ERP015893 PRJEB14258 ena-STUDY-INRA-CMSE-03-06-2016-09:48:34:682-186 ena-STUDY-INRA-CMSE-03-06-2016-09:48:34:682-186 Lasting effect of organic waste products on soil microbial communities, a dependence of agricultural practices The use in agriculture of organic waste product (OWP) makes possible to increase productivity with lower cost, while side effects on soil biology are less known. Yet, soil biological communities are of major importance for the delivery of many soil ecosystem services. The objective of the present study was to assess the effect of OWP on soil bacterial and fungal communities using quantitative PCR and high throughput sequencing. Soils were sampled on two long-term observatories: QualiAgro and Colmar. Both sites received different OWP compared to a control treatment. The application rate of OWP was different between observatories; QualiAgro: 4 TC ha-1, and Colmar: 0.84 to 2.2 TC ha-1. At Colmar all crops residues were restituted. Soils samplings were achieved one year after the input. At QualiAgro, the application of OWP induced an increase of microbial biomass, modifications of bacterial and fungal communities’ structures and a change in fungal community composition. The effects observed were OWP dependent and thus globally more marked with the biowaste compost. This could be explained by the high organic matter amount contained in this input. At Colmar, no effect of OWP were observed excepted on fungal community’s composition. Our results suggest that, in case of long-term observatories, the lasting effect of OWP on soil microbial communities depended on the quantity of OWP applied, more precisely the organic matter amount, and/or some agricultural practices such the crops residues restitution which could attenuate the effect of OWP. The use in agriculture of organic waste product (OWP) makes possible to increase productivity with lower cost, while side effects on soil biology are less known. Yet, soil biological communities are of major importance for the delivery of many soil ecosystem services. The objective of the present study was to assess the effect of OWP on soil bacterial and fungal communities using quantitative PCR and high throughput sequencing. Soils were sampled on two long-term observatories: QualiAgro and Colmar. Both sites received different OWP compared to a control treatment. The application rate of OWP was different between observatories; QualiAgro: 4 TC ha-1, and Colmar: 0.84 to 2.2 TC ha-1. At Colmar all crops residues were restituted. Soils samplings were achieved one year after the input. At QualiAgro, the application of OWP induced an increase of microbial biomass, modifications of bacterial and fungal communities’ structures and a change in fungal community composition. The effects observed were OWP dependent and thus globally more marked with the biowaste compost. This could be explained by the high organic matter amount contained in this input. At Colmar, no effect of OWP were observed excepted on fungal community’s composition. Our results suggest that, in case of long-term observatories, the lasting effect of OWP on soil microbial communities depended on the quantity of OWP applied, more precisely the organic matter amount, and/or some agricultural practices such the crops residues restitution which could attenuate the effect of OWP. ENA-FIRST-PUBLIC 2017-06-01 ENA-LAST-UPDATE 2016-07-08