Abstract
To support the adaption of soybean [Glycine max (L) Merrill] cultivation across Central Europe, the availability of compatible soybean nodulating Bradyrhizobia (SNB) is essential. Little is known about the symbiotic potential of indigenous SNB in Central Europe and the interaction with an SNB inoculum from commercial products. The objective of this study was to quantify the capacity of indigenous and inoculated SNB strains on the symbiotic performance of soybean in a pot experiment, using soils with and without soybean history. Under controlled conditions in a growth chamber, the study focused on two main factors: a soybean cropping interval (time since the last soybean cultivation; SCI) and inoculation with commercial Bradyrhizobia strains. Comparing the two types of soil, without soybean history and with 1–4 years SCI, we found out that plants grown in soil with soybean history and without inoculation had significantly more root nodules and higher nitrogen content in the plant tissue. These parameters, along with the leghemoglobin content, were found to be a variable among soils with 1–4 years SCI and did not show a trend over the years. Inoculation in soil without soybean history showed a significant increase in a nodulation rate, leghemoglobin content, and soybean tissue nitrogen concentration. The study found that response to inoculation varied significantly as per locations in soil with previous soybean cultivation history. An inoculated soybean grown on loamy sandy soils from the location Müncheberg had significantly more nodules as well as higher green tissue nitrogen concentration compared with non-inoculated plants. No significant improvement in a nodulation rate and tissue nitrogen concentration was observed for an inoculated soybean grown on loamy sandy soils from the location Fehrow. These results suggest that introduced SNB strains remained viable in the soil and were still symbiotically competent for up to 4 years after soybean cultivation. However, the symbiotic performance of the SNB remaining in the soils was not sufficient in all cases and makes inoculation with commercial products necessary. The SNB strains found in the soil of Central Europe could also be promising candidates for the development of inoculants and already represent a contribution to the successful cultivation of soybeans in Central Europe.
Highlights
Soybean (Glycine max [L.] Merr.) is one of the most extensively cultivated crops worldwide, representing approximately 57 and 79% of the global pulse area and production in 2018, respectively (FAO, 2020)
Nodulation and shoot nitrogen concentration differed among the varying Soybean cropping interval (SCI) in non-inoculated soils, but there was no consistency in the trend in both locations
A significant variability between the locations in response to inoculation with commercial inoculants was observed in the soils with soybean history
Summary
Soybean (Glycine max [L.] Merr.) is one of the most extensively cultivated crops worldwide, representing approximately 57 and 79% of the global pulse area and production in 2018, respectively (FAO, 2020). In Europe-28, areas under soybean cultivation are still below 1 million ha, and the region depends largely on imports from North and South America to meet its protein demand (Watson et al, 2017). In areas where soybeans were domesticated centuries ago, soybean-nodulating Bradyrhizobia (SNB) usually survive and are present in soils in high diversity, making the utilization of commercial inoculants less important (Zhang et al, 2011). Enhancing soybean expansion and productivity in Europe will depend on effective inoculation, and farmers currently cultivate soybeans, using commercially available Bradyrhizobium inoculants (Zhang et al, 2003; Zimmer et al, 2016; Reckling et al, 2020)
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