Covering soil improvement method after culture of agaricus bisporus

The invention discloses a covering soil improvement method after culture of agaricus bisporus, including the steps of (1), rejecting and removing covering soil from the compost after reaping all agaricus bisporus and clearing residual bodies of agaricus bisporus, and transferring the separated covering soil to a cleaning area; (2), sterilizing the covering soil; (3) adding gamma-PGA to the covering soil, to be specific, watering the covering soil with 1.5-3 L/m of gamma-PGA extraction solution and then uniformly mixing fully, watering the covering soil with 1.5-2 L/m of water after 1-2 hours and then mixing uniformly fully, watering the covering soil with 1.5-2L/m of water again after 1-2 hours, until reaching the initial water absorption capacity of the covering soil, while ensuring all moisture is absorbed by the covering soil completely, without any puddles or pondings formed. Without influence to quality and yield of agaricus bisporus, the method can prolong service cycleof the covering soil; the covering