Non-microbial bio stimulant increase soybean nodulation when inoculated or co-inoculated with beneficial bacteria

Plant bio stimulants (PBs) are suitable tools for increase plant performance in the field. Improving nitrogen biologic fixation on agriculture, notably on soybean may enhance food production and diminish environmental impacts. Nodulation – nodules number and weight - of soybean plants, treated with non-microbial plant bio stimulant (PB) [mixture of silicon fertilizer (SiO2), D-glucosamine (from chitosan), and extracts of the brown algae Ascophyllum nodosum] associated with Bradyrrhizobium (BR) spp. and or BR plus Azospirillum brasiliensi (AB) were assessed in in two greenhouse test. In the first assay, seeds from soybean cv. Fibra 64i61 received the treatments: Bradyrrhizobium japonicum SEMIA 5079 + Bradyrrizobium diazoefficienst SEMIA 5080 7x109 UFC Ml (BR), BR + PB (seed treatment); BR + PB and control (just water) BR, BR + PB (seed treatment); BR + PB (planting furrow) and control (just water). Treatments of the 2nd assay were control, BR, BR + PB (3 or 5 Ml/kg seeds), BR + Azospirillum brasiliensis (AB), BR + AB + PB (3 or 5 Ml/kg seeds). Plants were removed from the pots 50 days after emergence, when nodules were greater than 2 mm were counted and dried mass determined. In the first assay, adding PBs in the BR seed treatment leaded to higher number of nodules than remaining treatments. In the second assay, the highest nodule numbers and mass were observed when using BR + AB + PBs (0.3 or 0.5 ml/kg seeds). adding PBs to BR + AB increased up to 36 and 38% in nodules number and dried mass when compared with just BR + AB. Further investigation to establish if the results observed in this greenhouse assays may be consistent in the field are suggested such as studies including unfavorable climate conditions under the climatic changes scenario.