Evaluation on resource utilization of litters in pig-on-litter farming system

The pig-on-litter (POL) system is a new ecological pig farming model of reducing pig wastes. The resource utilization of litters requires further investigation. A study was carried out to investigate organic matter, nitrogen, phosphorus, potassium, heavy metals, antibiotics residues, salinities and maleficent bacteria of pig litters from five pig-on-litter farms in Shandong and Jilin in China. The results show that the pig litters rich in organic matter, nitrogen, phosphorus and potash. The contents of organic matter are in the range of 42.62%54.12%, the contents of total nitrogen are in the range of 1.54%2.12%, the contents of total phosphorus (P2O5) are in the range of 2.24%5.55% and the contents of total potassium (K2O) are in the range of 0.57%2.15%. The contents of copper, zinc, chromium, arsenic, nickel, plumbum, cadmium and hydrargyrum are lower than the respective values in the organic fertilizer national standards (NY 525-2012) and control standards for urban wastes for agricultural use (GB 8172-1987). The pig litters have low environmental risks for low contents of OTC, TC and CTC. The contents of ascaris eggs and E. coli are higher than the respective values in the two standards. The ascaris eggs mortalities are in the range of 90%94%, the numbers of E. coli are in the range of 1.29105 2.24106 CFUs/g. Moreover, salinities are high in pig litters. Conclusion: The pig litters have the fundamental properties of organic fertilizer, and must be harmlessly processed before land utilization for biological safety risks.