possibility of peat replacement with compost in mushroom production

one of the most important steps of agaricus bisporus production is casing. in this step a layer of soil is added on top of compost. peat is the most suitable casing soil for a. bisporus production. the lack of peat in iran is one of the major problems in a. bisporus production for mushroom producers. it seems that peat can be replaced by spent mushroom compost (smc). in order to study the possibility of peat replacement, a factorial experiment was conducted in a completely randomized design layout with two replications. the experimental factors consisted of spent mushroom compost with two levels (one and two years old), leaching with three levels (one (l1), two (l2) and three (l3) times) and edta with two levels (without edta (e1) and with edta, 0.3 m (e2)) and different casing soil with four levels (smc+loam, smc+azolla, smc+peat (1:1) and peat). the experiment was carried out in the mushroom production center of agricultural college, ferdowsi university of mashhad. the results showed that the highest mushroom yield was obtained in peat treatment (24%). the average of yield in smc+peat treatment was 11.78%. the diameter of mushroom cap in smc+peat treatment was 44.1 mm. the lowest yield (8.1%) and diameter of a. bisporus cap (37 mm) was observed in smc+azolla treatment. the results also showed that the edta had a negative effect on yield (44.3 %) and diameter of the mushroom cap.