Effect of wheat (Triticum aestivum L.) rhizosphere and sewage sludge application on zinc desorption with dilute citric acid

Rhizosphere processes have a major impact on Zn desorption and Zn uptake by plant. However, information about Zn desorption characteristics in the rhizosphere of wheat is limited. Therefore, a greenhouse experiment was performed to determine Zn desorption characteristics in the bulk and rhizosphere soil of wheat (Triticum aestivum L.) of 10 soils amended and un-amended with municipal sewage sludge using rhizoboxes. The kinetics of Zn desorption was determined by successive extraction with 10 mM citric acid in a period of 1–504 h at 25 ± 1°C in the bulk and rhizosphere of un-amended and amended soils. The results showed that the Zn amount extracted after 504 h in the rhizosphere soils was significantly (p < 0.01) higher than the bulk soils. The mean of Zn desorption in the bulk and rhizosphere of un-amended soils were 10.4 ± 0.34 and 11.4 ± 0.43 mg kg^?1, respectively, while the mean of Zn desorption in the bulk and the rhizosphere of amended soils were 13.2 ± 0.48 and 14.8 ± 0.67 mg kg^?1, respectively. Desorption kinetics of Zn conformed fairly well to the first-order, parabolic diffusion, power function, and zero-order equations. The results of Zn fractionation indicated that exchangeable Zn and Zn associated with organic matter decreased and Zn associated with iron-manganese oxides and residual Zn increased in the rhizosphere soils compared to the bulk soils. Zinc desorption after 504 h and residual Zn in the bulk and rhizosphere of un-amended and amended soils were significantly positively correlated (p < 0.05). Therefore, residual Zn was the main Zn pool that controlled Zn desorption after 504 h in the bulk and rhizosphere soils studied.     

Evaluation of copper desorption characteristics using DTPA and citric acid for wheat (Triticum aestivum L.) rhizosphere of soils amended with sewage sludge

A greenhouse experiment was carried out to determine copper (Cu) desorption characteristics in ten bulk and rhizosphere soils (Typic Calcixerepts) amended with sewage sludge (1% w/w) using rhizoboxes. The kinetics of Cu desorption in the bulk and the rhizosphere soils were determined after successive extraction with DTPA‐TEA and 10 mM citric acid in a period of 1 to 504 h at (25 ± 1)°C. The results show that Cu extracted after 504 h using DTPA‐TEA were significantly (P < 1%) lower in the rhizosphere than the bulk soils. However, Cu extracted after 504 h using citric was significantly (P < 1%) higher in the rhizosphere than in the bulk soils. The results illustrated that, on average, citric acid extracted 56% more Cu from the bulk soils than DTPA‐TEA, and citric acid extracted 85% more Cu from the rhizosphere soils than DTPA‐TEA. Desorption kinetics of Cu in the two extractants was well described by power‐function, parabolic diffusion, and first‐order equations. The results show that a 10 mM citric acid extractant may be recommended to determine the kinetics of Cu desorption in calcareous soils amended with sewage sludge.     

Behavior of heavy metals from sewage sludge in a Chernozem of the dry belt in Saxony‐Anhalt/Germany

In a small‐plot trial different doses of sewage sludge (equivalent 82‐330 tons of dry matter per hectare) were incorporated in 0—25 cm depth (1982—1985). The aim of the investigations was to study the fate of the heavy metals Zn, Cd, Cu, Ni, Pb, and Cr, to determine their concentration in different soil fractions using a sequential extraction method and to ascertain their uptake by Zea mays L. plants. Eleven years after the last application the metals supplied with the sludge had moved as far as 50 cm in depth. The concentrations of Zn, Cd, Cu, Ni, and Cr in the saturation extract of the sampled soil layers were closely correlated with the concentrations of dissolved organic carbon (DOC). This result suggests that the heavy metal displacement was partly connected with the DOC movement in the soil. Considerable amounts of Zn and Cd coming from sewage sludge were found in the mobile fractions of the soil. Cu, Ni, and Pb were located especially in organic particles, and Cr was obviously bound by Fe‐oxides. Nine years after the last application the binding species of heavy metals were still different compared with those in the untreated soil. The whole withdrawal of heavy metals by plants yielded <1 % of the applied amounts. In the case of Zn the uptake from the sludge amended soil decreased during the experimental period. No similar tendency was observed for the other elements. In any case their annual variations of uptake exceeded the effect of sludge application.     

Chemical fractions of copper and zinc in organic‐rich particles from aqueous extracts of a metal‐contaminated granite soil

Abstract

Chemical fractions of copper (Cu) and zinc (Zn) in the organic‐rich particles collected from filtered aqueous extracts (<20 μm) of an acid soil were determined. A sequential extraction procedure was used to partition the particulate Cu and Zn into four operationally defined chemical fractions: adsorbed (ADS), iron (Fe) and manganese (Mn) oxides bound (FeMnOX), organic matter bound (OM) and residual (RESD). Total extractable concentrations of Cu and Zn in the fine particles were higher than their total concentrations in the original bulk soil. The concentration of particulate Cu was usually much higher than that of particulate Zn. Addition of lime stabilized sewage sludge cake and/or inorganic metal salts markedly increased the concentrations of particulate Cu and Zn in aqueous extracts, especially from limed soil. The proportional distributions of particulate Cu and Zn were quite similar. The two particulate metals were present predominantly in the ADS and FeMnOX fractions, with less (about 20%) in the OM and RESD fractions. Some of the ADS metal fraction was associated with dissolved organic substances. The concentrations of particulate Cu and Zn in the various extractable fractions were significantly affected by the application of lime, lime stabilized sewage sludge cake, or inorganic metal salts.     

Distribution of Aluminum Fractionation in the Acidic Rhizosphere Soils of Masson Pine (Pinus massoniana Lamb)

The modified Tessier’s sequential extraction procedure and rhizobox cultivation were employed to investigate the distribution of aluminum (Al) fractions in the acidic rhizosphere soil of Masson pine (Pinus massoniana lamb) seedlings. The results showed that the Al in soils was fractionated into five operationally defined fractions. Three sets of soil samples used in the rhizoboxes were collected from the three forest sites in the southeast of China: Sichuan, Zhejian, and Jiangsu. At the end of 100-day cultivation, the rhizosphere Al fractions for the original or bulk soils were in the order of residual > iron-manganese (Fe-Mn) oxides > organic > carbonate > exchangeable. However, in rhizosphere soil, the Al fraction follows the order of residual > organic > Fe-Mn oxides > carbonate > exchangeable. On average, the rhizosphere experienced significant increase in organically bound Al and slight decrease in exchangeable Al contents, but had decreases in contents for the other three Al fractions compared to the nonrhizosphere. The correlation analysis indicated that the Al contents accumulated in roots were significantly and positively correlated with exchangeable Al contents in the rhizosphere, and also characterized by the major portion of organically bound Al, which exhibited a bioavailable transformation of Al fractions. Results indicated that decreases in both redox potential and soil pH, as well as increase in dissolved organic carbon (DOC), were observed in the rhizosphere. Exchangeable Al and organic Al fractions were dependent mainly on soil pH (hydrogen ion concentration) and DOC, accordingly. Decreasing rhizosphere pH from 5.93 to 3.42 accelerated the secretion of organic carbon. These data are helpful for understanding the mobility and bioavailability of Al fractions in the acidic rhizosphere soils of Masson pine.     

Responses of soil microbial communities to manure and biochar in wheat cultivation of a rice-wheat rotation agroecosystem in East China

Soil contamination in agroecosystems remains a global environmental problem. Biochar has been suggested as an organic amendment to alleviate soil pollution, sequester carbon(C), and improve soil fertility. However, information on how bacterial and fungal communities in acidic bulk and rhizosphere soils respond to swine manure and its biochar is still lacking. In this study, biochar and swine manure were applied at two rates of 1.5 and 3 t ha^-1 in a rice-wheat rotation field to assess ...     

Assessment of Heavy Metals in Spinach (Spinacia oleracea L.) Grown in Sewage Sludge–Amended Soil

The assessment of heavy metals in spinach (Spinacia oleracea) grown in sewage sludge–amended soil was investigated. The results revealed that sewage sludge significantly (P < 0.01) increased the nutrients and heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), and zinc (Zn) in the soil. The contents of metals were found to be below the maximum levels permitted for soils in India. The most agronomic performance and biochemical components of S. oleracea were found at 50% concentrations of sewage sludge in both seasons. The contents of Cd, Cr, Cu, Mn, and Zn in S. oleracea were increased from 5% to 100% concentrations of sewage sludge in both seasons. The order of contamination factor (Cf) of different heavy metals was Mn > Cd > Cr > Zn > Cu for soil and Cr > Cd > Mn > Zn > Cu for S. oleracea plants after application of sewage sludge. Therefore, use of sewage sludge increased concentrations of heavy metals in soil and S. oleracea.     

不同有机肥施用模式下黄壤稻田根际和非根际土壤有机碳的矿化特征

【目的】研究长期施用有机肥对土壤有机碳矿化特征的影响,为提高土壤碳库稳定性和培肥土壤提供理论依据。【方法】贵阳黄壤肥力与肥效长期定位试验始于1994年,种植制度为单季水稻。2021年水稻收获后,选取不施肥(CK),平衡施用化肥(NPK),25%和50%有机肥氮替代化肥氮(0.25MNPK、0.5MNPK)和单施有机肥(M) 5个处理的水稻植株,用抖根法采集根际和非根际土壤样品,分析活性碳组分含量,以采集的土样进行室内培养试验,研究有机碳矿化特征。【结果】1)与NPK相比,3个有机肥处理的根际土壤有机碳(SOC)含量提升了26%～43%,非根际土壤SOC含量提高了24%～32%;根际土壤微生物量碳(MBC)含量提升了16%～31%,且比非根际土壤高148%;非根际土壤易氧化有机碳(LOC)含量显著提升了36%～75%;0.5MNPK处理非根际土壤可溶性有机碳(DOC)含量显著提升了54%,且根际土壤的DOC含量平均高于非根际土壤10%。2)有机肥施用可明显增加黄壤稻田根际及非根际土壤有机碳矿化量,非根际土壤有机碳矿化量和矿化率分别高于根际土壤30%和33%;较CK和NPK处理,有机肥施用...     

Biological and physical resilience of soil amended with heavy metal-contaminated sewage sludge

Stability and resilience of a variety of soil properties and processes are emerging as key components of soil quality. We applied recently developed measures of biological and physical resilience to soils from an experimental site treated with metal‐contaminated sewage sludge. Soils treated with cadmium‐, copper‐ or zinc‐contaminated, digested or undigested sewage sludge were studied. Biological stability and resilience indices were: (i) the time‐dependent effects of either a transient stress (heating to 40°C for 18 hours) or a persistent stress (amendment with CuSO₄) on decomposition, and (ii) the mineralization of dissolved organic carbon (DOC) released by drying–rewetting cycles. Physical stability and resilience measures were: (i) compression and expansion indices of the soils, and (ii) resistance to prolonged wetting and structural regeneration through drying–rewetting cycles. Soil total carbon and DOC levels were greater in the sludge‐amended soils, but there were no differential effects due to metal contamination of the sewage sludge. Effects of metals on physical resilience were greater than effects on soil C, there being marked reductions in the expansion indices with Cd‐ and Cu‐contaminated sludge, and pointed to changes in soil aggregation. The rate of mineralization of DOC released by drying and wetting was reduced by Zn contamination, while biological resilience was increased in the Zn‐contaminated soil and reduced by Cd contamination. We argue that physical and biological resilience are potentially coupled through the microbial community. This needs to be tested in a wider range of soils, but demonstrates the benefits from a combined approach to the biological and physical resilience of soils.     

Phosphorus Availability and Some Biological Properties in the Bean (Phaseolus vulgaris) Rhizosphere

The objectives of this research were to evaluate the rhizospheric effects of bean (Phaseolus vulgaris) on phosphorus (P) availability and dissolved organic carbon (DOC), microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), alkaline phosphatase (ALP) and P in the particulate fraction (PF-P) in some calcareous soils under rhizobox conditions. The results showed that DOC, MBC, MBP and ALP strongly increased in the rhizosphere soils compared with the bulk soils (p < 0.05). Also, the amounts of PF-P and P extracted with different tests in the rhizosphere were lower compared to the bulk soils (p < 0.05). The correlation studies showed that plant indices (dry yield and P uptake) had a positive relationship with Olsen-P, MBP, DOC, ALP and PF-P in both the rhizosphere and the bulk soil. Therefore, bean rhizosphere caused increases of DOC, MBC, MBP and ALP and decreases of available P and PF-P in the studied soils. In addition, the results of this research showed that the Olsen-P method and MBP and PF-P could be used to estimate bean-available P in the studied calcareous soils.     

Effect of sewage sludge application to amelio‐rate iron deficiency of grain sorghum

Abstract

Recent research has indicated that land application of municipal sewage sludge to calcareous soils can be used to ameliorate iron (Fe) deficiency of grain sorghum [Sorghum bicolor (L.) Monech]. A greenhouse study was conducted to determine the response of grain sorghum grown on three different soils to application of sewage sludge. Sludge applied at rates of 0, 7.5, 15.0, and 25.0 g/kg soil did not completely ameliorate grain sorghum Fe deficiency. When FeEDDHA was soil applied, sewage sludge application significantly increased plant growth due to increases in soil phosphorus (P) availability. Application of sewage sludge at rates greater than 7.5 g/kg reduced dry matter production of grain sorghum in the FeEDDHA amended Orelia SC soil, the soil with the lowest total neutralizing potential. The decreases yield was possibly due to toxic levels of soil and plant copper (Cu) and zinc (Zn), and increased soil salinity.     

Sorption of s-Triazine Herbicides in Organic Matter Amended Soils: Fresh and Incubated Systems

Fresh amendment of soil with sewage sludge and composted sewage sludge resulted in increased sorption of three s-triazine herbicides: atrazine, ametryn and terbuthylazine. The extent of increased sorption (as evaluated by sorption coefficients K_d or K_f) was a function of soil type, such that sorption in amended organic carbon-poor soil (0.4% OC) was more enhanced than in amended organic carbon-rich soil (1.55% OC). Despite significant differences between the organic amendments in terms of humic and fulvic acid content, humin content, soluble organic matter content, total organic matter content, and H/C and O/C atomic ratios, organic matter composition had no discernible effect on either sorption distribution coefficients or on isotherm linearity in amended soils. Soils amended with composted sludge had the same sorption potential as did soils amended with the analogous uncomposted sludge. After incubating soil-sludge mixtures for a year at room temperature, organic matter content decreased to original pre-amendment levels. Sorption coefficients for the three compounds similarly decreased to initial pre-amendment values. Organic carbon normalized sorption coefficients (K_oc) were essentially identical in the soils, amended soils, and incubated amended soils, indicating that sludge and compost derived organic matter does not have a significantly different sorption capacity as compared with the original soils, despite compositional differences.     

Fractionation of residual cadmium,copper, nickel,lead, and zinc in previously sludge‐amended soil

Abstract

The fractionation of heavy metals in previously sludge‐amended soil is important to evaluate their behavior in the environment in terms of mobility and availability to crop plants. A surface soil that received two types of sludges at two different rates, plus fertilizer only and no treatment (control), having been fallow for nine years, was used in this study. The contents of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) fractions in previously sludge‐amended soils were governed by the total content of these metals in the sludges applied and by the rate of sludge application. The contents of these metals were higher for soils that received the Chicago sludge as compared to that receiving the Huntsville sludge. Furthermore, soils that received 20 Mg/ha/yr of sludge for five years generally had higher levels of these metals than those receiving a single dose at the 100 Mg/ha application rate. The percentage of the total content in the water soluble and exchangeable forms was very low (≤1%) regardless of sludge application. The application of sludges tended to reduce the residual fraction and to increase the organic and carbonate fractions. Overall, the predominant forms of the metals in the sludges were as the Cd‐, Ni‐, Pb‐, and Zn‐carbonate and Cu‐organic fractions.     

Effects of organic and mineral amendments on available P and phosphatase activities in a degraded Mediterranean soil under short-term incubation experiment

The aim of this study was to determine the effects of mineral and organic-P-fertilizers on soil P availability, bacteria densities and phosphatase activities, in a degraded Mediterranean soil characterized by low level in soil organic matter and nutrients. A typical degraded Mediterranean soil, originating from a siliceous mineral parent material, was amended with different organic or mineral P-sources: aerobically digested sewage sludge (SS), with or without physico-chemical treatment by ferric chloride; sewage sludge compost (SSC); Na or K mineral P-salts (Pi-salts). All the amendments were carried out in order to provide soil with a P total quantity equivalent to 0.5 g P₂O₅/kg of soil. Bacterial density, phosphatase activities (i.e. acid (APH) and alkaline (BPH) phosphomonoesterases and phosphodiesterases), BPH/APH ratio, and available P (P Olsen) were measured after 25 and 87 days of incubation. Results showed that all the P-sources used to fertilize soil during this study resulted in significant increase in P concentration. However, different responses in phosphatase activities and bacterial densities were obtained with regards to the amendment applied to soil. Indeed, it appeared clearly that sewage sludge (SS) considerably stimulated soil biological activity, and more especially the different kinds of phosphatases involved in P mineralization and P turn-over. On the contrary, sewage sludge compost (SSC) as well as P-salts amendments did not affected these parameters in most cases. Results showed also that the incubation time influenced almost all the biological and chemical parameters investigated during this study. As a consequence, P availability was considerably improved in the amended soils between the two sampling dates.     

Initial results from long-term field studies at three sites on the effects of heavy metal-amended liquid sludges on soil microbial activity

In a long‐term study of the effects on soil fertility and microbial activity of heavy metals contained in sewage sludges, metal‐amended liquid sludges each with elevated Zn, Cu or Cd concentrations were applied over a 3‐year period (1995–1997) to three sites in England. The experiments were sited adjacent to experimental plots receiving metal‐rich sludge cakes enabling comparisons to be made between the effects of heavy metal additions in metal‐amended liquid sludges and sludge cakes. The liquid sludge additions were regarded as ‘worst case’ treatments in terms of likely metal availability, akin to a long‐term situation following sewage sludge additions where organic matter levels had declined and stabilised. The aim was to establish individual Zn (50–425 mg kg^?1), Cu (15–195 mg kg^?1) and Cd (0.3–4.0 mg kg^?1) metal dose–response treatments at each site, but with significantly smaller levels of organic matter addition than the corresponding sludge cake experiments. There were no differences (P > 0.05) in soil respiration rates, biomass carbon concentrations or most probable numbers of clover Rhizobium between the treatments at any of the sites at the end of the liquid sludge application programme. Soil heavy metal extractability differed between the metal‐amended liquid sludge and metal‐rich sludge cake treatments; Zn and Cd extractabilities were higher from the liquid sludge additions, whereas Cu extractability was higher from the sludge cake application. These differences in metal extractability in the treated soil samples reflected the contrasting NH₄NO₃ extractable metal contents of the metal‐amended liquid sludges and sludge cakes that were originally applied.     

Effect of increased cobalt treatments on sewage sludge amended soil: Nitrogen species in soil and tranference to tomato plants

The effects of increased cobalt additions (0, 50, 100 and 200 v mg v kg m 1 soil) in sewage sludge-amended soil on organic matter, N Kjeldahl, ammonium and nitrate were studied in this experiment. Three different rates of sewage sludge were applied (0, 30 and 60 v tn v ha m 1 ) to soil as main plots, using tomato (Lycopersicum esculentum Mill var. Ramy) such testing cultivation. Plant biomass and nitrogen content in tomato leaf were also monitored. The organic matter in the soil was clearly affected by the fertilization. N Kjeldahl, ammonium and nitrate were favoured by organic treatments. Co seemed to reduce the transformation of ammonium to nitrate on amended soils, with accumulation of ammonium forms, especially at the higher application rates of sewage sludge. This incidence of Co on nitrogen species in soil decreased with the time of experiment, probably due to the reduction of availability of the pollutant. Aerial biomass production and nitrogen content in leaf were increased for the organic fertilization compared to the control. Only very high levels of Co in soil reduced significantly the aerial biomass production of tomato plants in amended soils. Co seemed to induce a decrease of the nitrogen in leaf in the amended soils, but not for the non-fertilized soils.     

Plant availability of heavy metals in a soil amended with a high dose of sewage sludge under drought conditions

The objective of this research was to study the effect of water deficit on soil heavy metal availability and metal uptake by ryegrass (Lolium multiflorum Lam.) plants grown in a soil amended with a high dose of rural sewage sludge. Three fertility treatments were applied: sewage sludge (SS), mineral fertilizer (M), and control (C); unamended). The levels of irrigation were: well-watered (W) and water deficit (D). Microbial respiration decreased the total organic C (TOC) in sludge-treated soils, but this did not enhance soil DTPA-extractable heavy metal concentrations. Indeed, Zn, Cu, Mn and Ni availability decreased during the experiment. C- and M-treated soils showed either no changes or increases of some trace element concentrations during the incubation. In the plant experiment, ryegrass dry matter (DM) yield, relative water content (RWC) and leaf water potential (_w) decreased in drought conditions. Sludge addition increased metal concentrations in plants. However, in some instances, SS-treated plants showed either similar or lower transfer coefficient (Tc) values than did plants in the C and M treatments. Water deficit decreased the concentration and the Tc of some metals in roots of M and SS plants. Results indicate that sludge-borne heavy metals were maintained in chemical forms of low availability. The lower metal uptake by SS and M plants under dry conditions cannot be attributed to a lower availability of these elements in soil.     

Chemical Speciation of Heavy Metals in the Fractionated Rhizosphere Soils of Sunflower Cultivated in a Humic Andosol

Chemical speciation and bioaccumulation factor of iron (Fe), manganese (Mn), and zinc (Zn) were investigated in the fractionated rhizosphere soils and tissues of sunflower plants grown in a humic Andosol. The experiment was conducted for a period of 35 days in the greenhouse, and at harvest the soil system was differentiated into bulk, rhizosphere, and rhizoplane soils based on the collection of root-attaching soil aggregates. The chemical speciations of heavy metals in the soil samples were determined after extraction sequentially into fractions classified as exchangeable, carbonate bound, metal–organic complex bound, easily reducible metal oxide bound, hydrogen peroxide (H₂O₂)–extractable organically bound, amorphous mineral colloid bound, and crystalline Fe oxide bound. Iron and Zn were predominantly crystalline Fe oxide bound in the initial bulk soils whereas Mn was mainly organically bound. Heavy metals in the exchangeable form accumulated in the rhizosphere and rhizoplane soils, comprising <4% of the total content, suggesting their relatively low availability in humic Andosol. Concentrations of organically bound Fe and Mn in soils decreased with the proximity to roots, suggesting that organic fraction is the main source for plant uptake. Concentrations of Mn and Zn in the metal–organic complex also decreased, indicating a greater ability of sunflower to access Mn from more soil pools. Sunflower showed bioaccumulation factors for Zn, Fe, and Mn as large as 0.39, 0.05, and 0.04 respectively, defining the plant as a metal excluder species. This result suggests that access to multiple metal pools in soil is not necessarily a major factor that governs metal accumulation in the plant.     

碱稳定污泥污水对土壤可提取有机碳和铜的影响

An incubation experiment was conducted to evaluate the potential for water contamination with sludge-derived organic substances and copper following land application of alkaline-stabilised sewage sludge. Two contrasting sludge-amended soils were studied. Both soils were previously treated with urban and ruralalkaline biosolids separately at sludge application rates of 0, 30 and 120 t ha^-1 fresh product. The air-driedsoil/sludge mixtures were wetted with distilled water, maintained at 40 % of water-holding capacity and equilibrated for three weeks at 4 ℃ before extraction. Subsamples were extracted with either distilled wateror 0.5 mol L^-1 K₂SO₄ solution. The concentrations of organic C in the aqueous and chemical extracts were determined directly with a total organic carbon (TOC) analyser. The concentrations of Cu in the twoextracts were also determined by atomic absorption spectrophotometry The relationship between the two extractable organic C fractions was examined, together with that between extractable organic C concentration and extractable Cu concentration. Application of alkaline biosolids increased the concentrations of soil mobile organic substances and Cu. The results are discussed in terms of a possible increase in the potential for leaching of sludge-derived organics and Cu in the sludge-amended soils.     

半干旱土添加有机改良剂后有机质的化学结构变化

A 9-month incubation experiment using composted and non-composted amendments derived from vine pruning waste and sewage sludge was carried out to study the effects of the nature and stability of organic amendments on the structural composition of organic matter (OM) in a semi-arid soil.The changes of soil OM,both in the whole soil and in the extractable carbon with pyrophosphate,were evaluated by pyrolysis-gas chromatography and chemical analyses.By the end of the experiment,the soils amended with pruning waste exhibited less organic carbon loss than those receiving sewage sludge.The non-composted residues increased the aliphatic-pyrolytic products of the OM,both in the whole soil and also in the pyrophosphate extract,with the products derived from peptides and proteins being significantly higher.After 9 months,in the soils amended with pruning waste the relative abundance of phenolic-pyrolytic products derived from phenolic compounds,lignin and proteins in the whole soil tended to increase more than those in the soils amended with sewage sludge.However,the extractable OM with pyrophosphate in the soils amended with composted residues tended to have higher contents of these phenolic-pyrolytic products than that in non-composted ones.Thus,despite the stability of pruning waste,the composting of this material promoted the incorporation of phenolic compounds to the soil OM.The pyrolytic indices (furfural/pyrrole and aliphatic/aromatic ratios) showed the diminution of aliphatic compounds and the increase of aromatic compounds,indicating the stabilization of the OM in the amended soils after 9 months.In conclusion,the changes of soil OM depend on the nature and stability of the organic amendments,with composted vine pruning waste favouring humification.