Novel liquid organic fertilizer: A potential way to effectively recycle spent mushroom substrate

A novel liquid organic fertilizer (LOF) was made from spent mushroom substrate (SMS) and then the resultant fertilizer (SMS-LOF) was applied on Pak-choi in this study. Results showed that SMS-LOF could enhance the production of Pak-choi by approximately 30% and improve the nutrients level of soil. The application of SMS-LOF also changed the microbial diversity of rhizosphere soil. At genus level, the microbial community was predominated by Bacillus (9.5%), RB41 (6.81%) and Sphingomonas (4.07%) for unfertilized soil, whereas they separately took up 8.65%, 5.27% and 4.81% under fertilized condition. The mechanisms exploration indicated that a plant hormone (indole-3-acetic acid, IAA) was synthesized probably through Pseudomonas and tryptophan during the anaerobic fermentation of liquid SMS, which together with macronutrients and microelements promoted the plant growth. On the whole, SMS-LOF can serve as an appropriate liquid organic fertilizer, most likely a potential way to effectively recycle spent mushroom substrate.