PRODUCTION AND ECONOMIC-EVALUATION OF WHITE GUINEA YAM (DIOSCOREA-ROTUNDATA) MINISETTS UNDER RIDGE AND BED PRODUCTION SYSTEMS IN A TROPICAL GUINEA SAVANNA LOCATION, NIGERIA

The productive and economic attributes of a local variety, Dan Onitcha, of white Guinea yam (Dioscorea rotundata Poir.) minisetts were assessed under two production systems - planting on ridges and on beds at the same plant population density of 40 000 stands ha-1 during the 1987 to 1989 production seasons. The bed system improved emergence percentage (E%) by 11, stand establishment by 18% and gave 28% increase in total tuber production over the ridge system. An average of 67% of total harvested tubers were classified as ware yams (401-3000 g) under the bed system, and 77% as seed yams (less than 400 g) under the ridge system. Based on gross margin analysis, the economic returns from the bed system was 275% more than returns from the ridge system, due in part to the high proportion of the more valuable ware yams realized from the bed system. On both technical and economic grounds, the bed system was superior to the ridge system.