Alexandre Joannon

Weed dispersal by farming at various spatial scales. A review

Reducing pesticide use in agriculture is necessary to preserve natural resources. However, pest control without pesticides is a challenging issue. In particular, weed infestation may cause severe losses of crop yield. Weeds have been traditionally managed solely at the field level. However, larger scales must be considered because invasive and herbicide-tolerant weeds are spreading over larger scales. This review discusses three spatial scales at which agricultural management might affect the dispersal of weeds and, in turn, their distribution and abundance in agricultural fields. The main points are: (1) at the field level, crop and margin management impact mass effect, i.e., local exchanges between the field margin and the cultivated field; (2) at the farm level crop allocation, the management of field boundaries and agricultural circulation in the farm strongly impact the intensity and direction of weed dispersal; and (3) at the landscape level, the spatial farms distribution controls the distribution of weed habitat and, in turn, landscape species pool and long-distance weed dispersal. We conclude that weed dispersal is driven by agricultural management at multiple scales. Weed scientists should thus extend their view on weed dispersal from within-field scales to among-field and landscape scales.

Crop patterns and habitat preferences of the grey partridge farmland bird

Agricultural changes such as intensification and specialization are thought to be the major source of the severe decline of farmland bird populations observed on large spatial scales and over long time spans in Europe. We studied farmers’ practices at a local level on 22 farms from the Beauce area, France, with regard to habitat preferences of grey partridge, Perdix perdix L. We focused on the study of vegetation cover because it influences grey partridge’s reproduction and survival. The results revealed a high diversity of vegetation cover over the municipal territory. This high diversity can be explained by (1) the difference in the crops cultivated by the farmers, only wheat being cultivated by all the farmers; (2) the diversity of elementary crop sequences implemented, as many as 51 having been identified; and (3) the field size, which varies from 0.5 ha to 57 ha, with 54% of fields smaller than 10 ha. Altogether, this potentially creates six different habitat types, 32% of the arable land surveyed being a likely suitable habitat for the grey partridge. We found that irrigation was the main driving factor of vegetation cover diversity. Indeed irrigation controls the farms’ crop acreage, the crop sequences and their spatial pattern and field size. Nonetheless, irrigation practices show both positive, e.g. crop diversity, and negative aspects, e.g. large fields and clutch failure, for ground-nesting birds such as the grey partridge. Based on these results, a GIS modeling of the municipal landscape related to grey partridge’s habitat requirements is possible and would allow a deeper analysis of the impact of crop diversity on grey partridge populations.

How farmers view their job in Pays de Caux, France: Consequences for grassland in water erosion

Abstract In Pays de Caux, runoff and erosion frequently generate damages. Ploughing up grassland is one of the causes of their increase. To apprehend this issue, the authors studied the conceptions of a group of farmers, farming the same catchment, through a socio-anthropological approach. According to this analysis, two types of farms are identified: the ‘managers’ looking at the profitability per hectare, and the ‘livestock farmers’, for whom the global income of farming is more important. The latter are severely depreciated, by the others and by themselves, and are generally not taken over. Nevertheless, their grasslands are more steady than the ‘managers’ ones, and their preservation is important to combat erosion. The Common Agricultural Policy (CAP) does not suggest any measures supporting grassland of these ‘small livestock farmers’. Local subsidies could not only support them economically but could also contribute to decrease their depreciation. This may be a way to manage the risk of soil erosion. However, the results are established at the catchment level and further enquiries are needed to extend them. It is possible to build a network of places in Europe, with the aim of thinking propositions at the CAP level.

Temporal variability of surface runoff due to cropping systems in cultivated catchment areas: Use of the DIAR model for the assessment of environmental public policies in the Pays de Caux (France).

This article proposes the use of a new model, DIAR (Diagnostic Agronomique du Ruissellement, or Agronomic Assessment of Runoff), for the prediction of the timing of the risk of runoff. DIAR is dedicated to loamy soils which are very sensitive to surface crusting, leading to runoff, soil erosion and muddy flows. The approach is proposed for the north-western European loess belt regions where muddy flows severely impact human activities. The likelihood of runoff is assessed from the sequence of soil surface states generated by cultivation practices. DIAR is based on the calculation of curve number values, for each stage of the soil-surface-state sequence, for calculating runoff for each of these stages. In this study, DIAR is applied to a catchment of 912 ha, cultivated by 26 farmers in the Pays de Caux (Normandy, France) where infrastructures located at the outlet have been damaged several times by muddy flows. Local public authorities involved in reducing muddy flows are eager to limit the agricultural upstream runoff by extending the planting of mustard as a winter cover crop. We tested the efficiency of such a policy on the reduction of the mean runoff. We also tested the year-to-year variability of this efficiency using the acreages of four successive years (1999-2000 to 2002-2003). Finally, the cost-efficiency of the policy was also considered. Though we used the same weather scenario, the initial situation (without much mustard cover) showed a wide year-to-year variation in the total runoff. This variation can be associated with the structure of the farms that cultivate the catchment (Utilised Agricultural Area (UAA) of each farm and percentage of this UAA inside the catchment). Our results showed that the widespread planting of winter cover crops could reduce the runoff by 10-20% compared with the initial situation (depending on the year), and also reduce the year-to-year variability of runoff. For each of the 4 tested years, the cost of the infiltrated m(3), due to each ha of mustard cover, decreases with the increase in mustard cover. It indicates that the present siting of the mustard cover is not as efficient as it could be. We should ask why farmers do not sow it elsewhere.

The determinants of local collective action on erosive runoff. An analysis of farmers' geographical proximities in Upper Normandy, France

Runoff disregards territorial boundaries, affects farmers as well as other users of space, and necessitates collective action if it is to be combatted. In this article, based on the case of Upper-Normandy, we show that geographical proximity can play a determining role in the struggle against erosive runoff, and we present a new tool for analysing relations of proximity between farmers. First, we use three examples to show that farmers have only limited knowledge of the problem of erosion and are largely incapable of carrying out concerted collective action. That is why Syndicats de basins versants were set up to provide organised proximity. Then we present a new tool for analysing relations of geographical proximity between farmed land and farmsteads, in order to assess the possibilities of coordination between farmers within catchment areas. Our results, based on the characterisation of 1409 communes, clearly show that long distances, the size of farmed agricultural land and the high number of external farmers constitute major obstacles to the creation of ad hoc cooperative processes.

A new plug-in under RECORD to link biophysical and decision models for crop management

Developing sustainable crop systems is a major challenge. Presently, management practices are simulated using either biophysical models or simple farmer decision models. As a result, there is a lack of generic models integrating both biophysical parameters and farmer decision parameters. Here, we developed an original graphical plug-in to sketch and implement decision-making models and to link them with biophysical models. For that, we used the RECORD platform, standing for REnovation and COORDination of agro-ecosystem modeling. Different pop-up windows allow to create the model using a decision formalism then to implement the model under the RECORD platform. The sequence of technical operations is formally modeled as a direct multi-graph without retroaction. The plug-in allows defining activities, relation between activities, and decision rules to trigger the different activities. The resulting model is independent of any biophysical model and can then be linked with different crop models. An example is given on an innovative cropping systems part of the MicMac-Design project. The decision-making model is then linked with the STICS crop model.

Questioning the work of farmers, advisors, teachers and researchers in agro-ecological transition. A review

The French Ministry of Agriculture has called for agro-ecological transitions that reconcile farming and the environment. In this review, we examine the transformations of farmers and AKIS (Agriculture Knowledge Innovation System) actors’ work during agro-ecological transitions, and argue that the content, organization, and aim of farmers’ work are influenced by agricultural training, agricultural development, and discussions between peers, research, and regulations. Our main findings concern those transformations. The first finding was that there is an increasing expression of local particularities (situated ecological processes, micro-climates, etc.) and farmers’ singularities (e.g., relationship with nature). These particularities challenge AKIS players’ forms of organization and intervention, which used to be built on generic knowledge. Our second finding was that AKIS players have to consider their action as one potential contribution to the development of farmers’ experience: Their interventions become part of the flow of the farmer’s activities. The question for AKIS players is then: How can farmers’ own discovery of their natural and technical environment from new perspectives be facilitated? Thirdly, we found that transformations of work are systemic: The “doing”, the knowledge applied, and the values and norms to which subjects refer change. Facilitating transition can no longer be considered as a problem of knowledge availability. Fourthly, production of agronomic knowledge and ways in which it is disseminated are being challenged. Not only does knowledge have to be certified by scientific norms and methods, it has also to be valued by actors if it is to have an impact. The prescriptive relationship of science and AKIS players towards farmers is likewise challenged. This review raises many questions: Do agro-ecological transitions contribute to reorienting the development of farmers’ activity? Are agro-ecological transitions conducive to the development of sustainable farm work? What transformations of AKIS players’ work are needed to better support agro-ecological transitions?