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 (C(1): 3 g kg(−1) and C(2): 5 g kg(−1)) at three distinct timings (t(1): at spawning, t(2): after first harvest, t(3): at spawning and after first harvest). Protein and fiber contents increased respectively by 0.64 and 0.2% in C(1)t(1) and by 0.46 and 0.8% in C(2)t(2) compared to control (C(0)t(0)). Total carbohydrates increased by 0.48–3.76%. Sucrose and glucose contents decreased in the majority of treatments, while fructose increased in C(2)t(1) (by 0.045%). Essential amino acids were the highest in C(1)t(1), wherein respective improvement of 0.31, 0.10, 0.05, 0.21, 0.18, and 0.09% compared to C(0)t(0). Similarly, C(1)t(1) was superior in non-essential amino acids. Potassium, sodium, calcium, iron, and copper contents decreased in all treatments, with minor exceptions, zinc decreased in C(1)t(1) and C(2)t(1), while nickel and lead increased in all treatments. Conclusively, despite important ameliorations in the mushroom nutritional value, mostly in C(1)t(1), the product should be further tested in lower doses (< 3 g kg(−1)) to counteract its effect on heavy metal bioaccumulation.