Bruno Colomb

Ex ante assessment of the sustainability of alternative cropping systems: implications for using multi-criteria decision-aid methods. A review

Sustainability is a holistic and complex multi-dimensional concept encompassing economic, social and environmental issues, and its assessment is a key step in the implementation of sustainable agricultural systems. Realistic assessments of sustainability require: (1) the integration of diverse information concerning economic, social and environmental objectives; and (2) the handling of conflicting aspects of these objectives as a function of the views and opinions of the individuals involved in the assessment process. The assessment of sustainability is therefore increasingly regarded as a typical decision-making problem that could be handled by multi-criteria decision-aid (MCDA) methods. However, the number and variability of MCDA methods are continually increasing, and these methods are not all equally relevant for sustainability assessment. The demands for such approaches are also rapidly changing, and faster ex ante assessment approaches are required, to address scales currently insufficiently dealt with, such as cropping system level. Researchers regularly carry out comparative analyses of MCDA methods and propose guidelines for the selection of a priori relevant methods for the assessment problem considered. However, many of the selection criteria used are based on technical/operational assumptions that have little to do with the specificities of ex ante sustainability assessment of alternative cropping systems. We attempt here to provide a reasoned comparative review of the main groups of MCDA methods, based on considerations related to those specificities. The following main guidelines emerge from our discussion of these methods: (1) decision rule-based and outranking qualitative MCDA methods should be preferred; (2) different MCDA tools should be used simultaneously, making it possible to evaluate and compare the results obtained; and (3) a relevantly structured group of decision-makers should be established for the selection of tool variants of the choosen MCDA methods, the design/choice of sustainability criteria, and the analysis and interpretation of the evaluation results.

MASC, a qualitative multi-attribute decision model for ex ante assessment of the sustainability of cropping systems

Realistic assessments of sustainability are often viewed as typical decision-making problems requiring multi-criteria decision-aid (MCDA) methods taking into account the conflicting objectives underlying the economic, social and environmental dimensions of sustainability, and the different sources of knowledge representing them. Some MCDA-based studies have resulted in the development of sustainable agricultural systems, but the new challenges facing agriculture and the increasing unpredictability of their driving forces highlight the need for faster ex ante (‘Before-the-event’) assessment frameworks. These frameworks should also (i) provide a more realistic assessment of sustainability, by integrating a wider range of informal knowledge, via the use of qualitative information; (ii) address alternative scales, such as cropping system level, improving granularity for the handling of sustainability issues and (iii) target a larger panel of decision-makers and contexts. We describe here the MASC model, which is at the center of a framework addressing these objectives. The MASC model has at its core a decision tree that breaks the sustainability assessment decisional problem down into simpler units as a function of sustainability dimensional structure (economic, social and environmental), generating a vector of 32 holistic ‘mixed’ (quantitative and qualitative) elementary criteria rating cropping systems. The assessment process involves the calculation of these criteria, their homogenization into qualitative information for input into the model and their aggregation throughout the decision tree based on ‘If-Then’ decision rules, entered by the user. We present the model and describe its first implementation for the evaluation of four cropping systems generated from expert knowledge, and discuss its relevance to the objectives cited above. The MASC model has several advantages over existing methods, due to its ability to handle qualitative information, its transparency, flexibility and feasibility.

Stockless organic farming: strengths and weaknesses evidenced by a multicriteria sustainability assessment model

Agronomists need methodologies to assess the sustainability of cropping systems. Few models such as MASC have been recently developed for evaluation. The effective use of those models is still a challenge, notably for low-input systems. Here a more specific model entitled MASC-OF was developed and applied to study stockless organic cropping systems. The MASC-OF model is original because it is based on agricultural advisers’ needs and expertises. Two groups of advisers supported by agronomic scientists were involved in a nine-step methodology to progress from preliminary meetings to data analysis. The methodology allowed advisers to design a model including their own views on what is a sustainable organic cropping system. Soil fertility and weed and pest control were integrated as a new branch in the original MASC model. We also developed evaluation criteria for each basic attribute, defining aggregation rules and weighting attributes. Tested case studies were based on 44 real cropping systems identified on 19 farms in the Midi-Pyrenees region of France and on 23 cropping system types developed by the advisers from the Centre, Ile-de-France, Pays de Loire, Poitou-Charentes and Rhône-Alpes regions of France. Our results show that a high score of economic sustainability is the most difficult to achieve. This finding is explained by low productivity of cereal crops and high variability of market prices for organic grain. Further, agronomic viability is also difficult to ensure, as a consequence of poor soil-fertility management practices. The ability to achieve social acceptability for the producer, including workload and health risk, is high. By contrast, acceptability for the society has a medium score due to reduced productivity and contribution to local employment. Environmental sustainability is the easiest dimension to achieve, despite nitrogen-loss risks in some situations and high water and energy consumption in irrigated systems. Overall our findings show that the potential for the development of more sustainable organic cropping systems in stockless farms is high.

Guidelines to design models assessing agricultural sustainability, based upon feedbacks from the DEXi decision support system

New agricultural systems are required to satisfy societal expectations such as higher quantity and quality of agricultural products, reducing environmental impacts, and more jobs. However, identifying and implementing more suitable agricultural systems is difficult due to conflicting objectives and to the wide diversity of scientific disciplines required to solve agricultural issues. Therefore, designing models to assess the sustainability of agricultural systems requires multi-criteria decision aid methods. The French agronomist community has recently developed 11 hierarchical and qualitative models to assess sustainability using the DEXi decision aid software. Here, we give guidelines to help designers to build their own specific models. First, we present the principles and applications of the DEXi software. Then, we provide guidance on the following steps of model designing: (1) initial analysis and planning of the design process, (2) selection and hierarchy of sustainability criteria, (3) indicator selection and building, (4) parameterization, (5) evaluation, and (6) model dissemination and uses. We then discuss advantages and drawbacks of this kind of modeling formalism, the role of a participatory approach, and the main properties to consider during the design process.

Soil Phosphorus Management in Organic Cropping Systems: From Current Practices to Avenues for a More Efficient Use of P Resources

Phosphorus (P) is a major nutrient for all living organisms and a key production factor in agriculture. In crop production, it is usually supplied to soils through fertilisers or recycled manure and compost. Organic production guidelines ban the use of highly soluble, manufactured P fertilisers and, thus, recommend recycling P from livestock manure and compost. In this chapter, after an overview of P dynamics in soils, we explore the consequences of such guidelines in terms of field- and farm-gate P budget, soil P availability and crop productivity. Moreover, we propose some avenues for the more effective use of P resources, ranging from rhizosphere-based processes (e.g., soil microorganism manipulation), genotype selection and cropping practices (e.g., intercropping), to farming system design (e.g., a combination of crops and animals at the farm scale). Finally, the potential benefits of these options are compared with respect to soil P status, field- and farm-P budgets.