Evaluation of rhizobial inoculants on the productivity of soybean varieties grown on an acidic soil in Rwanda

Abstract

Several high yielding soybean varieties have been introduced in Rwanda but yields have remained low and even declining especially in areas with acidic soils. Consequently a number of rhizobial inoculants were introduced to enhance biology nitrogen fixation but with varied quality and efficacy. Therefore, specific objectives of this study were to: i) determine the effectiveness of different soybean rhizobial inoculant products on soybean production in an acidic soil; ii) compare the response of different soybean genotype to rhizobial inoculants products to increase soybean yield on an acidic soil; and iii) to determine effectiveness of rhizobial inoculants on soybean grown under different soil texture for enhance soybean production. Screen house experiments were done at Rubona Station in Rwanda. Efficacy treatment included: (i) four biofertiliser products (Biofix, Legufix, RB.Asoy and RAB inoculants), (ii) two liming rates (0 and 2.5 t ha-1), (iii) absolute control and (iv) Urea at 100 kg N ha-1. Treatments to assess texture effect were: (i) four biofertiliser product (Biofix, Legufix, RB.Asoy and RAB inoculants) and (ii) two different soil textures (sandy and clayey texture), (iii) absolute control all tested on variety PK6. The treatments were arranged in Completely Randomized Design. All the inoculants products significantly (p< 0.05) increased nodulation, above ground biomass and tissue nitrogen concentration and strain N-fixing efficiency on all the soybean varieties. On the contrary, liming depressed the effectiveness effect of the inoculant products. Furthermore, nodulation and biological fixed N significantly (p<0.05) improved more in sandy than clayey soils. It was concluded that variety Sc SAGA should be inoculated with any of the products but Biofix and RAB products be used for PK6 then Legufix, RB.Asoy and RAB for SB24.