Yeah - like I said total crap shoot, a gamble.

I'm betting that the low nutrient value of the substrate, the aggressive fungi & the little bit of wood ash I added, will allow the substrate to colonize without contamination.

I didn't know what else to do with the big bag of grain other than inoculate a pile of wood chips.

I figured I should try the mushrooms before letting them loose in the garden.

I also used some of the grain to inoculate a bag of straight sterilized sawdust. I will probably add 30% wheat bran to the sawdust spawn bags in the future. Sawdust spawn bags seem less susceptible to contamination in the substrate but provide less yields.