When using food and green waste composts as peat-free plant growing media, there is a challenge that nutrient immobilisation and high pH and salts content limit plant growth. The present study explored the use of spent mushroom compost (SMC) of Agaricus subrufescens in a sustainable plant growing system where only vermicompost from digested food waste and composted green wastes were used, even for the seedling stage. However, negative effects of high compost inclusion were offset by adding SMC. Significantly higher plant yield was obtained in several of the SMC amended treatments in four out of five lettuce experiments and in one tomato experiment. In addition, an experiment with cucumbers showed that nutrients were not available to the plant when the mushroom mycelium was actively growing, but became available if the mushroom mycelium had been inactivated first by pasteurisation. A significant effect from SMC was not observed under full fertigation. This study demonstrated that the addition of pasteurised Agaricus mycelium colonised compost can successfully offset negative effects from high pH and EC as well as limited nutrient supply (and nitrogen immobilisation) in peat-free, compost-based growing media.

The present investigation aimed to study the utilisation of combined dairy manure-food waste digestate as a substrate (experimental mushroom substrate—EMS) for Pleurotus djamor (strain 2708, Mycelia) cultivation. Considering the lack of scientific information about the influence of elements concentration in growing substrates on the bioaccumulation of elements in cultivated mushrooms and their residual concentrations in substrates left after cultivation (spent mushroom substrate—SMS), a multi-elemental analysis of 38 elements was carried out. In the study, inductively coupled plasma optical emission spectrometry (ICP OES) was used for elemental analysis. The P. djamor cultivated on EMS resulted in a yield of 196.50 g/bag, achieving a biological efficiency (BE) of 39.90%. High variability in the elemental concentrations among substrates both before and after mushroom cultivation was evident. The studied elements accumulation in P. djamor was in an increasing trend in three subsequent flushes and was also reflected in the bioconcentration factors (BCFs). The highest BCF (2.35) was determined for Fe. Interestingly, the BCF values for all studied trace elements with detrimental health effects were lower than 1.00. The estimated daily intake (EDI) reflected that the P. djamor fruiting bodies grown on EMS can serve as an excellent dietary source of essential major and trace elements: Ca, Mg, Na, Mn, Mo, Ni, Se and Zn. On the other hand, EDI values for K, Cu, Fe, Ag, Ba, Cd, Al, Sb and Sr were greater than the referred guideline values corresponding to higher intake. Overall, the study presented an insight into elemental accumulations and demonstrated the potential utilisation of combined dairy manure-food waste digestate.