Effects of biofertilizers on grain yield and biological nitrogen fixation of tepary bean

Abstract

Tepary bean, a drought-tolerant bean, has become popular among poor small-scale farmers in semi-arid countries. Field experiments were conducted on the effect of biofertilizers (Bradyrhizobium japonicum (B. japanicum) inoculation, versicular arbuscular mycorrhizae, and seaweed extract) on grain yield and biological nitrogen fixation of tepary bean in two different locations, namely Syferkuil and Ga-Molepo farm. One-way, two-way, and three-way analysis of variance (ANOVA) were used to compare bradyrhizobium inoculation, versicular arbuscular mycorrhizae (VAM), and seaweed extract application performance on plant growth and yield parameters (50% emergence, 50% flowering, plant height, chlorophyll content, number of branches per plant, number of pods per plant, pod length, 90% maturity, number of seeds per pod, 100 seed weight, pod weight and grain yield). Amongst these plant growth and yield parameters, a significant difference was observed in emergence, plant height, chlorophyll content, number of branches per plant, number of pods, pod length and number of seeds per plant in response to location, VAM, and seaweed extract. The location had significant differences in 50% emergence, plant height, chlorophyll content, number of branches per plant and number of pods per plant. VAM showed a significant difference in plant height, chlorophyll content, pod length and the number of seeds per pod. Seaweed extract had a significant effect on plant height and pod length. The interaction effect of VAM and seaweed extract levels at Syferkuil showed no significant impact on the chlorophyll content of tepary beans. A significant difference was observed in chlorophyll content in response to the interaction effect of VAM, seaweed extracts and location. The interaction of location, VAM and seaweed extract on chlorophyll content also observed a significant difference. This study also determined the treatment effect on the tepary bean's biological nitrogen fixation (BNF). The 15N natural abundance approach was used to evaluate nitrogen fixation. Shoot dry matter, %Ndfa and N-fixed of tepary bean grown at Ga-Molepo increased significantly than at Syferkuil. Versicular arbuscular mycorrhizae, bradyrhizobium inoculation and seaweed extract had no significant difference in dry matter, %Ndfa and N-fixed. However, the results showed that treatments influenced these parameters. VAM (inoculated), seaweed extract (application) and bradyrhizobium (un-inoculated) fixed the most N at Ga-Molepo (164.96; 183. 81 and 180. 25 kg/ha, respectively) and therefore showed more significant dry matter accumulation. At Syferkuil, VAM (un-inoculated), bradyrhizobium (inoculated) and seaweed (no application) contributed the most symbiotic N (56. 1; 43. 48 and 42.97 kg/ha, respectively). Tepary beans planted at Ga-Molepo significantly obtained greater mean dry matter (32. 70) than Syferkuil (16. 47). Tepary beans grown at Ga-Molepo significantly received a greater mean %Ndfa (27. 19) at Syferkuil (12. 57). The percent N derived from fixation was 35% at Syferkuil and 22% at Ga-Molepo. These outcomes confirmed the view of this study that production and biological nitrogen fixation of tepary beans (and other grain legumes) can be enhanced using biofertilizers