Orange peel in combination with selected PGPR strains as seed treatment can improve soybean yield under field conditions

Background and aims Plant growth-promoting rhizobacteria (PGPR) can function as biofertilizers to enhance plant growth and crop yield in an environmentally sustainable manner. However, when PGPR are introduced into agricultural soils, their survival is restricted due to limited nutrients available in the rhizosphere. It has been demonstrated that selected Bacillus velezensis (Bv) strains can use pectin-rich orange peel (OP) as a growth substrate, but results have been scarce due to lack of strain screening. Therefore, it is important to select Bv strains for their capability to utilize OP and to test their ability to promote soybean growth with OP as an amendment. Methods Six Bv strains were selected by their growth in OP media and then tested for their ability to promote soybean growth in combination with OP in greenhouse and field experiments. Results Among six Bv strains tested in a greenhouse experiment, strains AP191, AP215, and AP216 showed the best results in plant growth promotion when supplemented with OP, where only AP191 with OP significantly enhanced pod dry weight by 15.9%. Inoculation with AP191 + OP showed the greatest yield under field conditions, being the only treatment significantly different from the control treatment (+ 0.5 ton ha −1 , 9.4% yield increase). Conclusions These results support the conclusion that soybean seed treatment with PGPR strains in conjunction with orange peel can produce a yield advantage under field conditions. This research opens the opportunity for more consistent yield increases when using biologics as a seed treatment for the biofertilizer industry.