Nano urea effects on Pleurotus ostreatus nutritional value depending on the dose and timing of application

The work investigated the effect of Lithovit-Urea50 on the composition of Pleurotus ostreatus (Jacq. Ex Fr.) P. Kumm. (1871) cultivated on spent oyster substrate mixed with wheat straw (1:1, w/w mixture). The product was applied in different doses (C₁: 3 g kg^-1 and C₂: 5 g kg^-1) at three distinct timings (t₁: at spawning, t₂: after first harvest, t₃: at spawning and after first harvest). Protein and fiber contents increased respectively by 0.64 and 0.2% in C₁t₁ and by 0.46 and 0.8% in C₂t₂ compared to control (C₀t₀). Total carbohydrates increased by 0.48-3.76%. Sucrose and glucose contents decreased in the majority of treatments, while fructose increased in C₂t₁ (by 0.045%). Essential amino acids were the highest in C₁t₁, wherein respective improvement of 0.31, 0.10, 0.05, 0.21, 0.18, and 0.09% compared to C₀t₀. Similarly, C₁t₁ was superior in non-essential amino acids. Potassium, sodium, calcium, iron, and copper contents decreased in all treatments, with minor exceptions, zinc decreased in C₁t₁ and C₂t₁, while nickel and lead increased in all treatments. Conclusively, despite important ameliorations in the mushroom nutritional value, mostly in C₁t₁, the product should be further tested in lower doses (< 3 g kg^-1) to counteract its effect on heavy metal bioaccumulation.