Effect of boron and copper contaminants in poultry manure on the growth of the common mushroom, Agaricus bisporus

The toxicity of boron (B) and copper (Cu) to cultivated mushrooms was tested in 2 experiments. The growth of mushroom mycelium (Agaricus bisporus) on potato dextrose agar in vitro was inhibited by additions of B as H3BO3 and Cu as CuSO4.5H20. Boron was more inhibitory than Cu to mycelial growth. Addition of B to compost at spawning decreased sporophore (i.e. mushroom) production and increased B concentrations in the sporophore. Boron added at 35 mg/kg of fresh compost gave a 10% yield reduction and this was associated with a sphorophore tissue B concentration of 170 mg/kg dry weight. Addition of Cu to the compost had no effect on the final yield of mushrooms but increased Cu concentrations in the sporophores. Boron added at 5, 10 and 20 mg/kg and Cu at 10 mg/kg of fresh compost stimulated sporophore growth at first flush but this was not evident in total mushroom yield from all flushes. There was a significant negative linear effect of mushroom tissue B (r2=0.98) and Cu (r2=0.54) at harvest 1 (day 1) on the change in tissue B or Cu from harvest 1 to 6 (day 17). This suggested that tissue B was buffered around 7 mg/kg and Cu around 73 mg/kg. The results indicate that the levels of B and Cu which are normally contributed to mushroom compost from poultry litter are unlikely to cause significant losses in mushroom production.