The Study Of Nitrogen Transformation On Composting Of Spent Mushroom Dreg

With the increasing requirement of edible mushrooms, the amount of spent mushroom dreg has a significant rise. A mass of spent mushroom dreg littered could not only cause serious environmental pollution, but also lead to a waste of resources. Aerobic composting is an important way to transform spent mushroom dreg to high quality organic fertilizer. This paper focused on aerobic composting using different ratios of edible fungi dreg to cow dung and its nitrogen transforming by measuring the contents of various nitrogen form, the number of nitrogen transformation microbes and the activity of some enzymes. This paper also investigated the nitrogen protection of compostng by adding matured compost and mixed microbial incoculant. The main conclusions are as follows:1. The ratio of mushroom dreg to cow dung (by weight) in 3 compost treatments were 2:1,1:1 and 1:2. respectively. Another 2 compost treatments with 2:1 of mushroom dreg/cow dung ratio were added with matured compost and composite cellulose-degrading microbe, respectively. The duration of thermophilic phase (> 55℃) were 6 days in the treatment of mushroom dreg/cow dung ratio 2:1,8 days in the treatment of 1:1 and 10 days in the treatment of 1:2. The results showed that the appropriate amount of cattle dung mixed was benefit to temperature rising of spent mushroom dreg compost. At the same time, the high temperature period was prolonged to 8 days in the treatments with matured compost and composite cellulose-degrading microbe. The pH of all 5 treatments also fit to the matured compost standards. The results demonstrated that the 5 treaments had been composted successfully.2. With the process of composting, the amount of NH4-N of all treatments increased firstly and then decreased, while the trend of NO3-N content was opposite. The main form of nitrogen was organic nitrogen, which had a similar trend as total nitrogen. At the end of composting, total nitrogen content in the treatments with additive increased compared to that in the treatment without additive. It implied that the matured compost and composite cellulose-degrading microbe added could reduce nitrogen loss in mushroom dreg composting.3. Ammonifier was dominant in nitrogen transformation microbes in the compost. In the 3 treatments, the number of ammonifiers increased greatly firstly and then declined gradually. However, the amount of nitrifying bacteria and nitrite bacteria increased in cooling stage and in maturation stage. The number of denitrifying bacteria also increased in the same stage of composting. The number of azotobacter was more than the amount of nitrifying bacteria and denitrifying bacteria during composting. At the end of composting, the number of azotobacter was slightly less than that at the beginning of composting. In addition, the number comparision of various kinds of microbe in composting was bacteria>actinomycetes>fungi. The activity of cellulose enzyme in 3 composts declined in thermophilic phase and subsequently increased in cooling phase. The activity of cellulose enzyme in the treatment added composite cellulose-degrading microbe was maximum on 21th day. It suggested that cellulose-degrading microbe added started to play a role in the matured stage of compost. The enzyme activities of protease and urease droped rapidly in thermophilic phase and were steady in cooling phase and in matured phase.