Purpose <p>Effectiveness of the applied fertilizers is low in silage maize cultivation due to excessive irrigation. This study investigated the primary and residual efficiency of rice husk biochar (RHBC)-based organo-mineral fertilizers (OMFs) in silage maize.</p> Methods <p>RHBC was treated with different N sources and acids to produce biochar-based OMFs, and the primary and residual effects of these fertilizers were compared with diammonium phosphate (DAP) fertilizer. The current experiment consisted of four treatments including a control, DAP, OMF1(RHBC + H₂SO₄+ DAP), OMF2 (RHBC + H₃PO₄ + NH₄NO₃), OMF3 (RHBC + DAP), OMF4 (RHBC + H₃PO₄ + Urea).</p> Results <p>In the first maize experiment, P treatments increased dry weight from 1.84 to over 3.80&#xa0;g plant^− 1, with OMF3 reaching the highest value (4.08&#xa0;g). While differences among P sources were minor initially, residual effects in the second crop were more evident, with OMF1, OMF3, and OMF4 yielding significantly higher biomass than DAP and OMF2. Plant N and P concentrations also increased with fertilization, peaking in OMF3 (31.3 and 4.35&#xa0;g kg^− 1, respectively), and remained elevated in OMF3 and OMF4 during the second crop. OMF3 also led to the highest chlorophyll, lowest anthocyanin levels, and maximum soil available P. DAP released N rapidly, posing leaching risks, while OMF3 provided slower N and higher P release, improving nutrient efficiency.</p> Conclusion <p>OMFs, especially OMF3, improved plant growth, nutrient uptake, and P availability in the soil, demonstrating their potential to enhance silage maize production and nutrient management.</p> Graphical Abstract <p></p>