Study On Nutrient And Heavy Metals Content In Feeds And Manure At Intensive Livestock Farms In Yangling, Shaanxi And The Related Environmental Management Implication

The scale of Chinese livestock industry continues to expand, however, livestock manure generated in the process has resulted in local environmental pollution. In order to stimulate growth and prevent disease, farmers often add heavy metals in feed additives or medicines, resulting that heavy metals are excreted with the manure. If high levels of heavy metals in the manure would continue be applied to farmland, the farmland soils will gradually accumulate and resulted in severe soil contamination. This trend is a great threat to the security of agricultural crops and poses human health hazards through the food chain. Therefore, a comprehensive understanding of the use of heavy metals in the process of livestock rearing which will help to control heavy metals in feed additives, and is of great significance to promote comprehensive utilization of resources manure and food safety.Yangling District is located in the hinterland of the Guanzhong Plain in Shaanxi Province, with a total area of 135 square kilometers. As the only agricultural high-tech industries demonstration zone is located, it enjoys various preferential policies. The demonstration bases of agricultural industrialization and modernization, and the agricultural level of demonstration zone represents the developmental trend of China’s future agriculture. Because of land circulation and other reasons, the use of livestock waste presents certain peculiarities in Yangling rural areas. Large number of farms, but more dispersed, and the scale, degree of specialization is different. Also there is a big difference in the processing of waste in the aquaculture industry. Scientific research on heavy metals in feed and pollution of livestock manure in Yangling Demonstration Zone farms, is important to understand the current intensive livestock farming industry in China, and seek manure resource utilization and safe processing. In order to assess the content of N、P、K and heavy metal in animal feeds and manures in livestock farms around Yangling, 54 animal manure samples and 58 animal feed samples were collected from 19 different scale farms in 2014. The results showed that:(1) the contents of N、P、K and Zn、Ni、Cd、Cu、Pb in animal feeds were 0.19%~5.64%, 0.34%~15.63%, 1.13%~3.64% and 43.65 ~95.20 mg/kg, 3.43 ~13.71 mg/kg, 0.54~1.99 mg/kg, 7.86~293.7 mg/kg, 3.55~15.84 mg/kg(2) the contents of N、P、K and Zn、Ni、Cd、Cu、Pb in manure were 0.71%~3.56%, 0.43%~7.42%, 1.20%~8.93% and 0.12~157.7 mg/kg, 0.57~14.88 mg/kg, 0.15~2.25 mg/kg, 2.67~319.3 mg/kg, 0.85~18.87 mg/kg, respectively. Manure EC ranged from 1.09 m S/cm to 8.21 m S/cm, and the manure p H varied from 6.34 to 10.85.(3) N content in animal feed was in the rule of pig > cattle > poultry> sheep in some extend, P and K content in cattle and sheep feeds were higher than that in pig and poultry. While the N and P content in pig and poultry manure were higher than that of cattle and sheep, K content in poultry and sheep manure were higher than that in pig and cattle.(4) The heavy metal contents present similar variation with Zn > Cu > Pb > Ni > Cd both in animal feed and manure. Although, all the Cd content in feed and part of feed Pb content exceeded the standard limit of hygiene in the livestock feeds(GB13078-2001). Compared with the pig feed in different years or regions, the content of Zn, Ni, Cd and Cu was lower, and the content of Pb was slightly higher.(5) The contents of heavy metals such as Cu, Zn, Cd, Ni and other heavy metals in livestock and poultry were generally lower than the corresponding values of different years in different regions of our country, but also lower than the limit values of heavy metals in the organic fertilizer(NY525-2012). The study indicated that the animal feeding in yangling is scientific, the feed additive utilization guidance is appropriate, and the livestock and poultry manure had the safety utilization potential in organic fertilizer production.