Prospects and Potential of Bradyrhizobium diazoefficiens Based Bio-Inoculants on Soybean Production in Different Agro-Ecologies of Mozambique

Abstract

Soybean production in sub-Saharan Africa is increasing as farmers open more land areas for cultivation and replace other crops, such as tobacco, in favor of this legume crop. Despite the production is increased in Mozambique, demand for animal feed and oil is not satisfied. As such, farmers explore ways to improve yield per unit area of soybean by using bio-inoculants from various sources and agroecological adaptability. These bio-inoculants are seldom available during planting time, and retail at almost similar prices although yield varied based on the product source, handling, and the rhizobia strain carrier. Mozambique does not produce bio-inoculants, so it obtains the product from neighboring countries or as far as the South American continent. In this study, we evaluated the performance, ecological adaptability, and soybean productivity of seven Bradyrhizobium diazoefficiens strain-based bio-inoculants from several countries with different carrier materials: Biofix, Masterfix, Nitrofix, NitroZam, N-Fixer, Soygro Peat, and Soygro Liquid against a control (non-inoculated) on two soybean varieties Storm and TGx 1904-6F. The trial was conducted in the 2016 and 2017 growing seasons in three agroecologies of Mozambique at Angonia, Nampula, and Ruace. Data on nodulation, plant growth, biomass nitrogen content at beginning of podding (R3) stage, yield, and yield components of soybean were evaluated. Analysis of variance and contrast comparisons were performed on the Statistical Analysis System® 9.4. Nodule weight per plant variedly increased from 7.7 to 167.6 mg with inoculation of both varieties across environments. Plant tissue nitrogen content at the R3 stage was higher in inoculated non-promiscuous variety at 3.9% than the promiscuous counterpart with 3.7%. Storm, a non-promiscuous short-maturity variety of soybean, responded to inoculation and accumulated more N than the medium-to-late maturity promiscuous TGx 1904-6F. Higher N tissue content is an indicator of better nutritive value, as well as high-quality recyclable biomass of inoculated soybean. Both Storm and TGx 1904-6F responded to all inoculants variedly with NitroZam yield of 2,750 kg ha−1 being highest, while Soygro Liquid was lowest with 2,051 kg ha−1 but more than the check with 1,690 kg ha−1 across sites. There were varietal differences in 100-seed weight after inoculation where Storm (15.4 g) had heavier seeds than TGx 1904-6F (13.1 g). The results show that inoculation improved plant growth and development, increased nodulation, and gave higher yields for better economic returns among farmers. Inoculation has the potential of increasing soybean yield, nutritive value, and biomass quality within Mozambique.

Symbiotic effectiveness of Bradyrhizobium strains on soybean growth and productivity in Northern Mozambique

“…In the present study, soybean variety Zamboane (TGx 1904-6F) demonstrated significant increase in nodulation and yield-related responses to inoculation with all the inoculant strains used. This is consistent with the results of other studies with this variety and others (Gyogluu et al, 2016;Savala et al, 2021Savala et al, , 2022. The success of inoculation depends on many factors including the presence or absence of indigenous rhizobia (Thies et al, 1991;Sanz-Saez et al, 2015), environmental conditions such as soil moisture and nutrient status (Zahran, 1999;Hungria and Vargas, 2000) and the quality of the inoculant applied (Rodríguez-Navarro et al, 2010).…”

“…In Mozambique, Gyogluu et al (2016) reported that rhizobia inoculated soybean fixed up to 200 kg N ha −1 which accounted for 90% of N nutrition leading to 500 kg ha −1 yield advantage over the non-inoculated counterpart. Similar results of better crop growth and development, higher grain yields and profitability using microbial inoculant have been reported in soybean from Mozambique (Chibeba et al, 2020;Savala et al, 2021Savala et al, , 2022. In a Large-scale study in 10 SSA countries including Mozambique, Malawi and Zimbabwe, van Heerwaarden et al (2017) reported more than 200 kg ha −1 yield increases in soybean due to rhizobial inoculation.…”

“…A promiscuous soybean variety can form nodules freely with indigenous rhizobia (Kueneman et al, 1984). As a result of this varietal trait, varied responses to inoculation have been reported (Okogun and Sanginga, 2003;Osunde et al, 2003;Thuita et al, 2012;Savala et al, 2022). In the present study, soybean variety Zamboane (TGx 1904-6F) demonstrated significant increase in nodulation and yield-related responses to inoculation with all the inoculant strains used.…”

“…It is difficult for smallholder farmers to apply the required external inputs such as N and P fertilizers since they are expensive and unaffordable (Kyei-Boahen et al, 2017). Therefore, a low costinvestment such as rhizobia inoculation which costs about $10 ha −1 is becoming increasingly important due to affordability and economic incentives associated with the practice (Kyei-Boahen et al, 2017;Savala et al, 2021Savala et al, , 2022. Maximizing N 2 fixation by selecting competitive and effective inoculant strains would improve soil N content, increase crop productivity, and contribute to agricultural sustainability.…”

“…Several studies have demonstrated the benefits of using microbial inoculants in SSA (Masso et al, 2016;Kyei-Boahen et al, 2017;van Heerwaarden et al, 2017;Chibeba et al, 2020;Savala et al, 2022). In Mozambique, Gyogluu et al (2016) reported that rhizobia inoculated soybean fixed up to 200 kg N ha −1 which accounted for 90% of N nutrition leading to 500 kg ha −1 yield advantage over the non-inoculated counterpart.…”