Effects Of Organic Manure Application On The Accumulation Of Heavy Metals In Soil And Maize

With the rapid development of society and population,people's demand for food is getting higher and higher.Therefore,the use of organic fertilizer has prominently increased in order to enhance crop yield by maintaining the ecological environment and soil fertility.Most of the organic fertilizers are animal husbandry based but recently,feed additives have extensively been used to promote animal growth,disease prevention and improving feed efficiency.Those feed additives contain large amount of heavy metals which excretes from the body as feces consequentially increase the content of heavy metals in the organic fertilizer.Therefore,an experiment was conducted at Hailin farm in Heilongjiang province to evaluate the soil organic matter,different heavy metals present in maize and the impact of organic manure containing heavy metals in soil.In this study,five treatments were being used,100% organic fertilizer(T1);30% organic fertilizer + 70% fertilizer(T2);20% organic fertilizer + 80% fertilizer(T3);100%fertilizer(T4);no fertilization(CK),the contents of heavy metals Cd,Cr,Ni,As,Hg,Pb,Cu and Zn in soil were measured for 3 years(2013-2015),and changes of Heavy Metal Cd,Cr,Ni,As,Pb,Fe,Mn,Zn and Cu of maize grain in 2015.(1)In the same year,In 2013?2014?2015,the contents of heavy metals Cd,Cr,Ni,As,Hg,Pb,Cu and Zn in CK treatment were not significantly changed(P <0.05).Comparing with other four treatments,the accumulation of Cd,Cr,Ni,As(P <0.05)in T1 were significantly higher than that of T2,T3,T4 and CK(P <0.05).The T1 of heavy metals Cd,Cr,Ni,As,Hg,Pb,Cu and Zn in soils was higher than that of CK in 2013,2014 and 2015,76.92% ? 126.43% ?175.86%;77.94%?76.62%?77.60%;23.95%?92.53%?136.35%;50.21%?70.48%?94.57%;34.57%?60.87%?83.56%;34.82%?45.94%?63.46%;69.19%?95.11%?124.47%;15.75%?47.88%?64.16%,respectively(P <0.05),and the proportion of CK was significantly lessr than that of the other four treatments(P <0.05).In 2014 compared with 2013,2015 compared to 2014 increased 37.83%?51.42%;1.80%?3.31%;67.16%?26.69%;14.69%?15.97%;19.55%?20.72%;14.64%?14.78%;16.25%?15.83%;27.19%?12.96%.The content of Cd and Ni in the soil is more than 6% and 2% of the national standard respectively;the maximum Pb content is 83.59 mg / kg,which is higher than the national standard of 80 mg / kg;The formation of pollution elements,although not the formation of pollution,but the increasing content of elements,the formation of a potential threat to soil pollution.(2)In 2015 experiment,with the increase of the proportion of organic fertilizer in the application of fertilizer,the content of heavy metals in maize grain increased,and the contentsof heavy metals Cd,Cr,Ni,As,Pb,Fe,Mn,Zn and Cu were higher than those of T2,T3,T4 and CK.The contents of T1 of heavy metals in maize grain were significantly higher than those in T2,T3,T4 and CK(P <0.05),T1 processing increased over CK 106.78%,145.88%,208.06%,23.53%,50.00%,22.07%,53.86%,106.78%,66.91%.However,the contents of Cd,Cr and Cu are close to the national pollution standard,which poses a potential threat to the pollution of corn kernels.A significant positive correlation was found between heavy metal in maize and soil.(3)Risk assessment studies have shown that more than the national standard of heavy metal elements Cd 0.48 more than 6% of national standards,Ni over the national standard of 2%,As maximum 20.82 mg / kg,although less than the national standard of 30 mg / kg,but The maximum value of Pb is 83.59 mg / kg,80 mg / kg higher than the national standard,the maximum value of Cu is 76.32 mg / kg,which is lower than the national standard of 100 mg / kg.The heavy metal Ni,As,Cd,Pb,Fe,Mn,Cu,Zn and Cr contents,the contents of heavy metals in the soil increased with the increase of the ratio of organic manure applied to the soil and the continuous fertilization test.The contents of heavy metals Cd,Cr,Cu The maximum value is close to the national food security standards,other elements are constantly increasing,so the application of organic fertilizer on the soil of some elements have been formed pollution,and no pollution of the elements are also increasing the soil and grains.The heavy metal content has a potential threat.(4)The relationship between organic matter and heavy metals has shown that,The contents of Cd,Hg,Pb,Cr,Ni,Cu,As and Zn in the soil were significantly correlated with the contents of four organic matter in the soil.The contents of Ni,As,Cd,Pb,Fe,Mn,Cu and Zn in maize had significant positive correlation with four organic contents in soil.