The significance of gypsum applied to mushroom compost, in particular in relation to the ammonia content.

Abstract

With gypsum treatment the nitrogen loss in the compost is slightly reduced and the pH is decreased. Curvilinear relationships were established between the NH4 content of the compost at filling and the yield in the presence or absence of gypsum and with or without supplementation with soya bean meal. These curves (four parabolas) give a clear picture of the significance of gypsum under various circumstances. The optimum gypsum treatment was 25 kg per 1000 kg of horse manure. Time of application of the gypsum was not very important, but an early application favoured a more uniform distribution and prolonged its action. The drop in pH caused by gypsum influences the dissociation of NH4+ ions considerably, i.e. in the presence of gypsum less NH3 is present in the compost. A possible mechanism by which gypsum lowers the pH is discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)