Can yield variability be explained? Integrated assessment of maize yield gaps across smallholders in Ghana

•Estimated maize yield gaps ranged between 67% and 84% of water-limited potential yield.•Demonstration experiments showed the potential of improved varieties and fertilizers.•Farmers’ yields are determined by interacting, and often strongly varying, household, soil and management factors.•Integrated assessment of yield gaps using multiple methods avoids over-simplified conclusions.