Studies On The Biogas Fertilizer Fertility, Potential Pollution Risk And Safety Evaluation Of The Soil After Application

Biogas fertilizer is defined to be remnants after the fermentation of faeces of human and animals and various crop stalks within sealed digesters. It has a positive impact on promoting the quantity and quality of agricultural products as well as improving soil situation and is an important organic fertilizer resource. Although biogas fertilizer has a good effect on increasing agricultural production, improving soil situation and livestock farming, there are few reports about the influences of antibiotics veterinary drugs and heavy metal remnants resulting from biogas fertilizer on soil. Therefore, it is necessary to study the source and elements of biogas fertilizer and antibiotics veterinary drugs and heavy metal remnant in soil after its application. In this paper, we investigated the whole process from production to application of biogas fertilizer in ChangTu (Liaoning Province), LiuMinYing (Beijing), YangLing (Shaanxi Province), MianZhu (Sichuan) and FangChengGang (Guangxi Province) by the method of sampling survey. The quantity of veterinary drugs and heavy metal in Feed-Faeces-Biogas fertilizer-Soil were also tested. In addition, we compared effects of biogas fertilizer and the change in soil from different sources and production modes. We expect to provide scientific evidence for safe application of biogas fertilizer. The key results are as follows:1. Total nitrogen (N), phosphorus (P), Potassium (K), organic matter and other nutrient were rich in biogas fertilizer. After the application, total N, P, K and organic matter content in soil was significantly higher than those of control soil. Biogas fertilizer can promote the soil fertility and improve soil nutrient content after long-term used.2. The long-term application of biogas fertilizer resulted in the increase of the detection rate of antibiotics veterinary drugs in soil. Drug detection rate of biogas fertilizer soil was significantly higher than that of control soil among the 5 experimental sites. The application of biogas fertilizer brought about the potential safety problems of soil.3. Biogas fertilizer contains a certain amount of heavy metals, particular in Cu and Zn contents. Cu and Zn contents in soil after the long-term application of biogas fertilizer were significantly higher than those in controls, but not beyond the national soil safety standards. The contents of As and Cr in biogas fertilizer were in the normal level. As and Cr contents in soil showed a slight downward trend or no significant change in the same condition. Through the soil quality evaluation, we found that all samples of soil after the application of biogas fertilizer were consistent with the national soil safety standards level one or two.4. Among the three different materials biogas fertilizer, cow dung biogas fertilizer contained the highest nutrient, while chicken manure was lowest. However, the long-term application of biogas fertilizer from pig manure was most significant in elevating soil nutrients.