In perennial crops such as grapevine, there is a considerable risk of soil degradation caused by mechanization. Organic farming may increase traffic and result in more intensive soil structure degradation, especially on wet soil. Soil structure was observed in 69 soil profiles from 12 vineyards (Languedoc‐Roussillon, Bordeaux, Provence, Burgundy, Rhône Valley) to study the relationships between permanent soil characteristics (texture, stoniness, waterlogging), cultivation practices (technical operations, traffic, farm equipment) and soil structure. Compaction zones were identified in soil profiles viewed perpendicularly to the grapevine rows. The percentage of compacted area and a score for compaction intensity were assessed in the top 0.5 m of the soil profile in three soil compartments defined by the distance from the grapevine row: (1) 0 to 0.2 m (2) 0.2 m to 0.5 m and (3) 0.5 m to the middle of the inter‐row. Most soil profiles exhibited considerable compaction: 75% of the soil profiles were compacted in compartments 2 or 3. Intensity correlated with depth of compaction in compartment 2 – the deeper the compaction, the greater the compaction intensity. Four types of soil profiles could be identified, depending on the location of compacted zones and of their intensity of compaction. The factors that determined the types of soil profiles were as follows: soil vulnerability to compaction, use of moderating practices (practices that limit the risk of compaction) and traffic geometry. A statistical analysis resulted in a decision tree that provides a useful basis to choose cultivation practices that limit damage to or improve soil structure.

Dans le contexte actuel d'augmentation de la pression sur la ressource en eau, quels sont les moyens pour économiser de l'eau en améliorant l'efficience d'irrigation d'une culture tout en préservant la production ? Le travail agronomique présenté ici combine expérimentation, enquête et modélisation pour évaluer l'efficience du mode d'irrigation gravitaire des prairies de la plaine de Crau et proposer de nouveaux scénarios de gestion adaptés aux différents usages et usagers de la ressource en eau.

Conventional water management in the Crau plain needs to be modified to ensure higher irrigation efficiency, better crop production and quality, and reduced environmental impacts. Because experimental approaches to test modifications of water management are difficult in relation to border irrigation, simulation may provide an alternative. We describe the development of a conceptual model of the decision-making process that determines the irrigation management of a cropping system, on which a simulation model is to be based. Interviews focused on water management were carried out, to understand how farmers manage their irrigation and how their decisions determine the technical system applied on the farm. These interviews were then analyzed using the “model for action” concept, to generate a conceptual model of the decision system, which is organized as a sequence of decision rules describing irrigation management. This model contains five elements: (1) spatial and temporal factors relevant to decision-making in terms of irrigation and hay cropping; (2) no interaction between the grassland cropping system and the sheep rearing system; (3) five rules to describe irrigation management in the cropping system; (4) major water distribution constraints; and (5) two inter-related operations, hay mowing and irrigation. The rules for irrigation decision-making are written as: “If Then Else ”. This conceptual model was used as the basis of a decision support system that includes models of grass growth and hydrology.

OBJECTIVE:To describe the implementation and initial results of a specific educational and counseling intervention to examine and improve adherence to antiretroviral therapy (ARV) in HIV-infected patients. METHOD:Four patient profiles were defined: 1) discontinuation and 2) failure: patients with virological failure (defined as two consecutive viral loads>200 copies/mL) at ARV discontinuation or under treatment, both seen after the fact; 3) preparation: naive patients seen before starting treatment, and 4) reinforcement: patients in treatment seen for counseling to prevent virological failure. A clinical psychologist, nurse and hospital pharmacist jointly conducted the session. Data collected include standardized information about the characteristics of HIV infection and ARV regimens, and demographic, behavioral, social and cultural indicators. CD4 cell counts and HIV viral loads were recorded at D0, M1, M3, M9 and M12. The effectiveness of the adherence intervention was defined separately for each patient profile based on some combination of taking or restarting an ARV regimen, virological response, and M12 follow-up. RESULTS:The study included 139 patients between November 1998 and April 2000. The intervention was defined as effective in 50% and 40% of the discontinuation (n=26) and failure (n=61) patients respectively, 84% of those with preparation profile (n=37) and 93% (14/15) of reinforcement patients. Only undetectable HIV viral load at M3 was significantly associated with the effectiveness of the adherence intervention for all 4 profiles. The preventive interventions (preparation and reinforcement) were less effective in patients from outside Europe (p=0.013). CONCLUSION:The adherence intervention was more effective in preventing virological failure than in restoring ARV effectiveness among patients who had already experienced virological failure. It should therefore be proposed primarily before starting ARV, to prevent failure in treatment-naive patients, especially those from outside Europe.

*Philippe Martin, INA P-G, Dpt AGER, 16 rue Claude Bernard 75231 Paris cedex 05, France; François Papy, INRA SAD INRA SAD Ile de France BP 01, 78850 Thiverval Grignon, France; Alain Capillon, CIRAD direction du dept des cultures annuelles Agropolis BP 5035 34032 Montpellier cedex 1, France. *Corresponding author: pmartin@inapg.inra.fr ABSTRACT In order to characterize the effects of agricultural field state on runoff in the Pays de Caux (France), a range of actual agricultural practices has been tested under natural rainfall during two intercrop periods (1993-1994; 1994-1995). Work was conducted on 20 m2 experimental plots. Plot state descriptors included soil surface descriptors (tortuosity index in the tillage direction (TI-L), percentage of surface covered by vegetation (COV), macroporosity (MAC)) and soil profile descriptors (percentage of the anthrophic horizon tilled during intercrop period (TSW), percentage of compacted zone in the anthrophic horizon (COMP)). Climate descriptors, defined for each rainfall sequence, included cumulative rainfall (CR), mean rainfall intensity (I) and cumulative daily climatic balance (precipitation minus evapotranspiration) during the three days preceding the maximum rainfall intensity (CB3). The LIFEREG linear regression method (SAS), chosen because it allowed taking into account collector tank overflowing. The LIFEREG method, conducted on 1993-1994 results, only excluded the MAC and TSW variables (0.01 probability level). The regression equation was: Runoff (mm) = 0.419-0.200*(TI-L)0.015*COV+0.018*COMP+ 0.054*CR+0.530*I+0.018*CB3 A runoff grid composed of four classes has been set up. After all runoff sequences had been split into these four classes the regression equation has been used to determine the runoff class of each runoff sequence. The calculated class was correct for respectively 52 % of the runoff sequences in 1993-1994 and 56 % in 1994-1995. More-than-one-class error frequency only reached 3 % in 1993-1994 and 9% in 1994-1995. The equation would be useful (i) to compare different plot state at the same time and (ii) to discuss the best way to decrease runoff risk on agricultural plots.

Recent work on decision processes on French farms and irrigated systems in Africa has shown that farmers plan their cyclical (recurrent) technical operations, and that one can model this planning process. Taking the case of cotton crop management in North Cameroon, we show that with certain adjustments, modelling of this kind can also be done for rainfed crop farming in Africa. The adjustments are needed to take account of the differences in social status between different fields on one farm and the implications of the fact that farm work is primarily manual. This produces decision models with a similar structure to that described for technical management of an annual crop break in a temperate climate using mechanised implements. Not only do these models give us a detailed understanding of the variability of farming practices, we can also classify them into categories according to weather scenarios yield level as a function of weather scenario. We show that one can attribute farms to these types of model using simple indicators concerning work organisation. By analysing North Cameroon farmers' decision processes for managing cotton crops we can thus produce an effective tool for organising technical supervision of farmers at the regional level: advisers can work with these decision model types by measuring some simple indicators at farm level to predict which types of model are applicable, without the onerous work of constructing individual decision models.

Pour mieux orienter la recherche de solutions techniques qui limitent le ruissellement et l'érosion, les auteurs utilisent des modèles de décision dans les exploitations agricoles. En appréciant les marges de manoeuvre des agriculteurs, on évite de proposer des solutions non réalisables. Dans une région très sensible au ruissellement et à l'érosion, le Pays de Caux (Seine-Maritime, France), après enquête auprès d'agriculteurs, on a modélisé les décisions d'assolement et d'organisation du travail. On teste ainsi s'il est possible de localiser autrement les successions de cultures sur le territoire de l'exploitation, de façon à réduire le ruissellement des zones où il est le plus nocif et s'il est envisageable d'introduire dans l'organisation du travail de nouvelles techniques. Il ressort de l'application de ces modèles qu'il est impossible de reconsidérer la localisation des cultures. En revanche, on peut introduire de nouvelles techniques pendant les périodes de culture et surtout d'interculture, avec un résultat qui reste aléatoire. Les techniques qui n'ont d'autres finalités que de réduire le ruissellement ne sont évidemment pas prioritaires aux yeux de l'agriculteur lorsque leur réalisation entre en concurrence avec les objectifs de production. Plutôt que d'introduire de nouvelles techniques, il faut donc plutôt rechercher des modalités d'intervention qui rendent compatibles maîtrise du ruissellement et élaboration du rendement.

On-farm technical management of annual crops is a recurrent task, so farmers can to a large extent plan their cropping operations. Taking winter wheat on arable farms in one part of France as an example, this planning is represented in a conceptual model consisting of a set of descriptive variables and decision-making rules. Six descriptive variables and five types of decision-making rule have been identified. Three of the variables describe the intended timing of cropping operations, one determines the possible modes of operation and one groups the fields sown to wheat into sets so that different management modes can be applied to each set. We demonstrate that this model accounts for the kinds of planning practised by the farmers in our survey: taking 3 successive years' wheat crops on these farms, with sharp year-to-year differences in weather patterns, we show that planning largely determines the technical management actually exercised. The model proposed enables one to classify and understand the observed variability in farmers' practices, putting the weather in its place among other factors. This representation of decision-making processes in the form of a ‘model for action’ has been validated on wheat in other parts of France and is currently being validated for other annual crops.

In areas of intensive agriculture, e,g, 'Pays de Caux' in France, which was the study area, field observations have shown that runoff directions were modified by agricultural activities. In order to account for factors responsible for modifications of the runoff direction (roughness, tillage direction and agricultural patterns, e,g, dead furrow or dirt tracks), we constructed a discriminant function based on field observations, This function enables us to decide whether flow direction for slopes of up to 15% was imposed by slope direction or tillage direction. It can be applied to any location, provided there are known roughness, known slope intensity, known aspect and known tillage azimuth.In order to examine the effects of these agricultural activities at the catchment scale, we compared two models by analysing the same hydrological variables: the area contributing to runoff and the flow network. The first model (Topo) was built according to the runoff direction derived from a Digital Elevation Model (DEM). The second model (Tillage) was constructed by combining information from the DEM, and information from rules based on field observations or resulting from statistical analysis.For 23 basic catchments, the result of the comparison between the two models (Topo and Tillage) showed that a major part of the catchments and the drainage network was affected by modifications related to the introduction of man-made agricultural factors. For example, for 20 of 23 catchments, the runoff flows over more than 50% of the surface of such areas were produced along the direction imposed by tillage, The introduction of tillage effect brings about modifications of both the shape and size of catchments, (C) 1998 Elsevier Science B.V. All rights reserved.

SUMMARY In areas of intensive agriculture such as the "Pays de Caux" in northern France, prior work showed that incision in a point of a thalweg depended on the local slope, sensitivity of the soil to incision and the area contributing to runoff. Very commonly, runoff surfaces connected to a point of the thalweg are quantified by using digital elevation models (DEM) that integrate only topographical data. Field observations, however, show that agricultural patterns such as tillage, roads and tracks, timing of farming operations and rainfall change both soil infiltration capacities and water flow direction. Our aim was to determine the spatial and temporal effects of man-made factors and to quantify their impact in small agricultural catchments that suffer chronic erosion. In order to examine these effects, we constructed a model by combining data from a DEM and informations from field observations of agricultural effects on soil surface. For 23 basic catchments, the results showed that the majority was affected by modifications related to the introduction of man-made factors., i.e. in 20 of 23 catchments, runoff flows over more than 50% of their surface were produced along the direction imposed by tillage. The results are consistent with discussing the location of ephemeral gullies and can be used to determine protection for thalwegs in order to control damage downstream from agricultural lands.

Abstract This paper presents a framework for a diagnosis of the sustainability of agriculture, from the plot up to the regional level. This framework isstructured by 4 questions, 3 levels and 2 kinds ofviewpoints. The case of a french small,region producing field vegetables is analysed. This leads to the idea that to take diversity into accounts is heuristic for the search of sustainable solutions. Problem and objectives In 1987 G.H. Bruntland defined the sustainable development,as: «...Humanity has the ability