Carbon and trace element fluxes in the pore water of an urban soil following greenwaste compost, woody and biochar amendments, inoculated with the earthworm Lumbricus terrestris

The benefits of adding composted organic materials to soils to enhance carbon storage could be countered by the mobilisation of some harmful pollutants commonly found in frequently degraded urban soils. Therefore non-composted materials could be a safer option. In the present study, carbon and trace element fluxes in soil pore water were studied in response to the surface mulch addition and the incorporation into an urban soil of greenwaste compost versus two non-composted amendments; a woody oversize material and biochar following inoculation with the vertical burrowing earthworm Lumbricus terrestris. The aim was to establish (i) to what extent the non-composted amendments impacted on mobility of soluble trace elements in the soil, compared to the composted amendment, and (ii) if/how this was regulated by earthworm activity.Both composted and non-composted amendments enhanced dissolved organic carbon (DOC) in soil pore water to ∼100-300 mg l⁻¹ in the upper depth of the soil profile above which they were applied as a mulch and similarly within the mesocosms in which they were mixed. Dissolved organic carbon, dissolved nitrogen (DTN) and trace metals, especially Cu and Pb, where enhanced to the greatest extent by greenwaste compost, because of strong co-mobilisation of metals by DOC. Biochar enhanced As and Cu mobility in the field profile and, additionally Pb in the mesocosms, with no effect on Cd. The woody, oversize amendment neither greatly increased DOC nor As, Cu, Pb or Zn mobility although, unlike the other amendments, earthworms increased DOC and Cd mobility when soils were amended with this material.This study concludes that non-composted amendments had a lower impact on DOC and thus trace element co-mobility than the composted greenwaste in this urban soil, whilst the general influence of earthworms was to reduce DOC and hence associated trace element mobility. In wider environmental terms the addition of non-composted materials to some urban soils, versus composted greenwaste could reduce the risk of mobilising potentially harmful elements, whilst usefully improving soil quality.     

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.     

Earthworm response to 10 weeks of incubation in a pot with acid mine spoil,sewage sludge,and lime

Applications of sewage sludge and lime have been used to restore some of the nearly 1.0 million ha of unreclaimed acid mine spoils in the United States. Earthworms might also aid in the reconstruction of mine spoils, but the earthworm response to mine spoils and sludge has not been widely studied. The objective of the present study was to examine growth of the earthworm Lumbricus terrestris in pots containing acidmine spoils, sewage sludge, and lime, and the growth of two common reclamation grasses, timothy (Phleum pratense L.) and tall fescue (Festuca arundinacea Schreb.), to the addition of earthworms. After 10 weeks, earthworms growing in the mine spoil treated with sewage sludge showed an increase in mean specific mass of 26.9% and in projected specific area of 24.5%. In contrast, earthworms growing on mine spoils without sludge decreased in mass by an average of 39.6% and in area by 21.0%. Soil pH influenced earthworm area, but not mass: earthworms growing on mine spoils (with or without sludge) showed an increase in mean surface area of 2.9% at pH 5.3 and a decrease of 11.2% at pH 6.5. The presence of earthworms significantly increased the belowground production of plant roots, but had no effect on either soil bulk density or above-ground production of plant biomass. The addition of earthworms to acid mine spoils treated with sewage sludge and lime might aid in the redevelopment of soil quality and biological diversity.     

Interactive effects of biochar and the earthworm Pontoscolex corethrurus on plant productivity and soil enzyme activities

Purpose

There is a growing interest in the use of soil enzymes as early indicators of soil quality change under contrasting agricultural management practices. In recent years, there has been increasing interest in the use of biochar to improve soil properties and thus soil quality. In addition, earthworms can also be used to ameliorate soil properties. However, there is no literature available on how biochar and earthworms interact and affect soil enzymes. The general objective of the present study was to test the suitability of adding biochar and earthworms in two tropical soils with low fertility status in order to improve their characteristics and productivity.

Materials and methods

Biochars were prepared from four different materials [sewage sludge (B1), deinking sewage sludge (B2), Miscanthus (B3) and pine wood (B4)] on two tropical soils (an Acrisol and a Ferralsol) planted with proso millet (Panicum milliaceum L.). In addition, in order to investigate the interaction between earthworms and biochar, earthworm Pontoscolex corethrurus was added to half of the mesocosms, while excluded in the remaining half. The activities of invertase, β-glucosidase, β-glucosaminidase, urease, phosphomonoesterase and arylsulphatase were determined. The geometric mean of the assayed enzymes (GMea) was used as an integrative soil quality index.

Results and discussion

Overall, earthworms and especially biochar had a positive effect on soil quality. GMea showed B1, B2 and B3 performing better than B4; however, results were soil specific. Plant productivity increased under both biochar and earthworm addition. Fruit productivity and plant growth was enhanced by B1 and B2 but not by B3 or B4.

Conclusions

Enhancements of productivity and soil enzymatic activities are possible in the presence of earthworms and the combination of the practices earthworm and biochar addition can be suggested in low fertility tropical soils. However, scientists should proceed carefully in the selection of biochars as the results of this study show a high specificity in the biochar–soil interaction.     

蚯蚓活动对城市生活污泥重金属的影响

采用塑料温棚内垄式堆积污泥培养蚯蚓方式,研究了蚯蚓处理对污泥重金属的影响。结果表明,污泥经蚯蚓处理后,理化性质发生了显著的变化,污泥的pH值、有机质、总氮和总磷都有不同程度的降低;蚯蚓能吸收富集污泥中的重金属,其中对重金属Cd有较强的富集能力;蚯蚓处理使污泥中重金属含量均出现不同程度的下降,重金属Cr、Zn、Pb、Cd、Cu、Ni分别减少27.98%、31.46%、32.81%、13.85%、23.86%和22.92%。利用盆栽试验,研究了污泥施用于土壤后生菜体内重金属积累的情况,结果表明,生菜体内重金属Zn、Cu、Pb和Ni的含量为污泥处理高于蚓粪处理;Cr和Cd则分别为差异不显著和略有降低。     

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.     

Growth and reproduction of Perionyx excavatus (Perr.) (Megascolecidae) as factors in organic waste management

 The life cycle of Perionyx excavatus has been studied and the potential of this epigeic earthworm species for breaking down and processing organic wastes is well known. Understanding of its optimal environmental requirements is required in order to optimize and accelerate the vermicomposting process. The rates of growth and reproduction of P. excavatus, on a variety of organic wastes, were evaluated in these experiments. The time of maturation and the rates of growth of this species, under various population density pressures and temperatures between 15  °C and 30  °C, were also assessed. Increasing temperatures up to 30  °C accelerated the growth of earthworms and lessened the time to sexual maturity. However, the highest rates of reproduction occurred at 25  °C both in cattle solids and sewage sludge. The mean time to egg hatching decreased and the degree of hatching success increased with increasing temperature. Earthworms grew at similar rates in cattle solids, pig solids and aerobically digested sewage sludge, but the earthworms did not grow well in horse solids and grew only poorly in turkey wastes. The maximum individual growth rates as a function of earthworm population and the maximum earthworm weights as a function of time with a constant food supply at four different temperatures were assessed. Received: 16 July 1997     

Earthworm activity affects soil aggregation and organic matter dynamics according to the quality and localization of crop residues—An experimental study (Madagascar)

Soil organic matter (SOM) plays a central role in the functioning of ecosystems, and is beneficial from agronomic and from environmental point of view. Alternative cultural systems, like direct seeding mulch-based cropping (DMC) systems, enhance carbon (C) sequestration in agricultural soils and lead to an increase in soil macrofauna. This study aimed at evaluating in field mesocosms the effects of earthworms on SOM dynamics and aggregation, as influenced by residue quality and management.In the highlands of Madagascar, buckets were filled with 2 mm-sieved clayey Inceptisol. The effects of earthworm addition (Pontoscolex corethrurus), residue addition (rice, soybean, and no addition), and localization of the residues (mulched or buried) were studied. After 5 months, soil from mesocosms with earthworms had significantly lower C concentration and higher proportion of large water-stable macroaggregates (>2000 μm) than those without earthworms, because of the production of large macroaggregates by earthworms. Earthworm effect on soil aggregation was greater with rice than with soybean residues. Casts (extracted from mesocosms with earthworms) were slightly enriched in C and showed significantly higher mineralization than the non-ingested soil (NIS), showing that at the time scale of our study, the carbon contained in the casts was not protected against mineralization. No difference in microbial biomass was found between casts and NIS.Complementary investigations are necessary to assess long-term effects of earthworm addition on SOM dynamics, the conditions of occurrence of physical protection, and the impact of earthworms on the structure of the microbial community.     

生物炭：一种新型改良剂能修复矿物、工业以及污水废弃物污染的土壤

Mine tailings, waste rock piles, acid mine drainage, industrial wastewater, and sewage sludge have contaminated a vast area of cultivable and fallow lands, with a consequence of deterioration of soil and water quality and watercourses due to the erosion of contaminated soils for absence of vegetative cover.High concentrations of toxic elements, organic contaminants, acidic soils, and harsh climatic conditions have made it difficult to re-establish vegetation and produce crops there. Recently, a significant body of work has focussed on the suitability and potentiality of biochar as a soil remediation tool that increases seed emergence, soil and crop productivity, above ground biomass, and vegetation cover on mine tailings, waste rock piles, and industrial and sewage waste-contaminated soils by increasing soil nutrients and water-holding capacity, amelioration of soil acidity, and stimulation of microbial diversity and functions. This review addresses: i) the functional properties of biochar, and microbial cycling of nutrients in soil; ii) bioremediation, especially phytoremediation of mine tailings, industrial waste, sewage sludge, and contaminated soil using biochar; iii) impact of biochar on reduction of acid production, acid mine drainage treatment, and geochemical dynamics in mine tailings; and iv) treatment of metal and organic contaminants in soils using biochar, and restoration of degraded land.     

Impact of soil engineering by two contrasting species of earthworms on their dispersal rates

By burrowing galleries and producing casts, earthworms are constantly changing the structure and properties of the soils in which they are living. These changes modify the costs and benefits for earthworms to stay in the environment they modify. In this paper, we measured experimentally how dispersal behaviour of endogeic and anecic earthworms responds to the cumulative changes they made in soil characteristics. The influence of earthworm activities on dispersal was studied in standardised mesocosms by comparing the influence of soils modified or not modified by earthworm activities on earthworm dispersal rates.The cumulative use of the soil by the earthworms strongly modified soil physical properties. The height of the soil decreased over time and the amount of aggregates smaller than 2 mm decreased in contrast to aggregates larger than 5 mm that increased. We found that: (i) earthworm activities significantly modified soil physical properties (such as bulk density, soil strength and soil aggregation) and decreased significantly the dispersal rates of the endogeic species, whatever the species that modified the soil; (ii) the decreasing in the dispersal proportion of the endogeic species suggests that the cost of engineering activities may be higher than the one of dispersal; (iii) the dispersal of the anecic species appeared to be not influenced by its own activities (intra-specific influences) or by the activities of the endogeic species (inter-specific influences). Overall these results suggest that the endogeic species is involved in a process of niche construction, which evolved jointly with its dispersal strategy.     

Earthworm populations in a savanna-agroforestry system of Venezuelan Amazonia

 In the forest-savanna ecotone around Puerto Ayacucho, Amazonas State, Venezuela, characterized by sandy entisols and ultisols with very low natural fertility, some producers have established agroforestry systems (AFS) of production on savanna soils by adding animal manure as the main fertilizer. This paper examines the earthworm communities in a natural savanna (NS) and in an AFS supplied with organic fertilizers established over 25 years ago. Organic matter management of the savanna soils has strongly modified the earthworm populations in the studied AFS as compared with the original savanna soil. Earthworm density was found to be 1.6–4.8 times higher in the AFS than in the original savanna. The correlations among earthworm populations and soil parameters suggested that earthworms in AFS can be limited by the amounts of food (organic matter) present in the soil. Moisture, in turn, affects other parameters that are important for earthworm distribution. Our results emphasized the importance of appropriate organic-matter management and the relevance of earthworms in such agroecosystems. By promoting the use of the earthworm population as an agroecological factor linked to low levels of organic fertilization, it is possible to promote major agroecological sustainability in sandy savanna soils. Received: 29 April 1998     

Earthworm biomass and population structure are negatively associated with changes in organic residue nitrogen concentration during vermicomposting

Vermicomposting is an efficient and environmentally friendly technology to dispose of agricultural organic residues. The efficiency of organic residue decomposition during vermicomposting is directly affected by the biomass and population structure of earthworms. In this study, we investigated how the earthworm biomass and population structure responded to changes in the physicochemical properties of six types of organic residue (cattle dung, herbal waste, rice straw, soybean straw, garden waste, and tea residues) during vermicomposting. Each type of organic residues was placed in a pot with earthworms Eisenia fetida, and the physicochemical properties of the organic residues and earthworm growth dynamics were recorded at 0, 30, 60, and 90 d of vermicomposting. The biomass and population structure of earthworms were stable or increased in rice straw, garden waste, and cattle dung within 60 d of vermicomposting, whereas in tea residues and herb waste, very little earthworm activity (3 adults and 2 cocoons) was recorded on day 30. Among the physicochemical parameters, the substrate C/N ratio was negatively correlated with earthworm growth dynamics. Decomposing organic residues showed higher NH₄⁺-N and NH₃^--N concentrations but a lower total organic carbon content, which negatively affected earthworm growth and reproduction. We recommend that chemical properties of vermicomposting systems should be monitored regularly. At the threshold levels of decomposing organic residue NH₄⁺-N and NH₃^--N concentrations, earthworms should be removed and the vermicompost can be harvested. Small- and large-scale farmers thus need to monitor the physicochemical properties of vermicompost to sustain active earthworm populations.     

Effects of Linear Alkylbenzene Sulphonates (LASs) on Exogenous Organic Matter Content and Evolution in Sewage Sludge–Amended Soils

Abstract

Linear alkylbenzene sulphonates (LASs) are anionic surfactants commonly used in commercial detergents. A potential risk associated with the recycling of sewage waste materials is the presence of LASs and their primary degradation products, which could accumulate in sludge, especially during anaerobic processing. The long‐term accumulation of these contaminants in soils and especially the potential disturbance of soil functions need to be studied in more detail. In our study, the influence of the amendment added to an agricultural soil with different organic wastes containing LASs on organic matter content and nitrogen (N) content evolution and mineralization was studied in field conditions. A completely randomized 3×3 factorial arrangement, representing two sewage sludge types (composted and uncomposted) and three levels of LAS presence (0, 15, and 30 g/m²) in treated soils, was established using field plots (7×2 m); the results are compared with untreated plots. Statistical models based on covariance analysis were used to understand the dynamics of and the main factors influencing carbon (C) and N mineralization in sewage sludge amended–soils in the presence of LAS. LAS seemed to alter nitrogen mineralization, especially the nitrate dynamics.     

Carbon mineralization in an arid soil amended with thermally-dried and composted sewage sludges

Soil amendment with sewage sludge (SS) from municipal wastewater treatment plants is nowadays a common practice for both increasing soil organic matter and nutrient contents and waste disposal. However, the application of organic amendments that are not sufficiently mature and stable may adversely affect soil properties. Composting and thermal drying are treatments designed to minimize these possible deleterious effects and to facilitate the use of SS as a soil organic amendment. In this work, an arid soil either unamended or amended with composted sewage sludge (CSS) or thermally-dried sewage sludge (TSS) was moistened to an equivalent of 60% soil water holding capacity and incubated for 60 days at 28 °C. The C–CO₂ emission from the samples was periodically measured in order to study C mineralization kinetics and evaluate the use of these SS as organic amendments. In all cases, C mineralization decreased after the first day. TSS-amended soil showed significantly higher mineralization rates than unamended and CSS-amended soils during the incubation period. The data of cumulative C–CO₂ released from unamended and SS-amended soils were fitted to six different kinetic models. A two simultaneous reactions model, which considers two organic pools with different degree of biodegradability, was found to be the most appropriate to describe C mineralization kinetics for all the soils. The parameters derived from this model suggested a larger presence of easily biodegradable compounds in TSS-amended soil than in CSS-amended soil, which in turn presented a C mineralization pattern very similar to that of the unamended soil. Furthermore, net mineralization coefficient and complementary mineralization coefficient were calculated from C mineralization data. The largest losses of C were measured for TSS-amended soil probably due to an extended microbial activity. The results obtained thus indicated that CSS is more efficient for increasing total organic C in arid soils.     

Changes in the microbial activity of an arid soil amended with urban organic wastes

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     

Evolution of mercury content in agricultural soils due to the application of organic and mineral fertilizers

Purpose

Mercury pollution in agricultural soils associated to the use of fertilizers and its influence on crops is a cause of major concern. The purpose of this work was to investigate the impact of the application of different organic and mineral fertilizers on the Hg concentration in the agricultural soils and its uptake by barley.

Materials and methods

Hg concentration was studied through a field test in an agricultural land located in the province of Palencia (Spain) over a 5-year period. The impact of irrigation and of four different fertilizers (a mineral one and three different organic waste materials, namely municipal solid waste compost, sewage sludge, and dehydrated sewage sludge) was assessed. The amounts of the mineral and organic fertilizers added to the soil were determined according to agricultural fertilization needs. The experimental crop was barley (Hordeum vulgare L.), planted as an annual crop. Mercury analyses were conducted using a direct mercury analyzer and validated according to EPA Method 7473. BCR-141R was used as a certified reference material.

Results and discussion

After 5 years, whereas the application of the mineral fertilizer did not increase the mercury content in the agricultural soils, the application of the organic residues led to Hg contents 1.7–7.6 times higher than that of the control soil. The treatment with solid municipal waste compost (MSWC) led to the largest increase in Hg content in the soil, followed by composted sewage sludge (CSS) and by dehydrated sewage sludge (DSS). No significant differences were observed in the Hg content in the barley grains, although the highest values were associated to the sludge-treated plots.

Conclusions

The application of organic fertilizers such as sewage sludges and municipal solid wastes led to an increase in the mercury concentration in the agricultural soils, noticeable for soils with low initial Hg concentrations (similar to background levels). This increase differed depending on the type of waste and on the intra-organic matter diffusion mechanisms, as well as on the type of irrigation of the agricultural land. Conversely, no significant differences in the Hg content in grains were found among the soils with the different fertilization treatments, although the highest values were observed for those treated with sewage sludge. The resulting Hg levels in both soils and grains were within legal limits, posing no danger to the environment or to human health.

     

作物秸秆与城市污泥高温好氧堆肥产物对土壤氮矿化的影响

为揭示不同作物秸秆与污泥堆肥产物对土壤氮素矿化特征的影响,为科学施用城市污泥堆肥提供参考依据,通过室内培养试验研究了城市污泥与4种秸秆（小麦、水稻、玉米和油菜）高温好氧堆肥产物施入酸性紫色土、黄壤、石灰性紫色土后土壤氮矿化的差异。结果表明,4秸秆污泥堆肥均可显著提高3种土壤氮的潜在矿化势（N0）和矿化速度（k）,促进土壤氮的矿化,提高土壤NH4+-N、NO3--N质量分数,其中石灰性紫色土以油菜秸秆污泥堆肥和小麦秸秆污泥堆肥处理、黄壤以油菜秸秆污泥堆肥处理、酸性紫色土以小麦秸秆污泥堆肥处理提高幅度最大。作物秸秆与污泥堆肥施入土壤后,黄壤、酸性紫色土在培养60 d和30 d后趋于稳定,石灰性紫色土在培养60 d后仍有增高的趋势,但不同秸秆污泥堆肥对土壤氮矿化速度的影响无明显规律。结果说明秸秆污泥堆肥对土壤氮矿化的效应因土壤及秸秆类型的不同而异,根据研究结果提出了4种作物秸秆与城市污泥堆肥施用的建议。     

An overview of some tillage impacts on earthworm population abundance and diversity — implications for functioning in soils

Conflicting reports in the literature on the effects of tillage on earthworms are reviewed in the light of their roles in agro-ecosystem functioning. Tillage can change the abundance (by 2–9 times) as well as the composition (diversity) of earthworm populations. The actual impact is dependent on soil factors, climatic conditions and the tillage operations but hitherto this information was seldom provided in research reports. The declines in earthworm population often reported in conventionally tilled soils are associated with undesirable changes in the soil environmental conditions resulting from excessive tillage. Different species of earthworm respond differently to tillage. While the abundance of the deep burrowing species (anecic) tends to decline under tillage, particularly under deep ploughing, endogeic species can actually increase in number especially when there is increased food supply. Under conservation tillage systems, earthworms can potentially play a more important role than under conventional tillage in the functioning of the farming systems because of their abilities to modify the soil physical environment and nutrient cycling. However, adoption of conservation tillage does not automatically result in an optimal earthworm population in terms of abundance and diversity. There are opportunities to introduce more beneficial species to improve the ecological performance of agro-ecosystems. More research is needed to fully understand the ecology of different earthworm species, their interactions and their potential roles in promoting more sustainable farming systems.     

Effects of fertilization with urban and agricultural organic wastes in a field trial – Waste imprint on soil microbial activity

In the past decades a significant change in composition of urban organic waste products has occurred in many first world countries, due to cleaner technologies as well as outsourcing of heavy industries. However, the societal perception of organic urban waste has become increasingly negative, leading to widespread advocacy of incineration. Therefore we established the ‘CRUCIAL’ long-term field trial in 2003, with the rationale that by approaching the known limits for a number of heavy metals below which no profound disturbance should be observed on key soil ecological functions, it should be possible to discern if some of the many unknown components in the composite urban waste as well as agriculturally based fertilizers have measurable impacts. The following treatments were established: human urine, sewage sludge (normal N-level and accelerated level aiming at three times normal N-level), degassed and subsequently composted organic municipal waste (normal and accelerated level), deep litter, cattle slurry, cattle manure (accelerated level), NPK fertilizer, unfertilized but with clover undersown and an unfertilized control. After 4 years the soil organic matter (SOM) C content, basal CO₂ respiration and soil microbial biomass (SMB) C was significantly affected by treatments. All soils having received organic fertilizer had higher SMB C than those with no added fertilizer (unfertilized and unfertilized with clover undersown) and inorganic fertilizer. The treatment effect on qCO2 (CO₂/SMB C) was not significant, but the unfertilized treatments showed the highest values. Treatments with accelerated levels of composted household waste and sewage sludge had the highest number of colony forming heterotrophic bacteria. Sole carbon source utilization in EcoPlates indicated a very robust microbial community in the treatments. Cumulative input of heavy metals was less than that required for reaching the heavy metal ecotoxicological limits, even after accelerated loading with sewage sludge corresponding to approximately 55 years of normal application. This could indicate that it is possible use organic urban waste for an extended period on a given site, without compromising soil functioning as long as ecotoxicological guidelines for heavy metal content are observed.     

Heavy Metals in Water Percolating Through Soil Fertilized with Biodegradable Waste Materials

The influence of manure and composts on the leaching of heavy metals from soil was evaluated in a model lysimeter experiment under controlled conditions. Soil samples were collected from experimental fields, from 0- to 90-cm layers retaining the layout of the soil profile layers, after the second crop rotation cycle with the following plant species: potatoes, spring barley, winter rapeseed, and winter wheat. During the field experiment, 20 t DM/ha of manure, municipal sewage sludge composted with straw (SSCS), composted sewage sludge (SSC), dried granular sewage sludge (DGSS), “Dano” compost made from non-segregated municipal waste (CMMW), and compost made from municipal green waste (CUGW) was applied, i.e., 10 t DM/ha per crop rotation cycle. The concentrations (μg/dm³) of heavy metals in the leachate were as follows: Cd (3.6–11.5)?<?Mn (4.8–15.4)?<?Cu (13.4–35.5)?<?Zn (27.5–48.0)?<?Cr (36.7–96.5)?<?Ni (24.4–165.8)?<?Pb (113.8–187.7). Soil fertilization with organic waste materials did not contaminate the percolating water with manganese or zinc, whereas the concentrations of the other metals increased to the levels characteristic of unsatisfactory water quality and poor water quality classes. The copper and nickel content of percolating water depended on the concentration of those metals introduced into the soil with organic waste materials. The concentrations of Cd in the leachate increased, whereas the concentrations of Cu and Ni decreased with increasing organic C content of organic fertilizers. The widening of the C/N ratio contributed to Mn leaching. The concentrations of Pb, Cr, and Mn in the percolating water were positively correlated with the organic C content of soil.