Use of Tithonia Biomass, Maize Residues and Inorganic Phosphate in Climbing Bean Yield and Soil Properties in Rwanda

Abstract

Lack of adequate nutrient supplies from both organic and inorganic sources is the principal constraint to bean production in Rwanda. Field experiments were conducted in two sites, Rubona and Butare, Rwanda, in 2005/2006 to assess the effect of Tithonia diversifolia biomass and maize residues in the yield of climbing bean (Var. G2331) and soil chemical properties. The soil used for this experiment is Ultisols with contrasting properties; the soil of site 1 has high nutrient content compared to the soil of site 2. Seven treatments were studied including a control and either T. diversifolia biomass or maize residues applied alone, together or in combination with triple superphosphate. There was a significant positive effect (P < 0.01) in the yield of climbing beans in the two sites. Increased yields compared to the control were higher in site 1 than in site 2. The highest yield increase was achieved from the treatment of Tithonia plus maize residues and TSP (3.3 t ha^–1 for site 1 and 1.74 t ha^–1 for site 2). The combination of tithonia and TSP increased soil pH_w compared to control from 5.45 to 6.05 and 4.81 to 5.46, respectively, for sites 1 and 2. The high performance of Tithonia application in bean yield confirms its capacity to increase bean production compared to inorganic fertilizers at equal rates of P. It is therefore concluded that Tithonia and maize residues are a more effective source of nutrient resources for climbing beans apart from their positive attributes in positively influencing the chemical properties of the soils.