Comparative effects of mechanized and manual tillage practices on soil properties and the yield of seed yam in Southwest Nigeria

The effects of various tillage systems on soil physical and chemical properties and the yield of seed yam were investigated and compared in a research conducted in Akure (Latitude 7o18’N and Longitude 5o15’E)-Nigeria in 2008 and 2009. Three tillage systems comprising ploughing plus harrowing, ploughing plus harrowing plus ridging and manual ridging were replicated three times in a randomized complete block experimental design. Healthy yam tubers weighing about 1 kg were cut into minisetts of about 25 g, treated with a mixture of wood ash and demosan fungicide and planted in nursery made of moist sawdust. The minisetts sprouted after three weeks and at four weeks, transplanted to the field prepared under the various tillage methods. 100 kg/ha NPK 15-15-15 were applied at eight weeks after transplanting the seed yam seedlings while soil physical and chemical properties were taken at five months and the harvesting of seed yam done at six months after transplanting the seedlings. Soil bulk density was significantly high with a correspondingly lower porosity in the ploughed plus harrowing plot while the least values were observed in the ploughing plus harrowing plus ridging plot. The organic matter, nitrogen, phosphorus, potassium and the cation exchange capacity were in the medium adequate range for good seed yam growth. Bulk density was a major factor that influenced seed yam performance with the ridged plots producing lower bulk density and higher tuber weight and yield. The tuber weight and yield were comparable in both the mechanically and manually ridged plots.Keywords: Mechanized and manual tillage, comparative effects, soil properties, seed yam yiel