Bulk and water-extractable organic matter from compost: evaluation of the selective dissolution in water using infra-red absorbance ratios.

Alla Nasonova,Guy J Levy,Mikhail Borisover

doi:10.31220/osf.io/5pnkx

Abstract

Abstract Land application of composts affects concentration and composition of dissolved organic matter (OM) which plays important roles in soil functioning and may have effects on spreading of environmental pollution. Linking between the compositions of bulk compost OM and its water-soluble fraction may, therefore, allow better understanding and prediction of environmental impact of compost land use. The objectives of this study were to (i) examine compositional links between bulk compost OM and its water-extractable OM (WEOM), and (ii) evaluate and quantify selectivity of bulk compost OM dissolution, based on infra-red (IR) absorbing functional groups. For that, 8 different composts and their freeze-dried WEOMs were characterized by mid-IR transmission spectroscopy. Compositions of compost OM and WEOM were characterized in terms of ratios (R) defined on the basis of both areas and heights of specific IR bands in relation to absorbance by aliphatic CH groups. A simple novel approach is suggested, whereby selective dissolution of compost OM components is quantified by relating the R values determined for WEOM to those associated with compost OM. Significant similarities of IR spectra found in a series of WEOMs (and, to a lesser extent, in a series of compost OMs) suggest significant contributions of OM carboxylic groups to various bands. WEOM composition (characterized by the R values) is associated, to a certain extent, with compost OM composition expressed by similar type indices. The WEOM aromaticity estimated by specific UV absorbance correlated strongly with some R values determined for bulk OM.

Highlights

Land application of composted organic matter (OM) is a well-known practice for improving soil properties, adding nutrients and assisting in disposal and utilization of organic wastes (Serra-Wittling et al 1996; Ros et al 2006; Hargreaves et al 2008).Water-extractable organic matter (WEOM) is an active fraction of composts, and the changes in WEOM are commonly associated with changes in bulk compost material and compost maturity (Zmora-Naum et al 2005; Said-Pullichino et al 2007; He et al 2011; Lv et al 2013)
The composition of WEOM, characterized by the area- and peak height-based ratios between certain IR bands associated with hydrophilic groups and that of aliphatic CH
The extent of WEOM aromaticity expressed as SUVA254 exhibited a strong relation with IR-spectroscopic ratios connecting areas of some bands representing hydrophilic components in bulk compost OM with aliphatic CH absorbance

Summary

Introduction

Land application of composted organic matter (OM) is a well-known practice for improving soil properties, adding nutrients and assisting in disposal and utilization of organic wastes (Serra-Wittling et al 1996; Ros et al 2006; Hargreaves et al 2008).Water-extractable organic matter (WEOM) is an active fraction of composts, and the changes in WEOM are commonly associated with changes in bulk compost material and compost maturity (Zmora-Naum et al 2005; Said-Pullichino et al 2007; He et al 2011; Lv et al 2013). Land application of composted organic matter (OM) is a well-known practice for improving soil properties, adding nutrients and assisting in disposal and utilization of organic wastes (Serra-Wittling et al 1996; Ros et al 2006; Hargreaves et al 2008). Zmora-Nahum et al (2007) examined 37 commercial composts from different sources including manure, urban biowaste, green waste, coffee berries, wastes of olive oil press, and different countries (France, Greece and the Netherlands). They concluded that at the end of a complete composting process, the C functionalities were rather uniform for a variety of source materials, with aliphatic C ranging from 18.6% to 26%; polysaccharide C, 39–

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