How can more biomass be produced for direct seeding mulched-based cropping systems in sub-saharan Africa? Example in North Cameroon

In North Cameroon, from 2001 to 2006, more than 250 farmers tried direct seeding mulch-based cropping systems (DMC) in their fields. DMC systems were based on farmer traditional rotation i.e. cereal//cotton. Farmers compared on their own field cereals (maize, sorghum, millet) cultivated with conventional techniques and the same cereal conducted with DMC techniques i.e.: i) intercropped with a cover crop (Mucuna pruriens, Brachiaria ruziziensis, Crotalaria retusa, Vigna unguiculata, Dolichos lablab), ii) sowed without ploughing from the first or the second year of experimentation. Associations were made for the following objectives: i) produce aboveground biomass to produce mulch for the following crop (mainly cotton), ii) improve the soil's physical and chemical quality through the contribution of associated plants, iii) produce forage, iv) help to control weed, v) protect the soil surface against erosion and rain impacts, vi) produce grains for human or animals consumption. Each of the 5 cover crops used are different regarding their fulfilments of above objectives and their adaptation to North Cameroon local agro-climatic conditions (rainfall from 700 to 1200 mm). Thus, Brachiaria ruziziensis produces aboveground biomass in quantity (4-5 T of dry matter/ha even when associated with cereal) and quality (persisting of the mulch for over one year after production). Further, it seems to be very efficient in controlling Striga hermonthica and it is a good forage. However, it can impoverish the soil if its biomass is exported several times without any fertiliser or manure input. Crotalaria retusa is a nitrogen fixing legume and thus can improve soil fertility. Furthermore, this plant is non edible for cattle, which is an advantage for farmers who cannot protect their field from grazing during the dry season. C. retusa is also very efficient to fight against other weeds. -25 Six years of experimentation with farmers permits us to produce practical recommendations for intercropping of cereals with cover crops: sowing .