Effect of Fallow Species and Fallow Duration on Soil Fertility, Biomass and White Yam (Dioscorea rotundata Poir) Production

Abstract

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 (Aeschynomene histrix, Centrosema brasilianum, Centrosema pascuorum, Chamacrista rotundifolia, Mucuna georgia, Mucuna ghana, Pueraria phaseoloides and Stylosanthes guanensis) in comparison with natural fallow and natural fallow plus inorganic fertilizer (NPK Mg 12:12:17:2) at 400 kg ha−1. 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). Stylosanthes 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 2 years of fallow. Weed biomass was consistently lowest in Stylosanthes guanensis than in other legume cover crops except with Chamacrista rotundifolia, Mucuna ghana and Pueraria phaseoloides at 4 MAP and Aeschynomene histrix at 12 MAP. Yam tuber yields obtained with Centrosema brasilianum after 2 years of fallow was significantly higher than the yield obtained with each of the other fallow species and duration except with Aeschynomene histrix after one-year fallow and Centrosema brasilianum, Mucuna georgia and Mucuna ghana after two-year fallow.