Indigenous rhizobia strains: The silver bullet for enhanced biological nitrogen fixation and soybean (Glycine max (L.) Merr. ) yield under different soil conditions in South Kivu province, Democratic Republic of Congo

Abstract

Soybean is an important crop in the Democratic Republic of Congo, a country faced with high levels of war induced malnutrition but its productivity is limited by poor soil fertility coupled with low access to nitrogen mineral fertilizers. Commercial rhizobia strains introduced in 2010 failed to adapt and increase soybeans yields at desired level. We studied the performance of six indigenous rhizobia strains in enhancing soybean productivity compared to two commercial strains USDA110 and SEMIA5019. The study was carried out in the greenhouse and field of Kalambo station of International Institute of Tropical Agriculture (IITA), D. R. Congo during 2016/2017 cropping season. The treatments included: (1) N-, control without inoculation and N-fertilizer; (2) N+, non-inoculated control with 80 kg of N ha −1 ; and inoculated with (3) commercial strain Bradyrhizobium diazoefficiens USDA110; (4) commercial strain Bradyrhizobium elkanii SEMIA5019; (5) local strains Bradyrhizobium japonicum NAC17; (6) NAC22; (7) NAC37, (8) NAC42 (9) NAC 46 and (10) NAC78. Greenhouse and field experiments were laid out as completely randomized design and randomized complete block design respectively. The best inoculation treatments across all experiments were the indigenous strains NAC46 and NAC17 which nodulated equally or better than the commercial strain USDA 110. In the field NAC46 and NAC17 increased soybean grain yield from 2.4 to 3.3 t ha-1 and 3.4 t ha-1 ; indicating the increase of 68.7 and 70.8% respectively, over the commercial strain USDA110. The results demonstrated that indigenous rhizobia NAC46 and NAC17 would thus be the silver bullet to enhanced BNF and soybean yields in South Kivu province of Democratic Republic of Congo.

Di-ammonium phosphate (DAP) and plant density improve grain yield, nodulation capacity, and profitability of peas (Pisum sativum L.) on ferralsols in eastern D.R. Congo

“…Wasike et al (2009a, b) confirmed also that applying P could improve nodulation capacity of different soybean varieties. Differences in nodulation capacity can also be due to varietal effect, soil acidity level, and P concentration (Ndusha et al 2019). With better nodulation, BNF satisfies up 30-80% of plant N requirement (Erman et al 2009).…”

The role of Molybdenum in relation to Rhizobium sp. in increasing biological Nitrogen fixation and soybean growth

“…In line with previous research that N element plays a very important role in the formation and growth of vegetative organs (stems, leaves and roots), so that increasing the availability of N will increase the area of plant leaves which affects its assimilation. The N fixation process produces N which is released from the nodules in the form of urea (allantoin and allantoic acid) which is then translocated to the leaves and used for chlorophyll biosynthesis [14].…”

Soybean-Nodulating Rhizobia: Ecology, Characterization, Diversity, and Growth Promoting Functions

“…On the other hand, indigenous rhizobia have been observed to be more effective in fixing N than the commercial inoculants which have been previously used in soybean (Musiyiwa et al, 2005;Thuita et al, 2012;Thilakarathna and Raizada, 2017). The study conducted by Ndusha et al (2019) demonstrated the outperformance of indigenous species of B. japonicum over the commercial strain Bradyrhizobium diazoefficiens USDA110 by increasing the yield of soybean by 68.7 and 70.8% under greenhouse and field conditions, respectively. Similarly, Chibeba et al (2017) observed effective nodulation of 85 indigenous soybean nodulating rhizobia isolates under greenhouse conditions, whereby 10 isolates performed better than the best commercial reference strain, B. diazoefficiens USDA 110.…”