Impact of no tillage and mulching practices on cotton production in North Cameroon: A multi-locational on-farm assessment

The applicability of conservation agriculture (CA) in sub-Saharan Africa (SSA) is poorly documented. In the "Nord" and "Extreme-Nord" provinces of Cameroon, in a 2-year rotation between a cereal (maize or sorghum) and cotton, conventional techniques were compared with CA. The study was conducted from 2001 to 2006 in 662 plots in 243 farmers' fields. Cereal treatments compared were conventional management techniques and CA consisting in the production of mulch using cover crops (Brachiaria ruziziensis, Crotalaria retusa, Dolichos lablab, Mucuna pruriens, Vigna unguiculata) intercropped within the cereal. In the "Extreme-Nord" province up to 9.7 t ha(-1) of vegetative biomass was produced in the CA plots with sorghum and cover crops against up to 4.8 t ha(-1) for sorghum alone in conventional plots. In the "Nord" province maize + cover crops produced up to 5.2 t ha(-1) of biomass against up to 2.5 t ha(-1) for maize alone. In both provinces, the cereal grain yields were equivalent or higher in CA compared to conventional plots. In 18 fields of the "Extreme-Nord" province the mulch remaining the year after sorghum + B. ruziziensis is mainly comprised between 3 t ha(-1) and 5 t ha(-1). Cotton treatments compared were T (tillage), NT (no tillage), and NTM (no tillage with mulch). In both provinces these treatments differed in soil cover, number of localized herbicide sprays used, ridging, and amount of nitrogen fertilizer used. In the "Extreme-Nord" province treatments differed also for the number of weeding and the date of the first weeding. In the "Extreme-Nord" province cotton yields were 12% lower for T and 24% lower for NT than for NTM. Cotton yields were regressed on crop husbandry indicators and used inputs. After a manual backward removal in a multiple linear regression respectively no parameters were found to significantly influence yield for T, only one parameter for NT, the number of herbicide sprays used at sowing, and three parameters for NTM: difference between heavy clay and silty loam, application of NPK fertilizer, sowing date. In the "Nord" province no difference in cotton yield was observed between T, NT and NTM. The flowering period was longer for NTM vs NT in the "Extreme-Nord" and the "Nord" provinces and NTM vs Tin the "Nord" province, respectively 13, 9 and 8 days. Although we show that CA techniques can have benefits at field level, further studies are needed to assess their suitability at farm and village levels. (C) 2010 Elsevier B.V. All rights reserved.