Pollution de l'eau par les pesticides en milieu viticole languedocien. Construction d'un modèle couplé pression-impact pour l'expérimentation virtuelle de pratiques culturales à l'échelle de petits bassins versants

In Mediterranean catchments in which vineyards account for a major share of the area, cropping practices are an important factor with respect to increasing risks of diffuse pesticide pollution of water. This study was about developping an approach for pressure-impact modelling. The research question considered dynamics of agrosystem status variables modified by cropping actions. Two variables were identified : soil surface infiltrability and active material concentration on the soil. On a catchment scale, to assess impacts, we used the distributed hydrological model MHYDAS to simulate water and pollutant flows according to different cropping practice and climatic scenarios. To represent the spatiotemporal distribution of cropping operations on each plot, the decision model DHIVINE was built. It simulates vinegrowers's crop management sequences. For each farm in the catchment, the model is based on a representation of the vineyard annual technical management strategy in the form of activity plans. These plans involve agrosystem status indicators and take into account the characteristics of productive resources on the farm and arbitration between cultivation operations and competing plots. Biophysical models were developped to simulate decision indicators and impacts of cropping practices on soil surface characteristics which are drivers of soil surface infiltrability. A functional typology of soil surface states based on their soil infiltrabilty properties was used to develop an approach for temporally continuous modelling of infiltration. It was based on a parallel modelling of dynamics (i) of soil surface characteristics of bare soil and (ii) of weed cover development. Model coupling was realized with OpenFLUID platform. The approach developped herein allows simulating dynamics of agrosystem status variables as a function of cropping practices. It seems adapted for assessing hydrological impacts at the catchment scale in Mediterranean environments.Dans les bassins versants méditerranéens où les zones cultivées en vigne occupent une part importante de l'espace, les pratiques culturales sont un facteur important d'apparition de risques de pollution diffuse des eaux par les pesticides. Au cours de la thèse, une démarche de modélisation couplée pression-impact a été développée. La question de recherche a porté sur la prise en compte dans le modèle construit de la dynamique des variables d'état du milieu modifiées par les actions culturales. Deux variables ont été identifiées : l'infiltrabilité de la surface du sol et la concentration en matières actives au sol. A l'échelle du bassin versant, pour réaliser l'évaluation des impacts, on s'est appuyé sur l'utilisation du modèle hydrologique distribué MHYDAS qui permet de simuler les flux d'eau et de polluants selon différents scenarii de pratiques et climatiques. Pour représenter la répartition spatio-temporelle des opérations culturales sur chacune des parcelles du bassin versant, le modèle décisionnel DHIVINE a été construit. Il permet de simuler les itinéraires techniques des viticulteurs. Pour chaque exploitation du bassin versant, le modèle est basé sur une représentation de la conduite technique annuelle du vignoble sous forme de plans d'activités. Ces plans mettent en oeuvre des indicateurs d'états de l'agrosystème et prennent en compte les caractéristiques des ressources productives de l'exploitation ainsi que les arbitrages à réaliser entre opérations culturales et parcelles concurrentes. Des modèles biophysiques ont été développés pour simuler les indicateurs de la décision ainsi que l'impact des différentes pratiques sur les états de surface du sol qui conditionnent l'infiltrabilité du sol en surface. Une typologie fonctionnelle des états de surface basée sur leurs propriétés d'infiltrabilité du sol a été utilisée pour développer une démarche visant une modélisation continue dans le temps de l'infiltration. Elle intègre une modélisation parallèle de la dynamique des états de surface du sol nu et du développement de la couverture herbacée par les adventices. Un couplage des modèles a été réalisé sous la plate-forme OpenFLUID. La démarche adoptée ici permet de représenter les dynamiques différentes des variables d'état du milieu en fonction de différentes pratiques culturales et semble adaptée pour l'évaluation des impacts en terme de pollution de l'eau par les pesticides à l'échelle de bassins versants viticoles méditerranéens

From Integrated Pest Management to integrated resources management: a need to improve the coherence of cultural practices at the field scale

National audienc

Impact of land management on hydrological functioning in cultivated landscapes: a coupled model of functional assessment

International audienceIn cultivated landscapes, hydrological functioning is highly influenced by anthropic drivers. Indeed, spatiotemporal patterns in land management affect processes such as run-off or pollutant flow. Reciprocally, at the scale of a cropping season, hydrological functioning of land influences farmers’ actions on crops. Consequently, the assessment of the hydrologic impacts of land management needs recognition of the global functioning of the system which requires a close coupling between the modelling of land management actions and hydrological processes. Most of hydrological models take into account a spatial representation of the landscape mosaic created by land management. However the resolution used for the temporal evolution of this pattern is coarser than the one required by hydrological model which simulate processes over short time steps. Consequently, there is a need for more accurate temporal representation of land management which means an analysis of the crop management systems and the integration of bio-physical feedback mechanisms on management decisions. We propose an approach for assessing the hydrological impact of crop management system in the specific case of pollutant loading in a perennial crop area, based on the coupling of a distributed hydrological model with a farmer’s decision model. This latter model represents land management with decision rules applied by farmers to drive their collection of plots during the whole cropping cycle. It includes agronomic rules based on indicators of the state of the bio-physical system at plot levels as well as work organisation rules at farm level. Different types of crop management system induced by the diversity of farmers are thus represented by different rules set which can be spatially distributed. The spatial pattern in crop management represented by the decision model determines the hydrological functioning of the landscape. A feedback exists since the hydrological processes like the spatio-temporal evolution soil water content influence several farmer decisions like for example the choice of the dates of soil tillage. An application of the method is realised on a small (1 km2) Mediterranean catchment cultivated with vineyard with the prospect of providing a tool that can help farmers to evaluate different land management strategies

Coupler modélisation des décisions des agriculteurs et modélisation hydrologique pour quantifier les flux de pesticides à l'échelle d'un petit bassin versant. Application au cas d'un bassin versant viticole méditerranéen

National audienc

Modeling work organization in grape production to study its environmental impacts

International audienc

Modelling management practices in viticulture while considering resource limitations: the Dhivine model

International audienceMany farming-system studies have investigated the design and evaluation of crop-management practices with respect to economic performance and reduction in environmental impacts. In contrast, little research has been devoted to analysing these practices in terms of matching the recurrent context-dependent demand for resources (labour in particular) with those available on the farm. This paper presents Dhivine, a simulation model of operational management of grape production at the vineyard scale. Particular attention focuses on representing a flexible plan, which organises activities temporally, the resources available to the vineyard manager and the process of scheduling and executing the activities. The model relies on a generic production-system ontology used in several agricultural production domains. The types of investigations that the model supports are briefly illustrated. The enhanced realism of the production-management situations simulated makes it possible to examine and understand properties of resource-constrained work-organisation strategies and possibilities for improving them

Modeling dynamically the management of intercropped vineyards to control the grapevine water status

International audienceIn vineyards, introducing a grass cover as intercrop is a common practice around the world. Indeed, it can provide some ecological services such as mitigation of runoff and erosion, and control of grapevine vegetative development (Battany and Grismer, 2000; Smart et al., 1991). Moreover, it can constitute an interesting alternative to the systematic use of herbicides. However, introducing a new crop makes the system more complex, and farmers have to adapt their way to manage them. In Mediterranean vineyards, a major difficulty is to manage correctly the two crops, to satisfy production and environmental objectives with respect to the competition for soil resources and climate variability. As experiments are time consuming and difficult to carry out in these perennial systems, the use of a modeling approach is more appropriate to test and evaluate different types of intercrop management plans. A recent study showed the difficulty in finding robust management plans over a 30- years period. It can be explained by the fact that they did not manage responsively to observed states of the biophysical system and they did not take into account the high inter- and intra-annual climate variability (Ripoche et al., 2009). This study analyzes the merit of introducing some flexibility in the management of intercrops in vineyards. The investigation relies on a simulation model that reproduces the interactive dynamics of decision-making and biophysical processes. Simulation is used to support the design of more robust management plans enabling control of the grapevine water status in these cropping system

Modelling adaptive management of intercropping in vineyards to satisfy agronomic and environmental performances under Mediterranean climate

a b s t r a c t In the Mediterranean area, rainfed viticulture is exposed to irregular rainfall distribution. The impacts on production and environment can be mitigated by appropriate management practices like, for instance, the introduction of cover crop in the inter-rows in vineyards. This paper presents the VERDI simulation model created to study various adaptive intercrop management strategies at field scale. The purpose is to design management strategies that are responsive to the water status of the biophysical system (soil e grapevine e intercrop) and the past and current climatic conditions. VERDI realistically reproduces the dynamic interactions between the biophysical system and the decision system in varying Mediterranean rain regime. The decision system works as an interpreter of a management strategy, defined as a set of soil surface management activities (e.g. mechanical weeding of the intercrop) that are linked by temporal constraints (e.g. sequencing, synchronisation) and organisational or programmatic specifications (e.g. iteration). The adaptive capabilities of the strategies are distinguished according to the different sources of flexibility to be exploited at operational, tactical, and strategic levels. A simulation study is reported that involves more or less flexible strategies under different climate scenarios. The simulation results proved that, in case of severe drought, the most flexible strategy yields the best trade-off between agricultural production and environmental services over the years

Opening (OP) and closing (CP) predicates and other descriptors used in the predicates.

<p>Opening (OP) and closing (CP) predicates and other descriptors used in the predicates.</p