Applicable properties of the bio-fertilizer spent mushroom substrate in organic systems as a byproduct from the cultivation of Pleurotus spp

The spent mushroom substrate (SMS) is a byproduct of cultivation of oyster mushroom (Pleurotus spp.) and represents the composted substrate that remains after completion the harvested crop. This study mentioned the role of some effective date palm wastes in improving spent mushroom substrate properties which containing fibers of date palm Phoenix dactylifera L. (Fibrillum), mixed with white sawdust and wheat straw in three formulas. These mixtures of SMS namely, SMS1 (wheat straw), SMS2 (wheat straw 70%, sawdust 20% and date palm fiber 10%) and SMS3 (wheat straw 50%, sawdust 30% and date palm fiber 20%) were obtained from locally mushroom farm in western Iraq and sent to determine some properties such as moisture content, dry matter, EC, pH, ash, carbon, nitrogen, protein contents and C:N ratio. Generally, determinations of Hydrogen ion concentration (pH) for SMS extracts had acidic value at average 5.06. The higher EC was 3.30 ms/cm for SMS1-P. ostreatus (white), while the lower value reached to 1.13 ms/cm for SMS3 of same species. The higher nitrogen content was 9.98 g/kg for SMS3-P. ostreatus (white), SMS1 of Pleurotus salmoneostramineus and SMS2-P. ostreatus (white), while, SMS3-P. salmoneostramineus had lower nitrogen content (6.65 g/kg). The higher C:N ratio was reported with SMS3 of P. salmoneostramineus at value 35.36, while SMS2-P. ostreatus (grey) had ratio 22.03, significantly (p < 0.05). Overall, these SMS was suitable as a natural fertilizer and soil amender in agriculture and horticulture fields