Soybean response and profitability upon inoculation and nitrogen fertilisation in Belgium

Abstract

The recent introduction of soybean cultivation in Belgium and several other north-western European countries holds great potential for sustainable agriculture. Agricultural practices must be fine-tuned to optimise yield and quality before soybean will become a profitable crop for Belgian farmers. The effect of inoculation and N fertilisation on crop yield, protein content and relative profitability of soybean in Belgium was studied. Trials with nitrogen (N) fertilisation and inoculation of soybean were performed during two seasons (2016 and 2017) at two locations (Geel and Merelbeke) in Belgium. Nitrogen was applied as mineral fertiliser at different doses (0 N, 35 N, 70 N or 140 N) at the day of sowing and/or at the R1 stage. Highest yields and protein contents were obtained upon inoculation, showing that inoculation is the most appropriate practice to increase yield and protein levels of soybean in Belgium. Inoculation also increased thousand grain weight and improved several biophysical parameters calculated from chlorophyll a fluorescence measurements. Additionally, inoculation and N fertilisation raised chlorophyll content of the soybean leaves and N content and N uptake of the aboveground biomass. Application of N inhibited nodulation of inoculated soybeans. Tolerance to lodging and oil contents were lower upon inoculation or N application. Relative profitability (RP) of inoculated soybeans was higher than for non-inoculated soybeans. Application of N fertiliser to soybeans did not significantly increase RP. Optimisation of inoculation and nodulation is the best approach to maximise yield and protein content and thus to improve the economic viability of soybean cultivation for Belgian farmers in the short term.