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Reazione del Suolo
No full textLa reazione è il singolo parametro capace di fornire il maggior numero di informazioni relative alle proprietà del suolo. In questo capitolo si esaminano i principali fattori capaci di determinarla, le sue relazioni con la fertilità del suolo ed i metodi analitici che ne permettono la determinazione
Frazionamento del carbonio organico.
No full textIl capitolo 10 descrive la metodologia di estrazione, frazionamento e di determinazione del carbonio organico del suolo
Evolution of organic matter from sewage sludge and yard trimming during composting.
No full textTo use compost appropriately in agriculture it is extremely important to estimate the stabilization level of the organic matter. In this work, two different piles of compost were studied by means of (i) humification parameters (degree of humification––DH, humification rate––HR, humification index––HI) prior to and after enzymatic hydrolysis of the extracted organic carbon, (ii) watersoluble organic carbon (WSOC) and (iii) water-soluble nitrogen. A significant relationship between composting time, WSOC and humification parameters after enzymatic hydrolysis (DHenz; HRenz; HIenz) was found. 2003 Elsevier Ltd. All rights reserved
Organic fertilizers obtained from metal-free and chromium tanned leather: Evaluation of nitrogen release and the effects on the soil microbiome
Full text linkTannery industry generates over 4 million tonnes of waste annually, with 600,000 tonnes containing 2.5-6 % chromium (Cr). Tannery wastes can be employed as fertilizers due to their N and organic matter content. However, their use raises concerns about Cr and trace element contamination. Metal-free tanning processes (wet white, WW) offer an environmentally friendly alternative to Cr-based tanning (wet blue, WB), however 90 % of leather production still relies on WB tanning. The fertilizing potential of WW tanning residues has been little investigated, while this knowledge will be essential for a rational reuse of these materials in sustainable agriculture. This study evaluates fertilizers produced from hydrolysed leather residues (WW and WB) by assessing: i) N release dynamics; ii) effects on key soil fertility indicators; iii) microbial community physiological profiling; iv) Cr and trace element bioavailability to plants. Physicochemical characterization was first performed, afterwards, a soil incubation experiment was conducted. Both fertilizers released N fitting a first-order kinetics model, releasing 40-45 % of their total N after 42 days. DTPA-extractable Cr increased but remained low (31 mu g kg-1) in WB-treated soils. Biochemical indicators were positively affected by WW and WB fertilizers, and microbial community profiles were influenced by their composition but not by the presence of Cr in WB. Overall, WW and WB fertilizers effectively supplied N and enhanced microbial activity, without adversely impacting soil fertility indicators. Rhizotest suggested that Cr was not bioavailable for tomato plants in both fertilizers, even though total Cr reached about 60 mu g kg-1 in WB-fertilized soils
Thermal analysis (TG-DTA) and isotopic characterization (13C and 15N) of humic acids from different origins. Applied Geochemistry
No full textThermal analyses (TG-DTA), elemental composition and isotope analyses (13C and 15N) were performed on humic acids (HA) from peats (P), leonardites (Le) and lignites (L), in order to investigate their structure and the changes taking place during the humification process. Thermal analyses showed structural differences between HA samples in relation to their coalification rank. In particular the lignite HA were characterized by a more stable chemical composition at high temperatures.
The delta 13C and delta 15N values can provide information on the biogeochemical processes involved in HA formation. In particular, peat HA were linked to anoxic environments that enable plant residues to persist in their structure. In contrast, leonardite and lignite HA formation seems to be governed by different biogeochemical processes from those responsible for peat diagenesis. However, the isotopic analyses did not provide any distinction between leonardite and lignite HA. On the basis of the data presented in this study, it may be concluded that TG-DTA and isotope ratio measurements are powerful tools for investigating the formation pathway of humic substances fro
RELATIONSHIPS BETWEEN STABILITY, MATURITY, WATER EXTRACTABLE ORGANIC MATTER OF MUNICIPAL SEWAGE SLUDGE COMPOSTS AND SOIL FUNCTIONALITY
No full textCompost capability of restoring or enhancing soil quality depends on several parameters, such as soil characteristics, compost carbon, nitrogen and other nutrient content, heavy metal occurrence, stability and maturity. This study investigated the possibility of relating compost stability and maturity to water-extractable organic matter (WEOM) properties and amendment effect on soil quality. Three composts from municipal sewage sludge and rice husk (AN, from anaerobic wastewater treatment plants; AE, from aerobic ones; MIX, from both anaerobic and aerobic ones) have been analysed and compared to a traditional green waste compost (GM, from green manure, solid waste and urban sewage sludge). To this aim, WEOMs were characterized through chemical analysis; furthermore, compost stability was evaluated through oxygen uptake rate calculation and maturity was estimated through germination index determination, whereas compost impact on soil fertility was studied, in a lab-scale experiment, through indicators as inorganic nitrogen release, soil microbial biomass carbon, basal respiration rate and fluorescein di-acetate hydrolysis. The obtained results indicated that WEOM characterization could be useful to investigate compost stability (which is related to protein and phenol concentrations) and maturity (related to nitrate/ammonium ratio and degree of aromaticity) and then compost impact on soil functionality. Indeed, compost stability resulted inversely related to soil microbial biomass, basal respiration rate and fluorescein di-acetate hydrolysis when the products were applied to the soil
Current and residual phosphorous availability from compost in a ryegrass pot test
No full textCompost can provide nitrogen (N) and especially phosphorous (P) available for plant growth, thus representing a potential alternative to chemical P-fertilizers a non-renewable resource. However, little is known about their residual capacity to provide plant-available P. In this study four compost: a green waste compost (GWC), one from anaerobically-digested bio-waste (DC), one from sewage sludge (SSC), and one from bio-waste (BWC), were compared (10 and 20 Mg VS ha−1) in a ryegrass pot test (112 days), for their N- and P-relative mineral fertilizer equivalence (MFE; %) vs. a chemical fertilizer (NPK). After the test period, the exploited treatments were tested for their MFE during an additional ryegrass growth cycle (112 days) in an N-rich environment (N+). After 112 days, the pot test showed that DC and SSC produced dry biomass in the same range as did NPK, attaining the best N-MFE (80–100%) and P-MFE (100–125%), whereas GWC and BWC performed poorly (60–80 and 80–90%; N-MFE and P-MFE). At the end of the first growth cycle, DC and SSC still showed relevant Olsen-P (20–30 mg kg−1). This was reflected in the best ryegrass P-MFE in DC and SSC at the end of the second growth cycle (N+), after 224 days (100–110%), whereas BWC and GWC poorly performed (90–95%). DC and SSC may therefore represent valuable sources of N available for plant nutrition in the short term, and also represent medium-term valuable P sources, alternative to rock phosphate P fertilizers. This promising approach need further field-scale investigation to confirm the medium-long term capacity of composts to be alternative to rock phosphate P fertilizers
Biostimulants from Organic By-Products: a Good Way to Enhance Soil Functionality
No full textSoil loss by erosion and contamination are the main causes of soils degradation in Europe, and tipically soils degraded are characterized by low microbial functionality. One of the effective way to restore the functionality in degraded soils is the use of organic amendments. The use of hydrolysates from organic by-products as plant biostimulant increased in the recent years, but their effect of soil microbial
biomass is not well understood.
With this aim we used four biostimulants obtained through enzymatic and thermal hydrolysis of organic by-products: yeast extracts (YE) and animal collagen (AC). A degraded soil was treated with different doses of biostimulants, and the soil respiration rate (SRR), the soil microbial activity (SMA), and the soil microbial biomass (SMB) were monitored over a 30 days period. SRR increased quickly in the soil treated with YE (maximum 2-3 days after adding), than AC (maximum 5-9 days after adding). After 3 weeks, the SRR reached the steady state, and it was higher in the soil treated with YE, than AC. The trend of SMA was similar to SSR, and after 4 weeks of incubation was not possible to observe significant differences between treatment. All treatments increased SMB compared to the untreated soil: biostimulants from AC are those that showed the highest increase.
The results here obtained demonstrate that it is possible to increase the functionality of degraded soils using hydrolysates from agro-industrial by-products, although the results were influenced by the raw material and the production process used
Phosphorus in Digestate-Based Compost: Chemical Speciation and Plant-Availability
No full textA compost (CHW) from the residue of the dry-batch digestion of household waste and one (CSD) from the solid fraction of anaerobically digested maize were tested for their phosphorus (P) release by means of sequential extraction. The products were then compared in a soil incubation (30 mg P kg-1) for their capacity to supply potentially available P (Olsen-P), and in a pot trial to test plant-available P on Italian ryegrass over 112 days. A municipal solid waste compost (MSWC) and an inorganic P source (P-chem) were added as reference in addition to a not-fertilized control (Control). Sequential extraction showed that CSD had the greatest labile P (NaHCO3 30%> H2O 29%> HCl 23%> NaOH 10%). On the contrary, CHW showed the greatest recalcitrant P (HCl 44%> NaHCO3 10%> H2O 11%> NaOH 8%), being similar to MSWC (HCl 65%> NaOH 13% NaHCO3 12%> H2O 5%). This was in agreement with the different amorphous or crystalline degree of the sample as determined by XRD. Also in soil, CSD showed the highest level of Olsen-P at the beginning of incubation (28.5 mg kg-1), while CHW and MSWC had the lowest level of Olsen-P throughout incubation (4.6 and 6.0 mg kg-1 on average), very close to the Control (3.0 mg kg-1). Plant test showed that CSD also had the greatest available P (ARF: 12.5%), followed by P-chem (5.6%)> MSWC (4.2%)> CHW (2.5%). From sequential extraction and physical analysis, it therefore appears that the presence of significant amounts of Ca, such as in CHW and MSWC, shifted P toward low soluble Ca-P compounds, thus reducing the P available for plant nutrition
Plant Phosphorus Efficiency from Raw and Composted Agro- and Bio-Waste Anaerobic Digestates
Full text linkThe rising generation of organic waste (OW) can be a concern, representing at the same time a valuable opportunity for the phosphorous (P) recycling; however, yet little is known about plant-available P release from this source. In this work, two anaerobic digestates, from agro- (AWD) and bio-waste (BWD), and their respective composts (AWC and BWC), were selected to assess their P-release via sequential chemical extraction (SCE) and P species via solution 31P-NMR in NaOH+EDTA extracts. These products were also tested for the relative-P efficiency (RPEsoil) in a soil incubation (30 mg P kg−1), in comparison with a chemical-P source and a reference compost. The organic products were also compared for the ryegrass relative-P efficiency (RPEtissue) at the same P-rate (30 mg P kg−1), in a 112-day pot experiment in an Olsen-P poor soil (<3 mg kg−1), under a non-limiting N environment. The NaOH+EDTA extractions showed that inorganic P prevailed in all samples as proven by solution 31P-NMR. SCE showed very different labile-P (H2O+NaHCO3) and AW doubling BW products (84 vs. 48%); this was also confirmed by the soil incubation test in which AWD and AWC attained the best RPEsoil. Pot tests generally confirmed laboratory outcomes showing that AWD and AWC attained the best RPEtissue, from 3 to 4-folds of the BWD and BWC performance. The results showed that the feedstock mainly affects plant P availability from recycled OW and that their SCE are very informative in the description of plant-available P from this type of products to be used in rational fertilization plan
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