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1.
The capability of organic wastes to release available N in soil varies largely, depending on their source and form of production, or rather on their composition and biodegradability. Our purpose was to predict mineralization rates of different materials using their analyses joined with a simulation model, and to evaluate the influence of soil type and application rate of the organic materials on N and C transformations in soil. Four organic materials, sewage sludge (SS), sewage sludge compost (SSC), cattle manure compost (CMC), hen and cattle manure compost (HCMC), were applied to two soils at rates of 2 and/or 4%. The soils were incubated aerobically for 168 days at 30°C, during which CO2 evolution rates and mineral-N concentrations were measured periodically. Hot water extractable C and N of all organic amendments correlated well with short term C and N mineralization, except HCMC that immobilized N although its soluble N content was large. NCSOIL, a computer model that simulates C and N cycling in soil with organic amendments, predicted well C and N mineralization of SS, SSC and CMC when considered as three-pool materials that decomposed at specific rates of 0.4, 0.024 and 10?4 d?1, using hot water soluble C and N as the labile pool. N immobilization by HCMC could be simulated only if the distribution of N between the labile and resistant pools was derived by optimization of NCSOIL, while hot water soluble C was labile. Laboratory methods to determine an intermediate pool or components that contribute to immobilization are required for improving the predictions of C and N mineralization from organic amendments. 相似文献
2.
The use of organic amendments requires an adequate control of the chemical quality of their humic acid (HA)-like fractions and of the effects that these materials may have on the status, quality, chemistry and functions of native soil HAs. In this work, the compositional, functional and structural properties of the HA-like fractions isolated from a liquid swine manure (LSM), a municipal sewage sludge (SS), and two municipal solid waste composts (MSWCs) were evaluated in comparison to those of HAs isolated from three unamended soils and from the corresponding soils amended with LSW, SS, and MSWC at various rates in three field plot experiments conducted in Minnesota, USA. With respect to the unamended soil HAs, the HA-like fractions of the three amendments featured a greater aliphatic character, a marked presence of proteinaceous, S-containing and polysaccharides-like structures, an extended molecular heterogeneity, small organic free radical contents and a small degree of humification. The MSWC-HAs featured a larger degree of humification than LSM-HA and SS-HA. The three amendments affected in different ways and by various extents the compositional, structural and functional properties of soil HAs depending upon the nature, origin and application rate of the amendment. In general, the data obtained suggested that proteinaceous, S-containing and aliphatic structures contained in HA-like fractions of organic amendments were partially incorporated into native soil HAs. 相似文献
3.
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. 相似文献
4.
E. Witter 《Biology and Fertility of Soils》1996,23(1):33-37
Soil C balances were calculated in a field experiment started in 1956. Treatments include a fallow and soils receiving different N fertilizers or organic amendments. By assuming the absence of a priming effect, the degree of mineralization of crop residues and organic amendments was calculated. Crop residue mineralization was not affected by a more than 50% decrease in the size of the microbial biomass in soil fertilized with (NH4)2SO4, which had caused the pH of this soil to drop from 6.6 to 4.4. More C had accumulated per unit C input in peat-and sewage sludge-amended soils than in any of the other soils, suggesting that peat and sewage sludge were more resistant to microbial attack. Recalcitrance of substrate C was an adequate explanation for the low ratio of biomass C to soil C in the peat-amended soils, but not in the sewage sludge-amended soil. There was a close linear relationship (r=0.94) between the content of microbial biomass C in the soil measured in 1990 and cumulative C losses from the soil since 1956. Compared to the relationship between soil biomass C and soil organic C concentrations, the linear relationship between microbial C and cumulative C losses suggested that the significantly reduced biomass in the sewage sludge-amended soil was at least partially due to the presence of toxic substances (presumably elevated heavy metal concentrations) in this soil and was probably not affected by the somewhat low pH (5.3) in this soil. 相似文献
5.
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 Kd or Kf) 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 (Koc) 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. 相似文献
6.
Increasing use of N fertilizer for crop production necessitates more rapid estimates on N provided by the soil in order to prevent under‐ or overfertilization and their adverse effect on plant nutrition and environmental quality. A study was conducted to investigate the responses of arginine ammonification (AA), L‐glutaminase activity (LG), soil N–mineralization indices, corn (Zea mays L.) crop–yield estimation, and corn N uptake to application of organic amendments. The relationships between corn N uptake and the microbial and enzymatic processes which are basically related to N mineralization in soil were also studied. The soil samples were collected from 0–15 cm depth of a calcareous soil that was annually treated with 0, 25, or 100 Mg ha–1 (dry‐weight basis) of sewage sludge and cow manure for 7 consecutive years. Soil total N (TN), potentially mineralizable N (N0), and initial potential rates of N mineralization (kN0) were significantly greater in sewage sludge–treated than in cow manure–treated soils. However, the amendment type did not influence soil organic C (SOC), AA, LG, and anaerobic index of N mineralization (Nana). The application rates proportionally increased N‐availability indices in soil. Corn N concentration and uptake were correlated with indices of mineralizable N. A multiple stepwise model using AA and Nana as parameters provided the best predictor of corn N concentration (R = 0.86, p < 0.001). Another model using only LG provided the best predictor of corn N uptake (R = 0.78, p < 0.001). This results showed that sewage‐sludge and cow‐manure application is readily reflected in certain soil biological properties and that the biological tests may be useful in predicting N mineralization and availability in soil. 相似文献
7.
Changes produced in the biological characteristics of an arid soil by the addition of various urban wastes (municipal solid
waste, sewage sludge and compost) at different doses, were evaluated during a 360-day incubation experiment. The addition
of organic materials to the soil increased the values of biomass carbon, basal respiration, biomass C/total organic C ratio
and metabolic quotient (qCO2), indicating the activation of soil microorganisms. These biological parameters showed a decreasing tendency with time. Nevertheless,
their values in amended soils were higher than in control soil, which clearly indicates the improvement of soil biological
quality brought about by the organic amendment. This favorable effect on soil biological activity was more noticeable with
the addition of fresh wastes (municipal solid waste or sewage sludge) than with compost. In turn, this effect was more permanent
when the soil was amended with municipal solid waste than when it was amended with sewage sludge.
Received: 28 May 1996 相似文献
8.
The application of organic amendments on soils poor in organic matter (OM) can improve long-term soil fertility, but may also enhance the mineralization of native soil organic matter. Three organic amendments, compost, sewage sludge and horse manure used by urban market gardeners in Dakar, Senegal were analyzed for their OM maturity. Their fate was evaluated in a 45-d agronomic trial in a sandy Arenosol with lettuce. In each case, water-extractable organic matter (WEOM) and humic-like substances (HLS) were isolated from raw amendments and amended soils, and characterized using ultraviolet-visible (UV/Vis) spectroscopy. Results highlighted the general more aromatic character of HLS and WEOM fractions extracted from compost compared to the other two amendments. When applied to soils, however, these differences were not clearly observed. The aromaticity and humification degree of the labile fraction (WEOM) increased with depth in the first 30 cm for all amendments. This indicated the high lixiviation rates that fresh OM underwent in the studied sandy soil. Finally, a statistical analysis of the results was able to discriminate between surface and deeper horizons and between amended- and non-amended soil samples. Spectroscopic indices showed indeed strong increase/decrease with depth linked with the mineralization/humification processes that the fresh OM from amendments underwent during the 45 d of the agronomic trial. This study highlights the potential of spectroscopic techniques to study agricultural amendment organic matter fractions and their fate in soils. 相似文献
9.
《Communications in Soil Science and Plant Analysis》2012,43(19):2788-2795
The use of organic fertilizers in lands with low organic-matter content, such as those found in the Mediterranean region, is an attractive option for enhancing soil quality and fertility status. However, it is difficult to assess the nitrogen (N) mineralization rate and the quantity of the organic amendment to be added. Thus we conducted a 300-day incubation trial, where four commonly found organic amendments (three different animal manures and one sewage sludge) were mixed with two soils. Our aim was to assess the potentially mineralizable N with the use of the first-order exponential model. Our findings indicated that the N-mineralization data fitted well to the model we used and that the active N fraction (eluted available N per total N added) ranged from 28.4% to 50.3%, depending on indigenous organic carbon (C) content, as well as on the organic amendment C/N ratio and total N content. 相似文献
10.
In this study, mineralization of digested pig slurry and compost from municipal organic wastes in burned soils was followed for 60 days. The effects of amendments on organic matter fractions and microbial community level physiological profiles (CLPP) were also investigated at the end of the incubation period. Soil from a forest 10 days after a fire had a greater basal respiration, and more organic matter that a nearby soil that was not affected by fire, presumably as a consequence of black ash addition following the wildfire. Nitrification was inhibited in soils treated at 105 and 250 °C in the laboratory, but amendment application allowed nitrification to take place in the latter soil, and led to significant flushes of mineralization. Slurry amendment resulted in greater increases in mineral N compared with compost. Soil treated at 250 °C had the greatest content of water-extractable compounds (WE) at the expense of acid-extractable compounds (AE), but during the incubation the variations in these two fractions had an opposite trend, i.e. soil gained AE and lost WE fractions. The variation in N-acetyl-glucosamine-induced respiration was different between compost- and slurry-amended soils, with the greater values in the former. The effect of amendments could be further differentiated by principal component (PCA) and cluster analyses based on the variations in organic matter fractions and CLPP between the beginning and the end of the incubation period. Amendment application led to shifts on the PCA maps that depended both on the amendment and soil treatment. In fresh soil and in that treated at 250 °C, the unamended, compost- and slurry-amended treatments remained relatively close on the PCA maps and had linkage distances <1.0. In contrast, amendment application to other soils led to large shifts on the PCA maps and to linkage distances >1.0. Pig slurry led to the greatest changes in burned soil, while compost induced the greatest shifts in soil treated at 105 °C.This study suggests that an application of organic amendments after a severe fire event may contribute to a faster recovery of soil functions. 相似文献
11.
《Communications in Soil Science and Plant Analysis》2012,43(7-8):835-846
Abstract This work investigated the kinetics of carbon (C) mineralization when different doses of organic materials with varying degrees of stability were added to an arid soil. Respiration assays showed that the incorporation of wastes led to a greater emission of carbon in the form of CO2 and greater degree of microbial activity than those occurring in the control soil. Soils treated with fresh waste (municipal solid waste and sewage sludge) gave off more CO2 than that treated with compost, with higher values being obtained at high than at low doses. Carbon dioxide emission was reduced with the length of time the organic materials remained in the soil. The data of cumulative CO2 were fitted to the equation C=C0(1‐e‐Kt)+C1. The parameters derived from this model were used as indices of organic matter decomposition, because the product of C0 and K was more precise than either value separately. In all cases, an initial rapid phase of mineralization was clearly differentiated from a second slower phase. 相似文献
12.
The present study was conducted to assess the suitability of sewage sludge amendment in soil for Beta vulgaris var. saccharifera (sugar beet) and Triticum aestivum (wheat) by evaluating the arsenic and selenium accumulation and physiological responses of plants grown at 10%, 25%, and 50% sewage sludge amendment rate. Sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently with higher accumulation in plant parts. The chlorophyll contents increased after the sewage sludge treatments except for 50%. The sewage sludge amendment led to a significant increase in arsenic and selenium concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency. The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake in the leaves and root concentrations of arsenic and selenium in plants as compared to those grown on unamended soil. Accumulation was more in roots than shoots and leaves for most of the heavy metals. Concentrations of arsenic and selenium were more than the permissible limits of national standards in the edible portion of sugar beet and wheat grown on different sewage sludge amendments ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet and wheat may not be a good option due to risk of contamination of arsenic and selenium. 相似文献
13.
The influence of tillage and nutrient amendment management on nutrient cycling processes in soil have substantial implications for environmentally sound practices regarding their use. The effects of 2 years of tillage and soil amendment regimes on the concentrations of soil organic matter variables (carbon (C), nitrogen (N) and phosphorus (P)) and C and N mineralization and P release were determined for a Dothan fine-sandy loam soil in southeastern Alabama. Tillage systems investigated were strip (or conservation) and conventional tillage with various soil nutrient amendments that included no amendment, mineral fertilizer, and poultry waste (broiler litter). Surface soil (0–10 cm depth increment) organic matter variables were determined for all tillage/amendment combinations. Carbon and N mineralization and P release were determined on surface soils for each field treatment combination in a long-term laboratory incubation. Soil organic P concentration was 60% greater in soils that had been conventionally tilled, as compared with strip-tilled, both prior to and following laboratory incubation. Carbon and N mineralization results reflected the effects of prior tillage amendment regime, where soils maintained under strip-till/broiler litter mineralized the greatest amount of C and N. Determination of relative N mineralization indicated that strip tillage had promoted a more readily mineralizable pool of N (6.1%) than with conventional till (4.2%); broiler litter amendments had a larger labile N fraction (6.7%) than was found in soils receiving either mineral fertilizer (4.1%) or no amendment (4.7%). Tillage also affected P release measured during the incubation study, where approximately 20% more inorganic P was released from strip-tilled soils than from those maintained under conventional tillage. Greater P release was observed for amended soils as compared with soils where no amendment was applied. Results from this study indicate that relatively short-term tillage and amendment management can significantly impact C, N, and P transformations and transfers within soil organic matter of a southeastern US soil. 相似文献
14.
Biological and physical resilience of soil amended with heavy metal-contaminated sewage sludge 总被引：4，自引：0，他引：4
B. S. Griffiths P. D. Hallett H. L. Kuan Y. Pitkin & M. N. Aitken 《European Journal of Soil Science》2005,56(2):197-206
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. 相似文献
15.
An incubation experiment with composted sewage sludge (CSS) just added to the soil was conducted to determine its initial
effects on C decomposition, N nitrification and the transformation of organic matter. CSS was mixed with a sandy loam soil
from uncultivated ochric epipedon of a Typic Haploxeralf at rates of 0, 40 and 80 t ha–1 (dry weight). The data obtained showed that with regard to the unamended soil, both the 40 and the 80 t ha–1 treatments produced the same result in decreasing respiratory activity, but the addition of increasing amounts of CSS progressively
delayed C decomposition. The nitrification index (NI), defined as the relation between nitrate-N and nitrate-N + ammonium-N,
increased in correlation with the C mineralization coefficient. Total organic matter decreased after incubation whereas the
humic substances increased in relation to the total C mineralized.
Received: 28 October 1999 相似文献
16.
Mohammad Arifur RAHMAN Mohammad Abdul KADER Mohammad JAHIRUDDIN Mohammad Rafiqul ISLAM Zakaria Mohammad SOLAIMAN 《土壤圈》2022,32(3):475-486
Subtropical recent alluvial soils are low in organic carbon (C). Thus, increasing organic C is a major challenge to sustain soil fertility. Biochar amendment could be an option as biochar is a C-rich pyrolyzed material, which is slowly decomposed in soil. We investigated C mineralization (CO2-C evolution) in two types of soils (recent and old alluvial soils) amended with two feedstocks (sugarcane bagasse and rice husk) (1%, weight/weight), as well as their biochars and aged biochars under a controlled environment (25 ±2 ℃) over 85 d. For the recent alluvial soil (charland soil), the highest absolute cumulative CO2-C evolution was observed in the sugarcane bagasse treatment (1 140 mg CO2-C kg-1 soil) followed by the rice husk treatment (1 090 mg CO2-C kg-1 soil); the lowest amount (150 mg CO2-C kg-1 soil) was observed in the aged rice husk biochar treatment. Similarly, for the old alluvial soil (farmland soil), the highest absolute cumulative CO2-C evolution (1 290 mg CO2-C kg-1 soil) was observed in the sugarcane bagasse treatment and then in the rice husk treatment (1 270 mg CO2-C kg-1 soil); the lowest amount (200 mg CO2-C kg-1 soil) was in the aged rice husk biochar treatment. Aged sugarcane bagasse and rice husk biochar treatments reduced absolute cumulative CO2-C evolution by 10% and 36%, respectively, compared with unamended recent alluvial soil, and by 10% and 18%, respectively, compared with unamended old alluvial soil. Both absolute and normalized C mineralization were similar between the sugarcane bagasse and rice husk treatments, between the biochar treatments, and between the aged biochar treatments. In both soils, the feedstock treatments resulted in the highest cumulative CO2-C evolution, followed by the biochar treatments and then the aged biochar treatments. The absolute and normalized CO2-C evolution and the mineralization rate constant of the stable C pool (Ks) were lower in the recent alluvial soil compared with those in the old alluvial soil. The biochars and aged biochars had a negative priming effect in both soils, but the effect was more prominent in the recent alluvial soil. These results would have good implications for improving organic matter content in organic C-poor alluvial soils. 相似文献
17.
This work sets out to verify whether the application of municipal solid waste compost (MSWC) or treated urban sewage sludge (USS) organic amendments efficiently promote organic matter (OM) increases in a Haplic Podzol (PZha) and in a Calcic Vertisol (VRcc). For that purpose, carbon (C) mineralization and C kinetic parameters were studied, using a laboratory experimental incubation setup. The results showed that the addition of the amendments to the soils increased their mineralization capacities, and that the highest C mineralization rate was reached at the end of the first 2 d of incubation. The different characteristics of the soils seem to have influenced the C mineralization rates during the 28-d incubation. The USS induced higher C mineralization than the MSWC, and the PZha soil gave rise to higher C mineralization than VRcc. For all treatments, C mineralization adjusted well to an exponential plus linear kinetic model, suggesting that the organic C of the amendments was made up of two organic pools of differing degrees of stability. With the exception of the application of USS 60 t ha−1, all the treatments increased the OM content on both soils, or at least the OM remained constant throughout the incubation. 相似文献
18.
《Communications in Soil Science and Plant Analysis》2012,43(15-16):1833-1844
Abstract In the search for an approach which could be used to predict available nitrogen (N) in organic amendments, biological and chemical methods were investigated in laboratory and growth chamber studies. Two biological methods [maize plants (Zea mays L.) grown in pots, and soil‐amendment mixtures incubated aerobically at 2, 4, 6, 8, 12, and 16 weeks], and four chemical methods [autoclave, 0.5M potassium permanganate (KMnO4), pepsin, and 6M hydrochloric acid (HCl)] were compared to determine N availability in 36 organic amendments applied to soil. Total N mineralized in a soil amended with different organic amendments ranged from‐12 to 428 mg N/kg soil. The highest value was obtained from sludge number 11 and the lowest from cow manure 2, urban refuse, and grape‐marc. In general, the aerobically‐treated sewage sludges gave higher N‐mineralization rates than other amendments. The 6M HCl and autoclave methods were more suitable for predicting N availability in these organic amendments than either the pepsin or KMnO4 methods. Prediction of N availability in the growth chamber experiments improved if several chemical and biological methods were combined in a multiple regression analysis. 相似文献
19.
Muhammad Asghar Malik Khalid Saifullah Khan Petra Marschner Safdar Ali 《Biology and Fertility of Soils》2013,49(4):415-425
Organic amendments could be used as alternative to inorganic P fertilisers, but a clear understanding of the relationship among type of P amendment, microbial activity and changes in soil P fractions is required to optimise their use. Two P-deficient soils were amended with farmyard manure (FYM), poultry litter (PL) and biogenic waste compost (BWC) at 10 g?dw?kg?1 soil and incubated for 72 days. Soil samples were collected at days 0, 14, 28, 56 and 72 and analysed for microbial biomass C, N and P, 0.5 M NaHCO3 extractable P and activity of dehydrogenase and alkaline phosphomonoesterase. Soil P fractions were sequentially extracted in soil samples collected at days 0 and 72. All three amendments increased cumulative CO2 release, microbial biomass C, N and P and activity of dehydrogenase and alkaline phosphomonoesterase compared to unamended soils. The increase in microbial biomass C and N was highest with PL, whereas the greatest increase in microbial biomass P was induced with FYM. All three biomass indices showed the same temporal pattern, with the highest values on day 14 and the lowest on day 72. All amendments increased 0.5 M NaHCO3 extractable P concentrations with the smallest increase with BWC and the greatest with FYM, although more P was added with PL than with FYM. Available P concentrations decreased over time in the amended soils. Organic amendments increased the concentration of the labile P pools (resin and NaHCO3-P) and of NaOH-P, but had little effect on the concentrations of acid-soluble P pools and residual P except for increasing the concentration of organic P in the concentrated HCl pool. Resin P and NaHCO3-Pi pools decreased over time whereas NaOH-Pi and all organic P pools increased. It is concluded that organic amendments can provide P to plants and can stimulate the build-up of organic P forms in soils which may provide a long-term slow-release P source for plants and soil organisms. 相似文献
20.
José Luis Moreno Carlos García Teresa Hernández Miguel Ayuso 《Soil Science and Plant Nutrition》2013,59(3):565-573
To elucidate the mechanism of transfer of heavy metals into the food chain, an experiment was carried out with a calcareous soil, to which two different doses of a sewage sludge compost contaminated with either Cd or Zn, Cd, Cu, and Ni were applied. A crop of lettuce was then grown in the amended soils. The application of sewage sludge composts to a calcareous soil lowered the soil's pH, although the value was always around 8 at the end of the experiment. Electric conductivity rose with organic amendment. As anticipated, such an amendment improved the nutritional level of the soils, particularly Nand P, both total and available. Plant yields were negatively affected by organic amendments contaminated with heavy metals, the most dangerous in our experiment being Cd and Zn since this metals easily taken up by plants. As Ni and Cu form insoluble complexes with the organic matter of the sewage sludge composts they are not readily absorbed. Of the metals studied, Cd and Zn showed the highest bioavailability index. 相似文献