Optimum ratio of pig manure to edible fungi residue improving quality of organic fertilizer by composting

Abstract: In order to solve the current problems about environmental pollution of agricultural waste and explore the technology of producing organic fertilizer by composting with pig manure and edible fungi residue, an experiment was conducted to study dynamic changes of several parameters including heat, pH value, organic carbon (C), germination index (GI), nutrient nitrogen (N), phosphorus (P) and potassium (K) during the natural fermentation. The experiment was based on the four ratios of 9:1, 8:2, 7:3 and 6:4 of pig manure and edible fungi residue in high-temperature composting experiment. The results showed as followed. The temperatures of all disposals were over 50 degrees centigrade at about the 3rd day. It maintained a high temperature for from 25 to 32 d, and then began to decrease. Duration of the high-temperature composting was longer while the ratio of the mushroom residue got more. From the experiment, we could see that the high-temperature duration of the disposal with the ratio of 6:4 was 7 d longer than the disposal with the ratio of 9:1. The pH values of all disposals, ranging from 6.83 to 8.62, increased rapidly and then decreased smoothly in the 22 d. Total N of the nutrient decreased with the loss of ammonia in the early, and then the relative quality of the total N began to rise while the total mass was reducing along with the loss of C content. At the end of the composting, the total N contents of the disposals A and B decreased by 2.9 and 1.0 g/kg, respectively, but the disposals C and D increased by 1.6 and 1.9 g/kg, respectively. The total P and total K contents have been on a slow upward trend, until the end of the composting they increased by 14.2%-36.4% and 28.1%-34.7% respectively. The organic C content decreased in general. At the end of the composting, the organic C contents of all disposals respectively decreased by 16.3%, 14.5%, 13.6% and 11.9%. Due to the rich source of N in the early time, microbes multiplied and let out large-scale ammonia N, which resulted in the rapid increase in the C/N ratio, and then the average ratio declined; and the 4 disposals decreased by 0.67, 2.08, 4.48 and 4.49 respectively in the end. Except the disposal with the ratio of 6:4, the GI of all disposals respectively reached 80% on the 23rd, 33rd, 47th day. At the same time, the toxicity of the piles extract liquid increased on plants due to the accretion of the ratio of fungi residue. The total nutrient contents of N, P and K were in a flat or a small decline and then continued to rise in the early period (in about 19 d), which were respectively 5.93%, 5.57%, 5.64% and 5.13% for all disposals at the end of the composting. In addition, the disposal with the ratio of 6:4 was less than 5% in the most period of the composting (within 45 d), but the rest disposals were more than 5% after about 21-25 d. Considering the factors of the compost quality and production cycle comprehensively, the appropriate ratio of manure to mushroom residue is 8:2 for making scale production of organic fertilizer. Furthermore, on account of the low C/N ratio of manure and mushroom residue, it is better to add some annexing agent with high C/N ratio such as rice bran for improving the efficiency of composting.