Seed pre‐inoculation with Bradyrhizobium as time‐optimizing option for large‐scale soybean cropping systems

Abstract

Nitrogen is a key nutrient for soybean cropping and can be fully supplied by the biological nitrogen fixation (BNF) process. Inoculation with elite Bradyrhizobium strains greatly improves the supply of N to soybean; however, inoculation of large areas in short-sowing windows delays the sowing process, demanding the development of technologies for pre-inoculation. Here we report the evaluation of a liquid formulation containing cell protectors that proved, in four field experiments located in different edaphoclimatic conditions of Brazil, symbiotic performance comparable to the peat-based inoculant, traditionally considered as the best carrier. The liquid inoculant was also effective when applied to seeds not treated with pesticides 15 days before sowing, providing efficient BNF and timeflexibility to the farmers. Benefits of the liquid inoculant in improving grain yield were confirmed in two areas cropped for the first time and devoid of Bradyrhizobium, with an average increase of 89%, and also in two areas traditionally cropped with inoculated soybean, with an average increase of 6.8%, both in comparison to the non-inoculated control without N-fertilizers (NI). It is worth mentioning that, also in comparison to the NI control, the addition of 200 kg N ha −1 impacted grain yield in +54% and −1,8%, in new and traditional areas, respectively, indicating that BNF was more effective than the application of N-fertilizer. Large increases in total N content in grains were observed as well in response to the liquid inoculant, on average 47% and 27%, when compared to the NI and NI + N controls, respectively.

Inoculant Formulation and Application Determine Nitrogen Availability and Water Use Efficiency in Soybean Production

“…Therefore, use of inoculation in this study indicated that soybean yield can be increased by 1052 kg ha À1 over the national average figure. Our study observed that inoculant application on seed (2308 kg ha À1 ) gave higher yield than soil application (2228 kg ha À1 ) agrees with the report by [57] where seed inoculation 2842 kg ha À1 was greater than 2678 kg ha À1 for soil inoculation on planting line. Seed inoculation plus good adhesive agent and proper mixing of the seeds in the bag enables better distribution of the rhizobia cells per seed-grain.…”

Response of Soybean (Glycine max (L.) Merrill) to Mineral Nitrogen Fertilization and Bradyrhizobium japonicum Seed Inoculation

“…In the study carried out in Poland and reported by Lorenc-Kozik and Pisulewska [32], cv. Aldana inoculated with B. japonicum yielded 22.7% higher without N fertilization than after applying the rate of 30 kg N. Additionally, Hungria et al [45] state that inoculation improves seed yield and there is no need for N fertilization in Brazil. Our research showed that in some cases N fertilization in combination with inoculation excels the inoculation alone.…”

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

“…A study conducted in Vietnam also reported that peat-based bio-inoculants yielded 2.00 and 2.18 t ha −1 against the liquid-based counterparts 1.96 and 2.12 t ha −1 for two rhizobia strains designated as G5 and G6, respectively (Thao et al, 2001). Contrasting studies have also shown that liquid-based bio-inoculant yields more than peat-based bioinoculants (Hungria et al, 2020;Gatabazi et al, 2021). This justifies that both liquid and peat-based bio-inoculants lead to increased yield in soybean although their effectiveness would depend on handling and the prevailing agroecological conditions.…”