Composting and Evaluating a Pulp and Paper Sludge for Use as a Soil Amendment/Mulch

Composting could be used in the pulp and paper industry to treat primary sludges as an alternative to landfilling. The objective of this project was to compost and evaluate a pulp and paper sludge for use as a soil amendment/mulch. Primary sludge, tailings, wood ash (0, 5 or 10 percent by volume), and paunch (cattle stomach contents and tissue) from a slaughterhouse were composted in a 91 m windrow that was turned one to two times per week. The pile moisture content and temperature were controlled at 50 percent and 57–63°C during 14 weeks of composting. The compost was then cured for 4 weeks for a total treatment time of 18 weeks. Sludge dry mass decreased by approximately 50 percent, pH increased slightly to 8.2 to 8.5, and carbon-nitrogen ratio decreased from 270:1 to 14–67:1 after composting and curing. Electrical conductivity of all final composts was over 4 dS/m. Shoot biomass of tomato plants grown in a compost-amended medium (50 percent compost, 25 percent sand, 25 percent perlite by volume) improved with composting time but was still only 35–65 percent that of plants grown in a peat moss-amended medium (control). Shoot weight and height of poplar plants grown in soil amended with aged compost were unaffected by compost application rate (incorporated or as a mulch) at less than or equal to 180 Mg/ha. In summary, this study demonstrated that a pulp and paper sludge and wood ash mixture yielded a compost that could be used as a low quality mulch or soil amendment for poplar.     

Residual effects of sewage‐sludge application on plant and soil‐profile chemical composition

Abstract

Long‐term effects on plant and soil‐profile chemical composition imposed by a residential sewage sludge were studied on an Oxisol from Hawaii. Sludge was applied at 0, 45, 90, and 180 Mg/ha in 1983. An NPK‐fertilized treatment was included for comparison. Sudangrass (Sorghum bicolorL. Moench) was grown as a test crop in the 1983–84 and 1986–87 seasons. Soil samples for chemical analysis were taken in 1987 at three depths: 0–23 cm, 23–46 cm, and 46–69 cm.

Beneficial effects of sludge, measured 3 years after application (beginning of the 1986's planting), were evident by large yield increases on sludge‐amended soils relative to the unamended and the NPK‐fertilized soils. The first cutting produced approximately 5 Mg/ha of dry matter from the sludge treatments, regardless of rate, as compared with 3 and 1.5 Mg/ha from the NPK and the 0 treatments. Regrowths showed similar effect, though less dramatic; average yields were 2.6 Mg/ha with sludge and 1.6 Mg/ha without.

Heavy‐metal concentrations in plants were generally unaffected by sludge applications; probably because (i) heavy‐metal contents of the sludge were low, and (ii) soil pH was increased by sludge.

Remarkable increases in pH, exchangeable Ca and extractable P, and resultant decreases in exchangeable Al, in all three soil layers of sludge‐amended soils suggest that surface application of a low heavy‐metal sludge could serve to correct subsoil acidity and enhance subsoil P availability.     

Response of tall fescue to composted sewage sludge used as a soil amendment

A pot experiment was conducted in the greenhouse to investigate the effects of composted sewage sludge as a soil amendment on growth and mineral composition of ‘Mustang’ tall fescue (Festuca arundinacea Schreb.). Three desert soils (loamy sand, sandy loam, clay) were amended with two different composted sewage sludges (city and county) at rates of 0, 7.5, 15, 30 and 60% by volume. Tall fescue was grown in the amended soils for four months. Growth rates, measured as harvested clippings, increased with sludge loading rate and also with clay content of the soil. Higher growth rates were maintained with the city as compared to the county sludge, although for both sources, growth declined for most treatments after nine weeks. Turf color ratings and percent N in the tissue increased with sludge loading rate and were highly correlated. Tissue analysis indicated a varied response between soil types.     

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.     

Organic matter and aggregation in a degraded potato soil as affected by raw and composted pulp residue

Soils under intensive potato (Solanum tuberosum L.) production are often low in organic matter content and microbial activity. Pulp fibre residue addition may restore the quality of these soils. An experiment was initiated in which raw or composted pulp fibre waste was added to a Fredericton sandy loam (Orthic Humo-Ferric Podzol) in New Brunswick (Canada). Each material was applied at 45 Mg (dry weight) ha^-1 and 90 Mg (dry weight) ha^-1 before planting. Soil was under continuous potato (cv. Russet Burbank) for 3 years. The raw and the composted pulp greatly increased soil organic matter (SOM) content, the C/N ratio, macroaggregation, C mineralization, microbial biomass C (MBC) and enzyme activities for the whole duration of the experiment but had no effect on its total N. Most of the SOM increase was found in the macroorganic matter fraction. The SOM, C/N ratio, macroaggregation, C mineralization and MBC decreased from the time of application. No major difference was found between materials except for CO₂-C release in the incubation which was higher for the composted than for the raw pulp. This study indicated that pulp fibre, either applied raw or composted, increased SOM and macroaggregation and promoted microbial growth and activity in this potato soil which was low in C content. The beneficial effects on soil physical and biochemical properties were still present after 3 years of continuous cropping.     

Effects of cover crops,compost, and manure amendments on soil microbial community structure in tomato production systems

Soil microbial community structure and crop yield was investigated in field tomato production systems that compared black polyethylene mulch to hairy vetch mulch and inorganic N to organic N. The following hypotheses were tested: (1) hairy vetch cover cropping increases crop yield and significantly affects soil microbial community structure when compared to the standard plastic mulch and synthetic fertilizer-based system; (2) within plastic mulch systems, organic amendments will increase crop yield and significantly affect soil microbial community structure when compared to synthetic fertilizer; (3) crop yields and microbial community structure will be similar in the hairy vetch cover cropping and the organic amended plasticulture systems. Treatments consisted of ammonium nitrate (control), hairy vetch cover crop, hairy vetch cover crop and poultry manure compost (10 Mg/ha), three levels of poultry manure compost (5, 10, and 20 Mg/ha), and two levels of poultry manure (2.5 and 5 Mg/ha). Black polyethylene mulch was used in all treatments without hairy vetch. Fatty acid analysis was used to characterize the total soil microbial community structure, while two substrate utilization assays were used to investigate the community structure of culturable bacteria and fungi. Crop yield was not significantly increased by hairy vetch cover cropping when compared to black polyethylene mulch, although microbial community structure was significantly affected by cover cropping. Under black polyethylene mulch, crop yields were significantly increased by the highest levels of compost and manure when compared to inorganic fertilizer, but there was no detectable effect on soil microbial community structure. When cover cropping was compared to organic amended plasticulture systems, crop yields were similar one year but dissimilar the next. However, hairy vetch cover cropping and organic amendments under black plastic mulch produced significantly different soil microbial community structure.     

Heavy metals in crops as affected by soil types and sewage sludge rates

Abstract

A municipal sewage sludge was applied at three application rates to three soils in field lysimeters to study the effects of soil and sludge application rate on cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) absorbed by ‘Larker’ barley (Hordeum vulgare L.) and by Swiss chard (Beta vulgaris L. ‘Cicla'). Sludge applied at 20, 40, and 100 Mg/ha oven‐dry equivalent were mixed into the top 0.15 m of soil in each lysimeter. In addition, a nil sludge rate (control) received 125 kg N/ha. Metal contents were relatively low in barley grain, higher in barley straw, and highest in Swiss chard. Metal contents in plants increased with increasing sludge loading. Most plants grown on soil amended with the higher sludge rates were too high in Cd (greater than 0.5 mg/kg of dry feed material) to be suitable for animal consumption. No plant materials tested exceeded the suggested maximum Zn, Cu, or Ni levels.     

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

Abstract

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

Ammonium bicarbonate‐DTPA extraction of elements from waste‐amended calcareous soil

Abstract

Use of soil testing for both nutrient and heavy metal interpretations could prove to be a readily available tool for management of calcareous soils amended with solid waste products. The ammonium bicarbonate‐DTPA (di‐ethylenetriaminepentaacetic acid) [AB‐DTPA] extradant was used in this study, based on its successful use in other calcareous regions, and existence of interpretations for both nutrients and selected heavy metals. In southern Florida, addition of large volumes of composted waste products to shallow agricultural soils formed from crushed Oolitic limestone appears to be a viable disposal alternative to rapidly expanding lanfills or incineration. For two years, the effects of processed wastes (PW) on selected, AB‐DTPA‐extractable soil mineral element concentrations were determined for tomato (Lycospresicon esculentum Mill.) and squash (Cucurbita maxima Duch. Ex Lam.) grown with three different irrigation rates (3.78, 2.53, or 1.25 L/min). The PW composts were added at supplier‐recommended rates for soil addition, resulting in a range of loading rates varying with source, with which the AB‐DTPA extradant could be evaluated. The PW composts were: i) Agrisoil Compost (processed municipal garbage and yard clippings) applied at 48 Mg/ha, ii) Daorganite (processed sewage sludge) applied at 16 Mg/ha, and iii) Eweson Compost (processed municipal garbage and sewage sludge) applied at 24 Mg/ha, and iv) no PW (control). There were no significant interactions between irrigation and PW treatment or effects of irrigation treatment on any of the soil‐extracted elements following either crop, with the exception of AB‐DTPA‐extractable copper (Cu) following squash in 1991. Treatment with Agrisoil resulted in the greatest increase in mineral element accumulation in the soil followed by Daorganite and Eweson sources for both crops during each year. Although there was variability among crops and years, mineral element concentrations, particularly manganese (Mn), lead (Pb), nickel (Ni), and Cu, were generally higher in the Agrisoil‐amended soil than in the other treatments. These observations could be traced to loading rates of individual elements. The lowest mineral element concentrations were in the non‐amended soil. The results of this study indicate that nutrients and selected heavy metals can be monitored successfully using the AB‐DTPA extractant. Accumulation of nutrients, including metals, in PW‐amended soil was minimal when supplied to the soil at manufacturers’ recommended rates, which were well below the U.S. Environmental Protection Agency's maximum loading rates.     

Physicochemical characteristics of a new organic soil conditioner from composted sludges from a pulp deinking process

Abstract

A new organic soil‐conditioner from composted sludge produced from a newspaper deinking process was examined compared with raw uncomposted sludge, its physical and chemical characteristics tested in order to study its effectiveness. The water‐holding capacity of the conditioner was almost 7.6 and 1.8 times higher than that of the pure soil and the raw sludge, respectively, and remained stable at temperatures between 9°C and 27°C. The composted sludge had a 53% organic matter content and 35% in humic substances which was 3.5 and 2.0 times lighter than the pure soil and the raw sludge. Incorporation of this‐material into the soil in concentrations of up to 25% resulted in a 1.7 times increase of the water‐holding capacity of the mixture, whereas 90% of the water‐holding capacity was achieved in less than 10 min. The apparent density of the mixture was decreased and was not affected by the residence time of the samples into the water. The pH of the mixture's eluates was shifted to higher values (pH=7.0). The specific conductivity of the eluates was increased. Due to this parameter, a limit was observed in the use of this conditioner. The amount of ammonium‐nitrogen (NH ‐N), phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu)⁴, and manganese (Mn) in the eluates increased, while the amount of potassium (K) and iron (Fe) decreased in comparison to what would be expected from the separate contributions of soil and conditioner. Therefore, there exists an interaction between this material and soil that occurs when the conditioner is incorporated into soil.     

Utilization of MSW Compost In Nursery Stock Production

This three year study was conducted to evaluate the suitability of municipal solid waste (MSW) compost as a soil amendment or a mulch to suppress weeds in the production of field grown nursery stock. In the soil amendment experiment, compost was applied at the rates of 0, 56, and 112 t/ha and incorporated into the soil prior to planting. In the mulch/weed control experiment, 224 t/ha of compost was applied to one set of plots as a mulch after planting and compared to plots treated with herbicide and untreated controls. Each plot in both experiments contained four rows with one each of red maple (Acer rubrum L.), sugar maple (Acer saccharum Marsh.), white pine (Pinus strobus L.), and pin oak (Quercus palustris Muenchh.). Mortality and weed counts were determined during the first growing season. Annual measurements of crown height, crown width, and caliper (at the 1 foot level) were made the following three winters. Two inches of compost mulch (224 t/ha) provided adequate weed control only in the first year. Mowing suppressed the weeds that invaded the plots beyond the first year. For maples, first year mortality in plots mulched with 224 t/ha compost or amended with 112 t/ha compost was significantly less than unamended controls. In subsequent years, the mulched maples grew more than trees in the unamended controls. In the plots amended with 56 or 112 t/ha compost, sugar maples had increased height, canopy, and caliper growth compared to the unamended controls. The hearty pin oak saplings survived transplanting and there was a significant increase in caliper growth in plots amended with 112 t/ha (1 inch) of compost. Mortality of white pine increased when mulched with 224 t/ha compost. Increased mortality was most likely due to high concentrations of ammonium and soluble salts in the immature compost. Beyond the first year, there were no negative impacts on the growth of white pine from any of the compost treatments.     

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。     

Carbon sequestration in a limestone quarry mine soil amended with sewage sludge

To reclaim a limestone quarry, 200 and 400 Mg/ha of municipal sewage sludge were mixed with an infertile calcareous substrate and spread as mine soil in 1992. Soil samples were taken 1 week later and again after 17 yr of mine soil rehabilitation so as to assess changes in the amount and persistence of soil organic carbon (SOC). Sludge application increased SOC as a function of the sludge rate at both sampling times. Seventeen years after the sludge amendments, the nonhydrolysable carbon was increased in the 400 Mg/ha of sludge treatment. The recalcitrance of SOC was less in sludge‐amended soils than in the control treatment at the initial sampling, but 17 yr later this trend had reversed, showing qualitative changes in soil organic carbon. The CO₂‐C production had not differed between treatments, yet the percentage of mineralized SOC was less in the high sludge dose. When the size of active (C_active) and slow (C_slow) potentially mineralizable C pools was calculated by curve fitting of a double‐exponential equation, the proportion of C_active was observed to be smaller in the 400 Mg/ha sludge treatment. Soil aggregate stability, represented by the mean weight diameter of water‐stable soil aggregates, was significantly greater in mine soil treated with the high dose of sludge (18.5%) and SOC tended to be concentrated in macro‐aggregates (5–2 mm). Results suggest that SOC content in sludge‐amended plots was preserved due by (i) replacement of the labile organic carbon of sludge by more stable compounds and (ii) protection of SOC in aggregates.     

Growth of Impatiens ‘Accent Red’ In Three Compost Products

Growth of Impatiens wallerana Hook. ‘Accent Red’ was evaluated in three composted urban waste materials (composted biosolids and yard trash (SYT): 20 percent biosolids/sewage sludge, 44 percent yard trimmings, and 36 percent mixed paper; composted refuse fuel residues with biosolids and yard trash (RYT): 74 percent refuse-derived fuel residuals, 10 percent biosolids/sewage sludge, and 16 percent yard trimmings; and composted municipal solid waste (MSW): 100 percent municipal solid waste). Treatments consisted of 100 percent composted waste and media in which the composted wastes were combined with control medium components at 60 percent, 30 percent, or 0 percent composted waste, by volume. Shoot dry mass of plants grown in SYT increased as the percentage of SYT in the medium increased, while shoot dry mass of plants grown in MSW linearly decreased from 1.24 g to 0.15 g. There were no significant differences in shoot dry mass of plants grown in different percentages of RYT. Initial medium soluble salt concentrations in MSW media were more than double concentrations measured in SYT and RYT media. Soluble salt concentrations in both the 100 percent and 60 percent MSW media exceeded 1.75 dS.m^?1, while the soluble salt concentrations in 100 percent SYT and 100 percent RYT were 0.50 dS.m^?1 and 0.61 dS.m^?1, respectively. The C:N ratios in 100 percent SYT and RYT were 17 and 15, respectively, while 100 percent MSW had a C:N ratio of 29. The relatively higher level of compost maturity as indicated by lower C:N and soluble salt concentrations contributed to superior growth of impatiens plants in 100 percent SYT and RYT compared to 100 percent MSW.     

Availability and plant uptake of nutrients following the application of paper pulp and lime to tropical acid soils

Availability and plant uptake of nutrients were evaluated in three tropical acid soils (Kandiudult) amended with paper pulp and lime under greenhouse conditions. Amendments were applied to attain target pH values of 5.5, 6.0, and 6.5. A control treatment (no paper pulp or lime added) was also included. Rye grass (Lolium perenne L.) as a test plant was grown for three successive cycles of 40 days each. Extractable nutrients and cumulative nutrient uptake were determined. The application of paper pulp or lime resulted in a significant increase in exchangeable Ca and K and a decrease in exchangeable Mg and extractable Fe, Mn, and Zn. Amendment of soils with paper pulp or lime increased plant uptake of Ca and Mg and decreased that of K, Mn, and Zn. Both amendments behaved similarly, but the effect of lime seemed generally greater than that of paper pulp. Paper pulp in tropical acid soils behaved as a liming agent rather than an organic amendment. Similar to lime, amendment of soils with paper pulp resulted in an increase in availability of Ca and Mg and in a decrease in availability of K, Mn, and Zn for plants. Soil extractions appeared to be appropriate for assessing the availability of Ca, Mn, and Zn. Soil pH and effective cation exchange capacity positively influenced the availability of Ca and negatively the availability of Mn and Zn. Thus, the precision of predicting nutrient availability in paper pulp amended tropical acid soils could be improved by including soil pH or effective cation exchange capacity in relevant regression equations.     

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.     

The Phytotoxicity Changes of Sewage Sludge-Amended Soils

The aim of the present study was the estimation of changes in the phytotoxicity of soils amended with sewage sludge with relation to Lepidium sativum, Sinapis alba and Sorghum saccharatum. The study was realised in the system of a plot experiment for a period of 29?months. Samples for analyses were taken at the beginning of the experiment, and then after 5, 17 and 29?months. Two kinds of sewage sludge, with varying properties, were added to a sandy soil (soil S) or a loamy soil (soil L) at the dose of 90?t/ha. The addition of sewage sludge to the soils at the start of the experiment caused a significant reduction of both seed germination capacity and root length of the test plants, the toxic effect being distinctly related to the test plant species. With the passage of time the negative effect of sewage sludge weakened, the extent of its reduction depending both of the kind of sewage sludge applied and on the type of soil. Phytotoxicity of the soils amended with the sewage sludges was significantly lower at the end of the experiment than at the beginning. The species of the plants grown on the soils also had a significant effect on their phytotoxicity. The greatest reduction of toxicity was observed in the soil on which no plants were grown (sandy soil) and in the soil under a culture of willow (loamy soil). Solid phase of sewage sludge-amended soils was characterised by higher toxicity than their extracts.     

Growth of apple seedlings on sludge‐amended soils in the greenhouse

Abstract

Open pollinated ‘York Imperial’ apple (Malus domestica Borkh.) seeds were germinated and grown for a period of 7 months in: (1) sand with complete nutrient solutions added; (2) limed and unlimed soil, (3) limed and unlimed soil amended with two different sewage sludges at rates of 25, 50 or 100 dry kg ha^‐1. A third composted, lime stabilized sludge was added either sieved or non‐sieved (to remove wood chips) at the same rates. The sludge materials used were: (1) a high metal, composted sludge from Baltimore, MD (BALT); (2) a high Cd sewage sludge (CITY) and (3) a low metal, composted sewage sludge from Washington, D.C. (DC).

Germination was unaffected by treatments. After 7 months, the best growth was obtained from the sand plus nutrient solution media. Two of the three sludge materials increased seedling growth over that of the soil, either limed or unlimed. The BALT compost treated soils produced the lowest growth, particularly when unlimed. Elevated tissue metal levels indicated that Mn, Zn, Cu and Ni were the probable causes of reduced growth noted from the BALT compost treatment. The use of soil with or without low metal sludges as media for early apple seedling growth when compared to standard sand culture is not recommended.     

Colza (Brassica napus, v. Jaguar) Responses to Low Level of Metal Inputs Through Sewage Sludge Application: Induction of phytochelatin synthesis (10 pp)

Background, Aim and Scope   Most studies of sewage sludge disposal effects on plants have focused on high metal loadings. Less attention has been paid to plant responses to trace metal loadings below the recommended limit values. Materials and Methods: Here, a lysimetric experiment was conducted to assess the uptake, distribution and binding of trace metals by metal-induced, sulfhydryl-rich peptides (phytochelatins) in colza (Brassica napus, v. Jaguar) grown on a clayey, silty soil amended with a sewage sludge compost containing trace metal contents far below the recommended limit values established by French legislation. Chemical fractionation of unamended and sludge-amended soils was performed using a sequential extraction technique. Results: Copper concentrations in plant tissues were not affected by compost disposal. Its application at a single rate equivalent to 30 t/ha stimulated the growth of plants. Lead was not detectable in the plant material (< 1 mg g-1 dry wt.). Plants grown on the amended soil accumulated significantly more zinc than control plants. These phytochelatin complexes detected in leaves had a lower molecular weight than those extracted from roots. Those extracted from roots were composed of one type of phytochelatins (PCs) such as in leaves or a mixture of glutathione, PC2 and PC4. In comparison with control plants, sewage sludge compost application caused the synthesis of longer chain PCs in roots and in leaves. Furthermore, in comparison with control roots, glutathione and phytochelatin mixtures of higher molecular weight were detected in roots produced on the amended soil, whereas no significant increase in \total\ Cu and Zn content was observed in these organs after sludge application. Discussion: Compost application induces a significant increase in the proportion of the most labile forms of zinc and especially its pH 4.7 acid-soluble forms and, as a consequence, a higher accumulation of zinc in plants. Effects of copper are limited due to its strong affinity for humic substances and lead does not seem to be transported in any organ of plants. The presence of phytochelatins, even in plants grown on the unamended soil, proved the ability of colza to synthesize them in the presence of zinc and copper. Conclusions: These primary results seem to prove, on one hand, ability of colza (Brassica napus, v. Jaguar) to synthesize phytochelatins as well as in roots, in leaves and, on the other hand, the sensitivity of the PC induction as suggested by their identification in plants grown on the control soil. Synthesis of longer chain PCs in roots and in leaves, and formation of glutathione and phytochelatin mixtures in roots, are plant responses to sewage sludge compost application. Recommendations and Perspectives: Phytochelatin analysis is thus supposedly able to be one of the bioindicators that may be used as an ecotoxicological risk assessment of wastes. Due to its ability to synthesize phytochelatins, colza could be chosen as a plant test. Phytochelatin analysis could also be limited to roots (more sensitive than leaves). However, further experiments are needed. Quantitative analysis of phytochelatins had not been carried out due to insufficient amounts of pure phytochelatin standards, that had allow us to better study relationships between trace metal amounts to vegetal response.     

Zinc,copper, cadmium,and lead in minespoil,water, and plants from reclaimed mine land amended with sewage sludge

Sewage sludge from the city of Philadelphia has been used as a fertilizer and soil conditioner for twelve years to reclaim surface-mined land. Over 1,000 ha have been reclaimed using an application rate of 138 to 145 Mg ha^?1 (d.w.). Each of 49 sites was monitored for up to 2 yr following sludge application. Extractable Zn, Cu, Cd, and Pb in minespoil were determined before and after sludge was applied. Spoil percolate water, groundwater, and vegetation were also analyzed for metal concentrations. Data indicate that metals were retained mostly in the plow layer in which the sludge was incorporated, but there was evidence of smaller increases in metal concentrations at the 15 to 30 cm depth. Percolate water and groundwater quality appeared to be unaffected by sludge application. Foliar metal concentrations were within tolerance levels for agronomic crops and domestic animal diets. Other studies have shown that concentrations of metals in small mammals and rabbits consuming the sludge-grown vegetation were generally the same as those in animals living on areas not amended with sludge. Surface application of sludge containing low to median metal concentrations should pose no threat to soil, water, crop quality, or the food chain, even when applied in amounts higher than typical agricultural rates.