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Background: Soil animal communities include more than 40 higher-order taxa, representing over 23% of all described species. These animals have a wide range of feeding sources and contribute to several important soil functions and ecosystem services. Although many studies have assessed macroinvertebrate communities in Brazil, few of them have been published in journals and even fewer have made the data openly available for consultation and further use. As part of ongoing efforts to synthesise the global soil macrofauna communities and to increase the amount of openly-accessible data in GBIF and other repositories related to soil biodiversity, the present paper provides links to 29 soil macroinvertebrate datasets covering 42 soil fauna taxa, collected in various land-use systems in Brazil. A total of 83,085 georeferenced occurrences of these taxa are presented, based on quantitative estimates performed using a standardised sampling method commonly adopted worldwide to collect soil macrofauna populations, i.e. the TSBF (Tropical Soil Biology and Fertility Programme) protocol. This consists of digging soil monoliths of 25 x 25 cm area, with handsorting of the macroinvertebrates visible to the naked eye from the surface litter and from within the soil, typically in the upper 0-20 cm layer (but sometimes shallower, i.e. top 0-10 cm or deeper to 0-40 cm, depending on the site). The land-use systems included anthropogenic sites managed with agricultural systems (e.g. pastures, annual and perennial crops, agroforestry), as well as planted forests and native vegetation located mostly in the southern Brazilian State of Paraná (96 sites), with a few additional sites in the neighbouring states of São Paulo (21 sites) and Santa Catarina (five sites). Important metadata on soil properties, particularly soil chemical parameters (mainly pH, C, P, Ca, K, Mg, Al contents, exchangeable acidity, Cation Exchange Capacity, Base Saturation and, infrequently, total N), particle size distrib

Shade trees in agroforestry systems confer ecosystem services, such as enhanced soil fertility from diverse litter inputs, microclimate regulation via shade, and disease mitigation through trophic and abiotic interactions. With this thriving role of agroforestry in sustainable agriculture, particularly for tree crops, systematic and reliable methods to select shade trees for specific agroecosystem outcomes are crucial. Plant functional traits offer a framework to describe, select and manage shade trees. Over the last decade, shade tree leaf functional traits and whole plant traits have been assessed in agroforestry systems. Yet, we lack amalgamated information on (i) what we know about shade tree trait relationships with functions to achieve desired agroecosystem outcomes, (ii) how decades of shade tree selection by farmers impacts agroforests inter- and intraspecific trait diversity, and (iii) which shade tree traits should be considered for achieving farmer priorities. We consolidate literature on Coffea arabica (coffee) and Theobroma cacao (cocoa) agroforestry systems to summarize the role of shade tree functional traits in three key ecosystem functions: soil fertility, microclimate modification and crop productivity. We compile global and regional datasets on tree functional trait diversity to show the functional space of agroforestry tree species compared with the overall functional space observed in plants. Despite, or maybe because of, high shade tree diversity, shade tree trait characterization remains coarse and commonly measured at the community scale in the literature. Based on published trait data, we show that farmers adjust the functional composition of shade trees to increase the recycling of soil nutrients (high leaf nitrogen), the production of wood (skewing towards lower wood densities) and the production of fruits (tendency towards high seed size). Common shade trees in coffee and cocoa systems fall in the mid-range of leaf acquisitive to conserva

La faible productivité de l'agriculture en Afrique subsaharienne est due en grande partie à la dégradation de la fertilité des sols. Les agricultures familiales, pilier de la sécurité alimentaire de cette grande région, doivent relever le défi de la restauration et du maintien de la capacité productive des terres. Les pratiques endogènes des producteurs telles que les associations céréales-légumineuses, les jachères pâturées, les parcs arborés... ne permettent plus d'entretenir la fertilité sur des surfaces cultivées qui s'agrandissent, surtout lorsque les sols sont carencés. Durant quatre décennies, les décideurs et acteurs du secteur agricole ont privilégié la vulgarisation des engrais de synthèse. Mais l'utilisation des engrais minéraux demeure faible et bien en deçà de la moyenne de la consommation mondiale (15 kg/ha contre 135 kg/ha). Après avoir longuement promu l'utilisation de fumure organique, la recherche invite désormais à diversifier les sources de biomasse fertilisante via l'agroforesterie, les associations avec les légumineuses, l'agriculture de conservation. D'autres techniques de conservation de l'eau et du sol ont également été mises en avant. C'est bien la combinaison de différentes pratiques qui est à construire avec les agriculteurs pour chaque situation de production, en fonction des ressources disponibles localement, d'un apport raisonné d'engrais de synthèse et d'amendement, des savoirs paysans et scientifiques. Pour cela, il est nécessaire (i) de modifier les postures des chercheurs et des décideurs vis-à-vis des ruraux et (ii) de réviser les politiques publiques toujours focalisées sur l'usage des engrais minéraux, afin de fournir des services d'appui-conseil plus diversifiés, performants et intégrant les besoins de transitions agroécologiques indispensables aujourd'hui dans un contexte de changement climatique.

Ce fascicule, publié à l'occasion du Salon international de l'agriculture de Paris 2024, présente l'évolution des recherches sur la gestion de la fertilité des sols en Afrique subsaharienne, à partir d'un choix d'articles publiés au fil des ans par la revue Cahiers Agricultures.

Dicyandiamide decreased N2O emissions even under 40°C. Ammonia oxidizers and nirS were well adapted to 40°C in manured soils. Fungal nirK tolerated high temperature better in urea than manure treatment. Compared to nosZII, nosZI adapted to all temperature regardless of fertilization. nirS-denitrifier dominated N2O emissions at high temperature in fertilized soil. Heat waves associated with global warming and extreme climates would arouse serious consequences on nitrogen (N) cycle. However, the responses of the functional guilds to different temperatures, especially high temperature and the cascading effect on N2O emissions remain unclear. An incubation study was conducted to examine the effect of different temperatures (20°C, 30°C, and 40°C) and fertilizer types (urea and manure) on N2O-producers and N2O-reducers, as well as the efficacy of dicyandiamide (DCD) on N2O emissions in a vegetable soil. Results showed that ammonia oxidizers and nirS-type denitrifiers were well adapted to high temperature (40°C) with manure application, while the fungal nirK-denitrifiers had better tolerance with urea application. The nosZ clade I microbes had a strong adaptability to various temperatures regardless of fertilization type, while the growth of nosZ clade II group microbes in non-fertilized soil (control) were significantly inhibited at higher temperature. The N2O emissions were significantly decreased with increasing temperature and DCD application (up to 60%, even at 40°C). Under high temperature conditions, fungal denitrifiers play a significant role in N-limited soils (non-fertilized) while nirS-type denitrifiers was more important in fertilized soils in N2O emissions, which should be specially targeted when mitigating N2O emissions under global warming climate.

The distribution of plant communities in hot desert ecosystems is discontinuous and resembles the pattern of heterogeneous resource patches, known as “fertility islands”. Understanding the key factors that allow plants to establish in these conditions, as well as their associated microbial diversity, is crucial to the comprehension and preservation of these ecosystems. Saudi Arabia in the Arabian Peninsula, is one of the driest regions in the world, with a very low water regime and low soil nutrient contents. The establishment of ecosystems in these arid desert conditions is therefore subject to numerous constraints. Understanding the biotic and abiotic factors linked to the formation of fertility islands, from the perspective of soil composition and its associated microbiome, both in the soil and in the roots of associated plant community, is therefore a fundamental issue for the preservation of these ecosystems. In this study, we analyzed the soil composition between a fertility island and bare soil. The proportions of micro- and macro-elements important for plant nutrition, namely magnesium, phosphorus, potassium and iron were higher in the fertility island. We also observed that soil bacterial and fungal diversity increased in the fertility island. Key taxa such as Rhizobia and Glomeraceae which play important roles in ecosystem functioning were identified in both the fertility island soil and in the roots of the established plant community. These results confirm that plant establishment is linked to soil conditions, in line with the fertility island hypothesis, and that the microbial community in the fertility island differs both in diversity and in composition from that of the bare soil. Fertility islands soils and the roots of established plant community harbor a microbiome potentially crucial to ecosystem functioning, and are of major interest for conservation and agronomy programs.

La macrofaune du sol joue un rôle majeur dans la provision de services écosystémiques tels que le recyclage des nutriments, le stockage du carbone et la modification de la structure physique du sol. En particulier, les invertébrés saprophages, en consommant une grande quantité de litière, modifient sa dynamique de décomposition et ainsi la remise en circulation des éléments nutritifs essentiels à la croissance des plantes. Il existe une grande diversité d'invertébrés saprophages, chacun ayant un effet spécifique sur le processus de décomposition, conduisant à des complémentarités d'usage des ressources (synergies). Il existerait ainsi une relation positive entre la diversité fonctionnelle des invertébrés du sol et le processus de décomposition. L'objectif de cette thèse est d'étudier dans quelle mesure des pratiques agroécologiques novatrices peuvent restaurer la biodiversité du sol et les processus écologiques associés. Plus particulièrement, elle s'intéressera, i) d'une part au lien entre les pratiques agricoles et la composition des communautés d'invertébrés saprophages, ii) d'autre part, à la manière dont la composition de ces communautés influence le processus de décomposition et in fine la fourniture en éléments minéraux disponibles pour la culture ?

Despite the documented increase in greenhouse gas (GHG) emissions from Southeast Asian peat swamp forest degradation and conversion to oil palm over recent decades, reliable estimates of emissions of nitrous oxide (N2O) and methane (CH4) are lacking. We measured soil fluxes of N2O and CH4 and their environmental controls along a peatland transition from primary forest (PF) to degraded drained forest (DF) to oil palm plantation (OP) over 18 months in Jambi, Sumatra, Indonesia. Sampling was conducted monthly at all sites and more intensively following two fertilization events in the OP. Mean annual emissions of N2O (kg N ha−1 yr−1) were 1.7 ± 0.2 for the PF, 2.3 ± 0.2 for the DF and for the OP 8.1 ± 0.8 without drainage canals (DC) and 7.7 ± 0.7 including DC. High N2O emissions in the OP were driven by peat decomposition, not by N fertilizer addition. Mean CH4 annual fluxes (kg C ha−1 yr−1) were 8.2 ± 1.9 for the PF, 1.9 ± 0.4 for the DF, and 1.6 ± 0.3 for the OP with DC and 1.1 ± 0.2 without. Considering their 20-year global warming potentials (GWP), the combined non-CO2 GHG emission (Mg CO2-equivalent ha−1 yr−1) was 3.3 ± 0.6 for the PF and 1.6 ± 0.2 for the DF. The emission in the OP (3.8 ± 0.3 with or without DC) was similar to the PF because reductions in CH4 emissions offset N2O increases. However, considering 100-year GWP, the combined non-CO2 GHG emission was larger in the OP (3.4 ± 0.3 with DC and 3.5 ± 0.3 without) compared to both the PF and the DF (1.5 ± 0.2 and 1.2 ± 0.1, respectively). The increase in peat N2O emissions associated with the land-use change transition from primary forest to oil palm plantation at our sites provides further evidence of the urgent need to protect tropical peat swamp forests from drainage and conversion.

Can farmers in sub-Saharan Africa (SSA) boost crop yields and improve food availability without using more mineral fertilizer? This question has been at the center of lively debates among the civil society, policy-makers, and in academic editorials. Proponents of the “yes” answer have put forward the “input reduction” principle of agroecology, i.e. by relying on agrobiodiversity, recycling and better efficiency, agroecological practices such as the use of legumes and manure can increase crop productivity without the need for more mineral fertilizer. We reviewed decades of scientific literature on nutrient balances in SSA, biological nitrogen fixation of tropical legumes, manure production and use in smallholder farming systems, and the environmental impact of mineral fertilizer. Our analyses show that more mineral fertilizer is needed in SSA for five reasons: (i) the starting point in SSA is that agricultural production is “agroecological” by default, that is, very low mineral fertilizer use, widespread mixed crop-livestock systems and large crop diversity including legumes, but leading to poor soil fertility as a result of widespread soil nutrient mining, (ii) the nitrogen needs of crops cannot be adequately met solely through biological nitrogen fixation by legumes and recycling of animal manure, (iii) other nutrients like phosphorus and potassium need to be replaced continuously, (iv) mineral fertilizers, if used appropriately, cause little harm to the environment, and (v) reducing the use of mineral fertilizers would hamper productivity gains and contribute indirectly to agricultural expansion and to deforestation. Yet, the agroecological principles directly related to soil fertility—recycling, efficiency, diversity—remain key in improving soil health and nutrient-use efficiency, and are critical to sustaining crop productivity in the long run. We argue for a nuanced position that acknowledges the critical need for more mineral fertilizers in SSA, in combination

La diversification des cultures est un des leviers qui pourraient contribuer à stabiliser, voire améliorer, les rendements dans les régions soudano-sahéliennes contraintes par des conditions climatiques semi-arides et des sols très faiblement fertiles. Elle peut permettre aussi d'atténuer les risques liés aux marchés. Cette diversification peut être mise en oeuvre par la pratique des associations et des rotations ainsi que par l'enrichissement de celles-ci avec de nouvelles espèces. Pendant trois années d'expérimentation, nous avons comparé sept espèces, dont quatre légumineuses y compris le haricot mungo, cultivées seules ou en association avec le sorgho. Le haricot mungo est apparu comme une espèce très bien adaptée aux conditions semi-arides du Burkina Faso. Parmi les sept espèces testées, c'est celle qui a produit le plus de grains, entre 0,8 et 1,8 t ha−1 en culture pure et entre 0,35 et 0.9 t ha−1 en association avec le sorgho. Nos résultats confirment aussi le gain de rendement de la culture de sorgho associée avec les légumineuses par rapport à la culture pure. Vingt-cinq producteurs du centre nord du Burkina Faso ont testé le haricot mungo dans leurs parcelles et apprécié sa productivité et sa rusticité. Ils ont obtenu un rendement moyen de 0,7 t ha−1. Toutefois, l'absence de marché, par comparaison au niébé, reste un frein à sa diffusion.

Description of the subject. Farmers' knowledge is a significant source of information about cultivated soil knowledge. Objectives. This paper focuses on farmers in the Alaotra Lake Region in Madagascar to identify their knowledge of the soil and soil fertility and to propose a conceptual framework for developing participatory approaches. Method. The methodology is based on surveys conducted with 100 farmers randomly selected within five Communes (villages) to (i) study their knowledge on soil, (ii) design local soil map, and (iii) identify local soil fertility assessment. For each task, an exploratory survey with non-directive individual interviews followed by more in-depth surveys with semi-directive individual interviews and restitution workshops were conducted. Results. The results revealed two types of local soil classifications according to toposequence. Twelve and nine local soil types were identified respectively in the southern zone and in the northern zone. Moreover, farmers used 14 main local indicators to assess the fertility of these soils. Farmers' soil classification was found to comply with previous pedological studies and even provided complementary details to the reference French Soil Classification (CPCS). Finally, the local soil fertility indicators have been proved to be identical to those used by other farmers in other countries and are scientifically validated to be effective. Conclusions. This paper offers a new conceptual framework that may be effective for agricultural development service and scientific research in other contexts. It provides a foundation for supporting a common language between farmers and researchers, one that may prove instrumental in future projects including the co-conception of sustainable, innovative agricultural practices.

We hypothesized that the nitrogen-fixing tree Acacia mangium could improve the growth and nitrogen nutrition of non-fixing tree species such as Eucalyptus. We measured the N-mineralization and respiration rates of soils sampled from plots covered with Acacia, Eucalyptus or native vegetation at two tropical sites (Itatinga in Brazil and Kissoko in the Congo) in the laboratory. We used a bioassay to assess N bioavailability to eucalypt seedlings grown with and without chemical fertilization for at least 6 months. At each site, Eucalyptus seedling growth and N bioavailability followed the same trends as the N-mineralization rates in soil samples. However, despite lower soil N-mineralization rates under Acacia in the Congo than in Brazil, Eucalyptus seedling growth and N bioavailability were much greater in the Congo, indicating that bioassays in pots are more accurate than N-mineralization rates when predicting the growth of eucalypt seedlings. Hence, in the Congo, planting Acacia mangium could be an attractive option to maintain the growth and N bioavailability of the non-fixing species Eucalyptus while decreasing chemical fertilization. Plant bioassays could help determine if the introduction of N2-fixing trees will improve the growth and mineral nutrition of non-fixing tree species in tropical planted forests.

Despite the potential of subsoil carbon (C) to buffer or amplify climate change impacts, how fresh C and nutrients interact to control microorganismal effects on the C balance in deep soil horizons has yet to be determined. In this study, we aimed to estimate the impact of fresh C input at different soil depths on soil microbial activity. To conduct this study, Mediterranean soils from 3 layers (0–20, 20–50 and 50–100 cm of depth) were incubated over 28 days. Carbon and nutrient fluxes were measured after the addition of an amount of C equivalent to the postharvest root litter derived-C of a barley crop (4.3 atom% 13C), with and without nitrogen and phosphorus supply. We found that the microbial mineralization was C limited in the topsoil, while C and N colimited in the subsoil. These variations in stoichiometric constraints along the soil profile induced different microbial responses to C and/or nutrient addition. A stronger priming effect was observed in the topsoil than in the subsoil, and the sole C addition induced a negative C balance. Conversely, subsoil showed a positive C balance following fresh C addition, changing to critical soil C losses when nutrients were supplied with C. Our results show that fresh C input to subsoil (e.g., through deep-rooting crops) might foster soil C sequestration, but this positive effect can be reversed if such C inputs are combined with high nutrient availability (e.g., through fertilization), alleviating microbial limitation at depth.

La dégradation de la fertilité des sols est un problème majeur en Afrique subsaharienne. La forte croissance démographique, la demande locale de nourriture et la réduction des terres arables disponibles risquent d'accroître ce phénomène. Alors que les engrais minéraux sont peu utilisés, notamment à Madagascar, la gestion de la fertilité des sols est largement dépendante des matières organiques produites à la ferme. Afin d'augmenter l'efficacité du recyclage des nutriments à l'échelle de la ferme, il est nécessaire de comprendre les facteurs favorables à l'amélioration des pratiques de gestion des effluents d'élevage. Cette étude propose d'analyser les relations entre la structure d'exploitations agricoles intégrant agriculture et élevage dans la région de Vakinankaratra (Hautes Terres de Madagascar) et leurs pratiques de gestion des effluents. Des entretiens semi-directifs ont été réalisés auprès de 300 exploitations. Une typologie a été réalisée à l'aide d'une analyse en composantes principales (ACP). Sept types d'exploitation ont été retenus, permettant de distinguer des exploitations laitières d'autres exploitations d'agro-élevage (bovins de trait, porcs). Un test de Khi2 indique un effet significatif de la structure des exploitations sur le mode de gestion des effluents. En particulier, la présence d'un élevage laitier et de porcins semble favoriser des modes de gestion améliorés. L'analyse typologique contribue à la compréhension de l'adoption de pratiques améliorées de gestion des biomasses par les agro-éleveurs. L'adoption de telles pratiques est un prérequis pour améliorer le recyclage des nutriments vers les parcelles agricoles, et donc améliorer la durabilité des exploitations agricoles des Hautes Terres du Vakinankaratra.

In sub-Saharan Africa, maize is one of the most important staple crops, but long-term maize cropping with low external inputs has been associated with the loss of soil fertility. While adding high-quality organic resources combined with mineral fertilizer has been proposed to counteract this fertility loss, the long-term effectiveness and interactions with site properties still require more understanding. This study used repeated measurements over time to assess the effect of different quantities and qualities of organic resource addition combined with mineral nitrogen (N) on the change of soil organic carbon (SOC) contents over time (and SOC stocks in the year 2021) in four ongoing long-term experiments in Kenya. These experiments were established with identical treatments in moist to dry climates, on coarse to clayey soil textures, and have been conducted for at least 16 years. They received organic resources in quantities equivalent to 1.2 and 4 t C ha−1 yr−1 in the form of Tithonia diversifolia (high quality, fast turnover), Calliandra calothyrsus (high quality, intermediate turnover), Zea mays stover (low quality, fast turnover), sawdust (low quality, slow turnover) and local farmyard manure (variable quality, intermediate turnover). Furthermore, the addition of 240 kg N ha−1 yr−1 as mineral N fertilizer or no fertilizer was the split-plot treatment. At all four sites, a loss of SOC was predominantly observed, likely because the sites had been converted to cropland only a few decades before the start of the experiments. Across sites, the average decline of SOC content over 19 years in the 0 to 15 cm topsoil layer ranged from 42 % to 13 % of the initial SOC content for the control and the farmyard manure treatments at 4 t C ha−1 yr−1, respectively. Adding Calliandra or Tithonia at 4 t C ha−1 yr−1 limited the loss of SOC contents to about 24 % of initial SOC, while the addition of sawdust, maize stover (in three of the four sites) and sole mineral N addition show

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

The soil microbial community plays important roles in nutrient cycling, plant pathogen suppression, decomposition of residues and degradation of pollutants; as such, it is often regarded as a good indicator of soil quality. Repeated applications of mixed organic and inorganic materials in agriculture improve the soil microbial quality and in turn crop productivity. The soil microbial quality following several years of repeated fertilizer inputs has received considerable attention, but the dynamic of this community over time has never been assessed. We used high-throughput sequencing targeting 16S ribosomal RNA genes to investigate the evolution of the bacterial and archaeal community throughout 6 years of repeated organic and inorganic fertilizer applications. Soils were sampled from a field experiment in La Mare (Reunion Island, France), where different mixed organic-inorganic fertilizer inputs characterized by more or less stable organic matter were applied regularly for 6 years. Soil samples were taken each year, more than 6 months after the latest fertilizer application. The soil molecular biomass significantly increased in some organically fertilized plots (by 35–45% on average), 3–5 years after the first fertilizers application. The significant variations in soil molecular microbial biomass were explained by the fertilization practices (cumulated organic carbon inputs) and sometimes by the soil parameters (sand and soil carbon contents). The structure of the bacterial and archaeal community was more influenced by time than by the fertilization type. However, repeated fertilizer applications over time tended to modify the abundance of the bacterial phyla Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. To conclude, the present study highlights that the soil bacterial and archaeal community is lastingly modified after 6 years of repeated fertilizer inputs. These changes depend on the nature of the organic input and on the fertilizati

A basic understanding of the fertilization resources (FR) characteristics is required to drive soil functions following the FR application, and to improve crop productivity. The datasets presented include the FR characteristics, i.e. their nutrient contents and biochemical quality, and their effects on soil in carbon (C) and nitrogen (N) mineralization. We selected nineteen FR from local farmers, from laboratory institution and from commercial producers. The soil used in experiment was sampled in Imerintsiatosika locality, located in the Central Highlands of Madagascar. Nutrient contents of FR were evaluated by measuring total carbon, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur contents. Biochemical quality of the products was assayed by fractioning organic matter of organic resources in soluble compartments, hemicelluloses, celluloses and lignin equivalent. Laboratory incubations in microcosm experiments were conducted with the mixture of soil and fertilization resources to determine C and N mineralization rates. Carbon mineralization rate was measured using microgas chromatography, and nitrogen mineralization rates were analyzed by colorimetry on a continuous flow analyzer.

Cet article vient clore une série de cinq consacrés à la gestion de la fertilité par les exploitations agricoles familiales de deux zones agroécologiques de Madagascar. Ce dernier article présente les performances technico-économiques des exploitations à travers les revenus agricoles et d'élevage, mais aussi le revenu global (y compris non agricole) en lien avec la gestion de la fertilité. Les performances sont appréciées en termes de rémunération des actifs familiaux et de pauvreté monétaire.

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.

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.

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

Tropical Savannas cover an area of approximately 1.9 billion hectares around the word and are subject to regular fires every 1 to 4 years. This study aimed to evaluate the influence of burning windrow wood from Cerrado (Brazilian Savanna) deforestation on the spatial variability of soil chemical properties, in the field. The data were analysed by using geostatistical methods. The semivariograms for pH(H2O), pH(CaCl2), Ca, Mg and K were calculated according to spherical models, whereas the phosphorus showed a nugget effect. The cross semi-variograms showed correlations between pH(H2O) and pH(CaCl2) with other variables with spatial dependence (exchangeable Ca and Mg and available K). The spatial variability maps for the pH(H2O), pH(CaCl2), Ca, Mg and K concentrations also showed similar patterns of spatial variability, indicating that burning the vegetation after deforestation caused a well-defined spatial arrangement. Even after 20 years of use with agriculture, the spatial distribution of pH(H2O), pH(CaCl2), Ca, Mg and available K was affected by the wood windrow burning that took place during the initial deforestation.

Plant diversification through crop rotation or agroforestry is a promising way to improve sustainability of agroecosystems. Nonetheless, criteria to select the most suitable plant communities for agroecosystems diversification facing contrasting environmental constraints need to be refined. Here, we compared the impacts of 24 different plant communities on soil fertility across six tropical agroecosystems: either on highly weathered Ferralsols, with strong P limitation, or on partially weathered soils derived from volcanic material, with major N limitation. In each agroecosystem, we tested several plant communities for diversification, as compared to a matching low diversity management for their cropping system. Plant residue restitution, N, P and lignin contents were measured for each plant community. In parallel, the soil under each community was analyzed for organic C and N, inorganic N, Olsen P, soil pH and nematode community composition. Soil potential fertility was assessed with plant bioassays under greenhouse controlled climatic conditions. Overall, plant diversification had a positive effect on soil fertility across all sites, with contrasting effects depending on soil type and legumes presence in the community. Communities with legumes improved soil fertility indicators of volcanic soils, which was demonstrated through significantly higher plant biomass production in the bioassays (+18%) and soil inorganic N (+26%) compared to the low diversity management. Contrastingly, communities without legumes were the most beneficial in Ferralsols, with increases in plant biomass production in the bioassays (+39%), soil Olsen P (+46%), soil C (+26%), and pH (+5%). Piecewise structural equation models with Shipley's test revealed that plant diversification impacts on volcanic soil fertility were related to soil N availability, driven by litter N. Meanwhile, Ferralsols fertility was related to soil P availability, driven by litter P. These findings underline the import

Cocoa production is impacted by major resource constraints, such as the soil's capability, and in some areas, by unreliable access to markets. A multifaceted approach that employs both biophysical and socio-economic conditions is developed here for mapping areas that are suitable for cocoa production in Papua New Guinea (PNG). This manuscript presents a case study of using multi-criteria decision making by the Analytic Hierarchy Process for mapping the fundamental criteria for cocoa suitability. The results show that temperature, precipitation and soil reveal sections within Western, Gulf and Central (along the west coast joining to National Capital District) province that have very low suitability for cocoa production. In our analysis, precipitation, soil, slope and road, were ranked as the four most important criteria. Additionally, we included stream networks because they may help irrigation and allow cocoa transport via water (e.g. Manus Island). Comparing an already existing cocoa suitability map for PNG to the one created in this study, we found some similarities. For example, the Central, Gulf, and Western (Fly) areas are either unsuitable for cocoa production or have very low potential, and exceptional areas around Rabaul and Kokopo in East New Britain, Popendetta, and Bouganiville were identified. Some new areas suitable for cocoa production in East Sepik, East New Britain, and a major stretch within West New Britain may show low to moderate suitability. The most important finding is the potential to grow cocoa in the highlands, especially, Chimbu (Simbu), Eastern Highlands, Enga, Hela, Jiwaka regions. We found that currently the majority of farmers are growing cocoa in highly suitable areas (76% in class 4, 20%in class 3 and 4% in class 5). The inclusion of slope and roads impacts the impact of flooding conditions and the amount of work and ease of access to markets as important indicators of the connection farmers make between soil suitability and their d

The development of agroecosystems that can provide multiple ecosystem services with a reduced need of external inputs, requires management practices that foster ecological processes to enhance soil quality and crop productivity. We assessed the direct and indirect impacts of farmers' management practices on plant diversity, soil quality and crop productivity in coffee and pasture fields belonging to different types of farms: agroeco-logical, conventional, and large-scale. The study was carried out in twelve farms in the Zona da Mata, Brazil. For each of the total of 24 fields (twelve pastures and twelve coffee) we recorded 41 variables associated with management practices, indicators of plant diversity (taxonomical, structural and functional diversity) and soil quality (biological, chemical and physical properties). The direct and indirect effects of management on plant diversity, soil quality and in the case of coffee, crop productivity, were assessed using structural equation models. In the case of pastures, we found that increased plant diversity due to agroecological management resulted in higher soil quality, probably due to higher soil litter cover and plant structural heterogeneity. Yet, practices presented in the agroecological farms also had a direct negative effect on soil quality, which indicates that increased plant diversity in pastures needs to be combined with other agroecological management practices than currently adopted. In the case of coffee, we show that despite the higher weeding intensity and higher use of external inputs in large-scale and conventional coffee farming systems, these practices did not result in increased soil quality or coffee productivity as compared to agroecological systems. In contrast, agroecological coffee management was associated with increased plant diversity, which, in turn, was positively associated with soil microbial biomass carbon. Our results highlight a causal pathway of agroecological management leading to incr

Cet article est basé sur des données empiriques qui permettent de caractériser, pour chaque exploitation agricole, les pratiques de gestion de la fertilité effectivement utilisées sur les parcelles cultivées au cours de l'année agricole 2016/17. A partir des budgets de culture, établis pour toutes les parcelles, la part des charges de fertilisation est mise en relation avec les marges brutes dégagées par culture.

Daou et Shipley (2019) proposent une définition opérationnelle et une méthode basée sur un modèle de mesure variable latente de modélisation par équations structurelles (SEM) pour quantifier la « fertilité » des sols en écologie des communautés végétales. Leur méthode est très prometteuse, car il est possible de la généraliser aux sols de différentes régions dont la « fertilité » comporte plusieurs causes. L'objectif de ce mémoire est de tester l'hypothèse fondamentale de ce modèle selon laquelle toute espèce végétale répondra dans la même direction au gradient de "fertilité" du sol en termes de croissance. Nous avons testé cette hypothèse avec neuf espèces très différentes et 25 sols provenant d'un gradient de « fertilité » dans le sud du Québec, au Canada. À partir des neuf espèces, nous avons testé toutes les combinaisons d'espèces possibles à intégrer dans le modèle. Nous avons constaté que deux ensembles de combinaisons composés de sept espèces répondent à la même direction, validant ainsi le modèle de Daou et Shipley (2019) pour la plupart des espèces. Nos résultats ont également montré que le concept de « fertilité » du sol inclut une deuxième dimension associée au pH du sol. Trois espèces ont réagi différemment à cette deuxième dimension, entraînant le rejet du modèle complet. Nous avons ensuite proposé un modèle alternatif qui inclut le pH du sol comme seconde variable latente et avons comparé la capacité de prédiction des deux modèles. Nous avons constaté que dans les deux modèles, les prédictions de la « fertilité » du sol étaient extrêmement corrélées (r=0.98). Ceci constitue des résultats encourageants pour un concept de « fertilité » généralisée, mais nous devons tester l'importance relative d’autres dimensions potentielles dans différents systèmes d'étude.