Commercial mushroom production is based on composted locally available agro-industrial wastes rich in carbon and nitrogen such as wheat straw supplemented with chicken manure. Either component can be replaced by other kinds of grain straw: barley, oat, or a mixture of different straw types and combined with diary manure—food waste digestate after anaerobic biogas digestion. Original, unseparated liquid digestate is nutritious, rich in nitrogen and organic matter. This research aimed to investigate the effect of digestate and different straw ratios on the composting process and productivity and their consequent effect on mushroom cultivation parameters of Agaricus subrufescens. All investigated experimental mushroom compost (EMC) types worked well during the composting process, reaching the desired moisture of 65–75%, N content of 1.43–1.93%, and a C/N ratio ranging from 21.5 to 29.1, supporting growth of mycelium and producing mushrooms. Supplementation with barley straw resulted in better EMC structure with the highest yield and biological efficiency (BE) (157.9 g kg−1; 64%), whereas oat addition gave the lowest yield and BE (88.6 g kg−1 and 38%). Precociousness (yield at mid-cycle of the crop development) was higher for oat substrates (68.9%), while earliness (days to harvest from casing) was lower for barley EMC.

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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.

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