Effect Of Pig Manure Application On The Transfer Of Cd In Soil-Wheat Systems

Excessive use of heavy metals in feed additives is prominent in intensive breeding industry. Since the utilization of heavy metals in animal body is minor, most of them are excreted with feces. Under the circumstances of livestock manure used as fertilizers in farming, heavy metal may cause environmental and health risks. The Northeast Plain, Huang-Huai Plain, and Yangtze River Delta Area are major grain-producing areas of China. Thus, three soils from these areas, i.e., black soil in Heilongjiang Province, fluvo-aquic soil in Henan Province, and paddy soil in Zhejiang Province, were chosen as the experiment materials. Pot experiments were conducted with different Cd addition level in manure to study the effects of soil Cd on the biomass and Cd contents in different parts of wheat at different stages (tillering stage and mature stage), especially those in grains. The aim of this study is to investigate the effects of pig manure application on the transfer of Cd in different soil-wheat systems. The results showed:1) Pig manure can significantly increase grain yield in fluvo-aquic soil. Compared with the control, grain yield of 3% pig manure treatment in fluvo-aquic soil increased by 45.4% for 0.6 mg/kg Cd application. Pig manure application have no significant effect on grain yield in black soil and paddy soil.2) In this expriment, pig manure application can reduced food chain health risks of Cd in soil-wheat system to some extent. Cd contents of grain reduced significantly after the application of pig manure in black soil, fluvo-aquic soil and paddy soil. Compared with the control, Cd Contents of grain of 3% pig manure treatment in black soil, fluvo-aquic soil and paddy soil reduced respectively by 51.8%,16.7% and 74.2% for 1 mg/kg Cd application. Pig manure application reduced food chain health risk of Cd in 3 soils.3) Cd, whose effect was far more than manure, is the most important element which can affect Cd contents in different parts of wheat. And the effect for the three soils was different insignificantly. Whether pig manure application can cause food chain health risk of Cd depends on the Cd content of pig manure applied. Application of manure with 30 mg/kg Cd may cause food chain health risk once.4) When no manure is applied, Cd can transfer more easily to shoot of wheat in paddy soil than black soil and fluvo-aquic soil. When no manure is applied, Cd contents of grain in paddy soil are higher than those in black soil by 25.3% and higher than fluvo-aquic soil by 37.4% for 0.6 mg/kg Cd application. There is no differences between black soil, fluvo-aquic soil and paddy soil.The results can simulate the accumulation of soil Cd after long-term application of manure, or after the application of pig manure with high Cd contents, which is helpful to provide a scientific basis to plan the land use mode of solid waste in the breeding industry and establish soil environmental quality criteria.