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Abstract. Organomineral fertilizers (OMF) derived from treated sewage sludge (biosolids) were produced using a novel technique that enables addition of nitrogen (N) to biosolids (BS) to increase the N:P ratio of the sludge and improve its agronomic suitability. Two OMF products (OMF WWTP1 and OMF WWTP2) were formulated and tested in a glasshouse facility on pot-grown ryegrass (Lolium perenne L.). The agronomic performance of OMF was compared with urea and two types of biosolids (BS WWTP1 and BS WWTP2) sourced from different wastewater treatment plants located in southern Queensland, Australia. The fertilizer materials had the following N:P₂O₅ compositions: 5:12.5 (BS WWTP1), 5.5:6 (BS WWTP2), ≈15:10 (OMF WWTP1), ≈15:5 (OMF WWTP2), and urea (46:0), respectively. Cubical-shaped particles (median size: ≈5x5x5 mm) of BS and OMF, and granular urea were applied to soil (Red Ferrosol) in pots at field-equivalent rates ranging from 0 (control) to 750 kg N ha^-1 at regular increments of 75 kg N ha^-1, and six grass cuts performed at intervals of 30 days. Results showed that cumulative dry matter yield (DMY) was between 13% and 21% higher with OMF and BS compared with urea, depending on fertilizer type and rate (P<0.05). Fertilizer responses for BS (WWTP2) and the two OMF products showed that about of 90% of maximum DMY can be achieved with the optimum N application rate or about 50% of the N rate required for maximum yield. For BS (WWTP1) and urea, responses showed that 80% and 85% of the maximum DMY could be achieved with the optimum N application rate, which represented, respectively, 35% and 30% of the N rate required for maximum yield. When N inputs were optimized, agronomic efficiency (kg kg^-1) calculations were: 12.6 (BS WWTP1), 17.3 (OMF WWTP1), 14.7 (BS WWTP2), 15.7 (OMF WWTP2), and 20.4 (urea), respectively, and N fertilizer replacement values of OMF and BS were between 74% and 82%. The effects of BS and OMF on soil chemistry are presented and discussed by focusing upon soil phosphorus and heavy metals dynamics. There appears to be potential for further development of biosolids-derived OMF products.