Application Of Municipal Sewage Sludge Research Articles

Phytoextraction of heavy metals after application of bottom ash and municipal sewage sludge considering the risk of environmental pollution

Waste management to reduce the loss of natural resources has become a basis of sustainable development and a circular economy. When using waste, the heavy metal (HM) concentration must be taken into account since HMs can be potentially released to the environment, posing a toxicity threat. The aim of the study was thus to estimate the availability for plants of Cr, Ni, Cu, Zn, Cd, and Pb introduced into the soil with waste. We hypothesized that the prepared waste mixtures containing coal or biomass ash and municipal sewage sludge would reduce the environmental risk compared to the studied waste used separately. The research was conducted during a 6-year field experiment with grasses and legumes. HM concentration in soil, waste, and plant biomass; tolerance index; and uptake of HMs by plants were measured. The ash–sludge mixtures had a more favourable effect on the soil in terms of pHKCl, TOC, total nitrogen, and total exchangeable bases than the waste used separately. This provided beneficial conditions for plant growth and development. Consequently, the ash–sludge mixtures increased the plant yield as compared to ash alone, while the mixture containing the biomass ash also enhanced the yield in relation to the sewage sludge. The study showed that the mixtures allowed for a reduction of environmental risk arising from the HM input with waste to the soil. It was proven that HM availability for plants could be beneficially modified by mixing waste. Combining the coal ash with the sewage sludge is particularly recommended, owing to the unfavourable properties of coal ash for plants. The application of the higher dose of the coal ash–sludge mixture showed a better effect than the lower dose, while the influence of both doses of the biomass ash–sludge mixture was similar. Under the ash–sludge treatment, plants took up more HM than under the ash used separately, and the HM concentration in the obtained biomass did not generally exceed that observed under single wastes. This should reduce the accumulation of HMs in the soil during a long-term use of the waste and facilitates the utilisation of the produced biomass.

Agricultural application of microplastic-rich sewage sludge leads to further uncontrolled contamination

Municipal sewage sludge has been shown to be high in microplastics (MP) and is applied to agricultural land as fertiliser in many countries. The authors recently proposed in a viewpoint article that MP applied to land in this way may well contaminate other areas in an uncontrolled way. This study examined experimental plots with known history of application of sewage sludge. Results showed that 44% of the MP load found on sludge-applied land was found on nearby land never directly applied with sludge. Examination of polymer type compositions demonstrated marked similarity between the two fields indicating the sludge-applied field was a source of contamination for surrounding areas. Furthermore, MP was detected at a depth of 60–90 cm in the sludge-applied soil indicating that MP may also penetrate deep enough to reach agricultural drainage systems, although this effect is slight (1.6% of surface load). These results show that application of municipal sewage sludge on agricultural land can lead to further uncontrolled contamination, paving the way for future research to improve understanding of the extents of such effects on real farms to better inform future agricultural policy.

Land application of municipal sewage sludge: Human health risk assessment of heavy metals

Land application of municipal sewage sludge has become an attractive option and disposal method used worldwide. Hence, the suitability of the sludge with regards to toxic and carcinogenic chemicals is crucial to prompt informed decisions regarding its use on agricultural areas. This study aims to assess ecological and human health risks of heavy metals in sewage sludge samples collected from 22 different cities' wastewater treatment plants to determine their agricultural application potential in Turkey. The average metal concentrations of the samples decreased as the following order of Zn > Cu > Cr > Pb > Ni > Mo > As > Cd > Se > Hg without a significant seasonality. To evaluate the carcinogenic and non-carcinogenic health risks, site-specific overall total cancer risk (TCR) and Hazard Index (HI) values were calculated as the sum of all heavy metals’ ingestion, inhalation, and dermal contact exposures for children and adults. Contribution of the inhalation exposure due to the dust re-suspension during agricultural work to the total health risk has seemed be negligible when compared to ingestion and dermal contact. The carcinogenic risk for the adults were within the acceptable range (10−6 to 10−4) proposed by USEPA based on our estimations (2.4 ✕ 10−5), but the risk value was slightly exceeded the safe levels for children (1.6 ✕ 10−4). Similarly, HI values for adult subjects were below the reference value of 1, whereas they were higher for children (up to 2.52). Pb, As, and Cr were the major contributing metals to carcinogenic risks for both children and adults. Although the heavy metal concentration of collected samples was within the agricultural land application legal standards proposed by the Environmental Protection Agency (EPA) and the Ministry of Environment and Urbanization of Turkey (MEU), but the results of human health risk assessments showed that the risks may occur especially for sensitive individuals like children. This study showed that the evaluation of waste materials such as municipal sewage sludge should be applied only if it is proper for both ecological and health-safe, and assessing based on the regulatory limit values would not be enough to protect all population.

Energy Properties and Biomass Yield of Miscanthus x Giganteus Fertilized by Municipal Sewage Sludge.

The application of municipal sewage sludge as fertilizer in the production of non-food energy crops is an environmentally and economically sustainable approach to sewage sludge management. In addition, the application of municipal sewage sludge to energy crops such as Miscanthus x giganteus is an alternative form of recycling nutrients and organic material from waste. Municipal sewage sludge is a potential source of heavy metals in the soil, some of which can be removed by growing energy crops that are also remediation agents. Therefore, the objective of the research was to investigate the effect of municipal sewage sludge applied at three different rates of 1.66, 3.22 and 6.44 t/ha on the production of Miscanthus. Based on the analyses conducted on the biomass of Miscanthus fertilized with sludge from the wastewater treatment plant in three fertilization treatments, it can be concluded that the biomass of Miscanthus is a good feedstock for the process of direct combustion. Moreover, the application of the largest amount of municipal sewage sludge during cultivation had no negative effect on the properties of Miscanthus biomass. Moreover, the cellulose and hemicellulose content of Miscanthus is ideal for the production of second-generation liquid biofuels. Fertilizer treatments had no effect on the content of cellulose and lignin, while a significant statistical difference was found for hemicellulose.

Indirect application of sludge for recycling in agriculture to minimize heavy metal contamination of soil

In this study, an indirect application method was developed for safe recycling of nutrients from municipal sewage sludge (MSS) for use in agriculture. Permeable net bags were filled with MSS to prepare sewage-sludge net bags (SSN). The SSN were stacked next to banana, papaya, and corn crops. Cadmium (Cd), copper (Cu), lead, and zinc levels in the soil, crops, and MSS were monitored. After application of the SSN for 9 years, the levels of the four heavy metals did not exceed soil standard limits. By comparison, direct application of MSS resulted in soil Cd and Cu levels that exceeded China's soil standards in the 3rd and 4th years. The crop yields obtained with the SSN were not significantly different to those obtained using mineral fertilizer, and the heavy metal concentrations in the crops met the required food standards. With the SSN, more than 94% of the heavy metals were retained in the MSS, and these were mainly present in the residual fraction. In conclusion, indirect application of MSS could considerably reduce heavy metal pollution of soil and safely supply nutrients for crops.

Hemp-Based Phytoaccumulation of Heavy Metals from Municipal Sewage Sludge and Phosphogypsum Under Field Conditions

The aim of this study was to evaluate the ability of three hemp cultivars to accumulate heavy metals under sewage sludge (SS) and phosphogypsum (PG) application. The field study was carried out from 2014 to 2016 on Luvisol (loamy sand) in Poland. The experiment scheme included five treatments—T0: the control without fertilization, T1: 170 kg N (nitrogen) ha−1 from sewage sludge, T2: 170 kg N ha−1 from sewage sludge and 100 kg ha−1 of phosphogypsum, T3: 170 kg N ha−1 from sewage sludge and 500 kg ha−1 of phosphogypsum, and T4: 170 kg N ha−1 from sewage sludge and 1000 kg ha−1 of phosphogypsum. It was found that the application of municipal sewage sludge enriched the soil with the bioavailable forms of heavy metals to the greatest extent and contributed to the highest increase in their contents in vegetative and generative organs of hemp plants. These parameters showed a phosphogypsum dose-dependent decline, which could hinder the phytoextraction process. The greatest extractions of heavy metal(loid)s (HMs) from the soil treated with SS and PG were achieved by the Tygra variety, which had the highest bioconcentration factor (BCF) and biomass yield.

Sunflower growth and yield response to sewage sludge application under contrasting water availability conditions

Good knowledge of crop response to biosolids is necessary for optimizing their use as soil amendments. The present 2-yr study evaluated the impact of soil application of municipal sewage sludge on growth, dry matter translocation, achene and oil yield as well as on achene Fe, Cu, Zn and Mn content of field-grown sunflower (Helianthus annuus L.) under contrasting water availability in terms of seasonal rainfall. Treatments included three sewage sludge rates (9, 18, and 36 Mg dry weight ha−1 yr−1) compared with inorganic fertilizer (138 kg N plus 24 kg P ha−1 yr−1) and a non-amended control. Adding sewage sludge increased stem diameter, height, and early growth of sunflower plants compared with control. Dry matter at flowering was positively correlated with translocation of dry matter to achenes (r = 0.855**). However, high early dry matter was translated into enhanced achene yield only with adequate water availability along growth cycle, while water shortage resulted in fewer achenes and poor seed-filling. Sewage sludge application increased achene yield even under water shortage, suggesting a beneficial effect of sewage sludge on soil water status. Achene yield with added sewage sludge was similar to or greater than with the inorganic fertilizer. Sewage sludge decreased achene oil concentration and increased achene N concentration, compared with the non-amended control, without affecting Zn, Fe, Mn, and Cu content in achenes even at the high application rate of 18 Mg ha−1. Findings support that sewage sludge addition in soil at the rate of 9 Mg ha−1 was agronomically adequate and could replace inorganic fertilizer in sunflower production, irrespective of seasonal rainfall amount and distribution patterns.

Application of ash and municipal sewage sludge as macronutrient sources in sustainable plant biomass production

Owing to the growing volumes of ash and sewage sludge waste, there is a requirement for theoretical and practical research into the use of these wastes as a source of nutrients. However, there are relatively few studies on the transfer of macronutrients in soil-plant systems amended with ash-sewage sludge mixtures under field conditions. The aim of the study was to determine the effect of bituminous coal ash (AC), biomass ash (AB), and municipal sewage sludge (MSS) on the quantity and quality of a grass-legume mixture. During a 6 year field experiment on a sandy loam soil treated with the wastes, applied as mixtures or separately, the plant yield; N, P, K, Na, Mg, and Ca uptake by plants; macronutrient content and ratios in the plant biomass; and the recovery rate of macronutrients by plants were evaluated. The AB-MSS treatment increased the yield in comparison to that where the wastes were applied separately. The N, P, and Ca contents in the plant biomass and N and P uptake under ash-sludge treatments were in the range observed for the ash and sewage sludge. The AB-MSS co-application resulted in the highest K uptake. The AC-MSS treatment increased K and Mg uptake in relation to AC treatment. When AC or AB was added to the MSS, the Ca uptake increased relative to the MSS treatment. The plant biomass under the AB treatment was optimal for biofuel purposes in terms of the chemical composition. The co-application of AC or AB with MSS resulted in the optimum Ca:Mg ratio for fodder purposes. The recovery rate of the macroelements decreased in the following order: K, N, P, Mg, Na, and Ca. The results support the co-application of solid wastes such as ash and municipal sewage sludge to improve productivity, support the recycling of macronutrients, improve sustainability through the reduction of ash and sewage sludge disposal, and reduce reliance on mineral fertilizer.

Effect of Municipal Sewage Sludge on Soil Chemical Properties and Chemical Composition of Spring Wheat

Abstract Municipal sewage sludge from rural sewage treatment plants is characterized by a substantial content of organic matter and macronutrients, which can be used in cultivation of cereals. In a farm located in the commune of Iwanowice in the south of Poland (Malopolska province), municipal sewage sludge was applied under spring wheat cultivation. The experiment was set up on heavy soil with slightly acid reaction and medium content of available forms of P, K, Mg. Application of sewage sludge in a dose of 23 Mg fresh matter per hectare (4.21 Mg d.m.) led to no significant changes in chemical properties of the soil. Application of sewage sludge significantly increased yield of spring wheat. That increase led to a significant decrease in the content of N, P, K, Na, Mg and Ca in spring wheat. Utilization of N, Mg, K, P and Ca from sewage sludge by spring wheat was at a level of 82, 63, 44, 36, 9 %, respectively, of the amount introduced with the waste. Application of municipal sewage sludge significantly decreased the value of Ca : P ratio in spring wheat grain and straw. The sewage sludge did not cause a significant change in the values of Ca : Mg, K : Na, K : (Ca+Mg), K : Mg and K : Ca ratios in spring wheat grain and straw. Municipal sewage sludge can be used environmentally, including for fertilization of cereals, provided that environmental standards are kept.

Municipal Sewage Sludge application on cotton cultivations. Effect on yields soil chemical properties and heavy metal concentrations

<p>Application of municipal sewage sludge (MSS) to agricultural soils is a current practice in EU. European legislation permits its use in agriculture when concentrations of metals in soil do not exceed the maximum permissible limits. In order to study the influence of MSS on cotton yield and soil properties, a filed experiment was conducted in a soil classified as Typic Xerochrepts located in Lamia area, central Greece, for two consecutive years. The experimental design was complete randomized blocks with four treatments: Control (C ), inorganic fertilization (IF), application of 6000 dry kg ha-1 MSS, and 10000 dry SS kg ha-1, each replicated 4 times. The results showed that MSS application in both rates, increased significantly cotton yield compared to control equally to inorganic fertilization. Soil properties, at the end of the second year of MSS application, were significantly affected by MSS application in a positive way i.e. pH decreased slightly, but organic matter content, available phosphorus, total nitrogen concentrations exchangeable potassium and available zinc and copper increased significantly. The potentially toxic elements lead, chromium, and nickel were not significantly affected by MSS application in both application rates compared to control.</p>

Utilization of coal fly ash and municipal sewage sludge in agriculture and for reconstruction of soils in disturbed lands: results of case studies from Greece and China

Coal fly ash (CFA) and municipal sewage sludge (MSS) management is a great concern worldwide. An alternative gaining high interest, is their use in agriculture and for reclamation of degraded lands. The purpose of this paper was to present very briefly the results of some case studies carried out in China and Greece related to land reclamation and agricultural use of CFA and MSS separately or combined. An experiment in Platanoulia area, central Greece showed clearly that CFA applied together with MSS at appropriate rates increased substantially wheat grain and biomass yield and improved soil quality (increased soil pH, organic matter content, total nitrogen, available P and boron). In a long-term experiment carried out in Huaibei city, Anhui province, China with a reconstructed soil in a subsided land by using CFA, it was found that physicochemical characteristics (infiltration rate, bulk density, total nitrogen, available P and extractable K) tended to be improved over time. In another experiment in Rodia area central Greece, MSS application improved soil quality of limestone mining spoils from bauxite mining activities. Several other experiments with MSS in Greece showed a clear positive effect on cotton and maize yield and on soil quality.

[Effect of agricultural application of municipal sewage sludge on plant-soil system: A review].

Currently, reasonable disposal of municipal sewage sludge is one of the important issues in the field of resources and environmental science. Sludge is rich in large amounts of organic matter and available nutrients, promoting soil fertility, soil physical structure and biological properties. However, sludge contains a variety of heavy metals, organic contaminants and other hazardous substance, especially heavy metals, which are the bottlenecks of agricultural application of sludge. To improve the sewage sludge utilization efficiency and decrease the effect on soil, this essay made a summary on domestic and foreign studies on plant-soil interaction ecosystem with sewage sludge to provide a theoretical basis and scientific guidance for advancing sewage sludge utilization efficiency.

Nutritional (Fe, Mn, Ni, and Cr) and growth responses of rice plant affected by perennial application of two bio-solids.

Trace toxic elements often restrict the land application of different bio-solids in agriculture. In order to evaluate the separate influence of the municipal solid waste compost (MSW), sewage sludge (SS) and combined application with inorganic fertilizers (chemical fertilizer (CF)) on nutritional (Fe, Mn, Ni, and Cr) and growth responses of rice plant, a research was conducted on paddy soil from 2013 to 2015. Obtained results showed that SS levels were superior to MSW in most studied traits. The maximum chlorophyll content (46.52), plant height (162.6cm), biomass (23.33tha-1), soil available Fe (206.26ppm), Ni concentration in the root (14.41ppm) and shoots (3.16ppm), Cr concentration in the root (12.43ppm) and grain (3.65ppm), and Mn concentration in grain (66.938ppm) belonged to SS levels, specially enriched 40tha-1, when it was added to the soil for three continuous years. The highest 1000-grain weight (29.89g), yield (6.86tha-1), harvest index (48.17%), and soil available Mn (712.7ppm), Fe, and Ni concentration in grain (107.92 and 8.79ppm, respectively) were recorded in 3years of applying the enriched 40tha-1 MSW. Accumulation of Ni in grain in critical levels and negative effects of CF treatments on toxic element entry to soil and plant were two important findings of this research that need management.

The effect of municipal sewage sludge on the content, use and mass ratios of some elements in spring barley biomass

Abstract Municipal sewage sludge contains considerable amounts of macro and microelements essential for plant nutrition. With decreasing use of natural and organic fertilizers, there is a need to search for alternative sources of organic matter (which is a substrate for humus reproduction). In a field experiment carried out on heavy soil with neutral reaction, the effect of single application of municipal sewage sludge in a dose of 5.34 Mg·ha−1 DM was compared to an equivalent dose of mineral fertilizers. The test plant was spring barley. After application of municipal sewage sludge, slight positive changes in the chemical properties of the soil were observed. The sewage sludge increased the yield of spring barley grain and straw by, respectively, 14 and 13% in relation to treatment with mineral fertilization. Spring barley fertilized with sewage sludge contained more elements than barley grown only on mineral fertilizers. It was shown that application of municipal sewage sludge to the soil had a significant effect on increase in nutrient uptake by spring barley. Fe was taken up in the highest amount, followed by Al and Mn, and Co was taken up in the smallest amounts. Utilization of Fe, Mn, Co and Al from sewage sludge by spring barley was at 6.0, 4.7, 0.7 and 0.7%, respectively of the amount applied to the soil with this waste. The mass ratios (Fe:Mn, Fe:Al, Mn:Co) analyzed in spring barley biomass were much wider in straw than in grain. In terms of grain feed value, Fe:Mn ratio in grain and straw was greater than optimum.

Agricultural use of sewage sludge in India: benefits and potential risk of heavy metals contamination and possible remediation options - a review

Application of municipal sewage sludge in agriculture is one of the best options for its safe disposal as it provides an opportunity to recycle plant essential nutrients (N, P, secondary nutrients and micronutrients) and improves soil physical, chemical and biological properties due to high organic matter content. Yield and productivity of a wide range of crops has been improved due to soil application of sewage sludge than that of well-fertilised control. Depending upon the origin, sewage sludge often contains very high amount of potentially toxic heavy metals and as such their excessive use for a longer period increases metal bioavailability in soil and ultimately causes food chain contamination. In this article we reviewed the available information on various aspects of land application of municipal sewage sludges on crop yield, soil fertility and problems of heavy metals accumulation in edible portion of the crops as well as possible options for remediation of heavy metals toxicity in contaminated soils to explore the possibility of safe recycling this waste in agriculture.

Agricultural use of sewage sludge in India: benefits and potential risk of heavy metals contamination and possible remediation options - a review

Application of municipal sewage sludge in agriculture is one of the best options for its safe disposal as it provides an opportunity to recycle plant essential nutrients (N, P, secondary nutrients and micronutrients) and improves soil physical, chemical and biological properties due to high organic matter content. Yield and productivity of a wide range of crops has been improved due to soil application of sewage sludge than that of well-fertilised control. Depending upon the origin, sewage sludge often contains very high amount of potentially toxic heavy metals and as such their excessive use for a longer period increases metal bioavailability in soil and ultimately causes food chain contamination. In this article we reviewed the available information on various aspects of land application of municipal sewage sludges on crop yield, soil fertility and problems of heavy metals accumulation in edible portion of the crops as well as possible options for remediation of heavy metals toxicity in contaminated soils to explore the possibility of safe recycling this waste in agriculture.

The effect of municipal sewage sludge on the chemical composition of spring barley

Abstract Due to the fact that soils in Poland are mostly light soils, there is a need to improve their physical, chemical and biological properties. In addition, as a result of the decrease in the number of farm animals, a decrease in production of natural fertilizers can be observed. Low production of natural fertilizers speaks in favor of agricultural use of municipal sewage sludge in Poland. Municipal sewage sludge is composed of large quantities of macronutrients necessary for plants. This waste also contains significant amounts of organic substance. Chemical properties, including a high content of nitrogen, phosphorus, and often calcium, speak in favor of environmental use of municipal sewage sludge. Increasing requirements with respect to environmental protection cause the necessity to assess the effects of using organic waste for fertilization. In a farm located in the commune of Iwanowice (Małopolska province), municipal sewage sludge was applied under spring barley cultivation. The soil on which municipal sewage sludge was applied was classified into the category of heavy soils with neutral reaction. When assessing the content of available nutrients (P, K, Mg) in the soil, their low content was determined. After application of municipal sewage sludge in a dose of 24 Mg fresh matter per hectare, which corresponded to 5.34 Mg DM·ha−1, under spring barley, beneficial changes in chemical properties of the soil were observed. An increase in soil abundance in organic carbon and total nitrogen was observed, as well as an increase in the content of available forms of phosphorus, potassium and magnesium. Based on the results of the conducted chemical analyses, it was established that biomass of spring barley fertilized with sewage sludge contained more macronutrients (N, P, K, Na, Ca and Mg), which improved its feed value. The field experiment showed that application of municipal sewage sludge increased uptake of macronutrients by spring barley.

The use of reed canary grass and giant miscanthus in the phytoremediation of municipal sewage sludge.

The application of municipal sewage sludge on energy crops is an alternative form of recycling nutrients, food materials, and organic matter from waste. Municipal sewage sludge constitutes a potential source of heavy metals in soil, which can be partially removed by the cultivation of energy crops. The aim of the research was to assess the effect of municipal sewage sludge on the uptake of heavy metals by monocotyledonous energy crops. Sewage sludge was applied at doses of 0, 10, 20, 40, and 60Mg DM · ha(-1) once, before the sowing of plants. In a 6-year field experiment, the effect of four levels of fertilisation with sewage sludge on the uptake of heavy metals by two species of energy crops, reed canary grass (Phalaris arundinacea L.) of 'Bamse' cultivar and giant miscanthus (Miscanthus × giganteus GREEF et DEU), was analysed. It was established that the increasing doses of sewage sludge had a considerable effect on the increase in biomass yield from the tested plants. Due to the increasing doses of sewage sludge, a significant increase in heavy metals content in the energy crops was recorded. The heavy metal uptake with the miscanthus yield was the highest at a dose of 20Mg DM · ha(-1), and at a dose of 40Mg DM · ha(-1) in the case of reed canary grass. Research results indicate that on account of higher yields, higher bioaccumulation, and higher heavy metal uptake, miscanthus can be selected for the remediation of sewage sludge.

Agricultural utilisation of municipal sludge in willow plantation

This paper presents the results of analyses of the monitoring selected energetic willow plantations (30 ha) located in Podkarpackie Province (Poland), which have been fertilised using a prototype trailer for land-applying municipal sludge. The fertilisation of the willow plantation is undertaken using this prototype for the subsurface application of municipal sewage sludge into soil. The presented prototype is a component of technology of energetic plant production that has been developed at the Rzeszow University of Technology. The results of soil investigations allow to us conclude that the deposition of sewage sludge using the presented prototype of the agricultural trailer is conducted in accordance with legal regulations and does not cause significant perturbation of the natural trophic chain.

Sewage sludge application strongly modifies earthworm impact on microbial and biochemical attributes in a semi-arid calcareous soil from Iran

Application of municipal sewage sludge (MSS) may modify the influence of earthworm activity on soil microbial and biochemical properties through an increase of substrate availability. However, the effect of earthworm activity on microbial community is poorly known in calcareous soils amended with MSS. Such knowledge would lead to better understanding of how earthworms and microorganisms interact following MSS application in agroecosystems. This study aimed to investigate how MSS application can modify the impact of earthworms on microbial performance and biochemical attributes of a calcareous soil amended with MSS. Experimental treatments were MSS application (without and with 1.5% MSS) and earthworm addition (no earthworm, epigeic Eisenia fetida, endogeic Aporrectodea caliginosa and a combination of the two earthworm species) setup as a 2×4 full factorial experiment using a completely randomized design with three replications for each treatment combination under greenhouse conditions over 90 days. Addition of MSS had a positive effect on the measured biochemical and microbiological indicators of the study soil. Municipal sewage sludge application resulted in a significant (p<0.001) increase in the amounts of microbial biomass carbon (MBC) and basal respiration rate (RR); but without an effect on the level of dissolved organic carbon (DOC). While the presence of earthworms decreased the quantity of DOC and MBC (p<0.001); other soil attributes such as basal respiration rate, the metabolic quotient (qCO2) and the ratio of fungal to bacterial (F/B) respiration were all increased significantly (p<0.001) with earthworm addition. Nevertheless, the magnitude of the earthworm effect was largely dependent upon the MSS treatment. Application of MSS decreased the stimulatory effect of earthworms on soil microbial indicators and this effect was less pronounced in the presence of E. fetida than A. caliginosa species. This is probably due to the preference of epigeic E. fetida to feed on MSS as an essential food resource rather than only feeding and grazing on microbial populations. In contrast, the endogeic A. caliginosa species was not dependent upon MSS as food resources. Moreover, the interaction effect between the two earthworm species on soil microbial and biochemical properties was mostly additive in nature (without interaction) in both MSS-amended and unamended soils. Results indicated that earthworm effect and its interaction with MSS were important factors for soil microbial biomass, community composition and performance and that earthworm effects should decrease in MSS-treated soils.