L’objectif de ce document de travail est de montrer les résultats des enquêtes faites sur les systèmes conventionnels(non SCV) dans paysans de la zone Alaotra. Les données sont les suivantes:  Extraction des données de 2007 à 2010, par type de culture non SCV à partir de la base de donnée RFR_BV_Lac avec scenarii 27_11_2010 48 exploitations RFR de 2007 à 2009 15 exploitations RFR en 2010 Document de référence: BASE DONNES NON SCV_Sarra_Colomban_2011.xlsx La détermination de classes par culture est basée sur lesrendementsdes campagnes 2006/2007, 2008-2009 et 2009/2010, issue de la base de donnée du RFR BV-Lac. Nous avons calculé des rendements moyens par classe sur trois zones confondues au lac (BRL NE, BRL VSE, et AVSF) et sur les trois campagnes.

Conservation Agriculture (CA) was introduced at the lake Alaotra, in Madagascar, in a context of yield drop and silting-up of rice fields in the low lands. Land tenure pressure linked to the attractiveness of the area leads to the colonization of surrounding uplands, very sensitive to erosion. Conservation agriculture deals with a double constraint: i) increase household income ii) preserve natural resources. This study assesses the economic impact of CA systems on the income of modelised representative farm holdings for each area, through a prospective analysis in the midterm, 10 years. The processing of the databases from the diffusion operators has highlighted a light increase of yield according to the age of CA systems. These systems also have a buffering effect on climate hazards. Parts of CA systems diffuse spontaneously within farming systems. Surveyed cropping systems have been deeply modified by the effect of BV-Lac project; the smallholder’s population at the lake has innovative practices. Modeling has highlighted that CA systems improve significantly net farm income at plot scale in the midterm. The results are not as clear at farm scale. Indeed, the higher the farl income generated by irrigated or PWC rice fields is, the lower is the impact of CA systems on farm income. For farm holdings with few irrigated rice fields, CA systems insure the income by stabilizing and improving yields of rain fed crops.

The Lake Alaotra basin, surounded by high hills, is one of Madagascar’s primary rice producing regions, with over 100,000 hectares of rice fields. The region, is known as the "Malagasy rice granary". It produces an annual surplus of rice, and plays an important role in inter-regional trade, serving as a critical supplier of rice for the country’s capital Antananarivo, and largest port city, Tamatave. Rice production of the Alaotra was greatly enhanced through the hydro-agricultural schemes managed by SOMALAC (Société Malgache d'Aménagement du Lac Alaotra) in the 1960s and 1970s (Devèze, 2007). For 40 years, the demographics of the region have been marked by the high rates of immigration of farming families attracted to the wealth of the region. High population growth,has tripled the population since 1960 (and is doubling it every 18 years) leading to land tenure saturation and an increasing pressure on natural resources (Durand et Nave, 2007). Land tenure is saturated in low land areas (Irrigated Paddy Fields (IPF), Poor Water Control Paddy Fields (PWCPF) and baiboho). Therefore, when seeking new land for cultivation, farmers tend to expand onto uplands, the tanety (hills), previously under- developed or reserved for grazing herds (Domas et al., 2009). Deforestation, repeated burning, and the exclusion of fallow periods have accelerated natural erosion processes in these degraded and fragile soils,, resulting in an alarming loss of soil fertility, siltation of downstream irrigation canals, and declining yields to fisheries. Today, on 30, 000 hectares of rice fields developed by the SOMALAC, between 10,000 and 15,000 hectares are currently under good water control (Durand and Nave, 2007). In the context of increasing degradation of natural resources, research and development programs (both Malagasy national and French) have set up projects for the extension of agro- ecological techniques, based on the principles of conservation agriculture (CA). Direct mulch cropping (DMC) is one of these techniques, introduced in the Lake Alaotra region in the 1990’s, with the objective of introducing new cropping systems to improve yields while preserving natural resources. Having encountered many problems (constrained access to inputs, technical complexity that is overwhelming for small farms), the adoption of CA grew significantly since 2000 with the launch of the project “Mise en valeur et protection des Bassins Versants du Lac Alaotra » (BVLac). The project, started in 2003 and was conducted in two phases over a period of five years each, from technical advisory at the field scale, to a holistic approach at the farm scale