Maize grain and straw yields over 14 consecutive years in burned and mulched Mucuna pruriens var. utilis and Pueraria phaseoloides relay cropping systems

The cover crops Mucuna pruriens var. utilis and Pueraria phaseoloides were introduced to African farmers to improve crop production on degraded soils, yet they appear not to be adopted at scale. In the humid forest zone of West and Central Africa, the dominant Acrisols and Nitisols are inherently poor even when not degraded through agriculture. In this zone, sole maize cropping and vegetable production systems are gaining importance, yet both suffer from nutrient deficiencies. Cover crops were often introduced along with a system change, requiring biomass retention, mainly for nutrient retention reasons. Farmers in the zone commonly use slash and burn systems due to added weed control and ease of operations on clean fields. This study evaluated mucuna and pueraria with and without burning the fallow biomass in an annual sole maize crop relay system against the burned and retained natural fallow. Over 14 consecutive years, biomass burning did not cause lower maize grain yields in any of the fallow types, on the contrary, the economically important marketable cob yields were higher when biomass was burned (mulched 2.10 cobs m(-2) vs. 2.26 cobs m(-2) when burned, p < 0.07). After cover crop fallow, maize grain yields were significantly higher than after natural fallow (1.92 Mg ha(-1)) over the 14 years, with maize yields in the pueraria treatment (2.63 Mg ha(-1)) out yielding those in the mucuna treatment (2.28 Mg ha(-1)). Maize produced 1.92 cobs m(-2) in natural fallow, significantly less than in the mucuna (2.23 m(-2), p < 0.013) and the pueraria (2.39 m(-2), p < 0.001) fallow. Introducing mucuna or pueraria cover crops into slash and burn systems appears as a suitable measure to increase yields without changing the land preparation approach.