In trials over 2 years at five locations in Northern Nigeria single inputs were removed from a package of maize practices. The improved variety was most important and increased the yield of the otherwise complete package by 86%. Early sowing and high plant population were not important in all trials. The high fertilizer treatment (125–50–50 kg NPK/ha) consistently exceeded the half rate, with a mean increase of 31%. It was suggested that, with clean weeding, priority should be given to the improved variety, high fertilizer and early sowing. High populations, involving changes to traditional techniques, may be introduced gradually.