Maize-cowpea intercropping as an ecological intensification option for low input systems in sub-humid Zimbabwe: Productivity, biological N2-fixation and grain mineral content

•Two years on-farm trials on intercropping in poor soils in low inputs systems.•Land productivity increased by maize-cowpea intercropping.•Same proportion of N derived from the atmosphere for sole or intercropped cowpea.•Maize and cowpea grain mineral contents not impacted by treatment but by season.•Cowpea grain mineral contents (Fe, Zn, Mn, Cu, Ca, Mg, P, K) higher than for maize.