Abstract

To assess short-term changes in nutrient uptake, plant stoichiometric balance, and fertilizer-borne trace metal inputs in ryegrass (Lolium perenne L.) following the application of poultry manure (PM), rock phosphate (RP), and their mixture (PMRP) under contrasting soil pH conditions. A seven-week greenhouse experiment was conducted using two soils with contrasting pH (moderately acid and alkaline). Soils were amended with PM, RP, or PMRP at an equivalent rate of 100 mg P kg(-)& sup1; soil. Soil concentrations of Co, Cr, Cu, Mn, Ni, Pb, Zn, and Fe were determined by aqua regia digestion and ICP-OES. Plant biomass production, nutrient uptake (N, P, K, Ca, Mg, Na), C:N: P stoichiometry, and nutrient translocation were quantified in shoots and roots. Treatment effects were evaluated using two-way ANOVA followed by Tukey's HSD test (p <= 0.05). PM significantly increased N, P, and K uptake (1.4-3.4-fold relative to the control), particularly in acidic soil, whereas RP showed limited effectiveness under alkaline conditions. PMRP resulted in intermediate nutrient acquisition. Stoichiometric ratios (C: P and N: P) indicated a clear alleviation of P limitation under PM and PMRP. Although soil trace metal concentrations increased after amendment application (PM > PMRP > RP), all values remained well below phytotoxic thresholds, and metals were not detected in plant tissues. Organic-based amendments, particularly PM, rapidly improved nutrient use efficiency and plant stoichiometric balance without inducing short-term trace metal risks.