The Alaotra Lake is a wide region. Thus, there are a lot of different types of farm depending on the location, the production activities, the size and many different situations ... That explains why the dissemination and adoption of CA systems and ICS (Innovative Cropping Systems) hasn’t reached the same level in all the different zones. But, in general, Alaotra farmers are not reluctant to CA adoption at the conditions that quality extension is available for technical support and monitoring for several years (3 to 5). It is just easier and faster when the proposed systems fit with the farmers’ expectations. Here, the first challenge is to find a variety of systems that respond to the variety of situations to increase the assimilation process; but the actual important challenge is to integrate these systems sustainably into the farm production systems. Indeed, with the current restrictive national context (no agricultural politics, no incentive measures), it is crucial to create “perennial” production systems trough perennial process of innovation which is probably the most important challenge in the next future.CA does not extend spontaneously with surroundings farmers. It might be too early to effectively measure or record any trend in dissemination. However, a heart of knowledge, know-how and CA practices has been created with around 1000 farmers on 600/700 hectares of CA since 10 year. The Vakinankaratra highland area suffers from major technical constraints linked with major socio-economic lead to a situation where CA does not provide a solution acceptable for local farmers. Three main factors are not in favor of C A with current systems : i) competition for biomass between CA cropping systems (mulch) and livestock feeding requirement, 2) Coldness of the dry season with unadapted cover or associated crops leading to insufficient mulch and iii) delay in growth of crops in CA systemsThe do observe a new situation an a new trend since 10 years with the recent boom on upland rice on tanety, opening a new field or research to suggest solutions for soil fertility maintenance with rice based cropping systems.

The project Observatory for World Agricultures wants to elaborate a worldwide observatory collecting information on agriculture nin different countries and its evolution. At the moment five countries have been chosen as countries of reference, Madagascar is one of them. The geographical area of the study which has been chosen is the lake Alaotra. The study of the notions of vulnerability, resilience, durability and viability has been the main point concerning the choice, the calculation and the analysis of the necessary indicators leading to the elaboration of the observatory. Three different data lines have been chosen : i) The data base from the ROR, ii) The database from RFR and iii) The database from the agricultural diagnosis Bv-Lac (Durand, Nave& Penot). This paper presents some results with farming systems modeling using the two databases from the BVlac development project showing the indicators used through the example of a technical change with adoption of conservation agriculture.

Conservation Agriculture (CA) was introduced at the lake Alaotra, in Madagascar, in the 2000’s in a context of traditionnal mining upland agriculture and silting-up of lowlands rice fields. Land tenure pressure linked to the attractiveness of the area lead to the progressive colonization of surrounding upland hills (Tanety), very sensitive to erosion. Conservation agriculture tackles with a double challenges: i) maintain and/or increase household income and ii) preserve natural resources through sustainable agricultural practices in the long term. This paper assesses the economic impact of CA adoption on farmers’s income trough modeling representative farms selected according to a local typology,based on the last 5 years with a prospective analysis for the next 5 years. The BV-lac Project Field database highlighted a light increase of yield according to the age of CA systems. A buffering effect on climate hazards has been as well identified trough production stability over the years leading to adoption as part of a risk limiting strategy. Elements of the CA techniques are adopted spontaneously within surrounding farming systems leading to improvment of conventionnal tillage based systems. Smallholders agricultural practices evolution displays a high capacity for innovation.Modeling with a dedidated tool (Olympe is a budget analysis oriented tool) has highlighted that CA systems improve significantly net farm income in the midterm (5 to 10 years) and gross margin at plot scale. For farm holdings with few irrigated rice fields, mainly relying on upland agriculture, CA systems increase farming systems resilience to climatic events and price volatility as well as sustainable agricultural practices maintaining localand fragile ressources

Soil erosion of productive top soils is an obstacle for achieving an increased food production in a more sustainable way. The three principles of Conservation Agriculture (CA) of no tillage, permanent soil cover and crop rotations, are often seen as a promising solution. This study was undertaken within the framework of the CA2AFRICA project which aims at understanding the physical effects of CA and the reasons of its (non)adoption in Africa. A field level modeling approach was chosen to assess the effect of three types of CA cropping systems on soil loss, compared to a traditional cropping system for the region of Lake Alaotra in central Madagascar, using the Revised Universal Soil Loss Equation (RUSLE). The most accurate method for estimating erosivity R was based on daily effective rainfall data, resulting in a value of 8487 (SI units). For erodibility K, the average of five estimation methods was taken, resulting in a value of 0.038 (SI units). Three slope scenario’s were chosen, with LS values ranging from 0.6 to 4. Together, these factors form a potential erosion of about 484 ton·ha-1yr-1. The crop cover C was divided into a crop component estimated with percentage of canopy cover, and a mulch component estimated with the Mulch Factor. C-values were determined at half month time intervals for four cropping systems: 1) ‘Traditional’, a two year rotation of upland rice and maize with an average C of 0.56; 2) ‘Stylo 1’, a three year rotation including Stylosanthes guianensi at test field yielding an average C of 0.04; ‘Stylo 2’ as Stylo 1, but for situation at farmers’ fields, yielding an average C of 0.14 and 3) ‘Dolichos’, a two year rotation including Dolichos lablab with an average C of 0.13. Support practice values P were set at 0.4 and 0.1 for respectively the traditional and the CA cropping systems. Resulting annual soil loss (ton·ha-1yr-1) was about 87 for ‘Traditional’, 2 for ‘Stylo 1’, 5.5 for ‘Stylo 2’ and 9 ton·ha-1yr-1 for ‘Dolichos. Although validation with a Unit Plot is necessary, the estimated parameters give an indication of the effect of CA on soil loss and allow for future scaling up of soil loss quantification.