Soybean Development and Productivity in Response to Organic Management above the Northern Boundary of Soybean Distribution in Europe

Abstract

Climate change, new varieties, better technological abilities, and increased demand for local resources provide significant reasons to introduce soybeans in northern regions, above the typical soybean distribution area in Europe. This research examined the effects of two delayed sowing times, wide 25 cm and 50 cm row spacings, seed inoculation with Bradyrhizobium japonicum, and the interaction of all these factors on soybean development and productivity in an organic farming system. Length of soybean vegetation varied from 142 to 161 days at latitude 55° N. Yield varied from 673 to 3154 kg ha−1 in response to management factors. In the dry 2015 year, the combination of later sowing dates and wide 50-cm row spacing significantly (p < 0.01) increased the number of pods per plant by 28%, aboveground dry biomass by two times, and seed yield by 36% plant−1. In the wet 2016, yield components reached their highest values of 16.8 g dry biomass, 19.9 pods plant−1 and 7.9 g seeds plant−1 when inoculated soybeans were sown earlier, with 50-cm row spacings. Protein content significantly varied from 27.4 to 35.3%, and fat content 17.4–21.5%. This study suggests that regular soybean development could be maintained in organically managed locations above the present northern soybean distributional region, but its development, productivity, and production quality significantly depends on management practices.