Effect agronomic practices on growth and yield of yam bean in Eastern Democratic Republic of Congo

Abstract

The yam bean (Pachyrhizus ssp) has three closely related species with different agro ecological origins that include, Amazonian yam bean (P.tuberosus), Mexican yam bean (P.erosus) and the Andean yam bean (P.ahipa) It is a leguminous crop closely related to soybean (Glycina max) but produces root tubers that can be consumed cooked, processed or even raw. However consuming raw seed should be avoided as these contain a toxin called rotenone. Flowers are often pruned to increase fresh tubers yield. Yam bean is a recent introduction in Democratic Republic of Congo, (DRC) and currently has less understood adaptation to the country’s various agro-ecologies. The objective of this study was therefore to investigate potential options for fitting yam bean into new or existing cropping systems of Eastern DRC. Two yam bean accessions were for two seasons 2013/B and 2014/A, evaluated across three locations of South-Kivu province namely, Cibinda (2000 m.a.s.l), Bushumba (1500 m.a.s.l) and Runingu (900 m.a.s.l). The effects of harvesting dates of yam bean at four, five and six months after planting were studied. Data was collected on growth, tuber yield, disease and pest incidence. Furthermore the influence of planting on either a flat seedbed or on ridges on yam bean tuber growth and yield was evaluated. The effects of intercropping yam bean with maize on yam bean tuber and maize growth, yield, disease and pest incidences were also investigated. The best growth, tuber yield and dry matter content were achieved at six months after planting. Yam bean grown on ridges yielded higher than the crop grown on flat seedbeds. Also observed was a marked advantage of in inter-cropping yam bean with maize as inferred from the Land Equivalent Ratio ¬(LER). Based on yam bean and maize growth and yields, Runingu was better site followed by Bushumba while season 2014/A was better than 2013/B. It was also observed that accession 209036 was better than 209034 based on yam bean growth, yield and dry matter. Yam bean harvested at six months after planting were more affected by pests and diseases. It was also observed that more pests and diseases affected yam bean and maize grown as monocrop compared to intercropped plants. We suggest evaluation of yam bean production in other parts of the country. Farmers could practice ridging and intercropping yam bean with maize for better production of yam bean. We recommend yam bean accession 209036 to farmers.