Re-supplementing and re-casing mushroom (Agaricus bisporus) compost for a second crop

Experiments were performed to determine the effect of adding nutrient supplements to colonized mushroom compost (MC) for the production of a second crop of mushrooms. Mushrooms were harvested for 1, 2 or 3 flushes, the casing removed and the MC then was fragmented and re-supplemented with delayed release supplements treated or non-treated with fungicide (thiophanate-methyl; Topsin M 70WP) and re-cased. Overall double-crop yields were higher when MC was re-supplemented after 1st flush (1st flush MC) as compared to re-supplementation after the 2nd or 3rd flushes. Mean double-crop BEs were 128, 119 and 109% when 1st-, 2nd- and 3rd-flush MCs were used, respectively. Treatment of delayed release supplement with thiophanate-methyl fungicide did not affect mushroom yields. Soluble salts and potassium concentrations increased 350 and 900%, respectively, in the casing overlay through three flushes suggesting that removal of the casing would help to alleviate the build up of these potential growth-limiting materials. Re-supplementing and re-casing of MC represents a potential opportunity for growers to increase revenues and reduce costs associated with preparation and disposal of compost. The ability to double-crop mushroom compost would provide growers a chance to increase yields by 40% or more, depending on whether they re-supplement and re-case after 1st, 2nd or 3rd flush.