CHANGES IN THE CONCENTRATION OF SOLUBLE ANIONS IN COMPOST DURING COMPOSTING AND MUSHROOM (AGARICUS-BISPORUS) GROWTH

The changes in the concentration of nitrate, phosphate, chloride, sulp hate, formate, acetate and oxalate anions extracted with water from co nventional compost during composting and mushroom growth, and mushroom fruit bodies during cropping, were measured using an ion exchange chr omatograph and a pulsed electrochemical detector. The addition of gyps um at Phase I in conventional composting dramatically increased the co ntent of sulphate but lowered the content of oxalate (dry matter basis ). Chloride in compost increased gradually during composting and mushr oom growth probably due to its introduction in water used to irrigate the crop. Phosphate increased during the early stages of composting bu t decreased in spawning and fruit body formation. In fruit bodies, the relative content of boiling water extract decreased in successive flu shes. Individual anions, acetate and oxalate increased steadily, phosp hate and chloride decreased gradually and sulphate and nitrate first d ecreased steeply and then more slowly. Formate did not change. Phospha te, acetate, chloride and oxalate were higher in small buttons than in large buttons, but there were no differences for sulphate, nitrate or formate.