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Soybeans in high latitudes: effects of Bradyrhizobium inoculation in Northwest Germany and southern West Siberia


In regions around the current high-latitude boundaries of agricultural production, the effects of climate change are likely to affect future growing conditions. Specifically for soybeans (Glycine max (L.) Merr.), this leads to a northward shift of the northernmost limit for cultivation. In two high-latitude regions with cold growing conditions (northwest Germany and southern West Siberia, Russia), similar field trials were conducted under different climate conditions (temperate oceanic, temperate continental). The effect of soybean seed inoculation with Bradyrhizobium japonicum was investigated in comparison to untreated control in five field site-years under organic farming conditions. SPAD meter readings were used to indicate differences in leaf chlorophyll content between inoculation and control at three phenological development stages. To make SPAD values from different varieties and development stages comparable, effect sizes (‘Hedges’ d’ of inoculation against control) were calculated. Inoculation was always successful, and significant numbers of active nodules developed only with inoculation. Effect sizes of SPAD values were significantly positive in inoculated plots at the beginning of seed filling but did not differ earlier. Except for the warmest site-year, inoculation did not affect seed yield. Protein content was significantly higher with inoculation at most varieties tested in Germany but only once in Russia. Protein yield was only in the warmest site-year significantly higher with inoculation. Under cold growing conditions of high-latitude regions, temperature sums seemed to limit soybean yield and the effectiveness of inoculation with B. japonicum. To implement soybeans as legumes in organic farming crop rotations, nevertheless, inoculation is mandatory, since soils at high latitudes lack soy-specific rhizobia bacteria.

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The trials at BK (RUS) were conducted as part of project SASCHA (‘Sustainable land management and adaptation strategies to climate change for the Western Siberian grain belt’). We are grateful for funding by the German Government, Federal Ministry of Education and Research within their SLM funding framework (funding reference 01LL0906D). The trials at WH (GER) took place within the project ‘Expansion of soybean cultivation in Germany through adaptation by breeding as well as optimization of crop production and processing technology’ funded by the German Government, Federal Ministry of Food and Agriculture within their BÖLN framework (funding reference 11NA002). We thank M. Kohlbrecher, M. Vergara and T. Zurheide for data collection at WH (GER) and A. Simerly for English language improvement. Finally, we acknowledge the valuable anonymous reviewer comments that helped to improve the manuscript.

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Correspondence to Insa Kühling.

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Table S1.

Mean values (± standard error) for nodulation (number of nodules during full bloom (R2)), seed yield, thousand seed weight (TSW), protein content and protein yield for the tested varieties at Waldhof (WH GER) and Biostation Kuchak (BK RUS). Multiple comparisons with Tukey HSD-test (p=0.05), no difference between same letters within each year (DOC 111 kb).

Table S2.

Mean effect sizes of all varieties at the three development stages (V3: third-node, R3: beginning pod, R5: beginning seed) and mean effect sizes of all stages for each variety at the two study sites Waldhof (WH GER) and Biostation Kuchak (BK RUS). n.s.: not significant, *: p<0.05, **: p<0.01, ***:p<0.001 (DOC 81 kb).

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Kühling, I., Hüsing, B., Bome, N. et al. Soybeans in high latitudes: effects of Bradyrhizobium inoculation in Northwest Germany and southern West Siberia. Org. Agr. 8, 159–171 (2018).

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  • Glycine max
  • Nodulation
  • Low root zone temperature
  • Climate change
  • SPAD-502
  • Organic agriculture