BACKGROUND: Environmentally friendly agriculture needs toreduce the use of synthetic fertilizers and to reclaim nutrients from organic wastes. In this study the effect of five doses (0, 12, 24, 48 and 96 t ha(-1)) of two two-phase olive mill waste (TPOMW)-based composts on the bioactivity and chemical characteristics of an agricultural soil and their potential to fertilize alfalfa (Medicago sativa) and stimulate nodulation were assessed during a two-year incubation experiment. The two composts were prepared either with the olive mill waste alone (compost A), which served as control, or mixed with a liquid fatty-proteinaceous hydrolyzate waste (FPH) from the pharmaceutical industry (compost AH). RESULTS: Compost AH resulted in greater N immobilization than compost A because the former supplied the soil with easily degradable C and N, which increased microbial biomass and activity. Both compost mineralizations during the first year of incubation supplied the soil with more nutrients (mainly N), more so with A than with AH. Nevertheless, plant growth was similar in soils amended with either A or AH. Both composts induced nodulation similarly and the highest dose (96 t ha-1) increased the formation of nodules by a factor of 11 compared with the four lower doses. CONCLUSION: TPOMW serves as an effective ground material for co-composting with liquid wastes such as FPH. TPOMW supplies key nutrients and stimulates nodulation in alfalfa. (C) 2014 Society of Chemical Industry This research was funded by the Spanish Ministerio de Educacion y Ciencia through the PETRI Programme (PTR1995-0894-OP-02-02). Rosana Garcia-de-la-Fuente thanks the Valencian Government for awarding her a pre-doctoral grant (BFPI/2007/055) and Profs Paolo Nanipieri, Loretta Landi and Giancarlo Renella from the Universita degli Studi de Firenze for their assistance in developing the N dynamics experiment. Claudia X Jaramillo thanks COOPEN European Commission for awarding her an exchange grant (2009-5124\001-001-ECW). The authors also thank Dr Debra Westall for revising the English and Mrs Joana Oliver for her technical assistance. Fornes Sebastiá, F.; Jaramillo, CX.; García De La Fuente, R.; Belda Navarro, RM.; Lidón Cerezuela, AL. (2014). Composted organic wastes from the pharmaceutical and agro-food industries induce soil bioactivity and nodulation in alfalfa. Journal of the Science of Food and Agriculture. 94(14):3030-3037. https://doi.org/10.1002/jsfa.6651