Chicken manure matches mineral P fertiliser in crop response and soil phosphorus dynamics in a wheat–canola–wheat system

The application of phosphorus (P) fertilisers is essential for global food production, yet their sustainable use is constrained by rising costs, finite P resources, and environmental concerns. Livestock manures are potential alternative P sources, but their effectiveness and behaviour in soil relative to mineral fertilisers remain poorly understood. This study compared crop responses to chicken manure and monoammonium phosphate (MAP) at increasing P rates (0 – 90 kg P ha −1 ) and assessed the fate of the applied P in soil (Ultisol) over three growing seasons in a wheat–canola–wheat system. Crop yield and P offtake increased with P rates, with no significant differences between the two P sources. The P budget was also similar for both chicken manure and MAP, with increasing surpluses at higher P rates (50 – 90 kg P ha −1 ). Concentrations of plant available P increased linearly with P rates, with both sources supplying sufficient P to crops over the study period. While increasing P rates increased NaOH-EDTA extractable inorganic P, concentrations of organic P remained unchanged despite the use of chicken manure as one of the P sources. Analyses of P sorption–desorption behaviour revealed that P sorption increased over time whilst desorption simultaneously decreased with no difference between the two sources. Overall, these findings indicate that chicken manure-derived P behaves similarly to mineral fertiliser, with applied P largely accumulating in inorganic soil P pools. This provides insights for the development of soil P management strategies that optimise crop P utilisation while substituting mineral P fertilisers with manures.