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La dégradation des terres liée à l'intensification agricole, principalement due à la baisse de la fertilité des sols et à l'érosion, est devenue une problématique majeure en Nouvelle-Calédonie. Le contexte insulaire et les spécificités pédoclimatiques rendent en outre les enjeux d'autosuffisance alimentaire, de préservation des agroécosystèmes et de la biodiversité, d'autant plus prégnants. Les systèmes de culture (sdc) doivent donc évoluer en mobilisant les processus biologiques afin d'être viables, performants et durables. L'agriculture de conservation (AC) consiste en un ensemble de pratiques culturales basé sur trois principes : une réduction, voire une suppression du travail du sol, une couverture végétale du sol permanente et une diversification des espèces cultivées. L'AC peut répondre à ces problématiques en alliant durabilité et productivité, et en favorisant un certain nombre de services écosystémiques. A travers une démarche originale intégrant approches fonctionnelle et systémique, cette thèse vise à quantifier les relations entre pratiques, fonctions et services écosystémiques au sein de sdc complexes. Dans le contexte spécifique de la côte ouest de la Nouvelle-Calédonie, afin de savoir si l'AC pourrait maximiser la fourniture de services écosystémiques, trois questions sont apparues importantes à aborder : quels sont les impacts des pratiques de l'AC sur la santé du sol et les performances agronomiques de sdc ?, quels sont les effets de l'AC sur la biodiversité fonctionnelle (macrofaune) ?, et quelles sont les performances et l'efficience d'utilisation des ressources de sdc en AC notamment sous couvert végétal vivant ? Afin de répondre aux deux premières questions, une expérimentation système, initiée en 2011, a permis de comparer en 2018 trois sdc en production de maïs : un sdc en monoculture et en labour, représentant la pratique de référence de la région (CT), un sdc en AC sous couvert végétal mort (mélange de 4 espèces annuelles) (CA-DM), et un sdc

Highly productive monoculture coffee (Coffea arabica L.) farms have rapidly expanded since the 1990s in Yunnan Province, China. In 2013, in order to initiate a large-scale transition towards more sustainable coffee growing practices, local government in southern Yunnan started distributing free shade tree seedlings to all coffee farmers in their jurisdictions. This study highlights the impact of three of these promoted shade tree species (Cinnamomum camphora, Bishofia javanica and Jacaranda mimosifolia) on soil fertility and coffee production only four years after their distribution to coffee farmers. Materials and methods Soil samples in the 0-20 cm soil layer were tested for chemical composition (soil organic matter, pH, total N, available P, exchangeable K, Ca and Mg), soil communities (free-living nematodes and microbial communities) and soil enzyme activities (β-glucodidase, N-acetyl-glucosaminidase and acid phosphatase) under shade trees (6 replicates per tree species) and in open areas (15 replicates), both in coffee rows and inter-rows, once during the rainy and once during the dry season. Additionally, we characterized root systems and soil water profiles to a depth of 1.2m, monitored litterfall for one year, as well as coffee production for two years. Major results We detected a clear positive impact of all three shade tree species on soil chemical, biological and biochemical fertility, despite the marked effect of 20 years of high mineral fertilizer inputs. In particular, we measured higher pH and soil organic matter; similar or higher soil enzyme activities throughout the year; more abundant fungi communities throughout the year; and more abundant microbial communities during the dry season below shade trees than in open areas. Furthermore, coffee trees shaded by B. javanica and J. mimosifolia yielded as much as open coffee trees. On the other hand, coffee trees shaded by C. camphora yielded less than open coffee trees, most likely as a result of high ro

It is said that trees improve soil fertility. It might be due to biological interactions with micro-organisms and especially with arbuscular mycorrhizal fungi. Is-it the case with olive trees in south of France? The field experiments were conducted in South of France at INRA DiaScope experimental unit. Durum wheat was sown in 3 conditions: (AF) yearly pruned olive orchard, (AF+) never pruned olive orchard, (C) open field. Mycorrhizal analysis was performed on 6 durum wheat cvs. For each treatment and cv, 3 replicates of 90 root fragments were analyzed at the LSTM lab. All the root fragments coming from AFs treatments were colonized, while 96.4% for C. The intensity of AMF colonization, thus the % of the root fragment length being colonized, was significantly higher in AFs treatments (+51% compared to C), as the arbuscular abundance in the root system (+74% compared to C). A wide variability was observed among genotypes within the same treatment. The intensity of AMF colonization ranged from 11% to 57% in C, and from 55% to 74% in AF. The genotype showing the highest intensity of AMF colonization and arbuscular abundance in AF had the lowest values in C. AM fungi are known to be an essential component of sustainable agricultural ecosystems (Jeffries et al. 2003). Olive trees seem to play the role of permanent reservoir of AMF diversity, available to associated cereals. Arbuscular mycorrhizal (AM) fungi help the understorey crop to catch soil nutrients (Wahbi et al. 2016).

Agroforestry systems (AFs), where agricultural and livestock crops are associated with woody plants, are known as sustainable systems, that conserve biodiversity and improve the provision of ecosystem services without compromising productivity. This work focuses mainly on cacao AFs, which have been related to different ecosystem services in tropical regions. Especially, our study focuses on the ability of the cacao AFs to improve soil ecosystem services in the Colombian Amazon region. We focused on soil ecosystems ecosystem services in the Colombian Amazonia because: of the social importance of cacao production system in the study region, specifically within the post conflict context; the lack of knowledge on the capacity of cacao AFs to offer soil ecosystem services in the study zone and its capacity in restoring ecosystem services in degraded soils. Aim The objective of our work was to evaluate the soil quality in different cacao agroforestry systems in the Colombian Amazonia, and to compare these evaluated soil quality of soil quality in Forest and Pasture. Material and methods The study was conducted at the Macagual Amazon Research Center, located west of the Colombian Amazon. We evaluated soil quality in four types of AFs Cacao, presenting different establishment, composition and structural characteristics; but also in a plot of native forest composed of characteristic species of the area, and in a plot of pasture composed of grasses. In the different plot of each land use, we evaluated the diversity of macrofauna, the morphology of aggregate, the physical properties and the soil chemistry. We summarized these variables in a General Indicator of Soil Quality GISQ, characterizing soil quality in the different land uses. Major results and Conclusion It was found that the level of intensification among land uses (Bosque>AFs>Pasture) affects the decrease of the macrofauna populations, which was related to soil compaction (physical properties). Chemical fertility im

Trees are usually eliminated in field due their possible competition with crops for water and nutrients. Our work aimed to investigate how to manage S. senegal trees to optimize their association with crops. A field trial was conducted under natural conditions in a S. senegal plantation 10 years old. Investigations were conducted during two years to evaluate the effect of S. senegal trees management on gum arabic yield, associated cowpea yield, soil mycorrhizal fungi spores density and enzymes activities reflecting soil fertility such as fluorescein diacetate (FDA), acid phosphatase and dehydrogenase. Four treatments of pruning were applicated (control, shoots, roots, shoots and roots pruning) and tapped in november. Soil samples were collected during dry and wet seasons at 0-25 cm layer. Cowpeas were sown at the beginning of rainy season in rows 0.5 m apart. Results showed that shoots pruning significantly increased gum arabic while a negative effect of roots pruning was noted. The presence of S. senegal increased soil fertility and cowpea yield. Any significant effect of treatments was noted on pods yield during the first year. However, shoots pruning, shoot and roots pruning increased significantly pods yield during the second year. Shoots and roots pruning seemed to decrease FDA and spores density depending on the season. Our results showed that shoots and roots pruning increased the positive effect on soil fertility and the association of S. senegal with annual crops.

Conventional, intensively managed coffee monocultures are environmentally damaging. The use of shade trees and organic management are welcome options to reduce coffee physiological stress, reduce synthetic inputs and restore soil biological balance. However, whether the effects of shade trees on soil functioning would be similar for different coffee management practices should be investigated. Here, we measured soil total C and N, inorganic N, Olsen P, pH, biomass produced in bioassay, nematode and microarthropod communities under three shade types (unshaded coffee, shaded with Terminalia amazonia, and shaded with Erythrina poepiggiana) combined with two management practices (organic and conventional) in a 17- year old experimental coffee plantation in Turrialba (Costa Rica). Under conventional management, soil nutrient availability and fauna densities were higher under shade, regardless of the shade tree species (Fig 1). Under organic management, only Erythrina, a heavily pruned, N2-fixing species, had increased soil nutrient availability and fauna density, while Terminalia shade had a null or negative impact. Soil N availability was linked to bacteria-feeding nematodes while soil P availability was more linked to detritivorous microarthropods. Higher fertility was recorded in soil with balanced foodwebs. This study highlights the importance of the choice of shade tree species for soil fertility in low input systems, more so than in fertilized systems.

To produce charcoal and prevent the deforestation around Kinshasa (Gond et al., 2017), 7,700 ha of Acacia auriculiformis were planted on savannah ecosystems, in 1987 (Bateke Plateau, DR Congo). Since 1995, the plantation was managed using the rotational woodlot system alternating agricultural and charcoal production on the same area (Kimaro et al., 2007). The 7,700 ha produced a large amounts of charcoal, cassava and maize during many years (Bisiaux et al., 2009). However, farmers have observed for a while a decline in wood and crop productivity. The aim of this study was to compare chemical properties of soils in six acacia stands in two farms having undergone different agroforestry trajectories: - one 22-year-old acacia stand, never-harvested; 4 stands in their 2nd rotation after 1 cropping cycle; and 1 stand in its 3rd rotation after 2 cropping cycles - and soils in the native control savannah. Compared to the original savannah, all acacia stands showed an increase in soil C, N and N-NO3- contents, but a decline in soil pH and exchangeable cations, and an increase in exchangeable Al and CEC (Fig 1). To maintain the sustainability of the system, we recommend different practices in order to improve the nutrient balance and decrease the soil acidity. Such practices are 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 (Dubiez et al., 2018).

Agroforestry systems have shown promising advantages in providing a number of key ecosystem services and many of them are directly linked with the soil compartment, such as fertility maintenance, carbon sequestration, erosion and landslide mitigation, fungi/bacteria-borne pest control, preservation of soil habitats etc. Today, managing a multifunctional agroforestry system has been a key quest for both researchers and practitioners. This is a challenging issue as it covers multiple disciplines stretching from biophysical to socio-economical domains. For this goal, this work will present a framework encompassing and highlighting some key issues on the multifunctionality of agroforestry systems, at both temperate and tropical conditions, with a focus on ecosystem services involving belowground functions. Bibliographical metrics based evidences will be presented showing the state-of-the-art and knowledge gaps in R & D on multifunctionality of worldwide agroforestry. Roadmap and emerging methodologies for optimisation of our management for promoting such multifunctionality are proposed and discussed.

Beninese smallholders associate food or cash crops with young oil palm stands to reduce field maintenance costs and gain income before the oil palm comes into production. However, little is known about the effects of these agroforestry systems on nutritional and growth status of the tree at end of its juvenile phase although it is well known that the tree production could be affected by the management in juvenile phase. We selected 15 plantations where the crop succession associated with the trees was mostly based on maize, cassava, tomato and pineapple respectively. Nutrient contents in soil and tree leaves, and the vegetative growth of the tree were examined at end of juvenile phase. We found that N and P nutrition of young palms was satisfactory but K nutrition was deficient in all systems especially in tomato and pineapple ones. There was a significant correlation between K contents in soil and palm tree leaves. In the pineapple- and tomato-based systems, the amount of K fertilizer did not compensate the exportations by the crop. We concluded that competition for K are particularly important in pineapple- and tomato-based systems although fertilizer inputs were the highest. Trade-offs between profitability of these associated crops and the productive performance of the tree could be sought. A better adaptation of mineral fertilization could help in satisfying these compromises.

Background: In the Sudanian region of North Cameroon, population growth has led to reduced fallow periods, soil fertility and trees (Peltier et al., 1993). Since 1984, CIRAD, Irad and Sodecoton have been testing techniques for planting tree legumes to restore soil fertility (Harmand et al., 2017). A 15-year-old A. senegal plot was harvested in 2011.It produced 1200 kg/ha of gum arabic for 8 years (750 €/ha) and 40 m3/ha of fuel-wood for 15 years (1100 €/ ha) (D'Andous et al., 2013). Aims: After A. senegal were harvested, we studied the evolution of chemical soil properties and the production of successive crops. Mat. & methods: On sandy ferruginous acidic soil, rainfall 1000 mm/year, the farmer planted successive crops of maize, cotton and groundnuts (2011-2013). In 2011 & 2015, the soil was analyzed (composite) on 2 plots of 12 x12 m after A. Senegal (Post=fallow = Pf) and on 2 control plots continuously cultivated (Cc). Results: Crop production was much higher for all 3 years and soil chemical properties (C, N, pH, CEC) were higher in Pf than in Cc (Table 1). Conclusion: Further studies are needed to determine for how long crop cultivation remains profitable (Dubiez et al. 2018). This will pave the way for farm and landscape management including plots planted with tree legumes, to improve biodiversity, carbon storage, wood energy production, food and cash crops of the territories, while limiting population migration and the destruction of the last Sudanese natural ecosystems.

Agroforestry systems (AFs), where agricultural and livestock crops are associated with woody plants, are known as sustainable systems, that conserve biodiversity and improve the provision of ecosystem services without compromising productivity. This work focuses mainly on cacao AFs, which have been related to different ecosystem services in tropical regions. Especially, our study focuses on the ability of the cacao AFs to improve soil ecosystem services in the Colombian Amazon region. We focused on soil ecosystems ecosystem services in the Colombian Amazonia because: of the social importance of cacao production system in the study region, specifically within the post conflict context; the lack of knowledge on the capacity of cacao AFs to offer soil ecosystem services in the study zone and its capacity in restoring ecosystem services in degraded soils. Aim The objective of our work was to evaluate the soil quality in different cacao agroforestry systems in the Colombian Amazonia, and to compare these evaluated soil quality of soil quality in Forest and Pasture. Material and methods The study was conducted at the Macagual Amazon Research Center, located west of the Colombian Amazon. We evaluated soil quality in four types of AFs Cacao, presenting different establishment, composition and structural characteristics; but also in a plot of native forest composed of characteristic species of the area, and in a plot of pasture composed of grasses. In the different plot of each land use, we evaluated the diversity of macrofauna, the morphology of aggregate, the physical properties and the soil chemistry. We summarized these variables in a General Indicator of Soil Quality GISQ, characterizing soil quality in the different land uses. Major results and Conclusion It was found that the level of intensification among land uses (Bosque>AFs>Pasture) affects the decrease of the macrofauna populations, which was related to soil compaction (physical properties). Chemical fertility im

L'initiative 4 pour 1000 a pour principal objectif de séquestrer du carbone dans les sols et d'en accroître la fertilité. Dans le cadre du projet ANR nanoSoilC, notre objectif est de déchiffrer les processus de stabilisation et de déstabilisation de la Matière Organique (MO) avec les minéraux nanométriques du sol en décrivant leurs mécanismes d'interactions. En effet, ces minéraux nanométriques jouent un rôle prépondérant dans le stockage du carbone. Les méthodes traditionnelles d'extraction de ces nanophases organo-minérales (séparation granulométrique et densimétrique) sont assez limitées. Cette étude se focalise sur le développement d'une nouvelle méthode par filtration en flux tangentiel (TFF) qui permettra d'accéder à des fractions permettant de quantifier le carbone associé à ces minéraux nanométriques faiblement cristallisés. Dans la TFF, le pompage du fluide s'effectue tangentiellement le long de la surface de la membrane de sorte que les composants retenus ne s'y accumulent pas. Ce procédé est peu utilisé pour séparer les particules < 2 µm dans les systèmes naturels. Ainsi, chaque phase du fractionnement a fait l'objet d'optimisation et a été appliqué sur un arénosol (sol dior) et un fluvisol (sol deck) du Sénégal. Les seuils de coupure (2000 µm, 50 µm, 2 µm) ont été effectués par tamisage et sédimentation ou centrifugation. Sur la fraction inferieure à 2 µm, le fractionnement par TFF a été réalisé aux seuils de coupures 0,2 µm et 3 kDa. Chaque fraction de sol a été séchée à l'étuve à 105°C puis pesée et conservée pour des analyses de carbone (total ou dissous). Une première filtration séquentielle a montré les répartitions suivantes : la fraction < 2µm représente 11 % pour le sol deck et 1 % pour le sol dior ; pour les deux types de sol environ 80 % de la fraction < 2µm est dans la classe 2-0,2µm. Chaque étape du fractionnement a fait l'objet d'optimisation et cette étude a permis : l'établissement d'une méthodologie innovante pour séparer les particules d

Rubber plantations (Hevea brasiliensis) are expanding in areas with low soil fertility, long dry seasons, and high risks of soil erosion in rainy seasons. The introduction of a N2 fixing legume cover crop in the interrows of the tree plantation might reduce runoff, soil erosion and increase the availability of nutrients and the growth of young trees. This study aimed at quantifying over a four year period (2007-2010), the impacts of a legume cover crop (Pueraria phaseoloides) to N nutrition, water status, and growth of young rubber trees planted along a toposequence with contrasted soil depths in north-east of Thailand. The biomass production and N released by the legume reached 8 Mg.ha-1y-1 and 240 kg N. ha-1y-1 respectively. The N2 fixation rates of the legume averaged 81% and N transfer from the legume to the rubber tree was also high; an average of 58% of tree leaf N was derived from atmosphere. Both variables were not significantly different along the toposequence. At the bottom of the toposequence, the combined improvement of nitrogen and water status of the trees in the rubber tree/cover crop system resulted in doubling the tree girth at seven-year age. At that position, the root profiles and soil water dynamic suggested that the cover crop allowed the rubber tree roots to tap water from deep soil layers during severe drought periods. Conversely, at the top of the toposequence where water was not available at depth, the legume had negative impacts on tree ability to survive intense drought. It is concluded that improving N nutrition of young rubber trees in marginal area could affect their resilience to drought. In a context of climate change, the questions of where and how the best trade-off between N and water nutrition of crops could be achieved would concern more and more areas. (Texte intégral)

On one hand, nurse plant designed those plant species which could have positive effects on the development of other plant species by several aspects. This technology could be a special key to mitigate the effect of climate change on farming by valuing natural resources present in each ecosystem. On the other hand, mycorrhizal soil infectivity and soil enzyme activity are the most sensitive parameters to the variation of plant species' structure and of land use. The long-term experimental site is located in the eastern part of Madagascar. The aim of this study was to select nurse plant among all plant species which are naturally associated with upland rice according to some criteria such as symbiotic status, endemicity, distribution, scattering method as well as mycorrhizal soil infectivity and soil enzyme activity related to each selected plant species. We recorded 17 plant species belonging to a functional group of mainly shrub and herbaceous species which are naturally associated with upland rice. There were 5 endemic and 2 naturalized species such as Aphloia sp, Casearia sp, Doratoxylon sp, Streblus sp etc. which were both described to be associated with Vesicular and Arbuscular Mycorrhizal Fungi (AMF). The analysis showed that compared to bare soil or rhizosphere soil of other plant species, their rhizospheric soil was characterized by a great diversity of AMF spores and significant activity of soil phosphatase. The most probable number of Mycorrhizal fungi propagules (MPN) in soil was significantly higher in soil colonized by these species. These results suggest that at least one of these selected plant species could be used as a nurse plant to enhance soil fertility for the benefit of upland rice production. (Texte intégral)

Soil degradation and fertility loss pose severe threats to the livelihood of farmers in sub-Saharan regions. Due to the need for land, continuous cultivation with staple food has gradually replaced previous shifting cultivation systems, so that fallow periods have considerably reduced and no longer fulfill their soil regeneration role. Here we explore the use and management of native woody resources for providing an in situ renewable organic amendment as a basis for increasing soil carbon and biological status, thus sustaining fertility, enhancing water capture and utilization and therefore buffering climatic stress. In areas such as the central plateau in Burkina Faso, slash- and drought-tolerant shrub species are commonly present in farmers' fields. Cut branches from these shrubs are sometimes placed on degraded soils as part of traditional soil restoration practices. Moreover, shrubs tend to intercept sediments and leaves and promote biological activity whereby they may form fertility islands of increased crop yield. We will review available data on traditional practices and current co-innovation efforts and outline first results from an EU-supported project we have initiated in Burkina Faso and Senegal (ERA ARD WASSA). This project is investigating if a sustainable use of native woody resources could be made, in combination with other organic sources such as crop residues or manure, to amend soils and help preserving fertility at the whole field scale. Through experimental plot trials and farmers' fields surveys, we are evaluating how woody residues use and management practices may impact agronomic performance and soil biological processes. Crop response to use of ligneous material will be linked with the availability and distribution of woody resource in the landscape, and the ways it could be eventually increased and sustainably managed. The socio-economic implications of implementing such practices are also considered. (Texte intégral)

In the suburban area of Dakar (Senegal), family smallholdings produce market gardening sometimes for several decades. Dior soils (arenosol) and Deck soils (fluvisol, calcareous with high clay content) are intensely cultivated and required frequent applications of organic matter (OM). The objective of this study was to assess whether long-term changes in chemical and physical properties of these tropical soils increase or reduce the yields and the vulnerability of these family smallholdings to global changes. After field surveys, we collected Dior soil (Dr) and Deck soil (Dk), cultivated for fifty years (50), and named Dr50 and Dk50 respectively, and nearby, the same soils, but which have never been cultivated (0), and named Dr0 and Dk0 respectively. On these four soils, we cultivated three successive cycles of lettuce and compared an optimum mineral fertilization (T1) with two types of OM, a sewage sludge and a poultry droppings, with the amounts corresponding to 50% (T2) and 150% (T3) of the nitrogen equivalent of T1. Before the experimentation, the cation exchange capacities and the initial concentrations of organic carbon and total phosphorus were significantly higher between both pairs of soils, Dr50 and Dr0 soils and between Dk50 and Dk0 soils. The structural stability of the Dr50 and Dk50 soils were respectively better than Dr0 and Dk0 soils. After each crop cycle, yields were higher (i) for Dr50 and Dk50 soils, respectively than for Dr0 and Dk0 soils, (ii) with input of poultry droppings rather than sewage sludge and (iii) for doses T3 as T1 and T2 respectively. These results showed that these two types of tropical soils, even if they were intensively cultivated for a long time, have acquired some protective physical and chemical characteristics and were better adapted to global changes mainly due to OM inputs in the long term. (Texte intégral)