ABSTRACT

Field experiments were conducted between 2003 and 2006 to study the effect of fallow species and fallow duration on biomass production, soil nutrient contents, weed control and yam production in Umudike, South Eastern Nigeria. The experiment was laid out as a split plot in a randomized complete block design (RCBD), with three replications. The main plot treatments were duration of fallow (1 and 2 years) and the sub plot treatments were eight legume cover crops (Aeschynornene histrix, Centrosema brasilianum, Centrosema pascuorum, '2hamacrisia rotundifolia, Mucuna georgia, Mucuna ghana, Pueraria phaseoloides and Stylosanthes guanensis) in comparisor with natural fallow and natural fallow plus inorganic fertilizer (NPK Mg 12:12:17:2) at 400kg/ha. The yam variety used was Dioscorea rotundata (cv. Nwopoko). Biomass production was significantly higher in Stylosanthes guanensis than in the other cover crop species except Aeschynomene histrix at 6 and 12 months after planting (MAP). Slylosanthes guanensis also gave higher biomass than natural fallow at 3 and 4 MAP. Soil P and K were significantly higher after Mucuna ghana than after other legumes and natural fallow. Soil N and P were significantly higher with one than with two years of fallow. Weed biomass was consistently lowest in Stylosanthes guanensis than in other legumes cover crops except with Chamacrista rotundfo/ja, Mucuna ghana and Pueraria phaseoloides at 4 MAP and Aeschynoniene histrix at 12 MAP. Yam tuber yields obtained with Centrosema brasilianum after two years of fallow was significantly higher than the yie14 obtained with each of the other fallow species and duration except with Aeschynomene histrix after one year fallow and Centrosema pascuoruin, Mucuna georgia and Mucuna ghana after 2-year fallow.