Influence of Beans and Spacing on Management of Weed and Soil Fertility to Improve Rice Productivity through Bean-Rice Sequential Cropping, Mbarali –Tanzania

Weed management on rice fields is necessary to reduce yield loss. A field experiment was conducted during the season 2020-21 at Mbuyuni Irrigation Scheme of Mbarali District to assess the effect of bean varieties and spacing on management of weed and soil nutrients in a bean-rice sequential cropping. The study was laid out as a 3×3 factorial experiment arranged in Complete Randomized Block Design (CRBD) with three replications. Treatments in bean phase were bean varieties (Wanja, Njano Uyole and Mshindi) and row spacing (50 cm × 20 cm (S1), 50 cm × 15 cm (S2) and 50 cm × 10 cm (S3)) while treatments in the rice phase were bean residues at the weight of 5 t/ha, 10 t/ha and 15 t/ha for each bean varieties, weight of 5 t/ha used as control since it is farmer practice. The data were collected weed biomass, weed height, bean yield and rice yield and analysed using Genstat software (16^th edition) and the means were separated using Tukey's significant test at a 5% level of significance. The results indicate significant effects (P=0.05) for treatments interaction of bean varieties and row spacing on weed count per m² and weed biomass. The interaction of Wanja 50 cm × 10 cm had weed count of 17 per m² and biomass of 7.3 gm^-2. The interaction of bean variety and row spacing were significant (P= 0.05) on the number of pods per plant, bean biomass and grain yield. The incorporated bean residues, significantly (P=0.001) improved spikelet count and weight of 1000 rice seeds whereby 15 t/ha had a high spikelet (20) and panicle weight of (24.7 g/panicle). From the results it is recommended that   farmers should adopt bean- rice sequential cropping using bush bean varieties at the spacing of 50 cm x 20 cm on weed management and farmer should applying 15 t/ha of crop residues to improve soil nutrients.