Impact of high carbon amendments and pre-crops on soil bacterial communities

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ORIGINAL PAPER

Impact of high carbon amendments and pre-crops on soil bacterial communities Catherine W. Kamau 1 & Richard van Duijnen 2 & Christoph A. O. Schmid 1 & Helga E. Balàzs 1,3 & Julien Roy 4,5 & Matthias Rillig 4,5 & Peter Schröder 1 & Viviane Radl 1 & Vicky M. Temperton 2 & Michael Schloter 1,6 Received: 14 July 2020 / Revised: 6 October 2020 / Accepted: 15 November 2020 # The Author(s) 2020

Abstract A 2-year outdoor mesocosm experiment was carried out to determine the effects of high C amendments (HCAs; wheat straw and sawdust) compared to a control with no addition of HCAs (no-HCA) and 2 different crop rotation systems (spring barley/winter barley and faba bean/winter barley) on soil bacterial communities using a molecular barcoding approach. Samples were analyzed after pre-crop harvest (T1) and harvest of winter barley (T2). Our data demonstrate a clear drop in bacterial diversity after winter barley harvest in the no-HCA and wheat straw treatment compared to the pre-crops. Sawdust application had a stabilizing effect on bacterial diversity compared to the pre-crops and induced an increase in carbon (C) stocks in soil which were however negatively correlated with yields. Main responders in the no-HCA and wheat straw treatment compared to the pre-crops were bacteria of the phyla Actinobacteria and Bacteroidetes which were enriched and bacteria belonging to Firmicutes, Gemmatimonadetes, Proteobacteria, and Gemmatimonadaceae which were depleted. Overall differences between wheat straw–amended and no-HCA control samples were small and included single ASVs from various phyla. In sawdust-amended samples, only a shift of some Proteobacteria families was observed compared to the no-HCA control. Overall, pre-crop plant species had small influence on the observed response pattern of the soil microbiome towards the amendments and was only visible for wheat straw. Keywords High carbon amendment . Crop rotation . Soil microbiome . Soil multifunctionality

Introduction

* Viviane Radl [email protected] 1

Research Unit for Comparative Microbiome Analysis, Helmholtz Zentrum München GmbH, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany

2

Institute of Ecology, Leuphana University of Lüneburg, Universitätsallee 1, 21335 Lüneburg, Germany

3

Botanical Garden “Alexandru Borza”, 42 Republicii St, 400015 Cluj-Napoca, Romania

4

Institute for Biology, Ecology of Plants, Freie Universität Berlin, 14195 Berlin, Germany

5

Berlin-Brandenburg Institute of Advanced Biodiversity Research, 14195 Berlin, Germany

6

Technical University of Munich, Chair of Soil Science, Emil-Ramann-Straße 2, 85354 Freising, Germany

The growing human population in the last century all over the world has necessitated an increase in agricultural productivity resulting in higher demands for fertilizer (Galloway and Cowling 2002; Smil 2002). However, the use efficiency of many fertilizers is still low. Consequently, the increased fertilizer application rates have induced high nutrient levels not only in agroecosystems but a