Farmers are facing serious plant protection issues and phytosanitary risks, in particular in the tropics. Such issues are food insecurity, lower income in traditional low-input agroecosystems, ...adverse effects of pesticide use on human health and on the environment in intensive systems and export restrictions due to strict regulations on quarantine pests and limits on pesticide residues. To provide more and better food to populations in both the southern and northern hemispheres in a sustainable manner, there is a need for a drastic reduction in pesticide use while keeping crop pest and disease damage under control. This can be achieved by breaking with industrial agriculture and using an agroecological approach, whose main pillar is the conservation or introduction of plant diversity in agroecosystems. Earlier literature suggest that increasing vegetational biodiversity in agroecosystems can reduce the impact of pests and diseases by the following mechanisms: (1) resource dilution and stimulo-deterrent diversion, (2) disruption of the spatial cycle, (3) disruption of the temporal cycle, (4) allelopathy effects, (5) general and specific soil suppressiveness, (6) crop physiological resistance, (7) conservation of natural enemies and facilitation of their action against aerial pests and (8) direct and indirect architectural/physical effects. Here we review the reported examples of such effects on a broad range of pathogens and pests, e.g. insects, mites, myriapods, nematodes, parasitic weeds, fungi, bacteria and viruses across different cropping systems. Our review confirms that it is not necessarily true that vegetational diversification reduces the incidence of pests and diseases. The ability of some pests and pathogens to use a wide range of plants as alternative hosts/reservoirs is the main limitation to the suppressive role of this strategy, but all other pathways identified for the control of pests and disease based on plant species diversity (PSD) also have certain limitations. Improving our understanding of the mechanisms involved should enable us to explain how, where and when exceptions to the above principle are likely to occur, with a view to developing sustainable agroecosystems based on enhanced ecological processes of pest and disease control by optimized vegetational diversification.
The realization of the contribution of peasant agriculture to food security in the midst of scenarios of climate change, economic and energy crisis, led to the concepts of food sovereignty and ...agroecologically based production systems to gain much attention in the developing world in the last two decades. New approaches and technologies involving application of blended modern agricultural science and indigenous knowledge systems and spearheaded by thousands of farmers, NGOs, and some government and academic institutions are proving to enhance food security while conserving agrobiodiversity soil and water resources conservation throughout hundreds of rural communities in the developing world. Case studies from Cuba, Brazil, Philippines, and Africa are presented to demonstrate how the agroecological development paradigm based on the revitalization of small farms which emphasizes diversity, synergy, recycling and integration, and social processes that value community participation and empowerment, proves to be perhaps one of the only viable options to meet present and future food needs. Given the present and predicted near future climate, energy and economic scenarios, agroecology has emerged as one of the most robust pathways towards designing biodiverse, productive, and resilient agroecosystems available today.
Abstract The extent to which weeds in arable land are useful to pollinators depends in part on the temporal pattern of flowering and insect flight activity. We compiled citizen science data on 54 ...bees and hoverflies typical of agricultural areas in southern Sweden, as well as 24 flowering weed species classified as pollinator‐friendly in the sense that they provide nectar and/or pollen to pollinators. The flight periods of the bees and hoverflies varied greatly, but there were also some consistent differences between the four groups studied. The first group to fly were the early flying solitary bees (7 species), followed by the social bees (18 species). In contrast, other solitary bees (11 species) and hoverflies (22 species) flew later in the summer. Solitary bees had the shortest flight periods, while social bees and hoverflies had longer flight periods. Flowering of weed species also varied greatly between species, with weeds classified as winter annuals (e.g., germinating in autumn) starting early together with germination generalists (species that can germinate in both autumn and spring). Summer annuals (spring germinators) and perennials started flowering about a month later. Germination generalists had a much longer flowering period than the others. Weekly pollinator records were in most cases significantly explained by weed records. Apart from early flying solitary bees, all models showed strong positive relationships. The overall best explanatory variable was the total number of weeds, with a weight assigned to each species based on its potential as a nectar/pollen source. This suggests that agricultural weeds in Sweden provide a continuous potential supply of nectar and pollen throughout the flight season of most pollinators.
In this article we use a food sovereignty frame to analyze the role of the State in favoring agroecological scaling, particularly in Cuba and in the Latin American countries that elected leftist ...governments in the first years of the 21st century and currently face an upsurge of right-wing political forces. As with social movement participation in international governance structures, at the national level social movements face risks when they allow themselves to become absorbed in collaborations with the State in order to build public policy for taking agroecology to scale. By participating in the institutionalization of agroecology, movements become part of the established rules of the game, having to move within limits defined by a system that exists to preserve the interests of the dominant class. On the other hand, by boycotting the arena of governance, agroecological movements allow resurgent political and economic elites to grab land, territories and resources needed for agroecological food systems to ever become a global substitute for industrial agriculture. At the heart of the matter is the political character of agroecology: shall we continue betting on reform, in times of (counter) revolution?
1. A substantial proportion of the global land surface is used for agricultural production. Agricultural land serves multiple societal purposes; it provides food, fuel and fibre and also acts as ...habitat for organisms and supports the services they provide. Biodiversity conservation and food production need to be balanced: production needs to be sustainable, while conservation cannot be totally at the expense of crop yield. 2. To identify the benefits (in terms of biodiversity conservation) and costs (in terms of reduction in yields) of agricultural management, we examined the relationship between crop yield and abundance and species density of important taxa in winter cereal fields on both organic and conventional farms in lowland England. 3. Of eight species groups examined, five (farmland plants, bumblebees, butterflies, solitary bees and epigeal arthropods) were negatively associated with crop yield, but the shape of this relationship varied between taxa. It was linear for the abundance of bumblebees and species density of butterflies, concave up for the abundance of epigeal arthropods and butterflies and concave down for species density of plants and bumblebees. 4. Grain production per unit area was 54% lower in organic compared with conventional fields. When controlling for yield, diversity of bumblebees, butterflies, hoverflies and epigeal arthropods did not differ between farming systems, indicating that observed differences in biodiversity between organic and conventional fields are explained by lower yields in organic fields and not by different management practices per se. Only percentage cover and species density of plants were increased by organic field management after controlling for yield. The abundance of solitary wild bees and hoverflies was increased in landscapes with high amount of organic land. 5. Synthesis and applications. Our results indicate that considerable gains in biodiversity require roughly proportionate reductions in yield in highly productive agricultural systems. They suggest that conservation efforts may be more cost effective in low-productivity agricultural systems or on non-agricultural land. In less productive agricultural landscapes, biodiversity benefit can be gained by concentrating organic farms into hotspots without a commensurate reduction in yield.
Legume growing has many benefits. Indeed legumes provide plant proteins for animal feed and human food. Legumes fix atmospheric N
2
and, in turn, provide cheap and green N fertilisers. Additionally, ...legumes are used as diversification crops in rotations based on oilseed rape and cereals. Despite those benefits, legume crops in Europe represent less than 4 % of arable lands, and European legume seeds are underused for animal and human nutrition. Nonetheless, European authorities are now fostering the development of legume crops for sustainable agriculture. Here, we analyse forage and grain legume-producing systems since 1950 in order to identify the actual constraints of legume development. We show that legumes can contribute to the agroecological transition for sustainable agriculture, food and energy and for sustainable agri-food systems. Then, we point out that high added-value niche markets are required for supporting legume production. The major research needs identified are (1) analysing the constraints of the current systems and identifying ways of moving towards systems that include more legumes, (2) identifying new and diversified uses for legumes in a sustainable food chain, (3) assessing and improving the ecosystem services provided by legumes at cropping system and territory scales and (4) promoting agroecology through and for legume crop management.
► Data on crop productivity after biochar application to soils quantitatively analysed. ► Grand mean effect is 10% increase in crop productivity. ► Large variation in data allows limited but useful ...insights in causative mechanisms. ► Auxiliary, temporal and spatial data is not currently sufficiently representative. ► Strategic research and full reporting on statistics and auxiliary data are needed.
Increased crop yield is a commonly reported benefit of adding biochar to soils. However, experimental results are variable and dependent on the experimental set-up, soil properties and conditions, while causative mechanisms are yet to be fully elucidated. A statistical meta-analysis was undertaken with the aim of evaluating the relationship between biochar and crop productivity (either yield or above-ground biomass). Results showed an overall small, but statistically significant, benefit of biochar application to soils on crop productivity, with a grand mean increase of 10%. However, the mean results for each analysis performed within the meta-analysis covered a wide range (from −28% to 39%). The greatest (positive) effects with regard to soil analyses were seen in acidic (14%) and neutral pH soils (13%), and in soils with a coarse (10%) or medium texture (13%). This suggests that two of the main mechanisms for yield increase may be a liming effect and an improved water holding capacity of the soil, along with improved crop nutrient availability. The greatest positive result was seen in biochar applications at a rate of 100
t
ha
−1 (39%). Of the biochar feedstocks considered and in relation to crop productivity, poultry litter showed the strongest (significant) positive effect (28%), in contrast to biosolids, which were the only feedstock showing a statistically significant negative effect (−28%). However, many auxiliary data sets (i.e. information concerning co-variables) are incomplete and the full range of relevant soil types, as well as environmental and management conditions are yet to be investigated. Furthermore, only short-term studies limited to periods of 1 to 2 years are currently available. This paper highlights the need for a strategic research effort, to allow elucidation of mechanisms, differentiated by environmental and management factors and to include studies over longer time frames.
•Forage mixtures should combine plant strategies for greater drought resilience.•A conceptual framework to analyze adaptive responses of forage species under drought.•A trade-off between resistance ...to moderate drought and survival of intense drought.•Concepts of community ecology are useful to the design of multi-specific grasslands.•Defining rules to associate genotypes should enhance functional complementarity.
In many regions of the world, such as Southern Europe and most Mediterranean areas, the frequency and magnitude of droughts and heat waves are expected to increase under global warming and will challenge the sustainability of both native and sown grasslands. To analyze the adaptive strategies of species, genotypes and cultivars, we aim both (i) to understand the composition and functioning of natural grasslands and (ii) to propose ideotypes of cultivars and optimal composition for mixtures of species/genotypes under water deficit and high temperatures. This review presents a conceptual framework to analyze adaptive responses of perennial herbaceous species, starting from resistance to moderate drought with growth maintenance (dehydration avoidance and tolerance of lamina) to growth cessation and survival of plants under severe stress (dehydration avoidance and tolerance of meristems). The most discriminating functional traits vary according to these contrasting strategies because of a trade-off between resistance to moderate moisture deficit and survival of intense drought. Consequently it is crucial to measure the traits of interest in the right organs and as a function of soil water use, in order to avoid misleading interpretations of plant responses. Furthermore, collaboration between ecologists, eco-physiologists, and agronomists is required to study the combination of plant strategies in natural grasslands as only this will provide the necessary rules for species and cultivars or ecotypes assemblage. This ‘agro-ecological’ approach aims to identify and enhance functional complementarity and limit competition within the multi-specific or multi-genotypic material associated in mixtures since using plant biodiversity should contribute to improving grassland resistance and resilience.
Comparative functional ecology seeks to understand why and how ecological systems and their components operate differently across environments. Although traditionally used in (semi)-natural ...situations, its concepts and methods could certainly apply to address key issues in the large variety of agricultural systems encountered across the world. In this review, we present major advances in comparative plant functional ecology that were made possible over the last two decades by the rapid development of a trait-based approach to plant functioning and prospects to apply it in agricultural situations. The strength of this approach is that it enables us to assess the interactions between organisms and their environment simultaneously on a large number of species, a prerequisite to address questions relative to species distribution, community assembly and ecosystem functioning. The trait concept will be first defined, before presenting a conceptual framework to understand the effects of environmental factors on plant community structure and ecosystem properties via plant traits. We will then argue that leading dimensions of variation among species can be captured by some selected traits and show that a combination of three easily measured traits—specific leaf area (the ratio of leaf area to leaf dry mass), plant height and seed mass—enables us to assess how different species use their resources, interact with neighbours and disperse in time and space. The use of traits to address central questions in community ecology will be reviewed next. It will be shown that traits allow us to (1) understand how plant species are sorted according to the nature of environmental gradients, (2) evaluate the relative importance of habitat filtering and limiting similarity in the process of community assembly and (3) quantify two main components of community functional structure, namely, community-weighted means of traits and community functional divergence. The relative impacts of these two components on ecosystem properties will then be discussed in the case of several components of primary productivity, litter decomposition, soil water content and carbon sequestration. There is strong support for the biomass ratio hypothesis, which states that the extent to which the traits of a species affect those ecosystem properties depends on the abundance of this species in the community. Assessing the role of functional divergence among species on ecosystem properties will require major methodological breakthroughs, both in terms of metrics and statistical procedures to be used. In agricultural situations, we show that trait-based approaches have been successfully developed to assess the impacts of management practices on (1) the agronomic value of grasslands and (2) the functional composition and structure of crop weed communities and how these could affect the functioning of the crop. Applications in forestry are still poorly developed, especially in temperate regions where the number of species in managed forest remains relatively low. The last decades of research have led to the constitution of large data sets of plant traits, which remain poorly compatible and accessible. Recent advances in the field of ecoinformatics suggest that major progress could be achieved in this area by using improved metadata standards and advancing trait domain ontologies. Finally, concluding remarks, unanswered questions and directions for research using the functional approach to biodiversity made possible by the use of traits will be discussed in the contexts of ecological and agronomical systems. The latter indeed cover a wide range of environmental conditions and biological diversity, and the prospect for reducing environmental impacts in highly productive, low-diversity systems will certainly imply improving our skills for the management of more diverse systems prone to a trait-based approach as reviewed here.
•Meta-analysis of nitrification and urease inhibitors effect on crop yield and NUE.•DCD, DMPP and NBPT were selected for analysis.•Grand mean effect is 7.5% and 12.9% increase in crop yield and NUE ...respectively.•Their effectiveness was dependent on environmental and management factors.•Informational gaps are identified and recommendations for further research provided.
Nitrification and urease inhibitors are proposed as means to reduce nitrogen losses, thereby increasing crop nitrogen use efficiency (NUE). However, their effect on crop yield is variable. A meta-analysis was conducted to evaluate their effectiveness at increasing NUE and crop productivity. Commonly used nitrification inhibitors (dicyandiamide (DCD) and 3,4-dimethylepyrazole phosphate (DMPP)) and the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) were selected for analysis as they are generally considered the best available options. Our results show that their use can be recommended in order to increase both crop yields and NUE (grand mean increase of 7.5% and 12.9%, respectively). However, their effectiveness was dependent on the environmental and management factors of the studies evaluated. Larger responses were found in coarse-textured soils, irrigated systems and/or crops receiving high nitrogen fertilizer rates. In alkaline soils (pH≥8), the urease inhibitor NBPT produced the largest effect size. Given that their use represents an additional cost for farmers, understanding the best management practices to maximize their effectiveness is paramount to allow effective comparison with other practices that increase crop productivity and NUE.
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