<p>Several studies have highlighted the potential of hydrochars as versatile soil amendments and effective alternatives to chemical phosphorus fertilisers. However, their effectiveness and impact on agricultural outputs still remain inconsistent. This research assess hydrochars for improving soil properties and perennial ryegrass <i>(Lolium perenne L.)</i> growth.&#xa0;Soil incubation and plant-growing experiments were conducted for 12 weeks using 60&#xa0;kg P₂O₅ ha⁻¹ of pig manure and maize digestates, derived hydrochars, and triple super phosphate (TSP), a conventional P fertiliser. Extractable plant-available P was measured using the Olsen method, while potentially available metals were extracted using the modified Community Bureau of Reference (BCR) procedure. Elemental and dissolved organic carbon (DOC) analyses were conducted on soil solutions, and biomass response was assessed through crop dry weight (DW).&#xa0;The potential availability of micronutrients was affected by the alkaline conditions, whereas plant-available P by 1.5 times compared to TSP, while hydrochars resulted in a slower, more gradual P release. Hydrochars from co-digestate with a 4-h residence time achieved similar DW and macronutrient uptake as mono-digestate and TSP, likely due to their enhanced aromaticity and porosity.&#xa0;Mono-digestate from pig manure was an effective and economical phosphorus fertiliser. Hydrochars improved soil properties but did not enhance crop yields compared to the mono-digestate and TSP. They could still serve as sustainable amendments, especially for metal-rich manure, but require combination with other organic fertilisers. Further research is needed to assess long-term soil and environmental impacts.</p>