Les brachiarias sont des graminées (Famille des Poaceae) pérennes herbacées de type C4, originaires d’Afrique mais très largement répandues dans le monde inter-tropical. Les différentes espèces présentées ici produisent toutes une forte biomasse (fourrage de qualité), sont capables de supprimer les adventices et ont un système racinaire puissant et profond, capable de décompacter les sols, de les restructurer, d’injecter du carbone en profondeur et de recycler efficacement les nutriments lixiviés (rôle de “pompe biologique”).

Stratégie retenue pour l'implication de tous dans la logistique semencière en accompagnement de la diffusion des SCV.

Experiments conducted in the 1990's in various ecological zones of Madagascar allowed to propose a large range of cropping systems based on direct seeding on permanent soil cover (DSPSC). To propose solutions and face the many constraints of Malagasy farmers, a unique set of references was developed, for various agro-ecological and socio-economic conditions, with different levels of intensification and risk (Séguy, 2005). However, although the proposed systems had demonstrated their high agronomic, environmental and economic performances, and proved to be sustainable, their extension remained limited'until the beginning of the 21st century. Main reasons identified to explain this situation, apart from the limited financial resources consecrated to this task, were the very limited human resources and the lack of an approach for extension of knowledge intensive systems, in a difficult environment: subsistence agriculture, smallholders with limited investment means, degraded soils, poor infrastructures, etc. (GSDM, 2004)

Following falling cotton yields in North Cameroon (17kg/ha/an) and the degradation of natural resources, the cotton development corporation (SODECOTON) has put in place many projects since 1994 with the assistance of French Agency for Development (AFD) and French Ministry of Foreign Affairs (MAE). The principal techniques used up till date consist essentially in slowing down soil run-off thanks to anti-erosion land management techniques or soil fertility improvement using manure or fertilising tree crops.

Bermuda grass (Cynodon dactylon) is known as a very invasive weed, difficult to get rid of. All over the world, practices have been developed to try to eradicate this widely spread and common weed (Burton and Hanna, 1984). They are often based on intense land preparation with several ploughings, especially at the beginning of the dry season, and important work for removing the rhizomes and weeding during the cultivation period. However, Cynodon dactylon is a good forage, widely used by farmers to feed their animals. But it also has several properties of a good cover crop: growing on poor soil, rapidly covering the soil and thus preventing erosion, having a deep and dense rooting system (improving soil structure, recycling nutrients), suppressing most other weeds, etc. Trying to get benefit from these qualities instead of fighting against this «weed», TAFA (Tany sy Fampandrosoana) and CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement), with farmers, have developed techniques of direct seeding, using Cynodon dactylon as a soil cover, in various agro-ecological areas of Madagascar.

Bermuda grass (Cynodon dactylon) is known as a very invasive weed, difficult to get rid of. All over the world, practices have been developed to try to eradicate this widely spread and common weed (Burton and Hanna, 1984). They are often based on intense land preparation with several ploughings and important work for removing the rhizomes and weeding. However, Cynodon dactylon is a good forage and has several properties of a good cover crop: growing on poor soil, rapidly covering the soil and thus preventing erosion, having a deep and dense rooting system (improving soil structure, recycling nutrients), suppressing most other weeds, etc. Trying to get benefit from these qualities, TAFA and CIRAD have developed with farmers techniques of direct seeding, using Cynodon dactylon as a soil cover.

L'analyse des systèmes de production et des pratiques de cultures dans le nord du Cameroun et dans l'ouest et le sud-ouest de Madagascar nous a permis d'identifier différentes contraintes des systèmes traditionnels (systèmes employés depuis des générations) et conventionnels (proposés par les vulgarisateurs). En considérant tout le système d'exploitation, dans son contexte économique ou environnemental, des nouveaux systèmes de culture ont été proposés, associant le semis direct et une couverture végétale permanente du sol. Ces nouveaux systèmes prennent en compte les principales contraintes des systèmes traditionnels ou conventionnels. , Ils permettent le semis précoce, réduisent les goulots d'étranglement des besoins en main d'oeuvre, ainsi que les coûts de production, tout en permettant de contrôler les adventices, d'optimiser l'usage de l'eau. La fertilité des sols n'est plus dégradée et une meilleure intégration de l'élevage aux systèmes de culture devient possible grâce à une augmentation de la qualité et de la quantité de biomasse produite...

Developing and maintaining water control in paddy fields is difficult, costly and requires sufficient water reserves. Thus, even in the main rice growing area of Madagascar, the Alaotra lake region (800 metres above sea level), only 30 000 ha of paddy fields can be properly irrigated when over 70 000 ha will remain under poor water control. In these fields, traditional techniques based on irrigated cropping practices are very unreliable: late transplanting (which can be done only when sufficient water is available) and occurence of dry conditions at the end of the plant cycle lead to usually low yields (0.8 to 1 t/ha on average) and production is very unreliable (from nil, during the dry years to 3t/ha when rains are favourable), which makes crop intensification very hazardous. For such situations, a change in paradigm is proposed: abandoning irrigated practice and making the choice of growing upland or ",poly-aptitude", rice varieties (SEBOTA) with agro-ecological practices adapted to the specific field water regime.

Ce rapport fait la synthèse des résultats agro-écologiques des systèmes de culture mis en oeuvre en 2002/2003 sur les sites de références. Les résultats obtenus sur les terroirs au Lac Alaotra sont détaillés et commentés.Il synthétise également les principaux enseignements de 5 années de recherche-action par TAFA dans les différentes éco-régions.

Early sowing,Reducing labor force bottleneck,Reducing production costs,Weeds control,Increasing water use efficiency, Stopping soil fertility degradation, Better integration between crops and livestock, Improving the quality and the quantity of the produced biomass