Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil Impact of the application of commercial and farm-made fermented liquid organic amendments on corn yield and soil quality Julen Urra a, ⁎ , Iker Mijangos a , Lur Epelde a , Itziar Alkorta b , Carlos Garbisu a a NEIKER, Department of Conservation of Natural Resources, Soil Microbial Ecology Group, c/ Berreaga 1, E-48160 Derio, Spain b Instituto BIOFISIKA (CSIC, UPV/EHU), Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain ARTICLE INFO Keywords: Metabarcoding Microorganisms Organic fertilization Soil health Sustainable agriculture ABSTRACT Organic amendments are being increasingly applied to agricultural soils as alternatives or complements to in- organic fertilizers. Organic amendments can increase the content of soil organic matter, concomitantly im- proving soil physical, chemical and biological properties. We evaluated the effect of the application of com- mercial vs. farm-made fermented liquid organic amendments, compared to mineral (NPK) fertilization, on corn yield and nutritional status, as well as on soil physicochemical and microbial properties as indicators of soil quality. In particular, we assessed the effect of two doses (optimal vs. suboptimal) and times of amendment application (basal dressing vs. basal + top dressing) for two consecutive growing seasons. Values of corn grain yield were lower in organically-amended plots than in those under NPK fertilization. At the optimal dose, the application of organic amendments led to significantly higher values of microbial activity (soil respiration; enzyme activities; potentially mineralizable N) and biomass (microbial biomass C, bacterial and fungal biomass), leading to an improvement in soil quality. The optimal application dose resulted in an enhanced soil nutrient pool. Conversely, soil properties were not significantly affected by the origin of the amendment (commercial vs. farm-made) or the time of application (basal dressing vs. basal + top dressing). 16S rRNA metabarcoding analysis revealed no significant changes in the diversity and composition of the soil prokaryotic communities between organically-amended and NPK-fertilized soils. It was concluded that the application of fermented liquid organic amendments at the optimal dose (according to the N requirements of corn) can be a beneficial agronomic practice for agricultural soil quality, posing a suitable alternative to mineral fertilization. 1. Introduction Intensive agriculture has resulted in a decrease in soil quality by adversely affecting soil biota, reducing soil organic matter (OM) con- tent and polluting the environment (Diacono and Montemurro, 2010; Das et al., 2014). Furthermore, agricultural intensification, along with animal husbandry and poultry breeding, has led to the generation of large amounts of wastes that need to be properly managed (He et al., 2019). In the last years and decades, the application of OM in the form of crop residues, manure, slurry, compost, sewage sludge, etc. into soil has gained much interest as a sustainable approach for the reutilization of these byproducts as soil amendments and as a realistic, cost-effective and environmentally sound alternative to landfill disposal (Mondini and Sequi, 2008; Diacono and Montemurro, 2010; Urra et al., 2018; Chojnacka et al., 2019). Organic amendments represent a valuable source of nutrients for impoverished agricultural soils, with the po- tential to act as alternatives or complements to mineral fertilizers (Riva et al., 2016; Aranguren et al., 2018; Ji et al., 2018). Organic amend- ments can replenish depleted soil organic carbon (C), thus stimulating soil biological activity and improving soil structure, water-holding ca- pacity, etc. and concomitantly enhancing crop yield (Lal, 2008; Powlson et al., 2014; Hernández et al., 2016). Organic amendments can posi- tively affect soil microbial activity, biomass and diversity, the latter being presumably linked to functional redundancy and ecological sta- bility (Stockdale et al., 2013; Larney et al., 2016), as well as to the provision of ecosystem services (Tilman et al., 2006; Delgado-Baquerizo et al., 2016). The long-term use of mineral fertilizers can negatively influence soil microbial diversity (Fließbach et al., 2007). In turn, the application of organic amendments has been reported to positively impact the diversity and composition of soil microbial communities (Chaudhry et al., 2012), with concomitant beneficial effects on soil health (Fließbach et al., 2007). However, the improper application and overuse of organic amend- ments (especially those derived from raw organic waste) to soil may https://doi.org/10.1016/j.apsoil.2020.103643 Received 18 October 2019; Received in revised form 20 April 2020; Accepted 26 April 2020 ⁎ Corresponding author at: NEIKER, Department of Conservation of Natural Resources, c/ Berreaga 1, E-48160 Derio, Spain. E-mail address: jurra@neiker.eus (J. Urra). Applied Soil Ecology 153 (2020) 103643 0929-1393/ © 2020 Elsevier B.V. All rights reserved. T