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In agriculture HS and HS-based products (solid and liquid) are generally used in plant nutrition: their role in increasing bioavailability of nutrients and biological activities is well supported in scientific literature. For a proper use of HS it’s fundamental to know their elemental composition as well as some basic features. In commercial products such data are often lacking. The main reason is that at national and especially at international level (EC Regulation n. 2003/2003) the specific rules, up to date, neglected HS. In fact, it must be kept in mind that even the recent European Regulation 2003/2003 (EC Regulation n. 2003/2003) has completely neglected organic and organic-based fertilizers and amendments. At the best the existing rules require the declaration of total content of organic and humic carbon (Ministerio de la Presidencia, 2005). Among others, the Italian Legislative decree 75/2010 (Decreto Legislativo 29 aprile 2010 n. 75) is one of the most advanced in Europe from this point of view (Table 1). The need of standardization and regulations of commercial humic and humic-based products is imperative in a modern agriculture and for a market globalization.

Energy crops are designed for biomass production to generate bioenergy. Their recent introduction in the Po Valley (North Italy) is connected to the mitigation of environmental effects of the intensive management. Intensive management has a dramatic impact on the soil ecosystem of the area, reducing soil organic matter, degrading soil structure and altering nutrient cycles by reducing microbial biomass, and thus compromising soil productivity. Soil organic carbon (SOC) content in the Emilia-Romagna region is the lowest in the Po Valley (

Il reimpiego dei sottoprodotti della vinificazione, consentito dalla scorsa vendemmia, va incontro a istanze di reddito e organizzative del viticoltore ma deve tenere conto anche delle caratteristiche fisico-chimiche di questo materiale, che sono in grado di influenzare l'equilibrio della microflora del terreno.

A survey of the role of organic vs. conventional on soil C sink/source was performed in 2007 in 8 typical organic vs. 8 conventional peach orchard farms located in Emilia-Romagna Region, Italy. Chemical analyses were carried out on top layer (0-15 cm depth). Determination included total (TOC), extracted (TEC) and humified (HA+FA) organic carbon, total nitrogen (TN) and isotopic signatures δ 13C and δ 15N. Principal component analysis (PCA) was carried using the following variables: TOC, TN, C/N, δ 13C, δ 15N. Conventional peach orchards showed lower values of all the parameters compared vs. organic orchards. PCA analysis has shown that in organic farms δ 13C and 15N are positively correlated with TOC and TN and δ 13C can be used for further discrimination concerning the type of fertilizer used. From the quantitative point of view an average increasing of TOC and HA+FA of 15.5 and 18.5%, respectively, was observed.

In this study, the distribution of the total (TOC) and humified (HA+FA) organic carbon (C) in a 16 years-old peach orchard was evaluated by comparing the row that is tilled and irrigated and the inter-row that is covered with perennial grass. The grass favoured the accumulation of TOC and humified C in the top layer (0-20 cm), indicating that the absence of tillage promoted the accumulation of humified compounds. In the deep layer (20-40 cm) the TOC content was higher in the row while the content of humic substances was similar. TG-DTA analysis pointed out structural variations related to the carbohydrates and aromatic compounds content in the humic fraction of the samples taken from both top and deep layers of the two soil management systems.

Long-term field experiments are crucial for studing the effects of different management practices on organic C storage capacity of agricultural soils. One of the most important pools of soil organic C (SOC) is that of the humic substances and in particular of humic acids (HA-http//ihss.gatech.edu/ihss2) that are complex macromolecules modified from plant compounds or newly synthesized during decomposition, that accumulate in soil. Because of their resistance to microbial degradation, they represent a crucial component of SOC where C tends to be stored for long periods and an important reservoir of nutrients. In the long-term field experiment at the Cadriano farm (Bologna University) different fertilization treatments have been compared for over thirty years on a continuous-wheat (used as a reference field) and a continuous-maize cropping. These two plant species have different C isotope composition because the C3 and C4 photosynthetic pathways differently fractionate against the heavier isotope of CO2-C, therefore the isotopic approach was used to quantify the C3 and C4-derived C in soil. In particular three fertilization treatments were compared: no fertilization (control) mineral fertilization and organic amendment, and the content of old C3 and new C4-derived C in soil and in the humic acids (HA) was determined. Moreover a structural characterization of HA was carried out with thermogravimetric (TG) and differential thermal analysis (DTA). After 36 years of continuous maize cropping the old C3-derived C similarly decreased in spite of the treatments. The new C4-derived C constantly increased with all the treatments, significant higher amounts compared the control were measured with the mineral, and even more with the organic treatment. In the HA the amount of C3-derived C decreased over the studied period in the control and in the mineral treatment, whereas it increased with the organic treatment. The amount of C4-derived C in the HA linearly increased over the studied period in all the treatments with the higher values measured for the mineral and organic one. TG-DTA data showed that the 36 years organic amendment caused in the HA an increase in aromatic compounds compared to the control and the mineral treatment.

Peat is the best substrate in growing media, but its rapid depletion needs at least a partial substitution. Composting of urban green wastes and agro-industrial by-products can produce good compost (Cm) for this purpose. Cm-based substrates are increasing in the market. However, physical and chemical characterization of Cm-based growing media is the first step for their proper use. This paper reports the results of the fractionation of the bulk organic matter (OM) of four growing media, containing increasing amount (v/v) of Cm [100% Peat; 80% Peat + 20% Cm (CP20); 40% Peat + 60% Cm (CP60); 100% Cm) into well-defined fractions: humic acid-like (HAL), non-humic fraction (NH) and dissolved OM (DOM) and their characterization by a combination of chemical, thermogravimetric (TG), differential thermal analysis (DTA), spectroscopic (Diffuse Reflectance Infrared Fourier Transform-DRIFT) and isotopic (δ 15N) techniques. TG-DTA of bulk growing media, HAL, NH and DOM showed significant differences among increasing Cm in Cm-based growing media. DRIFT spectra confirmed these differences. The N isotope ratio (δ 15N) of all the substrates increased with the amount of Cm in the substrate. The combination of chemical, TG-DTA, DRIFT and δ 15N techniques can be successfully applied for the chemical characterization of Cm based growing media with a good identification of different matrices.

The structural characterization of humic acids (HAs) is a focal point in understanding and establishing a relationship between their structure and biological properties. However, the complexity of HAs seriously limits the application of a single analytical technique. For a better understanding of HAs role in the environment, it is necessary to develop methods which can provide a complete characterization of HA structure. Humic acid extracted from the A horizon of a Chernozem (Boroll, USDA Soil Taxonomy) soil and their fractions (A, B and C+D) with different molecular size (MS) obtained by coupling size exclusion chromatography and polyacrylamide gel electrophoresis (SEC-PAGE) were investigated using thermal (TG-DTA), spectroscopic (DRIFT) and isotopic ( d 13C) analyses. Moreover, the molecular structure of the high temperature stable fraction (residues obtained by stopping the heating of the sample in TG-DTA apparatus at 400°C) was studied by DRIFT spectroscopy. The highest MS fraction (A) were characterized by the highest contents of aliphatic, carboxyl groups, carbohydrates and amino acids than the B and C+D fractions. Instead, the C+D fraction, that was 36% of HA (w/w), seems to be characterized by a higher content in aromatic compounds, in particular in benzoic derivatives, than the other fractions. A shift of δ 13C to more negative values was observed in the lowest MS fractions (B and C+D). The aromatic structure of A and B residues seems to be more complex than that of C+D residue.

1H HR MAS NMR is a powerful technique that allows examination of the chemical and physical properties of heterogeneous and polydisperse macromolecular systems such as soil organic matter (SOM). SOM plays a major role in the fate, transport, and bioavailability of organic and inorganic components and its dynamics depends on its chemical composition as well as physical protection mechanisms within soil fractions. Soil pH seems to be a variable that affects the rate and processes of SOM decomposition by influencing microbial activity, hydrolysis and protonation. Protonation regulates many soil processes such as solubilisation and complexation which controls sorption and desorption of organic C on mineral surfaces. Despite its documented importance as factor influencing SOM transformation, and despite the high frequency of acid soil in forest ecosystems, the effect of pH on SOM dynamics has been studied rather little. In the present study 1H HR/MAS NMR is applied to SOM extracted from two forest soils differing mainly in pH. The acid site (Geescroft) and the calcareous site (Broadbalk) are both temperate deciduous woodlands at Rothamsted Research, UK. The two soils were physically fractionated according to the procedure of Sohi et al (2001). SOM in three fractions for each site was investigated: free light fraction (FLF), intra-aggreagte light fraction (IALF) and fine silt and clay (S+C). Together these fractions represented 70-80% of the total SOM in the soils and the organic C content was above the threshold value of 3%, needed to obtain good signal/noise ratios in NMR spectra. 2-D 1H-1H homo-correlation spectroscopy (COSY), 1H-13C heteronuclear single quantum coherence (HSQC) and 1-D experiments were assessed for both a qualitative and a quantitative analysis of SOM in the the three fractions. For both sites the S/N (signal to noise) ratio is higher for FLF-SOM and IALF-SOM than for S+C-SOM fractions, in agreement with the lower carbon concentration in S+C-SOM. Amino acid residues, peptides and carbohydrates are the prevalent species and 6 typical chemical shift regions can be identified in each sample. The S+C-SOM fractions of both sites show strongly decomposed material compared to FLF and IALF, confirmed by the presence of sharp peaks at specific positions. The smaller content of aromatic groups in Geescroft extracts compared to Broadbalk suggests that the effect of acid pH influences degradation processes.

The effect of organic fertilisation on the level of total organic carbon (TOC) in an 18-years old pear orchard (cv. Abate Fetel) was evaluated vs. a conventional pear orchard mineral fertilized (control). In both orchards soil samples (Typic Udochrept loamy soil) were taken at two depths (0-15 and 30-50 cm) along the row (tilled and mainly amended with compost) and in the inter-row space (grassed with different Graminaceae species in the organic orchard, bare in the conventional orchard). The area (elevation 20 m), located in Bologna province, Emilia-Romagna Region (Italy), is characterised by mean annual temperature 13.1 °C and rainfall around 750 mm. In the horizon 0-15 cm of the row an increase of about 14 tons ha-1 of TOC has been calculated after 18-years of cultivation and amendment compared to the control soil, which had received just mineral fertilisation. A significant increase of TOC (about 6.3 tons ha-1) was also measured in the top layer (0-15 cm) in the grassed inter-row, where this C sink is exclusively due to the cover crop. A survey of the role of organic vs. conventional farming on soil C sink/source is started in 2007 in 8 typical organic orchard farms located in Emilia-Romagna Region and it is still running.

Soil organic carbon (C) preservation in agroecosystems is crucial point to maintain soil fertility and productivity, and to reduce losses of CO2 in the atmosphere. Agricultural management practices can differently affect the level of soil organic C (SOC). In the present paper or chapter the results of a long-term field experiment (30 years) were investigated to evaluate the effect of mineral fertilization and organic amendments on soil organic C content and on the humic acids (HA) that represent the most important and stable reservoir of soil organic C. The effect of the plant species was also evaluated by comparing wheat and corn monocultures. The amount of corn-derived C in soil and HA at the end of the experiment was calculated by 13C natural abundance measurements. After 30 years of cultivation, the SOC significantly decreased in both unfertilized (Control) cropping systems, especially with continuous corn. Mineral fertilization (Min) and organic amendments (Org) always caused an increase in SOC, especially with Org treatment on continuous corn. The C always increased in HA, except in the unfertilized plots of corn monoculture. Again the highest increase was observed with Org treatment. The amount of corn-derived C in total organic C (TOC) increased in the following order: unfertilized < Min < Org treatments, ranging from 19 to 29%. The turnover time of the older C3-derived C increased in the same order ranging between 55 and 86 years in the Control and Org treatment, respectively. In the HA the proportion of corn-derived C was similar in the Control and Org treatment (26.4%), lower in the Min treatment (23.7%). Nevertheless if we consider the total amount of corn-derived C in soil and the proportion recovered in the HA, the highest was measured in the unfertilized control. In general a proportion ranging from 35% (Org) to 40% (control) of the total corn-derived C in soil was recovered as humic C, confirming the important role of this pool as a C reservoir in soil.

The chemical characteristics of soil organic matter (SOM) can be influenced by management and amendment practices which effects can be measured only after long-term experiment. In this long-term study of over 30 years, with a rotation wheat-corn, we compared the effects of adding cattle manure (CM) and crop residues (CR) wheat straw or corn-stalks after each crop, on humic substances (HS). Potentiometric titration, thermal analysis (TG-DTA), and spectroscopic methods such as diffuse reflectance infrared Fourier (DRIFT) and liquid nuclear magnetic resonance (13C NMR) spectroscopies were used in order to investigate humic acid (HA) structure. The amendment practices clearly influenced the humic C and the COOH groups content that only increased in CM treatment. The quality of this humic fraction was affected by the different agricultural practices, so that when the soil did not receive any amendment, the aromatic and carboxylic C decreased, whereas the aliphatic C increased as an effect of the crop rotation. With the amendments, in contrast, the aromatic C generally increased, this increase was mainly due to the incorporation of aromatic groups in the structure of HA, arising from the phenolic groups present in the lignin of the crop residues.

Humic substances are the most important fraction of soil organic matter both in natural and an-thropic systems. Their elemental composition and chemical structure, influenced by the kind of organic residues and environment in which they are formed, are fundamental to preserve the soil fertility. Recently, emphasis has been devoted also on their effect on carbon (C) sequestration. The aim of the present study was to examine the effect of amendment with cow manure and crop residues added consecutively over a period of 30 yrs on soil humic acids. Briefly, the experimen-tal design included plots amended over a 30-year period with cattle manure and crop residues constituted by wheat straw or corn-stalks (wheat and corn were the two crops regularly cropped in succession), using un-amended soil as the control. The samples were taken from the 0-40 cm horizon of a long-term field experiment located in the experimental farm of the Agricultural Sci-ence Faculty of the Alma Mater Studiorum University of Bologna, Italy. The humic acids were characterized using chemical and spectroscopic techniques such as diffuse reflectance infrared Fourier spectroscopy (DRIFT), surface enhanced Raman spectroscopy (SERS) and nuclear magnetic resonance (13C NMR). The results showed that the quality of humic fraction was affected by the different agricultural practices, so that when the soil did not receive any amendment, the aromatic and carboxylic C decreased, whereas the aliphatic C increased as possible effect of the crop rotation. With the amendments the aromatic C generally increased, but with crop residues this increase was mainly due to preservation of undecomposed lignin components derived from the crop-residues added to the soil. With manure the composition of humic acids appeared enriched in carboxylic groups, aromatic rings highly substituted and alkyl-C. These results indicate the key role played by amendment practices on soil humic substances formation and on the ability of humic substances to sequester C.

Dynamics of chemical and biological parameters in a three years project comparing conventional and organic farming in two Italian experimental sites The multidisciplinary research group of BIOGEA project on soil fertility curried out a three years study comparing organic and conventional soil management performed in two sites in growing areas representative of two Italian environments: North East-Ravenna, lat. 44° 25' 4'' N and South-East - Foggia , lat. 41° 28' 0'' N. Materials and methods. The study was carried out on a three years rotation system under organic and conventional management with two final crops: sugar beet and processing tomato. Upon completion of three-years project, chemical (TOC, TEC, HA+FA, Nmin and Ntot dynamics), and biological (TOC, TEC, HA+FA, Nmin and Ntot dynamics) parameters are discussed. Organic management in the adopted agronomic conditions has not significantly improved chemical and biological parameters if compared to conventional farming. However, the dynamics of the majour part of the evaluated chemico-biological parameters is slow in soil environment and therefore, three years is a too short period to draw definitive conclusions.

The purpose of the present study is to investigate, by means of thermogravimetric analysis (TG) and differential thermal analysis (DTA), diffuse reflectance infrared Fourier transform (DRIFT) and 2D nuclear magnetic resonance (NMR) spectroscopies, the structural features of the humic-like fraction (HLF) from olive pulp (OP), its effluents originated from the fermentation processes for hydrogen (EH2) and methane production (ECH4) and humic acid (HA) from soil amended with each of these materials. A considerable structural modification emerged between the HLF, in particular from the ECH4 effluent, which was characterised by a high content of polyphenolic and polypeptidic substances. The short-term amendment trial with OP and EH2 indicated that no chemical or structural changes in soil HA appeared. In contrast, the amendment with ECH4 substantially influenced the chemical and structural composition of soil HA. The structural interpretation performed by 2D NMR indicated the presence of aliphatic and aromatic protons while the sugar-like content and O–CH3 groups decreased with respect to the soil control HA. It emerges from this study that olive wastes contain stabilised humic-like material that may be recycled as an amendment in areas where olive trees are cultivated.

Vengono comparati metodi diversi per la stima della deposizione radicale