Study On The Heavy Metals In Livestock And Poultry Manures And Their Effects On The Pakchoi And Radish

In the intensive animal production, more and more trace elements such as Cu, Zn, Se, Mn, As were added in the feeds of animals to prevent disease and make them grow faster. Due to low bioavailablity of these elements in animal bodies, most of them were excreted to the environment with animal feces. There will be environmental risks caused by the manure-born metals, when the manures containing high concentations of these heavy metals are applied to farmland as fertilizer. And even worse is that these heavy metals may affect human health through biological chain. This research is to investigate the heavy metal content of livestock and poultry manures from JiangSu and to study the effect on pakchoi and radish by the polluted soil and the change of heavy metal content in surface soil, in order to evaluate the risk of livestock and poultry manures to the vegetable and soil quality and provide some information of reasonable use of livestock and poultry manures.The contents of Cu, Zn, Pb, Cr, Cd, Ni were measured with atomaic absorption spectrophotometer method in 72 manure samples from JiangSu Province. Results showed that average contents of Cu and Zn in pig manure were as high as 571.3mg/kg and 578.3mg/kg respectively. The average contents of Zn in chicken and duck manures were as high as 453.2mg/kg and 365.3mg/kg respectively. According to the limit of matured compost in Germany , the percentage of Cu, Zn, Cd and Ni more than the limit were 44.4%, 61.1%, 66.7% and 66.7% respectively in chicken manure, were 76.9%, 69.2%, 57.7% and 38.5% respectively in pig manure.The Cd and Ni were 37.5% and 37.5% more than the limit respectively in goose manure, and the Cd was 40.0% more than the limit in duck manure and no heavy metals exceeded the limit in cattle manure.Pot experiment were conducted to study the influence of heavy metals in soil which was polluted by the livestock and poultry manure-born metals on vegetables and metal accumulation. Different heavy metal treatments (Cu, 0, 50, 150, 500, 750 mg/kg; Zn, 0, 100, 250, 500, 750, 1000 mg/kg; Pb, 0, 2, 10, 50, 100, 150 mg/kg; Cr, 0, 10, 50, 100, 200, 300 mg/kg) were designed in this research. Results showed that low concentrations of Cu, Zn and Pb would stimulate the growth of pakchoi and radish, while high doses of Cu and Zn appeared inhibition to pakchoi and radish(P<0.05). The pakchoi growth was affected at the dose of Cu 150mg/kg, Zn 500mg/kg, Pb 100mg/kg and higher dose respectively. The radish production was influenced at the level of Cu 150 mg/kg, Zn 250 mg/kg, Pb150 mg/kg and in higher treatments.The contents of Cu, Zn, Pb and Cr in pakchoi and radish increased with the increasing concentrations of these elements in soil, particularly Cu and Zn. The Cu, Zn, Pb and Cr concentrations of under-ground part of pakchoi were higher than the above-ground part, while Zn concentrations of the under-ground and above-ground part of pakchoi were similar. The Cu and Cr concentrations of under-ground part of radish were higher than that of above-ground part, while the Zn and Pb concentrations of the above-ground part of radish were higher than that of under-ground part. According to the Chinese Food Hygiene Standard, the contents of Zn and Cr of pakchoi with the treatments of Zn 500mg/kg, Cr 100mg/kg and the higher treatments exceeded the limit. The contents of Zn and Cr of the above-ground part of radish with the treatments of Zn 500mg/kg, Cr 50mg/kg and the higher treatments exceeded the limit. The contents of Cu and Cr of the under-ground part of radish with the treatments of Cu 500mg/kg, Cr 50mg/kg and the higher treatments exceeded the limit.The analysis of heavy metals and NH4OAc extractable metals in soil showed that: The heavy metal concentration in soil changed slightly. The eliminating speed of the content of Cu and Zn in soil was faster ralatively.And for Pb and Cr relatively slow.The content of Pb in surface soil had almost no change during the experiment time. The proportions of NH4OAc extractable Pb and Cr concentration were very small, for Cu and Zn larger relatively.The high content of heavy metals in livestock and poultry manures would affect the safety of fertilizer and might have long-term and potential risk to plant production and their quality.