Policy makers and farmers in north-west Europe are expressing a growing interest in soybean production. However, cool and wet climatic conditions in this region pose challenges for this crop in terms of reaching maturity and producing sufficient yield and create additional disease pressure from the fungal pathogens Sclerotinia sclerotiorum and Rhizoctonia solani. To increase the chance for successful introduction of this new crop in Belgium and to determine the main issues for local soybean breeding programmes, 14 early maturing varieties were screened over a 2-year-period for their agronomic performance. Based on novel bioassays, susceptibility to S. sclerotiorum and R. solani anastomosis group (AG) 2-2IIIB was evaluated. The varieties tested were able to reach sufficient maturity (average seed moisture content of 19.0%) by the beginning of October. Significant differences were observed in most agronomic characteristics, with seed yield and protein content ranging from 2002 to 2916 kg dry matter/ha and 35.5–43.3%, respectively. Taller varieties ripened later but reached higher protein levels compared with shorter varieties. Tolerance to lodging was correlated with seed and protein yield but was not correlated with plant height. Large seeds corresponded with a high protein content. Susceptibility to S. sclerotiorum reflected significant differences between varieties. In contrast, levels of susceptibility to R. solani AG 2-2IIIB were similar between most varieties, with only the variety Primus showing significantly less disease. The results of the current study hold promise for a successful introduction of soybean cultivation in north-west Europe and areas for further crop improvement have been identified.

Bacterial inoculation of soybean seeds to improve biological nitrogen fixation is a well-known practice to achieve higher seed and protein yield with reduced fertilization. The optimal inoculation strategy in temperate regions is unknown because soybeans are rarely cultivated under colder growing conditions. The aim of the present work was to determine the most suitable inoculation strategy for soybean cultivation in Belgium. Field trials were set up with four Bradyrhizobium inoculants (HiStick, Force 48, Biodoz and Optimize) at two locations over 2 years (2014–2015) and compared with a non-inoculated control treatment. In addition, HiStick was tested at three doses and Optimize at two time periods prior to sowing. Under Belgian conditions, all inoculants were effective in establishing rhizobial symbiosis, resulting in increased yield, protein content, protein yield and thousand-grain weight compared with the non-inoculated control. A single dose of HiStick was sufficient to establish symbiosis. Pre-inoculation with Optimize 2 weeks before sowing gave an intermediate performance for most parameters between the non-inoculated control treatment and inoculation with Optimize 24 h prior to sowing. Among the four products tested, Biodoz seemed the best product for inoculation under cool growing conditions. Based on the atpD gene, the bacterial strain of Biodoz showed complete similarity with Bradyrhizobium diazoefficiens, while strains of other products were identified as Bradyrhizobium japonicum. In vitro growing capacity of the Biodoz strain at 8 °C was higher compared with the other strains. Better cold adaptation of the Biodoz strain might be a possible explanation for the better performance of Biodoz in Belgium.

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