| Chicken manure is rich in nutrients with high contents of nitrogen,phosphorus and potassium.As one of the main raw materials of organic fertilizer,chicken manure can effectively improve soil fertility and increase crop yield.However,aditives containing heavy metals are usually added to chicken feed,and their utilization rate in animals is low.Therefore,heavy metals in additives enter the environment with livestock manure,which may increase the ecological risk of soil heavy metals accumulation and threaten the safety of agricultural products.The purpose of this study was to explore the effects of short-term and long-term application of chicken manure organic fertilizer on soil physical and chemical properties,heavy metal accumulation,and soil microbial community structure and diversity in vegetable fields,so as to provide theoretical basis for the realization of national"Zero Growth Action Plan for Fertilizer"and"Promotion of Organic Fertilizer in the Whole County"and other work goals.The main conclusions of this study are as follows:（1）The field experiment was conducted to study the the influence of different doses of chicken manure organic fertilizer on physicochemical properties and microbial phospholipid fatty acid（PLFA）composition characteristics of soils planted with Chinese cabbage（Brassica chinensis）,and to explore the correlation between them.Results showed that:the application of chicken manure organic fertilizer increased the soil fertility.Soil organic matter（SOM）,total nitrogen（TN）,total phosphorus（TP）,total potassium（TK）,nitrate nitrogen（Nitrate-N）,and available phosphorus（AP）increased respectively by34.1%,48.2%,47.9%,35.5%,3.9%,and 14.7%in T4 over that in CK.The Total PLFA contents,PLFA contents of each microbial group,and the fungus to bacteria PLFA ratios in middle and high fertilizer treatments were higher than that in the treatment without fertilizer.Among these treatments,the total PLFA contents,the bacterial,and the fungal PLFA in T4 increased by 53.4%,52.1%,and 108.3%,respectively in contrast to the control.The Shannon,Simpson,and Pielou indexes in T2 were the highest among all treatments.Microbial community structure was similar among treatments with no fertilizer（CK）,extremely low（T0.5）,and low fertilizer applications（T1）(?15 t·hm-2),and differed significantly from treatments with moderate（T2）and high fertilizer applications（T4）(?30 t·hm-2).The results of redundant analysis（RDA）showed that physical and chemical properties explained 87.2%of the changes in the community structural.The main driving factors were Nitrate-N,TK,and p H.Microbial PLFA were positively correlated with the AP,ammonium nitrogen（Ammonium-N）,nitrate-N,TN,and TP,while they were negatively correlated with soil cation exchange capacity（CEC）and p H.（2）A field experiment was conducted to investigate the effects of different doses organic fertilizers from chicken manure on the heavy metals accumulation and availability in soil,as well as soil microbial community structure in a facility vegetable soil.In addition,the correlation between soil microbial community structure and soil heavy metals was further discussed.The results showed that the contents of soil heavy metals cadmium（Cd）,chromium（Cr）,copper（Cu）,and zinc（Zn）increased with the increase of the amount of organic fertilizers,and all reached the maximum values with the highest increases of 21.30%,21.58%,17.40%,and 19.40%,respectively.Apparent accumulation of these heavy metals was found in the soil applied organic fertilizer.And the application of organic fertilizers increased the concentrations of soil available Cd,Cr,Cu,and Zn.While the total and available Pb concentrations in soil had no significant changes in different treatments.There were significant correlations between the total and available concentrations of soil heavy metals except of lead（Pb）,in which the relativity of Zn was the strongest.The results of PLFA analysis showed that the higher PLFA contents were 16:0,18:1ω7c,10Me16:0 and 18:1ω9c,and the order of total PLFA and soil microorganism groups PLFA contents showed as M0.5>M1>M2>M4.The results of correlation analysis showed that the total contents of Cu and the available contents of Cd,Cr,Cu,and Zn were negatively correlated with the total and various groups PLFA contents,and among them,the effects of soil available Cr and Cu on microbial community structure were very significant.（3）In order to explore the accumulation characteristics of soil heavy metals and the changes of soil microbial community under different application years of organic fertilizer,a long-term field fertilization experiment was conducted to evaluate the soil physical and chemical properties（p H and CEC）,fertility characteristics（SOM,available nitrogen（AN）,AP,and Available potassium（AK））,heavy metals（total and available form）and microbial（bacteria and fungi）community structure diversities after long-term application of chicken manure organic fertilizer.The results showed that the contents of SOM,AN,AP and AK in the surface soil applied organic fertilizer were higher than those in the control treatment,and the SOM content reached the maximum at 18 a.Soil p H under different fertilization years ranged from 6.62 to 7.45.Soil p H decreased with the increase of organic fertilizer application years and showed obvious acidification phenomenon.The total contents of soil heavy metals were basically increased with the increase of organic fertilizer application years.And the available contents of heavy metals were significantly higher than those in the control treatment,of which the available contents of Zn,Cu and Pb increased with the increase of fertilization years.In addition,the propotion of exchangeable fraction of soil Cr,Cu,Zn and Pb under different fertilization years were increased to varying degrees compared with the control.In the profile soil,the contents of soil organic matter and CEC decreased with the increase of soil depth,while the soil p H increased.In the 0-40 cm soil layer,the total contents and available contents of soil heavy metals basically increased with the increase of years of application organic fertilizationat at the same depth.In the 40-100 cm soil layer,there was no significant difference in the total content of heavy metals under different treatments.This study found that the years of Cd and Zn exceeding standard limits was short by predicting the years of heavy metals over standard limits.Soil geoaccumulation index increased with the increase of organic fertilizer application years,and the pollution degree of Cu,Zn,and Cd were relatively high in this study area.The results of potential ecological risk assessment of soil heavy metals showed that the multiple complex potential ecological risk was in the middle ecological risk when the fertilization year was 18.The diversities of bacterial and fungal communities in soils applied organic fertilizer were significantly lower than that in the control treatments.With the increase of organic fertilizer application years,the Shannon indexes of bacterial and fungal communities first increased and then decreased,while the Chao1 indexes of bacterial communities increased.Different application years of organic fertilizer significantly changed the community structure of bacteria and fungi.The main environmental factors affecting soil bacterial and fungal community structures were p H and AK,AK,AN and Cu,respectively. |
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