Rice-fish coculture incorporating spent mushroom substrate substitution alleviated microbial metabolism limitation...

It has been widely validated that spent mushroom substrates (SMSs) facilitate carbon (C) source utilization for soil fertility improvement. Therefore, we conducted a research on a novel pattern to produce mushroom in situ during the winter fallow period after rice-fish coculture (RFC) in the same paddy field, and then utilized the SMSs after mushroom harvesting to supply organic fertilizer for the coming year's RFC.

In order to investigate the effects and optimal use of SMSs, we employed a pot experiment with CK (organic fertilizer control), R (reduce 20% of organic fertilizer), SR (SMSs addition based on R treatment), and their combined with RFC to estimate nutrients availability, enzymes activities, and microbial resource limitation and C use efficiency. The results revealed that SR treatment significantly improved nitrate nitrogen (NO₃ ^--N) and dissolved organic carbon (DOC) contents, and RFC significantly reduced ammonia nitrogen (NH₄ ⁺-N) and increased DOC, respectively. Microbial C and phosphorus (P) limitations were significantly associated with NO₃ ^--N, DOC, TC:TP, TN:TP, but these factors had different responses to organic material management (OFM) and RFC. Our results also showed that the reductions in C use efficiency under SMSs substitution were associated with increased nutrient acquisition strategies; OFM increased available P to promote microbial P acquisition activity, while RFC might affect C decomposition in soils by regulating N availability. These results suggest that RFC and OFM practices can alter microbial investments in C-, N- and P-acquisition activities through shifts in the availability of nutrients in soils.

Our findings provide a new model of RFC combined with SMS application, which may facilitate microbial C source utilization and is also a good way to improve soil productivity. © 2025 Society of Chemical Industry.