Performance of sweet potato cultivars intercropped with maize. II: Total dry matter production and tuber yield responses to staggered maize planting dates

The effects of maize planting date on sweet potato growth and yield performance were examfined in two seasons. Sweet potato cultivars '049' and 'TIS 2328/6' and maize cultivar 'X304B' were used. During the mid-dry to mid-wet season, significantly (P < 0.05) lower total dry matter (DM) and tuber yields of 'TIS 2328/6' and '049' were obtained from mixtures with maize planted six weeks and three weeks, respectively, before the sweet potato cultivars. Sweet potato DM production was not significantly affected in the mixtures during the mid-wet to mid-dry season and tuber yield of 'TIS 2328/6' showed no response to maize planting date while '049' produced significantly (P < 0.05) lower yields in mixtures with maize planted simultaneously with or after sweet potato. In both seasons intercropping adversely affected tuber number and size. Seasonal variation in responses to maize planting date were attributed to genotypic differences in tolerance to environmental stresses. The Land Equivalent Ratio was highest when maize was planted simultaneously with, or earlier than, sweet potato.