Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil Microbial community structure and function respond more strongly to temporal progression than to the application of slurry in an Irish grassland Aaron Fox a,b,1 , Israel Ikoyi a , Rachel Creamer b,c , Gary Lanigan b , Achim Schmalenberger a, ⁎ a University of Limerick, School of Natural Sciences, Department of Biological Sciences, Limerick, Ireland b Environment Research Centre, Teagasc, Johnstown Castle, Co. Wexford, Ireland c Wageningen University, Soil Biology and Biological Soil Quality, Wageningen, The Netherlands ARTICLE INFO Keywords: Bacteria Fungi T-RFLP qPCR Soil enzymatic activity Carbon ABSTRACT The application of slurry to grassland for fertilization purposes is common practice, but its effect on the soil microbiota is mostly overlooked. This study investigated the short term response of the functionality and composition of the soil microbiome to slurry application. A 180 m 2 field was divided into 36 plots. Slurry was splash-plate applied at a rate of 30 t ha -1 . Sampling was conducted 5, 30 and 65 days after application. The functionality of the soil microbial community was examined using assays on 8 carbon cycling enzymes as well as basal respiration analysis. Microbial community structure was analysed via bacterial 16S rRNA gene and fungal internal transcribed spacer region terminal restriction fragment length polymorphism. Bacterial and fungal abundance was determined via quantitative PCR aiming at the same genetic targets. Furthermore, microbial biomass carbon and nitrogen were quantified. A significant increase in enzymatic activity with slurry treatment was reported on days 5 and 65, indicating a sequential response of the microbiota to slurry-derived carbon with the utilization of labile carbon on day 5 and the more stable carbon on day 65. This activity seemingly resulted from the microbial demand for N. In contrast, T-RFLP revealed that only bacterial community structures on day 5 were significantly affected by slurry application, all other bacterial and all fungal communities were not significantly altered by slurry. However, bacterial and fungal community structures, microbial biomass carbon and basal respiration significantly responded to temporal progression (day 5, 30 and 65). These findings suggest that soil microbial communities are responding to slurry applications via enhanced microbial activity but their structure remains largely unchanged with temporal progression having a greater impact. 1. Introduction Pasture-based livestock production is the predominant agricultural activity in Ireland and is common in temperate climates worldwide. Animals are typically kept out on pasture between March and November and are then over-wintered indoors. This is usually to protect the soil from trampling and compaction during the wetter winter months. This over-wintering produces a large quantity of slurry and its application back onto the land is an imperative practice for the re- cycling of nutrients in Irish agricultural systems (Holden et al., 2004). Despite the critical role the soil microbiome plays in the cycling of slurry derived nutrients, in particular carbon (C), the soil-slurry-mi- crobiota interactions is largely unknown (Harris et al., 2011). Slurry derived C is typically classified into labile and recalcitrant fractions. These fractions are differentially incorporated into the soil matrix (Rochette et al., 2000). The labile C fraction (glucose, xylose etc) is incorporated within a few days after slurry application while the more recalcitrant C fraction (cellulose, lignin) is incorporated over a period of weeks (Dungait et al., 2009; Rochette et al., 2000). This dynamic will correspondingly affect the soil microbial community. It is assumed that initially there will be a large increase in microbial (particularly bac- terial) biomass as the labile C fraction is utilized as an easily metabo- lizable energy source (Fontaine et al., 2003). As this energy source becomes exhausted, the microbial community will subsequently use the recalcitrant C component of the slurry and potentially the soil organic carbon (SOC) at increased rates (Bol et al., 2003b; Bourdin et al., 2010; Kuzyakov and Bol, 2006). The effect of slurry application on bacterial and fungal community structure is little understood and little reported in the literature and this is especially the case for field applications (Harris et al., 2011). The effect of cattle slurry on bacterial community structures in soils under laboratory conditions has been recently reported, where DNA- http://dx.doi.org/10.1016/j.apsoil.2017.07.032 Received 27 March 2017; Received in revised form 19 July 2017; Accepted 21 July 2017 ⁎ Corresponding author at: School of Natural Sciences, Department of Biological Sciences, University of Limerick, Park Road, Castletroy, Limerick, V94 T9PX, Rep. of Ireland. 1 Current address: Agroscope, Forage Production and Grassland Systems, Zürich, Switzerland. E-mail address: achim.schmalenberger@ul.ie (A. Schmalenberger). Applied Soil Ecology 120 (2017) 97–104 0929-1393/ © 2017 Elsevier B.V. All rights reserved. MARK