Effects of Pleurotus spp. spent mushroom substrate from NPK rich tree leaves on growth and bioactive compounds of Centella asiatica L.

Spent mushroom waste (SMW), a by-product of mushroom cultivation, is increasingly recognized for both its environmental impact and potential for resource recovery. Consequently, the effective recycling and valorization of SMW has become essential for the sustainable advancement of the mushroom industry, particularly within the context of circular economy principles. In this study,Pleurotus spp. were cultivated on paddy straw as the basal substrate, amended with nitrogen, phosphorous and potassium-rich tree leaves from Swietenia macrophylla (SM), Gliricidia sepium (GS) and Sesbania grandiflora (SG). The study assessed the effects of these amendments on the key properties of SMW, including moisture content, dry matter, electrical conductivity (EC), pH, ash, carbon, nitrogen, protein contents and the C:N ratio, to evaluate its suitability as a natural fertilizer and soil amender for medicinal crops. The basal substrate was supplemented with different proportions (25 %, 50 %, 75 % and 100 %) of SM, GS and SG to identify the most effective substrate composition for Pleurotus cultivation. In addition, this study also investigated the usefulness of SMW (obtained in the production of Pleurotus spp.,) in the pot cultivation of Centella asiatica (C. asiatica). It examined growth, plant biomass, photosynthetic pigments and triterpene content of plants grown in four pot sets viz., 100 % casing substrate derived SMW, 75 % sandand soil: 25 % casing substrate derived SMW, 50 % sand and soil: 50 % casing substrate derived SMW and 25 % sand and soil: 75 % casing substrate derived SMW. The results showed that the 25 % sand and soil + 75 % SMW treatment significantly (p < 0.05) enhanced plant growth, biomass production and triterpene accumulation in C. asiatica. The study highlights a new, environmental-friendly strategy to increase medicinal plant productivity and bioactive compound content by using SMW derived from Pleurotus spp.