Impact of Rhizobia Inoculation for Sustainable Soy Cultivation in Western Siberia

Abstract

Driven by an increasing demand for food and fodder and changing climate conditions, the production of soy (Glycine max L.) in Western Siberia increases. Higher temperature sums and longer growing seasons allow new crop rotations with partial substitution of peas by soybeans. Both legume crops need specific rhizobia bacteria to be supplied by biological nitrogen fixation. Whilst bacteria supply for peas usually is sufficient, Siberian soils lack the soy-specific strains (Bradyrhizobium japonicum). Therefore, bacteria material is usually added manually, especially if soy is planted on a field for the first time. This inoculation procedure of seeds is not common in Siberia, hence it is uncertain if soy benefits from legume N2-fixation potential there.Within the framework of the interdisciplinary German-Russian research project “SASCHA” on sustainable land management a study about the capability of soy cultivation in Western Siberia was carried out. In a field trial (completely randomized block design, 4 replications) the effects of rhizobia inoculation at 4 different varieties from Europe and Siberia were investigated by using Minolta SPAD-meter readings as indicator of fixation capacity and comparing yields as well as bean protein content.Results after two years show significant higher leaf chlorophyll content (SPAD) with inoculation compared to control (without treatment), differences were rising over time (Fig. 1). According to the measured SPAD differences also protein content at beans from treated plants was higher (+10%, significant p<0.01) at constant yields.