las principales preguntas de investigación que se abordarán; y iii) facilitar la construcción de redes o proyectos. Más de 150 participantes asistieron al seminario, que fue diseñado utilizando el método de facilitación ciudadana del tipo foro comunitario (Town Hall Meeting) que permite que todas las partes se expresen y un resumen en vivo por parte de expertos. Los resultados confirmaron las importantes lagunas de conocimiento sobre los suelos en los sistemas de AO y las necesidades de investigación. Las 20 preguntas resultantes de estos intercambios se relacionan con: i) el funcionamiento general de los suelos, más particularmente los principales ciclos biogeoquímicos Carbono, Nitrógeno, Fósforo (CNP) e interacciones biológicas; ii) los efectos a largo plazo de las prácticas agrícolas más o menos específicas de los sistemas de AO; iii) protección del suelo; y iv) herramientas de diagnóstico y manejo de suelos. La mayoría de los problemas identificados son genéricos y requieren una investigación multidisciplinaria, especialmente cuando se trata de responder a problemas sistémicos. El seminario identificó necesidades en cuanto a dispositivo y observatorio de investigación para obtener las referencias necesarias para validar o adaptar, en sistemas de AO, las herramientas y métodos de evaluación y manejo de suelos disponibles para sistemas convencionales. Las principales cuestiones dentificadas durante el seminario son discutidas y confrontadas con la dinámica reciente en términos de investigación y desarrollo de suelos., En novembre 2018, l'ITAB (Institut de l’agriculture et de l’alimentation biologiques) et l’INRA (Institut national de la recherche agronomique) ont organisé un séminaire transdisciplinaire pour : i) partager les enjeux associés à la gestion des sols dans les systèmes en Agriculture Biologique (AB), ii) définir collectivement les principales questions de recherche à traiter ; et iii) faciliter la construction de réseaux ou de projets. Plus de 150 participants ont assisté au séminaire qui a été conçu à partir de la méthode d’animation citoyenne de type forum communautaire (Town Hall Meeting), permettant à l’ensemble des parties de s’exprimer et à une synthèse en direct par des experts d’être réalisée. Les résultats identifient des manques importants de connaissances sur les sols dans les systèmes en AB et les besoins de recherche. Les 20 questions issues de ces échanges portent sur : i) le fonctionnement global des sols, plus particulièrement les grands cycles biogéochimiques Carbone, Azote, Phosphore (CNP), et les interactions biologiques ; ii) les effets à long terme des pratiques agricoles plus ou moins spécifiques aux systèmes en AB ; iii) la protection des sols ; et iv) les outils de diagnostic et de gestion des sols. La plupart des questions identifiées sont génériques et nécessitent des recherches multidisciplinaires, en particulier lorsqu’elles répondent à des enjeux systémiques. Le séminaire identifie des besoins en matière de dispositif et observatoire de recherche afin d’obtenir les références qui sont nécessaires pour valider ou adapter sur les systèmes en AB les outils et méthodes d’évaluation et de gestion des sols disponibles pour les systèmes agricoles conventionnels. Les principales questions identifiées lors du séminaire sont discutées et confrontées aux dynamiques récentes de la recherche et du développement sur les sols.

Inagroforestry systems, fine roots grow at several depths due to the mixture of trees and annual crops. The decomposition of fine roots contributes tosoil organic carbonstocks and may impactsoil fertility, particularly in poor soils, such as those encountered in sub-Sahelian regions. The aim of our study was to measure the decomposition rate of root litter from annual andperennialspecies according to soil depth and location under and far from trees in a sub-Sahelian agroforestry parkland. Soil characteristics under and far from the trees were analysed fromtopsoilto 200cm depth. Faidherbia tree,pearl milletand cowpea root litter samples were buried in litterbags for 15 months at 20, 40, 90 and 180cm depths. Rootlitter decompositionwas mainly impacted by soil moisture and soil depth. Faidherbia decomposed more slowly (36±12% remaining mass after 15 months) than cowpea and pearl millet roots (23±7% and 29±11% respectively). Pearl milletaboveground biomass, at harvesting time, was twice as high under (992gm−2) than far (433gm−2) from the tree, andbelowground biomass(0–200cm of depth) was 30.9gm−2and 19.6gm−2under and far from the tree, respectively. Faidherbia fine roots contributed slightly (p-value < 0.1) to higher stocks of C under the tree (7761±346gm−2) than far from it (5425±558gm−2) and from 0cm down to 200cm depth.

Salinity is becoming a serious threat to global food security, as it can significantly reduce crop yields and irreversibly damage soil fertility. Moreover, this problem is currently exacerbated by the impact of climate change, especially in drylands. Hence, introducing and adapting salinity-tolerant species, such as quinoa (Chenopodium quinoa, Willd.), could be among the ways to enhance the value of saline land, increasing its productivity and improving small farmers' income in rural areas. Quinoa, originally cultivated in the Andean region, has gained more attention throughout the Mediterranean region because it yields well even in marginal soils. It is also considered one of the world's healthiest foods, as its grains contain a balanced composition of minerals, vitamins, dietary fiber, fats, and high-quality, gluten-free proteins, with a balanced profile of all amino acids. In Morocco, quinoa was introduced in 2000, but its expansion is still limited to certain regions. In Eastern Morocco, for the first time, an experiment was carried out in 2019–2020 aiming to assess the response of five quinoa cultivars (INIA-420 Negra, Titicaca, Puno, ICBA-Q4 and ICBA-Q5) to saline irrigation. For this, we used two levels of water irrigation salinity: 1.50 dS.m−1 as a no-salt control from Tagma's source in Tafoghalt village and 10.5 dS.m−1 as salt treatment from local water drilling. Agronomic parameters, mainly dry matter, leaf area, grain yield and 1000-kernel weight, were measured to assess quinoa cultivars' responses to saline irrigation. Statistical analysis revealed that all investigated parameters were significantly affected by salinity, quinoa variety and their interaction (p < 0.05). Furthermore, significant differences in terms of salinity tolerance among the five quinoa cultivars were observed, with the highest (2.17 t.ha−1) and lowest (0.33 t.ha−1) yields recorded for ICBA-Q5 and INIA-420 Negra, respectively. However, the same varieties tested previously in Southern Morocco tolerated a higher level of salinity (12 dS.m−1). We assume that other factors interfered with salinity and variety, such as the sowing date, which was relatively late and exposed the flowering and grain filling stages to high heat in May and June

Summary Cassava flour is the main source of carbohydrates for family farmers in the Amazon region of Brazil. Cassava is mainly grown under shifting cultivation, in recurrent cultivation periods initiated through slash-and-burn. Its sustainability is, however, questioned due to the associated deforestation and often rapidly decreasing crop productivity. There is an urgent need to make these cassava systems more sustainable and more profitable, but we currently lack a deep understanding of the key factors governing their productivity. We conducted an on-farm study on 37 cassava fields of smallholder farmers at three locations that spanned a range of crop-fallow frequencies, some of which were initiated through slash-and-burn while others through fire-free land clearance. First, we analysed how cassava plant density at harvest was related with pedoclimatic and management factors in slash-and-burn systems. Second, we assessed the relationship between plant density and cassava root yield at harvest and conducted a yield gap analysis to better understand which factors govern cassava productivity beyond plant density in slash-and-burn systems. Finally, we compared cassava productivity between slash-and-burn and the fire-free land clearing techniques that some farmers started to adopt in the study region. Cassava yields averaged 7.2 ± 5.4 Mg ha–1 (50% of the average yield of 14.2 Mg ha–1 in the Pará State), and ranged from 0 (in case of root rot diseases) to 24 Mg ha–1. Cassava yield was associated with plant density at harvest (ranging from 0 to 10 000 plants ha–1), suggesting that managing plant density is a key determinant of the attainable yield levels. In addition, differences in cassava root yields could be largely explained by differences in labour inputs for weeding and fallow clearing, the effect of the latter depending on soil texture. Therefore, our results suggest that labour is a key production factor for cassava in the shifting cultivation systems of the Eastern Amazon in which the use of external inputs, such as chemical fertilizers and herbicides, is limited. Further, root yields were influenced by the method of field preparation, whereby yields were about 50% lower (and more variable) when fields were prepared by slash-and-burn than by mechanical ploughing or herbicide application. Despite the significantly higher yields, these alternatives to burning the vegetation are, however, still hardly adopted in Paragominas. Hence, there is a need for supporting more sustainable production systems through local and national public policies. These new systems should not only focus on soil fertility management but also on weed control and, more generally, on labour productivity.

Made available in DSpace on 2021-06-25T10:27:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-07-01 While a recent study showed that significant amounts of the nitrogen (N) requirements of young Eucalyptus trees can be provided by nitrogen-fixing trees (NFTs) in mixed-species plantations through short-term belowground N transfer, the consequences of soil fertility on this facilitation process remain unknown. We assessed the effect of fertilization on the percentage of N derived from transfer (%NDFT) from Acacia mangium trees to Eucalyptus trees in mixed-species plantations. A complete randomized block design with two treatments (fertilized vs unfertilized) and three blocks was set up in mixed-species plantations of A. mangium and Eucalyptus in Brazil, with 50% of each species at 2.5 m × 2.5 m spacing. Collection of litterfall and forest floor made it possible to estimate the annual N release from forest floor decomposition between 46 and 58 months after planting, close to harvest age. 15N-NO3- was injected into the stem of one dominant Acacia tree in each plot, 58 months after planting. The x(15N) values of Acacia and Eucalyptus fine roots sampled within 1.8 m of the labelled A. mangium tree were determined at 7, 14, 30 and 60 days after labelling. The x(15N) values in wood, bark, branch and leaf samples were also determined for the 6 labelled Acacia trees and their two closest Eucalyptus neighbours, just before and 60 days after labelling. The amount of N released from forest floor decomposition was 31% higher in fertilized (F+) than in unfertilized (F-) plots. Sixty days after labelling, the aboveground compartments of Eucalyptus trees were significantly 15N enriched in both treatments. The x(15N) values of Acacia fine roots were higher than background values from 7 days after labelling onwards in F+ and 30 days after labelling in F-. The x(15N) values of Eucalyptus fine roots were higher than background values in both treatments, from 30 days after labelling onwards. Mean %NDFT values were 18.0% in F+ and 33.9% in F- over the first 60 days after labelling, and 22.8% in F+ and 67.7% in F- from 30 to 60 days after labelling. Fertilization decreased short-term transfer belowground of N from Acacia trees to Eucalyptus trees. Our study suggests that belowground facilitation processes providing N from NFTs to Eucalyptus trees in mixed-species plantations are more pronounced in low-fertility soils than in nutrient-supplied stands. USP ESALQ Forest Science Department Eco&Sols INRA CIRAD IRD Montpellier SupAgro University of Montpellier CIRAD UMR Eco&Sols UNESP School of Agriculture São Paulo State University ‘Julio de Mesquita Filho,’ Department of Forest Science and Wood UFES IPEF Instituto de Pesquisas e Estudos Florestais UNESP School of Agriculture São Paulo State University ‘Julio de Mesquita Filho,’

International audience; Conventional, intensively managed coffee plantations are currently facing environmental challenges. The use of shade trees and the organic management of coffee crops are welcome alternatives, aiming to reduce synthetic inputs and restore soil biological balance. However, little is known about the impacts of the different types of shade tree species on soil functioning and fauna. In this paper, we assess soil nutrient availability and food web structure on a 17-year old experimental coffee plantation in Turrialba in Costa Rica. Three shade types (unshaded coffee, shaded with Terminalia amazonia, and shaded with Erythrina poepiggiana) combined with two management practices (organic and conventional) were evaluated. Total C and N, inorganic N and Olsen P content, soil pH, global soil fertility, and nematode and microarthropod communities were measured in the top 10 cm soil layer, with the objective of determining how shade tree species impact the soil food web and soil C, N and P cycling under different types of management. We noted a decrease in soil inorganic N content and nematode density under conventional management (respectively -47% and -91% compared to organic management), which suggested an important biological imbalance, possibly caused by the lack of organic amendment. Under conventional management, soil nutrient availability and fauna densities were higher under shade, regardless of the shade tree species. Under organic management, only soils under E. poeppigiana, a heavily pruned. N-2 -fixing species, had increased nutrient availability and fauna density, while T amazonia shade had a null or negative impact. The effects of coffee management and shade type on soil nutrient availability were mirrored by changes in soil food web structure. Higher fertility was recorded in soil with balanced food webs. These results emphasize the importance of the choice of shade tree species for soil functions in low input systems, more so than in fertilized systems

Made available in DSpace on 2021-06-25T10:21:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Aims: Belowground interactions are still poorly understood in mixed-species forests. We investigated the effects of soil fertility on belowground processes in mixed planted forests. Methods: The dynamics and traits of Eucalyptus and Acacia mangium fine roots (diameter < 2 mm) in plantations with 50% of each species were studied in a randomized block design established in a nutrient depleted soil. Stands with NPK fertilization applied at planting (F+) were compared to unfertilized stands (F-). Results: In the 0–15 cm soil layer, Eucalyptus root mass density (RMD) was higher than Acacia RMD by 50% in F+ and 10% in F-, considering both ages. At 34 months of age, Eucalyptus RMD was 94% higher near Acacia trees than near Eucalyptus trees in F-. In this layer, Eucalyptus specific root length (SRL) was 21% higher than Acacia SRL at 16 months of age and was 10% higher in F- than in F+ at 34 months of age. The cumulative Eucalyptus fine root length production between 16 and 34 months was 66% higher in F- than in F+ in the 0–1 m soil layer. Conclusions: Fertilization increased the competition between species and led to a partial exclusion of Acacia fine roots from the nutrient-rich topsoil. Soil exploration by Eucalyptus roots in the vicinity of Acacia trees was higher in F- than in F+, which suggests that unfertilized trees benefited from facilitation through higher soil N availability and direct N transfer from Acacia trees. ESALQ Forest Science Department Escola Superior de Agricultura Luiz de Queiroz Universidade de São Paulo Université de Lorraine AgroParisTech INRAE UMR Silva School of Agriculture São Paulo State University (UNESP) Eco&Sols CIRAD INRA IRD Montpellier SupAgro Univ Montpellier CIRAD UMR Eco&Sols ESALQ Soil Science Department Escola Superior de Agricultura Luiz de Queiroz Universidade de São Paulo UFES Centro de Ciências Agrárias e Engenharias Alto Universitário, S/N Guararema School of Agriculture São Paulo State University (UNESP)

Alley cropping systems are composed of tree rows alternating with crop alleys. Their interest in providing ecosystem services is increasingly acknowledged. In particular, they could have a positive impact on nutrient accessibility, soil carbon content and could increase the biodiversity of soil invertebrates associated with the provision of ecosystem services (carbon and nutrient cycling, pest regulation, etc). However, few studies have taken into account the spatial heterogeneity of soil fertility and soil organisms within these systems. A key question, however, is whether soil functioning is impacted only below the tree row, or whether crop alleys benefit from the presence of the tree row. Moreover, the positive effects of alley cropping systems are often attributed to the tree. However, the tree row is not cultivated and not tilled, resulting in the development of predominantly herbaceous vegetation, either natural or seeded, forming an understory vegetation strip (UVS). This UVS could play a particularly important role in providing organic matter in the first few centimeters of the soil, and provide an interesting habitat for soil organisms. The objective of my PhD thesis is to determine the impact of the UVS on the spatial variation of soil fertility and some associated organisms (microorganisms and macrofauna), through various observations and an experimentation in situ.I studied in a first chapter the variations of soil fertility and soil organisms within the UVS (with the distance to the tree) and between UVS and crop alleys, in two young plots in South-West France. This study has shown on the one hand that the distance to the tree does not modify the properties of the UVS with sown UVS. On the other hand, it showed that young UVS can induce an increase in the C and available P contents in the first centimeters of soil under the UVS compared to the crop alley, but that their effect on the variation of soil microbial biomass and respiration and on the abundance of macrofauna is less clear. Soil organisms may even be negatively impacted by the proximity to the UVS. Secondly, I studied the variation of soil fertility and soil organisms with the distance from the UVS at different seasons within three shade treatments in a 22 year old market gardening plot in the South of France. This plot was sampled using a design that took into account the distance to the tree, but also the impact of herbaceous strips without trees. This study showed that the UVS has a strong impact on the abundance of soil macrofauna and the efficiency of microorganisms in the UVS independently of the presence and proximity to the tree, but that it induces little heterogeneity within the crop alley in its immediate vicinity. Moreover, the presence of trees has a greater impact on soil fertility than the UVS. Finally, there is a great variability in the response of soil organisms depending on the season, and the UVS can be a refuge for macrofauna in some seasons, while the distribution of macrofauna in the plot is more homogeneous in other seasons. In a final chapter, I studied the movement of earthworms near the UVS in a 23 year old plot near Montpellier. This study suggests that in spring, endogeic earthworms move more towards the UVS than towards the crop alley.; Les systèmes agroforestiers en allées cultivées sont composés d'une alternance de lignes d'arbres et d'allées cultivées. Leur intérêt dans la fourniture de services écosystémiques commence à être bien démontré. En particulier, ils auraient un impact positif sur l'accessibilité des nutriments, la teneur en carbone des sols et l'augmentation de la biodiversité des invertébrés du sol associés à la fourniture de services écosystémiques (cycle du carbone et des nutriments, régulation des ravageurs, etc). Cependant, peu d'études ont pris en compte l'hétérogénéité spatiale de la fertilité et des organismes du sol au sein de ces systèmes. Une question essentielle est pourtant de déterminer si le fonctionnement du sol est impacté seulement sous la ligne d'arbres, ou si les allées cultivées bénéficient de la présence de cette ligne d'arbres. De plus, les effets positifs des systèmes en allées cultivées sont souvent attribués à l'arbre. Cependant, la ligne d'arbres n'est pas cultivée et le sol n'y est pas travaillé, entraînant le développement d'une végétation majoritairement herbacée, naturelle ou semée, formant un linéaire sous arboré (LSA). Ce LSA pourrait jouer un rôle particulièrement important dans l'apport de matière organique dans les premiers centimètres du sol, et fournir un habitat intéressant pour les organismes du sol. L'objectif de mon projet de doctorat est de déterminer l'impact du LSA sur la variation spatiale de la fertilité du sol et de certains organismes associés (microorganismes et macrofaune), au travers de différentes observations et d'une expérimentation in situ.Pour cela, j'ai étudié dans un premier chapitre les variations de la fertilité et des organismes du sol au sein du LSA (avec la distance à l'arbre) et entre LSA et allée cultivée, dans deux jeunes parcelles en grandes cultures dans le Gers. Cette étude a montré d'une part que la distance à l'arbre ne modifie pas les propriétés de LSA semés. D'autre part, elle a montré que de jeunes LSA peuvent induire une augmentation de la teneur en C et en P disponible dans les premiers centimètres du sol sous le LSA en comparaison avec l'allée cultivée, mais que leur effet sur la variation de la biomasse et respiration des microorganismes du sol et sur l'abondance de la macrofaune est moins clair. Les organismes du sol peuvent même être négativement impactés par la proximité au LSA. Deuxièmement, j'ai étudié la variation de la fertilité et des organismes du sol en fonction de la distance au LSA à différentes saisons au sein de trois modalités d'ombrage, dans une parcelle de 22 ans cultivée en maraîchage dans le Gard. Cette parcelle a été échantillonnée selon un design permettant de prendre en compte la distance à l'arbre, mais également l'impact de bandes enherbées sans arbres. Cette étude a montré que le LSA impacte fortement l'abondance de la macrofaune du sol et l'efficience des microorganismes dans le LSA indépendamment de la présence et proximité à l'arbre, mais qu'il induit peu d'hétérogénéité au sein de l'allée cultivée dans sa proximité immédiate. De plus, la présence des arbres impacte davantage la fertilité du sol que le LSA. Enfin, il existe une grande variabilité de la réponse des organismes du sol en fonction de la saison, le LSA pouvant être un refuge pour la macrofaune a certaines saisons, alors que la distribution de la macrofaune dans la parcelle est plus homogène a d'autres saisons. J'ai étudié dans un dernier chapitre les mouvements de vers de terre à proximité du LSA dans une parcelle de 23 ans en grandes cultures près de Montpellier. Cette étude suggère qu'au printemps, les vers de terre endogés se déplacent davantage vers le LSA que vers l'allée cultivée.

This paper stemmed from a workshop 'Emerging challenges in large scale soil carbon sequestration' held in Paris on 8-10 October 2018; International audience; To respect the Paris agreement targeting a limitation of global warming below 2°C by 2100, and possibly below 1.5°C, drastic reductions of greenhouse gas emissions are mandatory but not sufficient. Large‐scale deployment of other climate mitigation strategies are also necessary. Among these, increasing soil organic carbon (SOC) stocks is an important lever because carbon in soils can be stored for long periods and land management options to achieve this already exist and have been widely tested. However, agricultural soils are also an important source of nitrous oxide (N$_2$O), a powerful greenhouse gas, and increasing SOC may influence N$_2$O emissions, likely causing an increase in many cases, thus tending to offset the climate change benefit from increased SOC storage. Here, we review the main agricultural management options for increasing SOC stocks. We evaluate the amount of SOC that can be stored as well as resulting changes in N$_2$O emissions to better estimate the climate benefits of these management options. Based on quantitative data obtained from published meta‐analyses and from our current level of understanding, we conclude that the climate mitigation induced by increased SOC storage is generally overestimated if associated N$_2$O emissions are not considered but, with the exception of reduced tillage, is never fully offset. Some options (e.g, biochar or non‐pyrogenic C amendment application) may even decrease N$_2$O emissions.; Pour respecter l'accord de Paris visant à limiter le réchauffement climatique à moins de 2°C d'ici 2100, et éventuellement à moins de 1,5°C, des réductions drastiques des émissions de gaz à effet de serre sont obligatoires mais pas suffisantes. Le déploiement à grande échelle d'autres stratégies d'atténuation du climat est également nécessaire. Parmi celles-ci, l'augmentation des stocks de carbone organique du sol (SOC) est un levier important car le carbone dans les sols peut être stocké pendant de longues périodes et les options de gestion des terres pour y parvenir existent déjà et ont été largement testées. Toutefois, les sols agricoles sont également une source importante d'oxyde nitreux (N$_2$O), un puissant gaz à effet de serre, et l'augmentation du SOC peut influer sur les émissions de N$_$O, provoquant probablement une augmentation dans de nombreux cas, tendant ainsi à compenser le bénéfice du changement climatique résultant du stockage accru du SOC. Nous passons ici en revue les principales options de gestion agricole pour l'augmentation des stocks de SOC. Nous évaluons la quantité de SOC qui peut être stockée ainsi que les changements qui en résultent dans les émissions de N$_2$O afin de mieux estimer les avantages climatiques de ces options de gestion. Sur la base des données quantitatives obtenues à partir de méta-analyses publiées et de notre niveau de compréhension actuel, nous concluons que l'atténuation du climat induite par un stockage accru du SOC est généralement surestimée si l'on ne tient pas compte des émissions de N$_2$O associées, mais, à l'exception du travail réduit du sol, n'est jamais totalement compensée. Certaines options (par exemple, le biochar ou l'application d'un amendement C non pyrogène) peuvent même réduire les émissions de N$_2$O.

International audience; This paper investigates the perceptions of a diversity of stakeholders supporting smallholders in the eastern Brazilian Amazon about ecosystem services and agricultural practices. Our results come from 30 semi-structured interviews with key stakeholders in two contrasting municipalities in this region (Paragominas and Irituia). We identified 17 different ecosystem services and 15 agricultural practices. Using a multidimensional scaling (MDS), we differentiated the stakeholders’ perceptions of co-production of ecosystem services. The most mentioned ecosystem services are food supply, regulation of water cycles, soil fertility and erosion prevention. Overall, there is a positive perception that agricultural practices are providing ecosystem services. Biodiversity-based practices are associated with the provision of a broad range of ecosystem services whereas mechanical-chemical practices are mainly linked to food supply. Use of fire, deforestation and use of chemical pesticides are perceived as having most negative effects on the provision of ecosystem services. The type of activity performed by the stakeholders and their municipality are the main factors influencing their perception of ecosystem services co-production. In conclusion, the concept of co-production of ecosystem services related to agroecosystems is relevant as local actors recognize a diversity of effects of agricultural practices on service provision.; Cette étude analyse les perceptions relatives aux services écosystémiques et aux pratiques agricoles, de différents acteurs venant en appui aux agriculteurs familiaux en Amazonie brésilienne orientale. Nos résultats se fondent sur 30 entretiens semi-directifs avec des acteurs clés de deux municipalités contrastées de cette région (Paragominas et Irituia). Dix-sept services écosystémiques différents et 15 pratiques agricoles ont été identifiés. Un positionnement multidimensionnel (MDS) a permis de différencier la perception des acteurs sur la coproduction de services écosystémiques. La production de nourriture, la régulation des cycles de l’eau, la fertilité des sols et la prévention de l’érosion, sont les services écosystémiques les plus mentionnés. Globalement, les pratiques agricoles sont perçues de manière positive en termes de fourniture de services écosystémiques. Les pratiques basées sur la biodiversité (principalement l’introduction de différentes plantes) sont associées à une grande diversité de services, tandis que les pratiques basées sur les intrants chimiques et l’énergie mécanique sont principalement associées à la production de nourriture. L’utilisation du feu, la déforestation et l’utilisation des pesticides chimiques sont considérées comme ayant principalement des effets négatifs sur la fourniture de services écosystémiques. Le type d’activité exercée par les acteurs et la municipalité sont les principaux facteurs influençant leur perception de la co-production de services écosystémiques. En conclusion, le concept de co-production lié aux agroécosystèmes est pertinent, car les acteurs locaux reconnaissent une diversité d’effets des pratiques agricoles sur la fourniture de services.

Dans les serres biologiques, les rotations de cultures sont généralement rapides et peu diversifiées, le repos des sols avec jachère ou engrais vert est rare et la production dépend fortement des intrants extérieurs. Par conséquent, les problèmes tels que la salinité du sol, les déséquilibres nutritifs et les dommages causés aux cultures par les ravageurs et les maladies sont courants. Dans le cadre du projet Greenresilient, l’utilisation de paillages organiques (ou mulch de transfert) est étudiée en tant que méthode « innovante » afin de déterminer si cette pratique est bénéfique pour la santé du sol et la biodiversité. Cette brochure explique les avantages, les risques et les défis du mulch de transfert, et fournit des recommandations pour une application pratique.

International audience; Soil acidification and declining fertility are widespread in sub‐Saharan Africa. Nutrient depletion is mainly related to nutrient mining driven by biomass removal without replenishment of nutrients through use of fertilisers. Concomitant acidification is due to the high ash alkalinity of harvested biomass. We determined the nutrient content and ash alkalinity of biomass of the main crops produced in smallholder mixed crop–livestock farming systems in the Malagasy Highlands of Madagascar and calculated the soil acidification/alkalinisation occurring through biomass transfer. Samples of rice and forage were collected from 70 rice plots and 91 cultivated forage plots, and 70 manure samples were collected from farms. Nutrient exports induced by crop harvesting resulted in annual losses of 57 kg nitrogen (N), 6 kg (phosphorus) P and 33 kg potassium (K) ha–1 for rice (grain + straw), and 31–51 kg N, 8–9 kg P and 29–57 kg K ha–1 for each forage cut (with three cuts per year on average). The ash alkalinity of samples, calculated as the difference between cation and anion contents, was 49–100 cmolc kg–1 for forage crops, 31 cmolc kg–1 for rice straw, and only 4 cmolc kg–1 for rice grains. Biomass removal caused a loss of nutrients and an increase in soil acidity. Owing to low nutrient retention efficiency during the handling and storage of manure, the traditional input of manure at 5 t fresh matter ha–1 is insufficient to balance nutrient and alkalinity losses in Malagasy mixed crop–livestock farming systems. Maintaining productive and sustainable mixed crop–livestock farming systems requires greater attention to ensuring a nutrient balance at both plot and farm levels.

Poor soil fertility and erratic rainfall constrain crop production in rain-fed smallholder farming systems in sub-Saharan Africa. Integration of drought tolerant and N2-fixing crops into maize-based cropping systems is a risk-averse strategy that also improves nitrogen cycling. A field experiment was carried out during the 2017/18 and 2018/19 cropping seasons in Goromonzi district in Zimbabwe. The trials were established on 14 farms, and on two field types (homefields and outfields), with eight treatments from a combination of cropping systems (maize and cowpea monocrops or maize/cowpea intercrops) and with or without nitrogen fertilizer (+N; -N). The trials were implemented on the same field plots for the two consecutive seasons. An improved cowpea variety and a landrace were used. The objectives were to determine 1) the productivity of the different cropping systems under variable soil fertility conditions, 2) N2-fixation of the two cowpea types when planted as monocrops or intercrops, and 3) mineral composition of maize and cowpea grains from intercrops and sole crops. Contrary to expected results, soil properties were not significantly different (P > 0.05) between field types. The land equivalent ratios (LER) were >1 for both seasons, implying improved land productivity under intercropping. Intercropping significantly reduced cowpea nodulation and active nodules, but not the total nodule weight, resulting in similar proportion of nitrogen derived from the atmosphere (%Ndfa) for cowpea grown as monocrop or in intercropping with maize. However, the total amount of fixed nitrogen was reduced in intercropping systems due to the smaller cowpea biomass compared to monocropping. Maize and cowpea grain mineral contents (Fe, Zn, Mn, Cu, Ca, Mg, P, K) were significantly affected by the cropping season only. We showed that intercropping maize with cowpea generally increases system productivity, in addition to substantial amounts of nitrogen being added to the system through N2-fixation. However, intercropping was not an agronomic biofortification option in these nutrient-depleted soils. Finally, annual variation in grain mineral quality can be larger than the annual variation in grain yield, potentially posing serious challenges to human nutrition.

International audience; Tropical forests are generally considered to stand upon nutrient-poor soils, but soil nutrient concentrations and availabilities can vary greatly at local scale due to topographic effects on erosion and water drainage. In this study we physically and chemically characterised the soils of 12 study plots situated along a catena with a shallow slope in a tropical rainforest in French Guiana both during the wet and the dry season to evaluate seasonal differences. Soils along the catena were all Acrisols, but differed strongly in their water drainage flux. Over time, this differential drainage has led to differences in soil texture and mineral composition, affecting the adsorption of various nutrients, most importantly phosphorus. The more clayey soils situated on the slope of the catena had higher total concentrations of carbon, nitrogen, phosphorus and several micronutrients, while extractable nutrient concentrations were highest in the sandiest soils situated at the bottom of the catena. We found that carbon, nitrogen and extractable nutrients all varied seasonally, especially in the surface soil layer. These results are interesting because they show that, even at the local scale, small differences in topography can lead to large heterogeneity in nutrient concentrations, which can have large impacts on plant and microbial community organisation at the landscape level.

Resorption is the active withdrawal of nutrients before leaf abscission. This mechanism represents an important strategy to maintain efficient nutrient cycling; however, resorption is poorly characterized in old‐growth tropical forests growing in nutrient‐poor soils. We investigated nutrient resorption from leaves in 39 tree species in two tropical forests on the Guiana Shield, French Guiana, to investigate whether resorption efficiencies varied with soil nutrient, seasonality, and species traits. The stocks of P in leaves, litter, and soil were low at both sites, indicating potential P limitation of the forests. Accordingly, mean resorption efficiencies were higher for P (35.9%) and potassium (K; 44.6%) than for nitrogen (N; 10.3%). K resorption was higher in the wet (70.2%) than in the dry (41.7%) season. P resorption increased slightly with decreasing total soil P; and N and P resorptions were positively related to their foliar concentrations. We conclude that nutrient resorption is a key plant nutrition strategy in these old‐growth tropical forests, that trees with high foliar nutrient concentration reabsorb more nutrient, and that nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level., Resorption is a key plant nutrition strategy in old‐growth tropical forests. Trees with high foliar nutrient concentration reabsorb more nutrients. Nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level.

Forest-wood sector is a strategic sector for the mitigation of climate change, in particular through the production of fuelwood. However, the intensive harvesting of biomass can lead to a loss of forest soil fertility in the long term. The thesis work focuses on the sustainability of energy wood harvesting with (1) an environmental component, which concerns the assessment of nutrient returns by leaching during the pre-drying period, the characterization of exported biomass as well as the evaluation of dead wood on the ground (2) an economic component with an assessment of the economic impacts of a potential drop in productivity and their highlighting with the possible choices of cutting and silvicultural treatments.The Pre-drying operation of the trees proved to be unsatisfactory for an optimal return of nutrients contained in leaves and twigs. More than half of the nutrients remain exported from the forest after three months of pre-drying. The volumes of dead wood left on forests to maintain soil fertility and biodiversity were low (, La filière forêt-bois est un secteur stratégique pour l’atténuation des changements climatiques, notamment grâce à la production du bois-énergie. Toutefois, les récoltes intensives de biomasse peuvent induire à une perte de fertilité des sols forestiers sur le long terme. Le travail de thèse s’articule autour de la durabilité de la récolte de bois-énergie avec (1) un volet environnemental, qui concerne la quantification des retours d’éléments minéraux via la lixiviation pendant la phase de réessuyage, la caractérisation de la biomasse exportée ainsi que l’évaluation des bois morts au sol (2) un volet économique avec une évaluation des impacts économiques d’une potentielle baisse de productivité et leur mise en relief avec les choix possibles de coupe et de traitement sylvicoles.Le réessuyage des arbres s'est avéré insatisfaisant pour un retour optimal de nutriments contenus dans les feuilles et brindilles. Plus de la moitié de nutriments reste exportée de la forêt après trois mois de réessuyage. Les volumes de bois morts permettant de maintenir la fertilité des forêts et leur biodiversité étaient faibles (

International audience; A growing concern on the deleterious effects of chemical inputs to the environment has been on the rise from the excessive use of chemical inputs leading to soil and water pollution, destruction to fauna and microbial communities, reduced soil fertility and increased crop disease susceptibility. In the Great Mekong Region (GMR), a large majority of the population relies on agriculture and faces severe challenges including decline in soil fertility, increased pests and diseases, leading to lower ecosystem productivity. In this region, over-dependence on chemical fertilizers also continues to impact negatively on soil health and the wider ecosystem. Agroecological practices, and beneficial microorganisms in particular, offer an affordable and sustainable alternative to mineral inputs for improved plant nutrition and soil health for optimal crop performance and sustainable production. Biofertilizers are a key component in integrated nutrient management as well as for increased economic benefits from reduced expenditure on chemical fertilizers, holistically leading to sustainable agriculture. To cope with the need for biofertilizer adoption for sustainable agricultural production, the countries in the GMR are putting efforts in promoting development and use of biofertilizers and making them available to farmers at affordable costs. Despite these efforts, farmers continue to use chemical fertilizers at high rates with the hope of increased yields instead of taking advantage of microbial products capable of providing plant nutrients while restoring or improving soil health. This study explored the current agricultural practices in the six countries in the GMR (China, Vietnam, Myanmar, Thailand, Cambodia and Lao PDR), the critical need for sustainable agroecological practices with a special emphasis on biofertilizers. We highlighted the current status, distribution, adoption and gaps of biofertilizer production in the GMR, in order to obtain an insight on the nature of biofertilizers, efficacy and production standards, adoption or lack of biofertilizers in the GMR.

International audience; In European temperate forests, whole-tree harvesting increases nutrient exports and could compromise soil fertility in long term, especially when leaves, nutrient-rich compartments (leaves, fine and small wood) are exported. Pre-drying felled trees may allow leaves, twigs and branches to fall down or break during skidding, thereby remaining in the stand. However, the recommended pre-drying time is often based on expert estimates, and currently ranges from two to three months.In this study, we developed an experimental device to quantify nutrient leaching via rainfall (pH: 6.8 +/- 0.4) from fully developed leaves (collected in summer period) of four broadleaf species. We first set up an outdoor experiment under natural rainfall conditions to monitor the kinetics of nutrient leaching over around two and a half months. Second, we set up two controlled experiments under simulated rainfall conditions to investigate the effect of rainfall intensity and frequency on nutrient leaching.Foliar K was highly leached 60-79%, followed by Mg: 19-50%, P: 22-30% and only small proportions for Ca and N, < 16%. Nutrient leaching was positively correlated with rainfall amounts of < 30 mm but small rainfall amounts < 4 mm were more effective in leaching per unit (mm) than heavier rainfalls. More nutrients were leached out when the same rainfall amount was fractioned into small rainy events over several days.However, leaf leaching remains unsatisfactory because a large part of nutrients is still exported by foliage. Total nutrient exports by whole-tree harvest including foliage increased nutrient exports by 1.2-1.6 times compared to conventional harvesting. The exports by foliage are of equal importance as fine and small wood exports and thus leaving the foliage on the forest would increase significantly nutrient saving. We therefore recommend harvesting during the leafless period when possible and otherwise, letting all the leaves fall to the ground before skidding not only for nutrient returns but also because easily degradable organic matter is very important for soil biological activity.

International audience; The livelihoods of millions of people living in the world's deltas are deeply interconnected with the sediment dynamics of these deltas. In particular a sustainable supply of fluvial sediments from upstream is critical for ensuring the fertility of delta soils and for promoting sediment deposition that can offset rising sea levels. Yet, in many large river catchments this supply of sediment is being threatened by the planned construction of large dams. In this study, we apply the INCA hydrological and sediment model to the Mekong River catchment in South East Asia. The aim is to assess the impact of several large dams (both existing and planned) on the suspended sediment fluxes of the river. We force the INCA model with a climate model to assess the interplay of changing climate and sediment trapping caused by dam construction. The results show that historical sediment flux declines are mostly caused by dams built in PR China and that sediment trapping will increase in the future due to the construction of new dams in PDR Lao and Cambodia. If all dams that are currently planned for the next two decades are built, they will induce a decline of suspended sediment flux of 50% (47–53% 90% confidence interval (90%CI)) compared to current levels (99 Mt/year at the delta apex), with potentially damaging consequences for local livelihoods and ecosystems.

Sustainable alternatives to slash-and-burn shifting cultivation in the (sub)humid tropics rely on the use of external nutrient inputs to address soil fertility decline. The use of organic inputs is widely accepted as a practice to improve soil fertility, in particular soil organic carbon (SOC). On the other hand, its combined use with mineral fertilizer has the potential to maintain or increase crop productivity through positive interactive effects between both resources. Few studies have investigated these effects in the long term. Therefore, the objective of this study was to investigate whether maize productivity and soil SOC can be sustained under permanent cropping with sole and combined use of compost and mineral nitrogen (N) fertilizer. Here, we report results from a long-term experiment carried out in Gagnoa, Ivory Coast, from 1971 to 1990. The experiment followed a randomized block design comprising eight replicates of 12 treatments. The two studied factors were compost (0 or 10 t DM ha−1 yr−1) and mineral N (0, 40, 80, 120, 160 or 200 kg N ha−1 yr−1) additions. Average maize grain yields of the first cropping cycles were significantly lower without compost (5.05 ± 1.57 t ha−1) than with compost addition (6.07 ± 1.31 t ha−1). The annual yield variability as shown by the standard deviation of the mean was reduced by 20% with compost addition. Without compost, 53% of the initial SOC stock in the 0–20 cm soil layer was lost, resulting in a SOC loss rate of − 0.62 t C ha−1 yr−1 compared to 21% with compost (−0.27 t C ha−1 yr−1). Compost addition therefore reduced SOC loss with an apparent SOC storage rate of 0.35 t C ha−1 yr−1. The conversion rate of organic carbon (OC) inputs to SOC was about 12%. The Introductory Carbon Balance Model (ICBM) reproduced well SOC dynamics, especially without compost. Without mineral N and without compost, maize grain yield decreased with decreasing SOC concentration until the introduction of leguminous crops in the second cropping cycle. We conclude that combined application of compost with mineral N fertilizers was effective at maintaining maize productivity but inadequate to prevent the decline of SOC stocks, despite large additions. Leguminous crops in the rotation were key for maize productivity, but probably due to effects non-related to supplementary N supply.

Many forest ecosystems are developed on acidic and nutrient-poor soils and it is not yet clearly understood how forests sustain their growth with low nutrient resources. In forestry, the soil chemical fertility is commonly defined, following concepts inherited from agronomy, as the pool of plant-available nutrients in the soil at a given time compared to the nutritional requirement of the tree species. In this two-part study, Part 1 (Hansson et al., 2020) showed, through the compiled dataset of 49 forest ecosystems in France, Brazil and Republic of Congo, the limits of this definition of soil chemical fertility in forest ecosystem contexts. In this study (Part 2), we investigated the nutrient pools and fluxes between the different ecosystem compartments at 11 of the 49 sites in order to better characterize the role of the biogeochemical cycling of nutrients in the chemical fertility of forest ecosystems, and in particular the roles of the biological and geochemical components of biogeochemical cycling.\ud \ud The analysis of our dataset shows different types of biogeochemical functioning. When the geochemical component (inputs through mineral weathering and/or atmospheric inputs, capillary rise) is predominant, sufficient nutrients are provided to the plant-soil system to ensure tree nutrition and growth. Conversely, when the geochemical component of the cycle brings too few nutrients to the plant-soil system, the biological component (litterfall, plant internal cycling) becomes predominant in tree nutrition and growth. In the latter case, forest production may be high even when pools of nutrients in the soil reservoir are low because small but active nutrient fluxes may continuously replenish the soil reservoir or may directly ensure tree nutrition by bypassing the soil reservoir.\ud \ud This study highlights the necessity to include biogeochemical cycling and recycling fluxes in the definition and diagnosis methods of soil chemical fertility in forest ecosystems. We show that the chemical fertility is not only supported by the soil in forest ecosystem but by the sum of all the ecosystem’s compartments and fluxes between these pools.

Nutrient cycling is considered as a key agroecosystem service of Conservation Agriculture (CA). CA brings together major nutrients and organic matter fluxes within the soil-micro-organism-plant system. It also generates organic and inorganic nutrient pools accessible through new biological pathways. This chapter addresses nutrient management practices and benefits in CA systems. Current trends in CA systems design are discussed, as is integrated nutrient management. The concept of the “forest model” is introduced and discussed in detail. Sections on nutrient pools, bioavailability of elements, and mineral use efficiency in CA systems are also included. The chapter concludes with two case studies from contrasting agroecosystems: one from a Brazilian Fazenda transitioning from "generic" CA to CA based on multifunctional mix species cover, and one from a French dairy farm, illustrating how CA, associated with important and diversified organic matter inputs from cover crops and crop residues, impacts and modifies plant nutrition management.

With the development of agroecology, soil plays an important role in the design of sustainable agricultural practices. The soils are the place of many processes operated by living organisms interacting with one another. They also provide much needed services provided by agrosystems and enable their sustainability. In the context of the agroecological transition, it becomes urgent to promote these ecological processes, to intensify them by appropriate practices considering the socio-economic constraints, and finally, to be able to measure them. First, we recall the ecological theories of the terrestrial ecosystem functioning to improve our consideration of the soil in the agroecological transition. Then, we describe the need to improve our knowledge of the relationships between biodiversity, processes, aggregated functions and agrosystem services in a global context where biodiversity, including the soil one, is highly threatened. This theoretical approach is illustrated by four studies conducted in the tropics demonstrating the possibility to intensify the soil processes and to solve an agronomic dysfunction. Finally, we highlight the need to define soil indicators based on ecological processes for an appropriate measurement of this intensification. In conclusion, we propose a methodological framework to optimize the ecological functions of the soil for a sustainable supply of services provided by agrosystems., Avec le développement de l'agroécologie, le sol prend une place importante dans la réflexion sur la mise en place de pratiques agricoles durables. Le sol est le siège de nombreux pro-cessus opérés par des organismes vivants agissant de façon interactive. Ces processus sont indispensables pour la durabilité des services rendus par les agrosystèmes. Dans le cadre de la transition agroécologique, il devient alors nécessaire et urgent de promouvoir ces processus écologiques, de les intensifier par des pratiques adaptées et partagées avec d'autres contraintes socio-économiques, et enfin, de pouvoir les évaluer. Dans un premier temps, nous rappelons les théories écologiques du fonctionnement des écosystèmes pour améliorer notre prise en compte du sol dans la transition agroécologique. Puis, nous décrivons le besoin d'améliorer notre connaissance de la relation entre biodiversité, processus, fonctions agrégées et services rendus par les agrosystèmes dans un contexte mondial où la biodiversité, y compris celle du sol, est menacée. Cette approche théorique est illustrée par quatre études menées en zone tropicale démontrant la possibilité d'intensifier les processus du sol pour résoudre un dysfonctionnement agronomique, suite à un examen scientifique rigoureux du fonctionnement de l'agrosystème. Enfin, nous rappelons le besoin de définir des indicateurs fonctionnels des sols basés sur les processus écologiques pour une évaluation appropriée de cette intensification. En conclusion, nous proposons un cadre méthodologique permettant d'optimiser les fonctions écologiques du sol pour une fourniture durable des services rendus par les agrosystèmes.

La contrainte majeure évoquée par les exploitations agricoles des zones cotonnières est la baisse progressive de la capacité des sols cultivables à produire à cause de la mauvaise gestion de la fertilité. L'intégration agriculture-élevage en est une solution à travers l'amendement de la matière organique dont elle offre. L'objectif de l'étude était d'identifier les déterminants de l'adoption de la pratique de l'intégration agriculture-élevage au sein des exploitations agricoles. Une analyse des caractéristiques socio-économiques d'un échantillon constitué de 120 exploitations sélectionnées de façon aléatoire a été réalisée. Des statistiques ont été utilisées pour décrire les caractéristiques socio-économiques des unités de recherches enquêtées. Un modèle Probit Bivariée a été utilisé pour analyser les facteurs déterminants l'adoption de l'intégration agriculture-élevage. Les résultats ont révélé que la présence de légumineuse dans l'assolement, l'alphabétisation, la possession d'un moyen de transport, la proximité d'un point d'eau en saison sèche, le nombre de bovin, la possession de la radio, et le droit de propriété ont d'effet positif dans l'adoption des pratiques d'intégration agriculture-élevage. Par contre, la taille de l'exploitation a un effet négatif mais significatif. Il urge donc pour les institutions de recherche et les décideurs de prendre en compte ces facteurs, afin d'apporter de l'innovation pour une meilleure adoption de ces pratiques dans une perspective de gestion durable de la fertilité du sol.

International audience; Manipulating plant functional diversity to improve agroecosystem multifunctionality is a central challenge of agricultural systems world-wide. In cocoa agroforestry systems (cAFS), shade trees are used to supply many services to farmers, yet their impact on soil functioning and cocoa yields is likely to vary substantially among tree species. Here we compared the impact of five shade tree species (Canarium schweinfurthii (Canarium), Dacryodes edulis (Safou), Milicia excelsa (Iroko), Ceiba pentandra (Kapok tree), Albizia adianthifolia (Albizia)) and unshaded conditions on the functioning of poor sandy savanna soils within eight cocoa farms in Central Cameroon. We assessed the effects of plant functional traits, leaf litterfall and fine root biomass on a range of soil functions and on cocoa yield. Shade trees generally improved soil pH, NH4+, NO3- and Olsen P content, biomass production of bioassays and soil total C and N content, while leaving cocoa yields unchanged. However, these effects varied largely among species. Improvements of soil functions were low under the two fruit trees (Canarium and Dacryodes), medium under the legume tree Albizia and high under the two timber trees (Milicia and Ceiba). Low litter recalcitrance was most strongly associated with increases in soil fertility indicators such as N and P availability, whereas soil C and N content increased with litter Ca restitution. Synthesis and applications. We demonstrate that cocoa agroforest multifunctionality is substantially influenced by the functional traits of shade tree species. Shade tree species with the most dissimilar traits to cocoa (cocoa showing the lowest leaf litter quality) showed the largest improvement of soil functions. Therefore, selection of shade trees based on their functional traits appears as a promising practice to adequately manage soil functioning. In order to fully assess the beneficial role of shade trees in these agroecosystems. Future research will need to extend this approach to other below-ground traits and other aspects of multifunctionality such as long-term cocoa health and yield.

In Africa, cocoa yields are low, partly due to soil fertility constraints and poor management. While peoples’ knowledge, aspirations, and abilities are key factors explaining their behaviour, little is known about the rationales that underpin soil fertility management practices (SFMPs) of cocoa farmers. To address this gap, we conducted an exploratory survey in two contrasting regions in Cameroon where cocoa is an important crop: the humid forest and the forest-savannah transition zone. Some 30% of farmers in the transition zone as opposed to 13% in the humid forest expressed concerns about soil fertility. The most relevant soil fertility indicators for farmers were high cocoa yield, dark soil colour, ease of tillage, and floral composition. To enhance and maintain soil fertility, farmers used residues from weeding (100%), planting of trees (42%), mineral fertilisers (33%), compost (16%), and manure (13%). More farmers in the transition zone than the humid forest implemented SFMPs. Our findings suggest that soil fertility perceptions, access to inputs, local practices, and experience influence farmers’ use of SFMPs. The limited use of mineral fertilisers was explained by poor access whereas the use of organic fertilisers and tree planting were mostly constrained by lack of labour and knowledge. Farmers prioritised practices to increase yield and viewed SFMPs to be the least important management practices, although they believe high cocoa yield is an important indicator of soil fertility. To foster sustainable cocoa intensification, it is necessary to enhance farmers’ knowledge on SFMPs, increase access to inputs, and ensure returns on investment while considering farmers’ priorities and practices.

International audience; In complex coffee-based agroforestry systems, quantifying the impact of shade trees on coffee disease regulation and coffee yield is crucial for improving these systems and designing more sustainable ones. To this end, we analyzed interactions amongst shade trees, coffee plants (cv. Catimor), the coffee foliar disease complex and soil characteristics. We studied systems characterized by 40 variables measured in 60 plots located on three farms (monitored for 2 years) in Nicaragua. These variables characterized six system components grouped in six statistical blocks: shade trees (shade percentage and species abundancy), soil characteristics (fertility), foliar diseases, coffee plant characteristics (age and size), coffee growth and yield. We used partial least square path modelling (PLS-PM), i.e. a structural equation modelling approach used to understand and quantify interactions between the six blocks. Shade trees (mostly the associated shade percentage) had direct positive effects on foliar disease severity and incidence and soil quality, while having negative effects on coffee growth and yield. Soil characteristics (carbon, nitrogen, litter index, water infiltration potential) were negatively correlated with foliar diseases. An excessive shade percentage then had an indirect negative effect on coffee growth and yield due to the increased prevalence of foliar diseases. Finding the optimal shade cover can help reduce foliar diseases and enhance coffee berry production. The 'dose effect' of shade cover must also be considered because excessive shade, as well as lack of shade, have negative impacts on coffee growth and yield. Overall, effective shade management requires an analysis of trade-offs between soil quality, disease regulation and yield gains. In conclusion, PLS-PM turned out to be a good tool for studying agroecosystem networks and enabled us to put forward some foliar disease management and coffee yield enhancement guidelines.

International audience; Much effort has been spent on formulating guidelines for inorganic fertilizer use in millet crops in Sub-sahelian farms. However, these guidelines do not take into account the diversity of manuring practices. In this study we analyzed over two years (2016–2017) the use efficiency of an inorganic NPK fertilizer as affected by the two most contrasted categories of organic manure strategies (OMS) found in millet fields of central Senegal. 19 farmers’ fields were selected in a village typical of that region, 11 and 8 of which respectively corresponding to categories OMS1 and OMS2 as follows: OMS1, locally referred to as Homefields, were fields continuously cropped with millet over the last 15 years, having received organic manure regularly in the past, and manured again at the onset of the 2016 rainy season. OMS2 fields locally referred to as Outfields, were not manured in 2016 and were rarely manured in the past. Four of them were continuously cropped with millet and the others had followed a triennial millet-peanut-fallow rotation. In 2017, no manure was applied in any of the OMS1 or OMS2 fields. A pairwise treatments with and without the same inorganic fertilizer dose was applied in each field in both 2016 and 2017 cropping seasons. In 2016, the higher the manure application, the higher the use efficiency of the inorganic fertilizer applied. The use efficiency of the inorganic N was most closely related to soil bulk density and P availability. In 2017, with no new manure amendment, millet yield in OMS1 was about three times higher than in 2016. It was close to the water-limited yield, suggesting that the residual effect of the manure applied in 2016 was high. The use efficiency of the inorganic N was generally low under these conditions. In OMS2, millet yield and use efficiency of inorganic fertilizer remained low in both years. The crop rotation with peanuts did not enrich the soil compared to the millet returning every year, but it reduced Striga hermontica infestation and increased the millet 1000-grain weight. The methodological approach developed here may help in formulating guidelines to deal with the diversity of farming practices in Sub-sahelian villages.

Intraspecific variation in leaf functional traits has gained widespread attention as a means to evaluate, predict, and manage plant responses to environmental conditions, however there are considerable uncertainties regarding the extent and drivers of intraspecific trait variation (ITV) in domesticated plants. In a coffee (Coffea arabica) agroforestry system, we quantified ITV in seven leaf traits [i.e. area (LA), mass per area (LMA), dry matter content (LDMC), thickness (Lth), nitrogen concentrations (LNC), maximum photosynthetic rate on area and mass bases (Asat, Amass, respectively)] across managed gradients of soil fertility and light availability. Leaf physiological traits (Asat, Amass), as well as LA, showed the greatest extent of variation within coffee, while morphological traits (LMA, LDMC, Lth) and leaf N were less variable. All traits differed significantly as a function of light and fertilization treatment, however light was more influential in driving ITV in coffee leaves. Low light availability resulted in greater ITV for physiological leaf traits (Asat and Amass), while high light constrained ITV in most morphological-(LA, LMA, LDMC), physiological-(Asat, Amass) and chemical-(LNC) traits. Fertilization treatments did not induce systematic shifts in the extent of ITV. In addition, shade management treatments explained 9.2% of the variation in multivariate trait syndromes, while nutrient management regimes explained only 2.9%. Our results indicate that highly heterogeneous aboveground resource environments such those created by agroforestry, results in greater ITV for key crop physiological parameters. Based on ecological theory, such patterns indicate that management systems promoting resource heterogeneity should promote higher rates of resource partitioning, and greater resource-use efficiency in agroecosystems.

Rotational woodlots with N2-fixing trees may be efficient agroforestry systems, allowing farmers to alternate agricultural and wood-energy production on the same area. However, their long-term effect on soil fertility is poorly understood. The aim of this study was to investigate the influence of successive phases of Acacia auriculiformis stands growing in rotation with crops on the chemical properties of sandy and very poor tropical soils. The study was conducted 22 years after the afforestation of humid herbaceous savannah in Mampu, Democratic Republic of Congo. The chemical properties of top soil (0–20 cm) from control savannah plots were compared with those from acacia plots that had undergone one, two or three rotations of acacia during the 22 year period. We found that the soil properties under non-harvested acacia stands in a 1st rotation and under acacia stands in a 2nd or 3rd rotation following charcoal production and maize and cassava cultivation were similar. Soils under all acacia stands had higher C, N and $${\text{NO}}_{3}^{ - }$$ –N contents, but were more acidic, and had lower contents of exchangeable Ca, Mg, K and Na than the control savannah soils. Despite the increase in soil C and N, the sustainability of the acacia rotational agroforestry system after 22 years of practice is in question due to the steady decrease of soil cations, soil acidification and the risk of a decline in tree and crop productivity. To improve the nutrient balance and the sustainability of this system, different practices are recommended such as the debarking of tree stems before carbonization, the restitution of small branches and charcoal residues to the soil, and the supply of natural rock phosphate.