Effects of farmland application of sewage sludge on crop yields and heavy metal accumulation in soil and crop.

Based on a 3 years located experiment,the heavy metals such as Mn,Cu,Zn,Pb,Cd concentration of soil and crop and crop yields were investigated for the different treatments on farmland application of sewage sludge,by comparing soil nutrient,heavy metal contents of soil and crop and crop yields,the treatments included three different kinds of sewage sludge,namely digested sludge,sludge compost and sludge compound fertilizer.The results indicated that three kinds of sewage sludge could significantly increase the contents of total organic matter and total nitrogen in soil.Compared to treatments of control and ordinary chemical fertilizeres,three different kinds of sewage sludge could increase Mn,Cu contents in soil,but had not significant influence to exchangeable heavy metals in soil.Three kinds of sewage sludge could increase Zn contents in wheat grain.Compared to the ordinary chemical fertilizer,the use of three different kinds of sewage sludge had no significant effect to yield of wheat and maize.Reasonable use of sewage sludge can be effective in raising crop yield.Sewage sludge application had a certain cumulative effect on soil heavy metals,but short-term application was relatively safe.