Agronomy for Sustainable Development最新文献

Conservation agriculture (CA) is the key agricultural soil management approach for Mediterranean rainfed systems facing extreme droughts and soil degradation. Yet, CA uptake and applicability is still marginal and disputed in the Mediterranean region, where smallholder farmers are most representative. Lack of widespread adoption of CA in the Mediterranean region despite international efforts is perplexing. In order to investigate this paradox and provide solutions, we set out to examine the perceived constraints to CA implementation among farmers and stakeholders. Our approach is based on systems analysis of Mediterranean grain production systems, considering plant and livestock production, as well as sustainability and social-ecological interactions. CA promotion efforts are rarely adapted to the context of the Mediterranean region. We argue for adopting a more pragmatic and flexible approach to CA. Such an approach should be based on site-specific bio-physical and sociocultural considerations and augmented with principles of agroecology. Our review of perceived constraints allows us to suggest five pathways that could promote CA adoption in the Mediterranean across two main areas: (i) introduction of flexible, context-specific technical solutions and (ii) change of social perceptions and literacy on soil. Our five pathways aim to enhance farmers’ resilience to challenges of climate and market shocks, while integrating agroecological principles that enhance ecosystem multifunctionality. We advocate using agroecological principles to enable a more pragmatic application of CA with respect to its strict application—such as continuous no-till—to rehabilitate degraded lands, to increase water use efficiency, and to improve food security and economic well-being of communities in the Mediterranean region.

In face of the current environmental challenges, developing multifunctional cropping systems is increasingly needed, and crop variety mixtures are particularly interesting since they can deliver diverse services including grain production, yield stability, N₂O production regulation, disease control, and reduction of N-fertilizer losses. However, the relationships between intraspecific diversity and ecosystem multifunctionality are poorly understood so far, and practitioners lack science-based guidance to design mixtures. We used a pool of 16 bread wheat varieties classified into 4 functional groups based on 26 below- and aboveground functional traits, to conduct a field trial (88 large plots cultivated with single varieties or mixtures of 2, 4, or 8 varieties), quantifying 15 provisioning and regulating services for each plot. To assess yield stability between local conditions and years, the trial was replicated at 4 other locations and for 2 years, using 2 managements each time. We analyzed how variety number and functional groups predicted the variance in services, and applied in an innovative manner the RLQ co-inertia analysis to relate the (variety × traits) matrix Q to a (plot × services) matrix R, using a (plot × variety) composition matrix L as a link. Our results show that using variety mixtures allowed delivery of baskets of services not reachable when cultivating single varieties, and that mixtures mitigated tradeoffs between different pairs of services. Variety number or functional groups poorly predicted the variance in services, but the RLQ approach allowed the identification of groups of plots delivering consistent baskets of services. Moreover, we demonstrated for the first-time significant relationships between specific baskets of services and bundles of variety traits. We discuss how our results increase our understanding of intraspecific diversity–agroecosystem multifunctionality relationships, and propose the next steps using our new approach to support practitioners for designing variety mixtures that provide particular baskets of services.

Abstract 

In Western Africa, agro-sylvo-pastoral systems are dominant and food demand is booming. To meet this demand, many farmers intensify the production with industrial inputs (mineral fertilizers, feeds, pesticides, herbicides). However, the price of these inputs is rocketing. To face this issue, some farmers reconsider crops, livestock, and tree synergies and by-product recycling to increase their production sustainably at a lower cost. The study aimed to characterize the diversity of Koumbia’s farming systems and to assess farming systems’ technical performance in an agroecological perspective. We surveyed 391 farms in the county of Koumbia (Burkina Faso). Considering 15 agricultural practices (4 on by-products recycling, 4 on soil protection, 4 on industrial inputs limitation, 2 on smart use of natural resources, and 1 on cropping diversification), a multivariate analysis (PCA+HAC) combined to an agroecology (Ae) scoring system (−15 to +15) based on 15 specific indicators (one/practice), we highlighted 3 agroecological farming systems clusters. These clusters are distributed along a gradient of agroecology intensity (Ae+: high degree of Ae, Ae+/−: medium degree, and Ae−: poor degree). Ae+ farms (Ae score: +3.0) group 17% of the farms, Ae+/− (Ae score: −4.5) group 58% of the farms, and Ae− (Ae score: −10.5) group 25% of the farms. Ae+ raise more livestock and recycle a higher rate of crop-livestock by-products in fodder, organic manure, and mulch. These recycling practices are facilitated by better levels of equipment for transportation and storage and soil water and crop residue conservation measures, including maintenance of the wooded park on the cultivated fields. This set of practices, which close better the agricultural system, produces a systemic effect which has a positive impact on yields and on the whole ecosystem. Our findings outline for the first time that crop-livestock synergies and by-product recycling are major factors of agroecological transition in agro-sylvo-pastoral systems.

Agriculture can benefit from crop diversification to facilitate its transition to more sustainable agrifood systems. However, these practices remain rare in Europe. One major barrier is the existence of sociotechnical lock-ins. To clarify the dynamics at work, we analyzed the relationships between actors involved in 23 crop diversification experiences across 11 European countries. The novelty of this paper lies in the systemic analysis of the network of actors involved in crop diversification experiences. Using data from qualitative interviews and cognitive mapping approaches, we identify and describe the role of actors and the key relationships in crop diversification and detect relationships that are currently missing. Our study shows that in the different European countries, similar relationships act as levers or barriers to crop diversification, with farmers and researchers playing a crucial role. The most important cognitive factors that influence the choice of farmers to diversify are environmental and health concerns and the desire to make profit and innovate. We relate the cognitive factors to organizational, technical, economic, and political factors and suggest levers for crop diversification based on successful crop diversification experiences.

Cover crops (CCs) can affect the cropping systems’ N dynamics and soil water content (SWC), but optimizing their potential effects requires knowledge of their growth pattern, N accumulation, and mineralization. For this purpose, a 3-year field experiment was initiated in northeast Italy involving a maize-soybean rotation. The objectives of this study were to (i) evaluate the use of time series vegetation indices (VIs) obtained from the Sentinel-2 satellite for monitoring the growth of CCs and estimating their biomass and N uptake at termination; (ii) investigate the effects of different CCs on cash crop yield and SWC; and (iii) use the simulation model CC-NCALC to predict the nitrogen contribution of CCs to subsequent cash crops. Three CC systems were tested: a fixed treatment with triticale; a 3-year succession of rye, crimson clover, and mustard; and a control with no CCs. Satellite imagery revealed that rye and triticale grew faster during the winter season than clover but slower compared to mustard, which suffered a frost winterkilling. Both grasses and mustard produced greater biomass at termination compared to clover, but none of the CC species affected SWC or yield and N uptake of the cash crop. A net N mineralization of all the CC residues was estimated by the model (except for the N immobilization after triticale roots residues). During the subsequent cash crop season, the estimated clover and mustard N released was around 33%, and the triticale around 3% of their total N uptake, with a release peak 2 months after their termination. The use of remote sensing imagery and a prediction model of CC residue decomposition showed potential to be used as instruments for optimizing the CCs utilization and enhancing cropping water and N fertilization management efficiency; however, it must be further analyzed with other CCs species, environmental conditions, and cropping systems.

The decoupling of crop and livestock in space is currently threatening the sustainable development of agriculture. One of the major challenges is to identify the imbalanced space between cropland and livestock farms. This paper proposes a new methodology to identify such areas at the raster scale, without being limited by traditional administrative division restrictions. The method takes into account nutrient flow, economic cost, and spatial distributions of cropland and livestock farms. The methodology was applied to the Heihe River Basin of China as an example. First, we calculated the nutrient demands on croplands and the supply of livestock manure. Second, we proposed a new method to capture the imbalanced space between cropland and livestock farms. The method was improved on the Gaussian two-step floating catchment area (2SFA) method. To our knowledge, this is the first time such a method has been applied in agriculture. Third, we applied the maximum coverage model to select sites for manure transfer hubs in the imbalanced space of cropland and livestock farms. In this way, the distance of transferring manure can be effectively reduced. Our results showed that the total amount of manure nutrients was sufficient to meet the requirements of local crops in over 90% of the counties located within the Basin. Despite the potential benefits of manure as a fertilizer, its adoption could be more expensive than chemical fertilizers on almost 92% of the croplands due to the high transportation costs associated with spatial separation. However, the identification of 119 transfer hub sites significantly enhanced the accessibility of manure for returning to croplands, ultimately resulting in the optimization of 32% of the previously imbalanced spatial relationship between cropland and livestock farms. The method facilitates raster-scale identification of imbalanced space between cropland and livestock farms, with wide applicability across regions globally.

Abstract 

Fruit tree productivity is generally low and highly variable in the tropics. Quantifying yield gaps and their determining factors provides levers to increase production, but yield gap of fruit trees remains poorly explored at the tree scale. In order to bridge this knowledge gap, we adapted the concept of yield gap to define the production gap at the tree scale to integrate tree endogenous factors (cultivar, age, and crown dimensions). The production gap (P_g) was defined as the difference between potential tree production (P_p) and actual tree production (P_a). The concept was implemented for mango trees in West Africa. We estimated these production indicators on 280 mango trees for two years, covering a wide range of fruit load, age, cultivars, and cropping systems (extensive, diversified, and intensive) found in Senegal. Actual production was estimated yearly using ground tree image analysis. Attainable production (P_att, a locally constrained approximation of P_p) was estimated based on tree endogenous and climatic factors using stochastic frontier analysis. Our results showed that attainable production increased with tree crown area and trunk diameter, whereas the effects of tree density, temperature, and solar radiation were cultivar-dependent. On average, the actual production reached 63% of the attainable production. The production gap was higher in extensive orchards (P_g = 58% of P_att) compared to diversified (P_g = 29% of P_att) and intensive (P_g = 32% of P_att) orchards. Based on production gap estimation, we identified the drivers of mango production variation among cultivars and cropping systems in West Africa. This study demonstrates the usefulness of adapting yield gap methodology to the tree scale to analyze production gaps in diverse fruit tree-based cropping systems. Measurement of production gaps allows the integration of tree features and their variability to upscale and improve the estimation of yield gaps at the orchard scale.

Legume inclusion into cropping systems has been proposed to maintain high crop yields while offering multiple environmental benefits. However, the effect of legumes as pre-crop on subsequent wheat yield and soil has not been well explored. Thus, a 7-year field experiment was used to determine the interactive effects of mineral fertilization and legumes (peanut, mung bean, soybean, adzuki bean) inclusion on wheat productivity and soil quality. Our results showed that legume inclusion led to a higher wheat yield advantage (52% on average) than maize–wheat rotation under no fertilization but the advantage decreased to 26% with fertilization. All legume–wheat rotation systems supported stable wheat production, where a stronger effect was observed after peanut than after maize. Meanwhile, the wheat yield under legume–wheat systems was more resistant (i.e., less variability in the yield after ceasing fertilization) and more resilient (i.e., recovering more quickly after fertilizer re-application) relative to maize-wheat. Furthermore, soil ecosystem multifunctionality increased by 0.8 times in the topsoil while maintaining soil organic carbon stocks, even with low C and N inputs under legume–wheat. Interestingly, we also observed a positive correlation between wheat yield and soil ecosystem multifunctionality. In conclusion, legume inclusion as a sustainable practice can optimize crop yields by enhancing soil multifunctionality while maintaining soil organic carbon stocks, particularly for integration into low-yielding agroecosystems.