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The aim of this study was to determine the availability of N and P resulting from the soil application of a novel organomineral fertiliser (OMF15 15:4:4) reported in earlier studies, in comparison with urea (46% N) and single superphosphate (SSP 0:18:0). A sandy loam and a clay loam soils were incubated over a period of 90 days at 25 degrees Celsius. N and P (as P2O5) were applied at rates equivalent to 0 (control), 150 and 300 kg ha-1 and the soils maintained near field capacity. The majority of the N was released from OMF15 within 30 from application (range 40%-72% of total OMF-N applied) with a further 10% to 28% in the following 60 to 90 days. OMF15 required an accumulated thermal time of 2250 dC to release between 68% and 79% of the total OMF-N applied. From this, it was suggested that mineralisation of the organic-N fraction in the OMF would progress beyond the harvest of winter cereal crops in-field conditions in the UK. The availability of P from OMF15 was low throughout the experiment ranging from -5.6% to 6.4% (% of total OMF-P applied). Despite this, a change in soil-P index from 5 to 6 was observed after the 90 days incubation period but the overall increase in soil-P status was marginal in both soils. For SSP, P-availability ranged from 16% to 46% (% of total SSP-P applied). The application of SSP induced a significant (p<0.001) increase in soil-P levels compared with the controls which led to an overall increase in soil-P index from 5 to 6. The results of this study aided the development of a strategy for the use of OMF in winter cereal crops.