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Modification of soil humic matter after 4 years of compost application
Waste Management 27 (2007) 319–324 www.elsevier.com/locate/wasman
Modification of soil humic matter after 4 years of compost application Fabrizio Adani
a,*
, Pierluigi Genevini a, Giuliana Ricca b, Fulvia Tambone a, Enzo Montoneri c
a Dipartimento di Produzione Vegetale, Universita` degli Studi di Milano, Via Celoria 2, 20133 Milano, Italy Dipartimento di Chimica Organica e Industriale, Universita` degli Studi di Milano, Via Venezian 21, 20133 Milano, Italy Dipartimento di Chimica Generale ed Organica Applicata, Universita` degli Studi di Torino, Corso Massimo D’Azeglio 48, 10125 Torino, Italy b
c
Accepted 4 April 2006 Available online 8 June 2006
Abstract Two soil plots, 1 ha each, were amended yearly for 4 years, respectively, with 35.8 and 71.6 Mg ha 1 yr 1 of mature compost (CM) obtained from food and vegetable residues. The compost, amended soils, and a control soil plot after 4 years (S4), were analyzed for humin (HUC), humic acid (HAC), fulvic acid (FAC), and non-humic carbon (NHC) content. Compared to S4, the amended soil contained more humified C (HAC, FAC and HUC) and less NHC. Further evidence of the effect of compost on soil organic matter was obtained by the analysis of the humic acid (HA) fractions isolated from both the compost and the soils. These were characterized by elemental analyses and Diffuse Reflectance Infrared Fourier Transformed spectroscopy. The HAs isolated from CM and from S4 were significantly different. The HAs isolated from the amended plots were more similar to HA isolated from CM than to HA isolated from S4. The experimental data of this work indicate that the compost application may affect significantly the soil organic matter composition, and that the approach used in this work allows one to trace the fate of compost organic matter in soil. Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction The assessment of changes in soil organic matter brought about by amending soil with compost is a key issue for soil quality, fertility and compost waste management (Maggioni, 1981; Garcia et al., 1992; Chefetz et al., 1998; Gigliotti et al., 2003). Humic substances (HS) are significant constituents of the organic matter in both soils and compost (Genevini et al., 2002). They are anionic polymeric materials, which contribute significantly to the chemical, physical and biological properties of the soil (Chen and Aviad, 1990; Varanini and Pinton, 1995). Due to their relatively slow biodegradation rate, their life time in soil is relatively long (Qualls, 2004). Therefore, compost addition to soil is expected to alter the content and nature of soil organic matter over a relatively long time range, and this
*
Corresponding author. Tel.: +39 02 503 16546; fax: +39 02 503 16521. E-mail address: [email protected] (F. Adani).
0956-053X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2006.04.004
in turn should change the soil’s properties and performance (Jakobsen, 1995; Que`draogo et al., 2001). Nevertheless, information on the modification of soil organic matter induced by compost addition is quite limited. The effects of compost on soil are expected to depend on several parameters, e.g., the compost quality, the soil type, the method used to apply the compost to the soil, the application rate, and environmental conditions. Compost quality itself depends on a multiplicity of factors, the main ones being the nature of the composted matter, the availability of oxygen in the composting pile, and the composting time (Bernal et al., 1998). Due to the number of parameters involved in soil amendment practice using compost, the few studies published on this subject yield a variety of results (Leifeld et al., 2002; Gonza`les-Vila et al., 1999; Que`draogo et al., 2001), which are difficult to compare. As the effect on soil humic substances is an important question for the use of compost in agriculture (Bernal et al., 1998; Jakobsen, 1995), this paper is focused on the effect of the compost on soil organic matter, with particular attention
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to the nature and content of the soil humic acid (HA) over a 4-yr amendment trial. In this study, cultivated soil from a maize farm was selected and amended with compost produced from food–vegetable residues. 2. Materials and methods 2.1. Compost
Table 1 Data from chemical analyses of compost (average of 4 samples) Component (g kg dm 1)
C distribution (g kg dm 1)
Ash VS TOC N C/N
TECb HAC FAC NHC HUC
a b
The compost (CM) (grain size <2 cm) was produced from a mix of food kitchen and gardening wastes (deciduous wood, brush, grass, etc.) in 1:1 v/v ratio to have optimal bulk density, in a facility located in Bergamo, Italy. Compost was obtained by an aerated composting pile operated for 120 days. A representative sample of compost was taken at the end of the composting, prepared and successively analyzed for ash content, volatile solids (VS), total organic carbon (TOC) and N (The US Composting The US Composting Council, 1997). Total organic C was then fractionated for 24 h at 65 °C by using an aqueous solution of NaOH 0.1 mol L 1 and Na4P2O7 0.1 mol L 1 at 1:50 compost/solution ratio under N2 atmosphere as previously reported (Ciavatta et al., 1988). Stirring was provided by means of a Dubnoff end-over-end shaking bath at 100shake min 1, equipped with a thermostat. The resulting suspension was cooled to room temperature and centrifuged at 6000 rpm for 20 min. The operation was repeated by adding distilled water until supernatant was clear (approximately three times). The insoluble fraction (humin fraction, HU) and the supernatant clear solution (total extractable fraction, TE) were separated. The HU fraction was repeatedly washed with distilled water until supernatant solution was clear. The collected liquid fractions were mixed, acidified with 50% sulphuric acid to pH < 1.5 to precipitate the humic acid fraction (HA), which was separated by centrifugation. As no purification of parent material was performed (e.g., lipid removing), humic acid could contain organic impurities (Adani et al., 1995). The supernatant acid solution was run through a polyvinylpirrolidone (Aldrich-Chemie Ò, St. Louis, Missouri, USA) packed column. The column was eluted with 10 mL of 0.05 mol L 1 aqueous sulphuric acid to yield non-humic compounds (NH), and then with 0.5 mol L 1 aqueous NaOH to yield the fulvic acid fraction (FA). The HA fraction separated as above was washed with distilled water to neutral pH, shaken with a 2.82 mol L 1HF at room temperature for 24 h to remove inorganic material, and then washed again with distilled water to neutral pH, dried at 60 °C under vacuum, and weighed. Average data of chemical analyses for the composts and the content of organic carbon fractions are reported in Table 1. 2.2. Soil Soil investigated (Calcaric Cambisol, FAO classification) was located in Voghera in the Cascinoni Gallini farm
527 ± 60 472 ± 64 239 ± 28 21.6 ± 4.0 11.4a
140 ± 31 52 ± 1 17 ± 1 72 ± 8 99 ± 13
Calculated based on mean values. TOC = TEC + HUC; TEC = HAC + FAC + NHC.
(Pavia province, Italy). Previous analyses performed on soil samples taken from different locations at the test site did not show appreciable differences in composition. These results are shown as S0 in Table 2. Therefore, the soil was divided into three different plots of 1 ha each: the unamended control plot (S0), a plot treated with 35.8 dry matter Mg ha 1 yr 1 of compost (CM36-S), and a plot treated with 71.6 dry matter Mg ha 1 yr 1 of compost (CM72-S). Compost application was repeated yearly at the end of October for 4 years. The soils plots were cultivated with maize (cv Eleonora, Pioneer) by usual agronomical technique using 230–120–150 kg ha 1 yr 1 of N–P2O5–K2O fertilizer for the whole duration of the amending experimental plan. Plants were sowed on April 3 and harvested completely on August 28, leaving 20 cm-stalks, which were tilled into the soils at the same time as the compost application. Weed control by herbicide Primigrand T2e Merlin was provided. No statistical differences in maize yield between plots were detected during the 4 years of the amending trials. 2.3. Soil sampling and analyses Sampling and analyses were performed according to published procedures (Boyd et al., 1980; MPAF, 2000). The soil plots were sampled at the end of September of the fourth year of the experimental plan. Composite samples of 3 kg each were obtained from each plot by mixing six randomly collected core samples. These composite samples were used to obtain the analytical data reported in Table 2. 2.4. Breakdown of organic C into humic and non-humic C Soil organic matter was fractionated into TE, HA, FA, HU and NH by the same procedure reported for the compost, except for using a 1:10 soil/solution ratio. The C content in the soil and in each organic fraction was determined by the Springer–Klee dichromate oxidation method (Ciavatta et al., 1988). As this method consisted of an oxidation under a hot condition (160 ± 2 °C), the total carbon content (TOC) determined for soils was higher than the C content determined by the ‘‘cold method’’ (Walklely and Black method) (see Table 2 and its legend). Although the cold method is generally used for soil analysis, it is unable to
F. Adani et al. / Waste Management 27 (2007) 319–324
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Table 2 Analytical data of soils Component
S0a
S4b
CM36-Sc
CM72-Sd
Clay (%) Silt (%) Sand (%) pH C (g kg 1 dm)e N (g kg 1 dm) C/N CEC (cmol+ kg 1) TOC (g kg 1 dm)f TEC (g kg 1 dm)g HAC (g kg 1 dm)g FAC (g kg 1 dm)g NHC (g kg 1 dm)g HUC (g kg 1 dm)g
48.7 ± 1.9 44.6 ± 2.2 6.7 ± 1.1 8.2 ± 0.2 10.0 ± 0.1 1.25 ± 0.03 8.0 ± 0.7 17.6 ± 1.4 ndh ndh ndh ndh ndh ndh
49.9 ± 0.9 43.2 ± 2.2 6.9 ± 1.5 8.2 ± 0.1 10.8 ± 0.9 1.40 ± 0.01 7.7 ± 0.7 17.8 ± 1.4 12 ± 0 6.62 ± 0.23 2.42 ± 0.14 0.88 ± 0.04 3.32 ± 0.26 4.18 ± 0.93
49.7 ± 1.4 42.8 ± 2.5 7.5 ± 1.4 8.2 ± 0.0 10.9 ± 0.8 1.54 ± 0.02 7.1 ± 1.4 19.0 ± 1.0 11 ± 1 5.35 ± 0.23 2.20 ± 0.11 0.95 ± 0.01 2.20 ± 0.24 5.55 ± 0.83
48.9 ± 0.7 42.5 ± 0.6 8.6 ± 0.55 8.3 ± 0.6 12.8 ± 0.7 1.55 ± 0.05 8.3 ± 0.5 23.0 ± 1.0 15 ± 1 6.52 ± 0.35 2.81 ± 0.02 1.13 ± 0.00 2.58 ± 0.34 6.28 ± 0.78
Values reported are the means and standard deviations based on triplicate analysis on three subsamples. a Control soil at time zero. b Control soil after 4 years. c Soil amended with 36 Mg ha 1 yr 1 of compost. d Soil amended with 72 Mg ha 1 yr 1 of compost. e Determined by Walkley and Black method. f Determined by Springer–Klee method. g TEC, total extractable C; HAC, humic acid C; FAC, fulvic acid C; NHC, non-humic C; HUC, humin C. h Not determined.
oxidize completely the more recalcitrant organic carbon (e.g., humified carbon). Data are reported in Table 2 as total organic carbon (TOC) for the soil, and total extracted C (TEC), humic acid C (HAC), fulvic acid C (FAC), non-humic substances C (NHC), and humin C (HUC) for the single organic fractions (TOC = TEC + HUC; TEC = HAC + FAC + NHC). The elemental composition of the humic acid (HA) fractions was determined by elemental analyzer (C. Erba analyzer, Rodano, Milan, Italy) NA-2100 elemental analyzer. 2.5. Diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy The humic acid fractions isolated from both compost and soils were studied by DRIFT spectroscopy. Spectra were recorded by Jasco FT/IR-300 E Spectrometer, equipped with a DLATGS detector and a Diffuse Reflectance device (Pike Technologies Inc., Madison, Wisconsin, USA), and corrected for Kubelka Munk (KM); 128 scans were used. Samples (7 mg), previously dried at 65 °C for 48 h under vacuum, and KBr (700 mg; FT grade, Aldrich Chemical Co, St. Louis, MI, USA) were finely ground in a Wig-L-Bug mill (Specamill-Greseby-Specac, Kent, UK) for 10 min, using an agate ball mill. 2.6. Statistical analyses Chemical analyses were performed in triplicate (analytical sub-samples) on each soil sample taken from the 3 kg mass. Since chemical analyses were performed on three analytical sub-samples withdrawn from the 3 kg composite
bulk sample, standard deviation values calculated from the three values were estimates of the variability due to both the analytical method and bulk sample homogeneity. Average and standard deviation values from chemical analyses were calculated according to standard procedure (Natrella, 1966). 3. Results and discussion The data in Table 2 show that the soil plot amended with the highest compost rate (CM72-S), compared to control soil (S4), is characterized by significant increases in TOC, N, apparent sand and CEC contents. On the contrary, for the soil amended with 35.8 Mg ha 1 yr 1 of compost (CM36-S), and looking only at the traditional parameters and not the extraction results, no significant changes of these traditional parameters are evident relative to S4, except for the increase of the N content. Compost effects on soil are often controversial, being dependent upon many factors such as compost and soil type, trial duration, application rate, and crop yield. Table 3 summarizes the results obtained in this work next to the results obtained in various studies on the effects of compost on soil. It may be observed that the experimental conditions and the type of effect indicators over the four sets of experiments listed in Table 3 are not homogeneous. Nevertheless, it can be concluded that the increase of soil C, N and CEC by amending with compost is confirmed in most cases. Relative to the data reported in soil amending trials performed with compost, we have added in this work new indicators based on the fractionation of organic C into humic and non-humic fractions in order to attempt to trace
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Table 3 Comparison of experimental conditions and results for various studies on the effect of compost (CM) on soil Gonza`les-Vila et al. (1999)
Que`draogo et al. (2001)
Leifeld et al. (2002)
This work
CM source
Urban wastes 7 weeks 200–400 16–23 6.7–7.0 30–40 Mg ha 1 ND 10–12% increase ND No change ND ND Higher phthalates and alkanes to fatty acids ratios ND
Biogenic waste of household and gardens ND 233–186 12–13 7.5 65–70 Mg ha 1 18 months 60–154% increase 83–121% increase ND ND 4–57% increase Higher phenolic lignin components ND
Food residues and wood chips
CM timea CM C (g kg 1) CM C/N CM pH CM/soilb Trial durationc Soil Cd Soil Nd Soil HA-liked Soil CECd Soil pHd Soil organic compoundse
Household refuses, animal manure, crop residues ND 160 12 7 5–10 Mg ha 1 16 weeks No change Increase ND 0–30% increase 9–12% increase ND
Crop yield
45–238% increase
17 weeks 239 11.4 ND 37–72 Mg ha 1 yr 1 4 years 0–19% increase 11% increase 0–16% increase 29% increase No change Higher humic substances No change
ND, not determined or not reported. a Duration of the composting process. b Weight of applied CM per soil hectare. c Duration of amendment trial is the time at which soil was characterized after CM application. d Changes of analytical values for amended soil relatively to control soil. e Class of compounds which was mainly affected in amended soil relatively
the fate of the compost humic substances in soil. Table 2 reports also the soil C distribution among the humic acid (HAC), fulvic acid (FAC), humin (HUC) and non-humic (NHC) fractions. It may be observed that the application of compost at the highest rate seems to cause significant changes in the organic C distribution, i.e., CM72-S compared to S4 contains significantly more humic C (HAC, FAC, and HUC) and less NHC. The results at the lower rate of compost application, CM36-S, are not so clear. The apparent decrease in HAC and TEC in Table 2 for this sample is inconsistent with the results from the high compost application rate. Because these are the only two results that are difficult to explain, it is likely that inadequate sampling has caused them. As HAs are conventionally taken as probes for rating compost quality such as required, also, by the Italian law (Repubblica Italiana, 1984) and compost HAs are known to be different from typical soil HAs, we have performed in this work deeper investigation on the HA isolates from the above soil plots and from CM. The data in Table 4 show a compositional difference between the HA fractions isolated from the above sources, the compost having higher C and N content, but lower O content than the control soil, S4. From the data obtained for the HAs isolated from the amended plots, it may be observed that as the rate of compost addition increases the soil HA elemental composition changes and tends to become more similar to that of the CM HA, i.e., the C and N content increases and the O content decreases. The significance of these trends was investigated further by DRIFT spectroscopy. The DRIFT spectra in Fig. 1 show common features for both compost and soils HAs. The following assignments are given according to previous work on humic substances ¨ ster and Kringstadt, 1988; Hatcher et al., 1987; Almend(O
Table 4 Data from chemical analyses of HA extracted from compost (CM) and from soil Cd Hd Nd Sd Od Ashe H/Cf C/Nf C/Of a b c d e f
CM (g kg 1)
S4a
CM36-Sb
CM72-Sc
546.8 ± 8.2 51.3 ± 0.1 76.1 ± 0.3 9.7 ± 1.8 316.1 ± 8.4 19.7 1.1 8.4 2.3
522.7 ± 2.3 49.7 ± 1.3 58.4 ± 0.3 6.8 ± 0.8 362.4 ± 2.9 42.0 1.1 10.4 1.9
533.4 ± 5.5 50.9 ± 0.4 62.9 ± 0.4 8.6 ± 0.7 344.2 ± 5.6 36.7 1.1 9.9 2.1
541.5 ± 1.3 50.2 ± 0.1 64.9 ± 1.1 9.1 ± 0.2 334.3 ± 1.7 23.2 1.1 9.7 2.2
Control soil after 4 years. Soil amended with 36 Mg ha 1 yr 1 of compost. Soil amended with 72 Mg ha 1 yr 1 of compost. Concentration (g kg 1) referred to ash free dry matter. Concentration (g kg 1) referred to dry matter. Atom/atom ratio.
ros and Sanz, 1991; Ramunni et al., 1992; Ricca and Severini, 1993) and on organic molecules (Silverstein et al., 1991). Bands at 1038 and 1231 cm 1 are well within the ranges of the typical absorptions at 1200–1260 cm 1and at 1000–1140 cm 1 of native lignin (Lawther et al., 1996). These bands are considered to reflect the ‘‘core lignin’’ structure (Jung and Himmelsbach, 1989). Therefore, both HA isolated from CM and the HAs isolated from the soil plots seem to save the memory of the vegetable parent lignin matter. The absorptions at ca. 2930 cm 1 due to C–H stretching vibration, and at 1700–1715 cm 1 due to the C@O stretching vibration in carboxylic acids and esters, indicate the presence of significant amounts of aliphatic carboxylic acids. The bands peaking at 1665 and at 1531 cm 1 are mainly contributed by amide C@O and NH stretching vibrations, respectively, although due to
1231 1038
CM72-S
References
KM
CM36-S
S4
CM
4000
3150
2300
323
improve soil amending practices and to help in the management of wastes.
1665 1531
2930
1714
F. Adani et al. / Waste Management 27 (2007) 319–324
1450
600
Wavenumber [cm-1] Fig. 1. DRIFT spectra for HA extracted from compost (CM), control soil (S4) and amended soil samples CM36-S and CM72-S.
their broadness some contribution from aromatic C@C stretching vibrations are also likely. The absorptions covering the 2500–3600 cm 1 range arise from OH and/or NH stretching vibrations and are consistent with the presence of carboxylic acids and amides functional groups. It may be observed in Fig. 1 that the CM HA, compared to S4 HA, is characterized by the relatively stronger absorption of the amide C@O band at 1665 cm 1, and that this feature correlates with the higher N content in the former (Table 4). The relative intensity of the above absorption at 1665 cm 1 seems also to increase in HA isolated from the amended soil plot CM72-S relative to the S4 plot. Both the DRIFT spectra and the elemental analysis data therefore appear consistent and indicate that the amended soil after four years retains a significant contribution from the compost organic matter. Further investigation by 1H NMR and 13 CPMAS NMR may support further this conclusion. 4. Conclusion The experimental data have shown that it is possible to trace the fate of compost organic matter used to amend soil after 4 years by virtue of the chemical differences between compost and soil organic matter. This objective has been achieved in this work by comparing compost, control soil and amended soil for the organic C distributions between humic and non-humic organic fractions, and for the elemental composition and IR spectral features of the isolated humic acid fractions. The approach used in this work should be extended using also additional analytical tools such as NMR spectroscopy. Also, investigation of the chemical structures of all humic fractions (fulvic acids, humic acids and humin) could help to increase the knowledge of the effects of organic amending agents on the turnover of soil organic matter. Such knowledge is necessary to
Adani, F., Genevini, P.L., Tambone, F., 1995. A new index for compost stability. Compost Sci. Util. 3, 25–37. Almendros, G., Sanz, J., 1991. Structural study on the soil humin fractionboron trifluoride-methanol transesterification of soil humin preparations. Soil Biol. Biochem. 23, 1147–1154. Bernal, M.P., Sa`nchez-Monedero, M.A., Paredes, C., Roig, A., 1998. Carbon mineralization from organic wastes at different composting stages during their incubation with soil. Agri. Ecosys. Environ. 69, 175–189. Boyd, S.A., Sommers, L.E., Nelson, W., 1980. Change in the humic acid fraction of soil resulting from sludge application. Soil Sci. Soc. Am. J. 44, 1179–1186. Ciavatta, C., Antisari, V.L., Sequi, P., 1988. A first approach to the determination of the presence of humified materials in organic fertilizers. Agrochimica 30, 510–517. Chefetz, B., Adani, F., Genevini, P.L., Tambone, F., Hadar, Y., Chen, Y., 1998. Humic acid transformation during composting of municipal solid waste. J. Environ. Qual. 27, 794–800. Chen, Y., Aviad, T., 1990. Effects of humic substances on plant growth. In: American Society of Agronomy and Soil Science Society of America, Humic Substances in Soil and Crop Sciences: Selected Reading. American Society of Agronomy, Madison, WI. Garcia, C., Hernandez, T., Costa, F., 1992. Comparison of humic acids derived from city refuse with more developed humic acids. Soil Sci. Plant Nutr. 38, 339–346. Genevini, P.L., Adani, F., Veeken, A., Nierop, G.J., Scaglia, B., Dijkema, C., 2002. Qualitative modifications of humic acidlike and core-humic acid-like during high-rate composting of pig faces amended with wheat straw. Soil Sci. Plant Nutr. 48 (2), 143–150. Gigliotti, G., Macchioni, A., Zuccaccia, C., Giusquiani, P.L., Businelli, D., 2003. A spectroscopic study of soil fulvic acid composition after 6year application of urban compost. Agronomie 23, 719–724. Gonza`les-Vila, F.J., Almendros, G., Madrid, F., 1999. Molecular alterations of organic fractions from urban waste in the course of composting and their further transformation in amended soil. Sci. Total Environ. 236, 215–229. Hatcher, G.P., Breger, I.A., Maciel, G.E., Szeverenyi, N.M., 1987. Geochemistry of humin. In: Aiken, G.R., McKnight, D.M., Wershaw, R.L., MacCarthy, P. (Eds.), Humic Substances in Soil, Sediment, and Water, Geochemistry, Isolation, and Characterization. Wiley–Interscience Publication, New York, pp. 275–302. Jakobsen, S.T., 1995. Aerobic decomposition of organic wastes 2. Value of compost as a fertilizer. Resour. Conserv. Recy. 13, 57–71. Jung, H.J.G., Himmelsbach, D.S., 1989. Isolation and characterization of wheat straw lignin. J. Agric. Food Chem. 37, 81–87. Lawther, J.M., Sun, R., Banks, W.B., 1996. Fractional characterization of wheat straw lignin components by alkaline nitrobenzene oxidation and FT-IR spectroscopy. J. Agric. Food Chem. 44, 1241–1247. Leifeld, J., Siebert, S., Kogel-Knaber, I., 2002. Changes in the chemical composition of soil organic matter after application of compost. Eur. J. Soil Sci. 53, 299–309. Maggioni, A., 1981. Changes of the humus-like material during composting. Mushroom Sci. 11, 47–61. MPAF – Ministero per le Politiche Agricole e Forestali, 2000. In: Violante A. (Ed.), Metodi di Analisi Chimica del Suolo. FrancoAngeli, Milano, Italy. Natrella, M.G., 1966. Experimental Statistics. In: Besson, F.S., Astin, A.V. (Eds.), National Bureau of Standards Handbook 91. US Government Printing Office, Washington, DC (Chapters 3–4). ¨ ster, R., Kringstadt, K.P., 1988. Oxidative sulfonation of kraft lignin. O Nordic Pulp Paper Res. J. 2, 68–74.
324
F. Adani et al. / Waste Management 27 (2007) 319–324
Qualls, R.G., 2004. Biodegradability of humic substances and other fractions of decomposing leaf litter. Soil Sci. Soc. Am. J. 68, 1705–1712. Que`draogo, E., Mando, A., Zombre`, N.P., 2001. Use of compost to improve soil properties and crop productivity under low input agricultural system in West Africa. Agric. Ecosys. Environ. 84, 259–266. Ramunni, A., Pignalosa, L., Amalfitano, C., 1992. The lignin input in the structure of the humic acids from a farm-yard manured soil as detected by FT-IR, UV–Vis and 13C NMR CP-MAS spectroscopy. Agrochimica 26, 269–281. Repubblica Italiana, 1984. Nuove norme per la disciplina dei fertilizzanti. Legge N. 748, 1988 e successive modificazioni.
Ricca, G., Severini, F., 1993. Structural investigations of humic substances by IR-FT, 13C NMR spectroscopy and comparison with a maleic oligomer of known structure. Geoderma 58, 233–244. Silverstein, R.M., Bassler, G.C., Morril, C.T., 1991. Spectrometric Identification of Organic Compounds, fifth ed. Wiley Inc., New York. The US Composting Council, 1997. Ash; Organic carbon. In: Leege, P.B., Thompson, W.H. (Eds.), Test methods for the examination of composting and compost. The US Composting Council, Bethesda, MA, USA, Method 07.02 and Method 09.07. Varanini, Z., Pinton, R., 1995. Humic substances and plant nutrition. Prog. Bot. 56, 97–117.
Modification of soil humic matter after 4 years of compost application Fabrizio Adani
a,*
, Pierluigi Genevini a, Giuliana Ricca b, Fulvia Tambone a, Enzo Montoneri c
a Dipartimento di Produzione Vegetale, Universita` degli Studi di Milano, Via Celoria 2, 20133 Milano, Italy Dipartimento di Chimica Organica e Industriale, Universita` degli Studi di Milano, Via Venezian 21, 20133 Milano, Italy Dipartimento di Chimica Generale ed Organica Applicata, Universita` degli Studi di Torino, Corso Massimo D’Azeglio 48, 10125 Torino, Italy b
c
Accepted 4 April 2006 Available online 8 June 2006
Abstract Two soil plots, 1 ha each, were amended yearly for 4 years, respectively, with 35.8 and 71.6 Mg ha 1 yr 1 of mature compost (CM) obtained from food and vegetable residues. The compost, amended soils, and a control soil plot after 4 years (S4), were analyzed for humin (HUC), humic acid (HAC), fulvic acid (FAC), and non-humic carbon (NHC) content. Compared to S4, the amended soil contained more humified C (HAC, FAC and HUC) and less NHC. Further evidence of the effect of compost on soil organic matter was obtained by the analysis of the humic acid (HA) fractions isolated from both the compost and the soils. These were characterized by elemental analyses and Diffuse Reflectance Infrared Fourier Transformed spectroscopy. The HAs isolated from CM and from S4 were significantly different. The HAs isolated from the amended plots were more similar to HA isolated from CM than to HA isolated from S4. The experimental data of this work indicate that the compost application may affect significantly the soil organic matter composition, and that the approach used in this work allows one to trace the fate of compost organic matter in soil. Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction The assessment of changes in soil organic matter brought about by amending soil with compost is a key issue for soil quality, fertility and compost waste management (Maggioni, 1981; Garcia et al., 1992; Chefetz et al., 1998; Gigliotti et al., 2003). Humic substances (HS) are significant constituents of the organic matter in both soils and compost (Genevini et al., 2002). They are anionic polymeric materials, which contribute significantly to the chemical, physical and biological properties of the soil (Chen and Aviad, 1990; Varanini and Pinton, 1995). Due to their relatively slow biodegradation rate, their life time in soil is relatively long (Qualls, 2004). Therefore, compost addition to soil is expected to alter the content and nature of soil organic matter over a relatively long time range, and this
*
Corresponding author. Tel.: +39 02 503 16546; fax: +39 02 503 16521. E-mail address: [email protected] (F. Adani).
0956-053X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2006.04.004
in turn should change the soil’s properties and performance (Jakobsen, 1995; Que`draogo et al., 2001). Nevertheless, information on the modification of soil organic matter induced by compost addition is quite limited. The effects of compost on soil are expected to depend on several parameters, e.g., the compost quality, the soil type, the method used to apply the compost to the soil, the application rate, and environmental conditions. Compost quality itself depends on a multiplicity of factors, the main ones being the nature of the composted matter, the availability of oxygen in the composting pile, and the composting time (Bernal et al., 1998). Due to the number of parameters involved in soil amendment practice using compost, the few studies published on this subject yield a variety of results (Leifeld et al., 2002; Gonza`les-Vila et al., 1999; Que`draogo et al., 2001), which are difficult to compare. As the effect on soil humic substances is an important question for the use of compost in agriculture (Bernal et al., 1998; Jakobsen, 1995), this paper is focused on the effect of the compost on soil organic matter, with particular attention
320
F. Adani et al. / Waste Management 27 (2007) 319–324
to the nature and content of the soil humic acid (HA) over a 4-yr amendment trial. In this study, cultivated soil from a maize farm was selected and amended with compost produced from food–vegetable residues. 2. Materials and methods 2.1. Compost
Table 1 Data from chemical analyses of compost (average of 4 samples) Component (g kg dm 1)
C distribution (g kg dm 1)
Ash VS TOC N C/N
TECb HAC FAC NHC HUC
a b
The compost (CM) (grain size <2 cm) was produced from a mix of food kitchen and gardening wastes (deciduous wood, brush, grass, etc.) in 1:1 v/v ratio to have optimal bulk density, in a facility located in Bergamo, Italy. Compost was obtained by an aerated composting pile operated for 120 days. A representative sample of compost was taken at the end of the composting, prepared and successively analyzed for ash content, volatile solids (VS), total organic carbon (TOC) and N (The US Composting The US Composting Council, 1997). Total organic C was then fractionated for 24 h at 65 °C by using an aqueous solution of NaOH 0.1 mol L 1 and Na4P2O7 0.1 mol L 1 at 1:50 compost/solution ratio under N2 atmosphere as previously reported (Ciavatta et al., 1988). Stirring was provided by means of a Dubnoff end-over-end shaking bath at 100shake min 1, equipped with a thermostat. The resulting suspension was cooled to room temperature and centrifuged at 6000 rpm for 20 min. The operation was repeated by adding distilled water until supernatant was clear (approximately three times). The insoluble fraction (humin fraction, HU) and the supernatant clear solution (total extractable fraction, TE) were separated. The HU fraction was repeatedly washed with distilled water until supernatant solution was clear. The collected liquid fractions were mixed, acidified with 50% sulphuric acid to pH < 1.5 to precipitate the humic acid fraction (HA), which was separated by centrifugation. As no purification of parent material was performed (e.g., lipid removing), humic acid could contain organic impurities (Adani et al., 1995). The supernatant acid solution was run through a polyvinylpirrolidone (Aldrich-Chemie Ò, St. Louis, Missouri, USA) packed column. The column was eluted with 10 mL of 0.05 mol L 1 aqueous sulphuric acid to yield non-humic compounds (NH), and then with 0.5 mol L 1 aqueous NaOH to yield the fulvic acid fraction (FA). The HA fraction separated as above was washed with distilled water to neutral pH, shaken with a 2.82 mol L 1HF at room temperature for 24 h to remove inorganic material, and then washed again with distilled water to neutral pH, dried at 60 °C under vacuum, and weighed. Average data of chemical analyses for the composts and the content of organic carbon fractions are reported in Table 1. 2.2. Soil Soil investigated (Calcaric Cambisol, FAO classification) was located in Voghera in the Cascinoni Gallini farm
527 ± 60 472 ± 64 239 ± 28 21.6 ± 4.0 11.4a
140 ± 31 52 ± 1 17 ± 1 72 ± 8 99 ± 13
Calculated based on mean values. TOC = TEC + HUC; TEC = HAC + FAC + NHC.
(Pavia province, Italy). Previous analyses performed on soil samples taken from different locations at the test site did not show appreciable differences in composition. These results are shown as S0 in Table 2. Therefore, the soil was divided into three different plots of 1 ha each: the unamended control plot (S0), a plot treated with 35.8 dry matter Mg ha 1 yr 1 of compost (CM36-S), and a plot treated with 71.6 dry matter Mg ha 1 yr 1 of compost (CM72-S). Compost application was repeated yearly at the end of October for 4 years. The soils plots were cultivated with maize (cv Eleonora, Pioneer) by usual agronomical technique using 230–120–150 kg ha 1 yr 1 of N–P2O5–K2O fertilizer for the whole duration of the amending experimental plan. Plants were sowed on April 3 and harvested completely on August 28, leaving 20 cm-stalks, which were tilled into the soils at the same time as the compost application. Weed control by herbicide Primigrand T2e Merlin was provided. No statistical differences in maize yield between plots were detected during the 4 years of the amending trials. 2.3. Soil sampling and analyses Sampling and analyses were performed according to published procedures (Boyd et al., 1980; MPAF, 2000). The soil plots were sampled at the end of September of the fourth year of the experimental plan. Composite samples of 3 kg each were obtained from each plot by mixing six randomly collected core samples. These composite samples were used to obtain the analytical data reported in Table 2. 2.4. Breakdown of organic C into humic and non-humic C Soil organic matter was fractionated into TE, HA, FA, HU and NH by the same procedure reported for the compost, except for using a 1:10 soil/solution ratio. The C content in the soil and in each organic fraction was determined by the Springer–Klee dichromate oxidation method (Ciavatta et al., 1988). As this method consisted of an oxidation under a hot condition (160 ± 2 °C), the total carbon content (TOC) determined for soils was higher than the C content determined by the ‘‘cold method’’ (Walklely and Black method) (see Table 2 and its legend). Although the cold method is generally used for soil analysis, it is unable to
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Table 2 Analytical data of soils Component
S0a
S4b
CM36-Sc
CM72-Sd
Clay (%) Silt (%) Sand (%) pH C (g kg 1 dm)e N (g kg 1 dm) C/N CEC (cmol+ kg 1) TOC (g kg 1 dm)f TEC (g kg 1 dm)g HAC (g kg 1 dm)g FAC (g kg 1 dm)g NHC (g kg 1 dm)g HUC (g kg 1 dm)g
48.7 ± 1.9 44.6 ± 2.2 6.7 ± 1.1 8.2 ± 0.2 10.0 ± 0.1 1.25 ± 0.03 8.0 ± 0.7 17.6 ± 1.4 ndh ndh ndh ndh ndh ndh
49.9 ± 0.9 43.2 ± 2.2 6.9 ± 1.5 8.2 ± 0.1 10.8 ± 0.9 1.40 ± 0.01 7.7 ± 0.7 17.8 ± 1.4 12 ± 0 6.62 ± 0.23 2.42 ± 0.14 0.88 ± 0.04 3.32 ± 0.26 4.18 ± 0.93
49.7 ± 1.4 42.8 ± 2.5 7.5 ± 1.4 8.2 ± 0.0 10.9 ± 0.8 1.54 ± 0.02 7.1 ± 1.4 19.0 ± 1.0 11 ± 1 5.35 ± 0.23 2.20 ± 0.11 0.95 ± 0.01 2.20 ± 0.24 5.55 ± 0.83
48.9 ± 0.7 42.5 ± 0.6 8.6 ± 0.55 8.3 ± 0.6 12.8 ± 0.7 1.55 ± 0.05 8.3 ± 0.5 23.0 ± 1.0 15 ± 1 6.52 ± 0.35 2.81 ± 0.02 1.13 ± 0.00 2.58 ± 0.34 6.28 ± 0.78
Values reported are the means and standard deviations based on triplicate analysis on three subsamples. a Control soil at time zero. b Control soil after 4 years. c Soil amended with 36 Mg ha 1 yr 1 of compost. d Soil amended with 72 Mg ha 1 yr 1 of compost. e Determined by Walkley and Black method. f Determined by Springer–Klee method. g TEC, total extractable C; HAC, humic acid C; FAC, fulvic acid C; NHC, non-humic C; HUC, humin C. h Not determined.
oxidize completely the more recalcitrant organic carbon (e.g., humified carbon). Data are reported in Table 2 as total organic carbon (TOC) for the soil, and total extracted C (TEC), humic acid C (HAC), fulvic acid C (FAC), non-humic substances C (NHC), and humin C (HUC) for the single organic fractions (TOC = TEC + HUC; TEC = HAC + FAC + NHC). The elemental composition of the humic acid (HA) fractions was determined by elemental analyzer (C. Erba analyzer, Rodano, Milan, Italy) NA-2100 elemental analyzer. 2.5. Diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy The humic acid fractions isolated from both compost and soils were studied by DRIFT spectroscopy. Spectra were recorded by Jasco FT/IR-300 E Spectrometer, equipped with a DLATGS detector and a Diffuse Reflectance device (Pike Technologies Inc., Madison, Wisconsin, USA), and corrected for Kubelka Munk (KM); 128 scans were used. Samples (7 mg), previously dried at 65 °C for 48 h under vacuum, and KBr (700 mg; FT grade, Aldrich Chemical Co, St. Louis, MI, USA) were finely ground in a Wig-L-Bug mill (Specamill-Greseby-Specac, Kent, UK) for 10 min, using an agate ball mill. 2.6. Statistical analyses Chemical analyses were performed in triplicate (analytical sub-samples) on each soil sample taken from the 3 kg mass. Since chemical analyses were performed on three analytical sub-samples withdrawn from the 3 kg composite
bulk sample, standard deviation values calculated from the three values were estimates of the variability due to both the analytical method and bulk sample homogeneity. Average and standard deviation values from chemical analyses were calculated according to standard procedure (Natrella, 1966). 3. Results and discussion The data in Table 2 show that the soil plot amended with the highest compost rate (CM72-S), compared to control soil (S4), is characterized by significant increases in TOC, N, apparent sand and CEC contents. On the contrary, for the soil amended with 35.8 Mg ha 1 yr 1 of compost (CM36-S), and looking only at the traditional parameters and not the extraction results, no significant changes of these traditional parameters are evident relative to S4, except for the increase of the N content. Compost effects on soil are often controversial, being dependent upon many factors such as compost and soil type, trial duration, application rate, and crop yield. Table 3 summarizes the results obtained in this work next to the results obtained in various studies on the effects of compost on soil. It may be observed that the experimental conditions and the type of effect indicators over the four sets of experiments listed in Table 3 are not homogeneous. Nevertheless, it can be concluded that the increase of soil C, N and CEC by amending with compost is confirmed in most cases. Relative to the data reported in soil amending trials performed with compost, we have added in this work new indicators based on the fractionation of organic C into humic and non-humic fractions in order to attempt to trace
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Table 3 Comparison of experimental conditions and results for various studies on the effect of compost (CM) on soil Gonza`les-Vila et al. (1999)
Que`draogo et al. (2001)
Leifeld et al. (2002)
This work
CM source
Urban wastes 7 weeks 200–400 16–23 6.7–7.0 30–40 Mg ha 1 ND 10–12% increase ND No change ND ND Higher phthalates and alkanes to fatty acids ratios ND
Biogenic waste of household and gardens ND 233–186 12–13 7.5 65–70 Mg ha 1 18 months 60–154% increase 83–121% increase ND ND 4–57% increase Higher phenolic lignin components ND
Food residues and wood chips
CM timea CM C (g kg 1) CM C/N CM pH CM/soilb Trial durationc Soil Cd Soil Nd Soil HA-liked Soil CECd Soil pHd Soil organic compoundse
Household refuses, animal manure, crop residues ND 160 12 7 5–10 Mg ha 1 16 weeks No change Increase ND 0–30% increase 9–12% increase ND
Crop yield
45–238% increase
17 weeks 239 11.4 ND 37–72 Mg ha 1 yr 1 4 years 0–19% increase 11% increase 0–16% increase 29% increase No change Higher humic substances No change
ND, not determined or not reported. a Duration of the composting process. b Weight of applied CM per soil hectare. c Duration of amendment trial is the time at which soil was characterized after CM application. d Changes of analytical values for amended soil relatively to control soil. e Class of compounds which was mainly affected in amended soil relatively
the fate of the compost humic substances in soil. Table 2 reports also the soil C distribution among the humic acid (HAC), fulvic acid (FAC), humin (HUC) and non-humic (NHC) fractions. It may be observed that the application of compost at the highest rate seems to cause significant changes in the organic C distribution, i.e., CM72-S compared to S4 contains significantly more humic C (HAC, FAC, and HUC) and less NHC. The results at the lower rate of compost application, CM36-S, are not so clear. The apparent decrease in HAC and TEC in Table 2 for this sample is inconsistent with the results from the high compost application rate. Because these are the only two results that are difficult to explain, it is likely that inadequate sampling has caused them. As HAs are conventionally taken as probes for rating compost quality such as required, also, by the Italian law (Repubblica Italiana, 1984) and compost HAs are known to be different from typical soil HAs, we have performed in this work deeper investigation on the HA isolates from the above soil plots and from CM. The data in Table 4 show a compositional difference between the HA fractions isolated from the above sources, the compost having higher C and N content, but lower O content than the control soil, S4. From the data obtained for the HAs isolated from the amended plots, it may be observed that as the rate of compost addition increases the soil HA elemental composition changes and tends to become more similar to that of the CM HA, i.e., the C and N content increases and the O content decreases. The significance of these trends was investigated further by DRIFT spectroscopy. The DRIFT spectra in Fig. 1 show common features for both compost and soils HAs. The following assignments are given according to previous work on humic substances ¨ ster and Kringstadt, 1988; Hatcher et al., 1987; Almend(O
Table 4 Data from chemical analyses of HA extracted from compost (CM) and from soil Cd Hd Nd Sd Od Ashe H/Cf C/Nf C/Of a b c d e f
CM (g kg 1)
S4a
CM36-Sb
CM72-Sc
546.8 ± 8.2 51.3 ± 0.1 76.1 ± 0.3 9.7 ± 1.8 316.1 ± 8.4 19.7 1.1 8.4 2.3
522.7 ± 2.3 49.7 ± 1.3 58.4 ± 0.3 6.8 ± 0.8 362.4 ± 2.9 42.0 1.1 10.4 1.9
533.4 ± 5.5 50.9 ± 0.4 62.9 ± 0.4 8.6 ± 0.7 344.2 ± 5.6 36.7 1.1 9.9 2.1
541.5 ± 1.3 50.2 ± 0.1 64.9 ± 1.1 9.1 ± 0.2 334.3 ± 1.7 23.2 1.1 9.7 2.2
Control soil after 4 years. Soil amended with 36 Mg ha 1 yr 1 of compost. Soil amended with 72 Mg ha 1 yr 1 of compost. Concentration (g kg 1) referred to ash free dry matter. Concentration (g kg 1) referred to dry matter. Atom/atom ratio.
ros and Sanz, 1991; Ramunni et al., 1992; Ricca and Severini, 1993) and on organic molecules (Silverstein et al., 1991). Bands at 1038 and 1231 cm 1 are well within the ranges of the typical absorptions at 1200–1260 cm 1and at 1000–1140 cm 1 of native lignin (Lawther et al., 1996). These bands are considered to reflect the ‘‘core lignin’’ structure (Jung and Himmelsbach, 1989). Therefore, both HA isolated from CM and the HAs isolated from the soil plots seem to save the memory of the vegetable parent lignin matter. The absorptions at ca. 2930 cm 1 due to C–H stretching vibration, and at 1700–1715 cm 1 due to the C@O stretching vibration in carboxylic acids and esters, indicate the presence of significant amounts of aliphatic carboxylic acids. The bands peaking at 1665 and at 1531 cm 1 are mainly contributed by amide C@O and NH stretching vibrations, respectively, although due to
1231 1038
CM72-S
References
KM
CM36-S
S4
CM
4000
3150
2300
323
improve soil amending practices and to help in the management of wastes.
1665 1531
2930
1714
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1450
600
Wavenumber [cm-1] Fig. 1. DRIFT spectra for HA extracted from compost (CM), control soil (S4) and amended soil samples CM36-S and CM72-S.
their broadness some contribution from aromatic C@C stretching vibrations are also likely. The absorptions covering the 2500–3600 cm 1 range arise from OH and/or NH stretching vibrations and are consistent with the presence of carboxylic acids and amides functional groups. It may be observed in Fig. 1 that the CM HA, compared to S4 HA, is characterized by the relatively stronger absorption of the amide C@O band at 1665 cm 1, and that this feature correlates with the higher N content in the former (Table 4). The relative intensity of the above absorption at 1665 cm 1 seems also to increase in HA isolated from the amended soil plot CM72-S relative to the S4 plot. Both the DRIFT spectra and the elemental analysis data therefore appear consistent and indicate that the amended soil after four years retains a significant contribution from the compost organic matter. Further investigation by 1H NMR and 13 CPMAS NMR may support further this conclusion. 4. Conclusion The experimental data have shown that it is possible to trace the fate of compost organic matter used to amend soil after 4 years by virtue of the chemical differences between compost and soil organic matter. This objective has been achieved in this work by comparing compost, control soil and amended soil for the organic C distributions between humic and non-humic organic fractions, and for the elemental composition and IR spectral features of the isolated humic acid fractions. The approach used in this work should be extended using also additional analytical tools such as NMR spectroscopy. Also, investigation of the chemical structures of all humic fractions (fulvic acids, humic acids and humin) could help to increase the knowledge of the effects of organic amending agents on the turnover of soil organic matter. Such knowledge is necessary to
Adani, F., Genevini, P.L., Tambone, F., 1995. A new index for compost stability. Compost Sci. Util. 3, 25–37. Almendros, G., Sanz, J., 1991. Structural study on the soil humin fractionboron trifluoride-methanol transesterification of soil humin preparations. Soil Biol. Biochem. 23, 1147–1154. Bernal, M.P., Sa`nchez-Monedero, M.A., Paredes, C., Roig, A., 1998. Carbon mineralization from organic wastes at different composting stages during their incubation with soil. Agri. Ecosys. Environ. 69, 175–189. Boyd, S.A., Sommers, L.E., Nelson, W., 1980. Change in the humic acid fraction of soil resulting from sludge application. Soil Sci. Soc. Am. J. 44, 1179–1186. Ciavatta, C., Antisari, V.L., Sequi, P., 1988. A first approach to the determination of the presence of humified materials in organic fertilizers. Agrochimica 30, 510–517. Chefetz, B., Adani, F., Genevini, P.L., Tambone, F., Hadar, Y., Chen, Y., 1998. Humic acid transformation during composting of municipal solid waste. J. Environ. Qual. 27, 794–800. Chen, Y., Aviad, T., 1990. Effects of humic substances on plant growth. In: American Society of Agronomy and Soil Science Society of America, Humic Substances in Soil and Crop Sciences: Selected Reading. American Society of Agronomy, Madison, WI. Garcia, C., Hernandez, T., Costa, F., 1992. Comparison of humic acids derived from city refuse with more developed humic acids. Soil Sci. Plant Nutr. 38, 339–346. Genevini, P.L., Adani, F., Veeken, A., Nierop, G.J., Scaglia, B., Dijkema, C., 2002. Qualitative modifications of humic acidlike and core-humic acid-like during high-rate composting of pig faces amended with wheat straw. Soil Sci. Plant Nutr. 48 (2), 143–150. Gigliotti, G., Macchioni, A., Zuccaccia, C., Giusquiani, P.L., Businelli, D., 2003. A spectroscopic study of soil fulvic acid composition after 6year application of urban compost. Agronomie 23, 719–724. Gonza`les-Vila, F.J., Almendros, G., Madrid, F., 1999. Molecular alterations of organic fractions from urban waste in the course of composting and their further transformation in amended soil. Sci. Total Environ. 236, 215–229. Hatcher, G.P., Breger, I.A., Maciel, G.E., Szeverenyi, N.M., 1987. Geochemistry of humin. In: Aiken, G.R., McKnight, D.M., Wershaw, R.L., MacCarthy, P. (Eds.), Humic Substances in Soil, Sediment, and Water, Geochemistry, Isolation, and Characterization. Wiley–Interscience Publication, New York, pp. 275–302. Jakobsen, S.T., 1995. Aerobic decomposition of organic wastes 2. Value of compost as a fertilizer. Resour. Conserv. Recy. 13, 57–71. Jung, H.J.G., Himmelsbach, D.S., 1989. Isolation and characterization of wheat straw lignin. J. Agric. Food Chem. 37, 81–87. Lawther, J.M., Sun, R., Banks, W.B., 1996. Fractional characterization of wheat straw lignin components by alkaline nitrobenzene oxidation and FT-IR spectroscopy. J. Agric. Food Chem. 44, 1241–1247. Leifeld, J., Siebert, S., Kogel-Knaber, I., 2002. Changes in the chemical composition of soil organic matter after application of compost. Eur. J. Soil Sci. 53, 299–309. Maggioni, A., 1981. Changes of the humus-like material during composting. Mushroom Sci. 11, 47–61. MPAF – Ministero per le Politiche Agricole e Forestali, 2000. In: Violante A. (Ed.), Metodi di Analisi Chimica del Suolo. FrancoAngeli, Milano, Italy. Natrella, M.G., 1966. Experimental Statistics. In: Besson, F.S., Astin, A.V. (Eds.), National Bureau of Standards Handbook 91. US Government Printing Office, Washington, DC (Chapters 3–4). ¨ ster, R., Kringstadt, K.P., 1988. Oxidative sulfonation of kraft lignin. O Nordic Pulp Paper Res. J. 2, 68–74.
324
F. Adani et al. / Waste Management 27 (2007) 319–324
Qualls, R.G., 2004. Biodegradability of humic substances and other fractions of decomposing leaf litter. Soil Sci. Soc. Am. J. 68, 1705–1712. Que`draogo, E., Mando, A., Zombre`, N.P., 2001. Use of compost to improve soil properties and crop productivity under low input agricultural system in West Africa. Agric. Ecosys. Environ. 84, 259–266. Ramunni, A., Pignalosa, L., Amalfitano, C., 1992. The lignin input in the structure of the humic acids from a farm-yard manured soil as detected by FT-IR, UV–Vis and 13C NMR CP-MAS spectroscopy. Agrochimica 26, 269–281. Repubblica Italiana, 1984. Nuove norme per la disciplina dei fertilizzanti. Legge N. 748, 1988 e successive modificazioni.
Ricca, G., Severini, F., 1993. Structural investigations of humic substances by IR-FT, 13C NMR spectroscopy and comparison with a maleic oligomer of known structure. Geoderma 58, 233–244. Silverstein, R.M., Bassler, G.C., Morril, C.T., 1991. Spectrometric Identification of Organic Compounds, fifth ed. Wiley Inc., New York. The US Composting Council, 1997. Ash; Organic carbon. In: Leege, P.B., Thompson, W.H. (Eds.), Test methods for the examination of composting and compost. The US Composting Council, Bethesda, MA, USA, Method 07.02 and Method 09.07. Varanini, Z., Pinton, R., 1995. Humic substances and plant nutrition. Prog. Bot. 56, 97–117.