Compost effect on soil humic acid: A NMR study Fabrizio Adani a, * , Pierluigi Genevini a , Fulvia Tambone a , Enzo Montoneri b a Dipartimento di Produzione Vegetale, Universita ` degli Studi di Milano, Via Celoria 2, 20133 Milano, Italy b Dipartimento di Chimica Generale ed Organica Applicata, Universita ` degli Studi di Torino, Corso Massimo D’Azeglio 48, 10125 Torino, Italy Received 19 January 2006; received in revised form 27 March 2006; accepted 29 March 2006 Available online 15 May 2006 Abstract The humic acid (HA) fraction of a food and vegetable residues compost (CM) was taken as indicator to trace the fate of CM organic matter in four years CM amended soil. 1 H and 13 C NMR spectroscopy were used to investigate the nature of the HA isolates from CM, control soil (S 4 ) and amended soil. The result indicated a significant structural difference between CM HA and S 4 HA, and supported the presence of both HA fractions in soil at the end of the amendment trials. However, the nature and content of CM HA in soil did not fully explain the increase of soil cation exchange capacity (CEC) after amendment. All CM humic fractions (i.e., fulvic acid, humic acid and humin) were found to contribute to the change of the soil organic matter composition. It is concluded that although CM HA is a suitable indicator of the survival of compost organic matter in soil during amendment, all three humic fractions should be monitored and ana- lyzed to fully understand changes in the composition and properties of amended soil. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: 13 C CPMAS NMR; Compost; 1 H NMR; Humic acids 1. Introduction In a previous paper (Adani et al., in press), we have reported that compost (CM), obtained from food and veg- etable residues added to soil, effectively contributes to change the physicochemical parameters of soil. The experi- mental data (Table 1) showed that the amended soil was characterized by higher cation exchange capacity, N and organic C content than control soil. The C increase was mostly due to humified C, i.e., fulvic acid C, humic acid C and humin C. A few other studies have also shown increase of soil C, N and CEC by amending with compost (Gonza `les-Vila et al., 1999; Que `draogo et al., 2001; Leifeld et al., 2002). However, a key issue for soil amending practices with com- post remains the capacity to trace the fate of compost organic matter in soil. This seems necessary in order to assess the changes brought by the compost to the nature and turn over of soil organic matter. In this paper, we wish to report our attempt to trace the fate of compost organic matter in soil amendment trials by comparing the humic acid (HA) fractions isolated from CM, control soil (S 4 ) and soil at the end of four years amend- ment trials. 1 H and 13 C NMR spectroscopy was selected as analytical tool for its capacity to selectively identify different types of C and H moieties and to compare difference in con- centration of main functional groups. The CM HA fraction was selected as indicator because HA is conventionally taken as probe to rate compost quality by virtue of its physical, bio- logical and chemical properties (Chen and Aviad, 1990; Varanini and Pinton, 1995). Compost HA is known to be dif- ferent from typical soil HA (Montoneri et al., 2003). The other humic fractions are traditionally neglected as indica- tors. Fulvic acid (FA) is present in low concentration. 0045-6535/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.03.070 * Corresponding author. Tel.: +39 02 503 16546; fax: +39 02 503 16521. E-mail address: fabrizio.adani@unimi.it (F. Adani). www.elsevier.com/locate/chemosphere Chemosphere 65 (2006) 1414–1418