Fertilization of SRC Willow,II: Leaching and Element Balances

Short rotation coppice (SRC) willow is an emerging cropping system in focus for production of biomass for energy. To increase production, the willow is commonly fertilized, but studies have shown differing effects of fertilization on biomass production, ranging from almost no response to considerable positive effects. Focus has also been on replacing mineral fertilizer with organic waste products, such as manure and sludge. However, the effect on biomass production and environmental impact of various dosage and types of fertilizer is not well described. Therefore we studied the environmental impacts of different doses of mineral fertilizer, manure and sewage sludge in a commercially grown SRC willow stand. We examined macro nutrient and heavy metal leaching rates and calculated element balances to evaluate the environmental impact. Growth responses were reported in a former paper (Sevel et al. “Fertilization of SRC Willow, I: Biomass Production Response” Bioenergy Research, 2013). Nitrogen leaching was generally low, between 1 and 7 kg N ha^?1 year^?1 when doses of up to 120 kg N ha^?1 year^?1 were applied. Higher doses of 240 and 360 kg N ha^?1 as single applications caused leaching of 66 and 99 kg N ha^?1 year^?1, respectively, indicating N saturation of the system. Previous intensive farming including high doses of fertilizer may be responsible for a high soil N status and the high N leaching rates. However, moderate fertilization input could not compensate P and K exports with the biomass harvest. No elevated leaching of heavy metals was observed for any fertilization treatments and more cadmium than applied with the fertilizer was removed with the biomass from the system.     

Switchgrass Biofuel Production on Reclaimed Surface Mines: I. Soil Quality and Dry Matter Yield

Growing food crops for biofuel on productive agricultural lands may become less viable as requirements to feed a growing human population increase. This has increased interest in growing cellulosic biofuel feedstocks on marginal lands. Switchgrass (Panicum virgatum L.), a warm-season perennial, is a viable bioenergy crop candidate because it produces high yields on marginal lands under low fertility conditions. In other studies, switchgrass dry matter (DM) yields on marginal croplands varied from 5.0 to 10.0 Mg ha^?1 annually. West Virginia contains immense areas of reclaimed surface mined lands that could support a switchgrass-based biofuel industry, but yield data on these lands are lacking. Field experiments were established in 2008 to determine yields of three switchgrass cultivars on two West Virginia mine sites. One site reclaimed with topsoil and municipal sludge produced biomass yields of 19.0 Mg DM ha^?1 for Cave-in-Rock switchgrass after the sixth year, almost double the varieties Shawnee and Carthage, at 10.0 and 5.7 Mg ha^?1, respectively. Switchgrass yields on another site with no topsoil were 1.0 Mg ha^?1 after the sixth year, with little variation among cultivars. A second experiment was conducted at two other mine sites with a layer of topsoil over gray overburden. Cave-in-Rock was seeded with fertilizer applications of 0, 34, and 68 kg N-P₂O₅-K₂O ha^?1. After the third year, the no fertilizer treatment averaged biomass yields of 0.3 Mg ha^?1, while responses to the other two rates averaged 1.1 and 2.0 Mg ha^?1, respectively. Fertilization significantly increased yields on reclaimed mine soils. Where mine soil fertility was good, yields were similar to those reported on agricultural soils in the Northeastern USA.     

Effects of different sewage sludge applications on heavy metal accumulation,growth and yield of spinach (Spinacia oleracea L.)

In this study, we present the response of spinach to different amendment rates of sewage sludge (0, 10, 20, 30, 40 and 50 g kg^?1) in a greenhouse pot experiment, where plant growth, biomass and heavy metal uptake were measured. The results showed that sewage sludge application increased soil electric conductivity (EC), organic matter, chromium and zinc concentrations and decreased soil pH. All heavy metal concentrations of the sewage sludge were below the permissible limits for land application of sewage sludge recommended by the Council of the European Communities. Biomass and all growth parameters (except the shoot/root ratio) of spinach showed a positive response to sewage sludge applications up to 40 g kg^?1 compared to the control soil. Increasing the sewage sludge amendment rate caused an increase in all heavy metal concentrations (except lead) in spinach root and shoot. However, all heavy metal concentrations (except chromium and iron) were in the normal range and did not reach the phytotoxic levels. The spinach was characterized by a bioaccumulation factor <1.0 for all heavy metals. The translocation factor (TF) varied among the heavy metals as well as among the sewage sludge amendment rates. Spinach translocation mechanisms clearly restricted heavy metal transport to the edible parts (shoot) because the TFs for all heavy metals (except zinc) were <1.0. In conclusion, sewage sludge used in the present study can be considered for use as a fertilizer in spinach production systems in Saudi Arabia, and the results can serve as a management method for sewage sludge.     

Fertilization of SRC Willow,I: Biomass Production Response

Short rotation coppice (SRC) willow is often regarded as one of the most promising crops to increase biomass production and thereby meet the growing demand for renewable energy. This study is based on the hypotheses that biomass production of SRC willow responds positively to increasing doses of nitrogen, and that similar biomass production response can be achieved by use of mineral fertilizer, sewage sludge and animal manure. A 2-year experiment was established with the clone Tordis grown on a sandy soil in northern Jutland, Denmark. The experiment included mineral fertilizer, sludge and manure, and treatments of different doses up to 360 kg nitrogen ha^?1. The fertilization led to a modest but significant increase in biomass production. The largest production of 11.9 oven dried tons/ha/year was obtained for the application of 60 kg nitrogen ha^?1 annually. Higher doses did not lead to increased biomass production; in fact, production seemed to decline with increasing fertilization application (not significant). We found no difference in production between different types of fertilizers. The limited response of the fertilization may be caused by a high fertility of the soil due to former agricultural fertilization. The number of sagging shoots increased significantly with increasing nitrogen dose.     

Feasibility of Using Phytoextraction to Remediate a Compost-Based Soil Contaminated with Cadmium

Greenhouse and in-situ field experiments were used to determine the potential for phytoextraction to remediate soil contaminated with Cd from municipal solid waste (MSW) and sewage sludge (SS) compost application at a Peterborough (Canada) site. For the greenhouse experiment, one native (Chenopodium album) and three naturalized (Poa compressa, Brassica juncea, Helianthus annuus) plant species were planted in soil containing no detectable Cd (<1.0 μg·g^?1), and soil from the site containing low (5.0 ± 0.3 μg·g^?1 Cd), and high (16.5 ± 1.2 μg?g^?1 Cd) Cd concentrations. Plant uptake was low (root BAFs ≤0.5) for all species except P. compressa in the low Cd treatment (BAF 1.0). Only B. juncea accumulated Cd in its shoots, though uptake was low (BAF ≤0.3). For the field experiment, B. juncea was planted in-situ in areas of low and high Cd concentrations. Brassica juncea Cd uptake was low (root and shoot BAFs <0.2) in both treatments. Sequential extraction analysis indicated that Cd is retained primarily by low bioavailability soil fractions, and phytoextraction is therefore not feasible at this site. Though low Cd bioavailability has negative implications for Cd phytoextraction from MSW/SS compost-based soils, it may limit receptor exposure to Cd sufficiently to eliminate the potential for risk at this site.     

Effect of Potassium and Nitrogen Fertilizer on Switchgrass Productivity and Nutrient Removal Rates under Two Harvest Systems on a Low Potassium Soil

Biomass demand for energy will lead to utilization of marginal, low fertility soil. Application of fertilizer to such soil may increase switchgrass (Panicum virgatum L.) biomass production. In this three-way factorial field experiment, biomass yield response to potassium (K) fertilizer (0 and 68 kg?K?ha^?1) on nitrogen (N)-sufficient and N-deficient switchgrass (0 and 135 kg?N?ha^?1) was evaluated under two harvest systems. Harvest system included harvesting once per year after frost (December) and twice per year in summer (July) at boot stage and subsequent regrowth after frost. Under the one-cut system, there was no response to N or K only (13.4 Mg?ha^?1) compared to no fertilizer (12.4 Mg?ha^?1). Switchgrass receiving both N and K (14.6 Mg?ha^?1) produced 18 % greater dry matter (DM) yield compared to no fertilizer check. Under the two-cut harvest system, N only (16.0 Mg?ha^?1) or K only (14.1 Mg?ha^?1) fertilizer produced similar DM to no fertilizer (15.1 Mg?ha^?1). Switchgrass receiving both N and K in the two-cut system (19.2 Mg?ha^?1) produced the greatest (P?<?0.05) DM yield, which was 32 % greater than switchgrass receiving both N and K in the one-cut system. Nutrient removal (biomass?×?nutrient concentration) was greatest in plots receiving both N and K, and the two-cut system had greater nutrient removal than the one-cut system. Based on these results, harvesting only once during winter months reduces nutrient removal in harvested biomass and requires less inorganic fertilizer for sustained yields from year to year compared to two-cut system.     

Mycorrhizal symbiosis and phosphorus fertilization effects on Zea mays growth and heavy metals uptake

Arbuscular mycorrhizal fungi (AMF) can promote plant growth and reduce plant uptake of heavy metals. Phosphorus (P) fertilization can affect this relationship. We investigated maize (Zea mays L.) uptake of heavy metals after soil AMF inoculation and P fertilization. Maize biomass, glomaline and chlorophyll contents and uptake of Fe, Mn, Zn, Cu, Cd and Pb have been determined in a soil inoculated with AMF (Glomus aggregatum, or Glomus intraradices) and treated with 30 or 60 µg P-K₂HPO₄ g^?1 soil. Consistent variations were found between the two mycorrhizal species with respect to the colonization and glomalin content. Shoot dry weight and chlorophyll content were higher with G. intraradices than with G. aggregatum inoculation. The biomass was highest with 30 µg P g^?1 soil. Shoot concentrations of Cd, Pb and Zn decreased with G. aggregatum inoculation, but that of Cd and Pb increased with G. intraradices inoculation. Addition of P fertilizers decreased Cd and Zn concentrations in the shoot. AMF with P fertilization greatly reduced maize content of heavy metals. The results provide that native AMF with a moderate application rate of P fertilizers can be exploited in polluted soils to minimize the heavy metals uptake and to increase maize growth.     

The long-term variation of Cd and Zn hyperaccumulation by Noccaea spp and Arabidopsis halleri plants in both pot and field conditions

Three Cd and Zn hyperaccumulating plant species Noccaea caerulescens Noccaea praecox and Arabidopsis halleri (Brassicacceae) were cultivated in seven subsequent vegetation seasons in both pot and field conditions in soil highly contaminated with Cd, Pb, and Zn. The results confirmed the hyperaccumulation ability of both plant species, although A. halleri showed lower Cd uptake compared to N. caerulescens. Conversely, Pb phytoextraction was negligible for both species in this case. Because of the high variability in plant yield and element contents in the aboveground biomass of plants, great variation in Cd and Zn accumulation was observed during the experiment. The extraction ability in field conditions varied in the case of Cd from 0.2 to 2.9 kg ha^?1 (N. caerulescens) and up to 0.15 kg ha^?1 (A. halleri), and in the case of Zn from 0.2 to 6.4 kg ha^?1 (N. caerulescens) and up to 13.8 kg.ha^?1 (A. halleri). Taking into account the 20 cm root zone of the soil, the plants were able to extract up to 4.1% Cd and 0.2% Zn in one season. However, cropping measures should be optimized to improve and stabilize the long-term phytoextraction potential of these plants.     

Phytoextraction of Heavy Metals from Highly Contaminated Soils Using Sauropus androgynus

It has been found that Sauropusandrogynus has a strong adaptive capacity in multiple heavy-metal-contaminated soils. Field trials in highly heavy-metal-contaminated soils were conducted to investigate the extraction efficiency of Cd, Cu, Pb, and Zn by S. androgynus. The yield of S. androgynus could reach 10.01 t ha^?1, and the amount of Cd, Cu, Pb, and Zn extracted by the plant was 57.36, 218.57, 2078.11, and 19.64 g ha^?1, respectively. S. androgynus removed 0.35%, 0.01%, 0.03%, and 1.37% of the total soil Cd, Cu, Pb, and Zn in one growing season, respectively. By comparing the extracting capability and yield with some hyperaccumulators reported in the literature, S. androgynus was considered to be a highly effective plant to extract heavy metals (Cd, Cu, Pb, and Zn). The plant should be useful for phytoextraction of soils contaminated by the heavy metals.     

Nickel in soil and maize plants grown on an oxisol treated over a long time with sewage sludge

Abstract

The major limitation for the use of sewage sludge in agriculture is the risk of soil contamination with heavy metals, and their possible transference to man via the food chain. The objective of this study was to evaluate the content of nickel (Ni) in soil by the two methods of digestion (HNO₃ + H₂O₂ + HCl and HClO₄ + HF), and in different parts of maize plants grown on a tropical soil classified as Typic Eutrorthox, that had been treated with sewage sludge for nine consecutive years, and the effects on dry matter and grain production. The experiment was carried out under field conditions in Jaboticabal-SP, using a randomized block design with four treatments and five replicates. Treatments consisted of: 0.0 (control, mineral fertilization), 45.0, 90.0 and 127.5t ha^?1 sewage sludge (dry basis), accumulated during nine years. Sewage sludge was manually applied to the soil and incorporated at 0.1 m depth before sowing the maize. Soil Ni evaluated by Jackson’s method was 76.8% higher than evaluated by the United States Environmental Protection Agency method that digests the samples by heating with concentrated HNO³, H²O² and HCl. Sewage sludge rates did not affect Ni content in the soil. Ni was accumulated in leaf and stem but was not detected in grain. Sewage sludge and mineral fertilization applied to soil for a long time caused similar effects on dry matter and grain production.     

The Effect of EDTA Addition on the Phytoremediation Efficiency of Pb and Cr by Echinochloa crus galii (L.) Beave and Associated Potential Leaching Risk

Metal-contaminated soils constitute a serious environmental problem with adverse consequences for human health. This study was conducted to determine phytoextraction efficiency of Echinochloa crus galii for Pb and Cr and the EDTA-assisted (0. 2.5, 5, 10 mmol kg^?1) phytoextraction and the potential for leaching of the metals during the phytoextraction process. The results revealed that the bioconcentration factors of roots of the plant were relatively higher than the bioconcentration factors of the shoot. Thus, the plant species of E. crus galii would be applicable for Pb and Cr phytostabilization. Addition of EDTA had virtually a significant effect on uptake of the metals by the plant and elevated Pb and Cr concentrations in plant organs as compared with the control. Optimum phytoextraction was observed when 5 mmol kg^?1 EDTA was added in a single dosage 60 days after the plant cultivation and consequently soil Pb and Cr concentration decreased with the passage of time.     

Application of Heavy Metal Rich Tannery Sludge on Sustainable Growth,Yield and Metal Accumulation by Clarysage (Salvia sclarea L.)

A field experiment was conducted to evaluate the effective utilization of tannery sludge for cultivation of clarysage (Salvia sclarea) at CIMAP research farm, Lucknow, India during the year 2012–2013. Six doses (0, 20, 40, 60, 80, 100 tha^?1) of processed tannery sludge were tested in randomised block design with four replications. Results revealed that maximum shoot, root, dry matter and oil yield were obtained with application of 80 tha^?1of tannery sludge and these were 94, 113 and 61% higher respectively, over control. Accumulation of heavy metals (Cr, Ni, Fe, Pb) were relatively high in shoot portion of the plant than root. Among heavy metals, magnitude of chromium accumulation was higher than nickel, iron and lead in shoot as well as in root. Linalool, linalyl acetate and sclareol content in oil increased by 13,8 and 27% respectively over control, with tannery sludge application at 80 tha^?1. Heavy metals such as chromium, cadmium and lead content reduced in postharvest soil when compared to initial status. Results indicated that clarysage (Salvia sclarea) can be grown in soil amended with 80 tha^?1sludge and this can be a suitable accumulator of heavy metals for phytoremediation of metal polluted soils.     

Long-Term Miscanthus Yields Influenced by Location,Genotype, Row Distance,Fertilization and Harvest Season

Long-term yield studies in perennial crops like miscanthus are important to determine mean annual energy yield and the farmer’s economy. In two Danish field trials, annual yield of two miscanthus genotypes was followed over a 20-year period. The trials were established in 1993 on loamy sand in Foulum and on coarse sand in Jyndevad. Effects of genotype, row distance and fertilization were investigated. In both trials, yield development over time was characterized by an increase during the first years, optimum yields after 7–8 years and a decrease to a lower level which remained relatively constant from year 11 to 20. Spring harvest reduced the yield by 34–42 % compared to autumn harvest. In Foulum annual fertilization with 75 kg ha^?1 N increased the yield of the genotype Goliath (Miscanthus sinensis) by 26 %. Additional N fertilization only increased the yield of Goliath little, and the genotype Giganteus (Miscanthus?×?giganteus) did not respond to fertilization at all. The highest mean yield in Foulum for the period 1997–2012 was obtained with the shortest row distance (～18,000 rather than ～12,000 plants ha^?1) and harvested in late autumn, namely 13.1 and 12.0 Mg ha^?1 DM annually for Giganteus and Goliath, respectively. In Jyndevad, where only Goliath was studied, the highest yield during 1995–2001 was obtained by short row distance, autumn harvest and annual fertilization with 75 kg ha^?1 N, with yield increasing up to 116 % in response to fertilization. A mean yield of 14.4 Mg ha^?1 DM was achieved over the period 1995–2012.     

Limitations for phytoextraction management on metal-polluted soils with poplar short rotation coppice—evidence from a 6-year field trial

Poplar clones were studied for their phytoextraction capacity in the second growth cycle (6-year growth) on a site in the Belgian Campine region, which is contaminated with Cd and Zn via historic atmospheric deposition of nearby zinc smelter activities. The field trial revealed regrowth problems for some clones that could not be predicted in the first growth cycle. Four allometric relations were assessed for their capacity to predict biomass yield in the second growth cycle. A power function based on the shoot diameter best estimates the biomass production of poplar with R² values between 0.94 and 0.98. The woody biomass yield ranged from 2.1 to 4.8 ton woody Dry Mass (DM) ha^?1 y^?1. The primary goal was to reduce soil concentrations of metals caused by phytoextraction. Nevertheless, increased metal concentrations were determined in the topsoil. This increase can partially be explained by the input of metals from deeper soil layers in the top soil through litterfall. The phytoextraction option with poplar short rotation coppice in this setup did not lead to the intended soil remediation in a reasonable time span. Therefore, harvest of the leaf biomass is put forward as a crucial part of the strategy for soil remediation through Cd/Zn phytoextraction.     

Establishment of reed canary grass with perennial legumes or barley and different fertilization treatments: effects on yield,botanical composition and nitrogen fixation

In two field experiments in northern Sweden, we investigated if intercropping reed canary grass (RCG; Phalaris arundinacea L.) with nitrogen‐fixing perennial legumes could reduce N‐fertilizer requirements and also if RCG ash or sewage sludge could be used as a supplement for mineral P and K. We compared biomass production, N uptake and N‐fixation of RCG in monoculture and mixtures of RCG with alsike clover (Trifolium hybridum L.), red clover (Trifolium pratense L.), goat's rue (Galega orientalis Lam.) and kura clover (Trifolium ambiguum M. Bieb.). In one experiment, RCG was also undersown in barley (Hordeum vulgare L.). Three fertilization treatments were applied: 100 kg N ha^?1, 50 kg N ha^?1 and 50 kg N ha^?1 + RCG ash/sewage sludge. We used a delayed harvest method: cutting the biomass in late autumn, leaving it on the field during the winter and harvesting in spring. The legume biomass of the mixtures at the inland experimental site was small and did not affect RCG growth negatively. At the coastal site, competition from higher amount of clover biomass affected RCG growth and spring yield negatively. N‐fixation in red clover and alsike clover mixtures in the first production year approximately covered half of recommended N‐fertilization rate. Goat's rue and kura clover did not establish well at the costal site, but at the inland site goat's rue formed a small but vital undergrowth. RCG undersown in barley gave lower yield, both in autumn and spring, than the other treatments. The high N treatment gave a higher spring yield at the inland site than the low N treatments, but there were no differences due to fertilization treatments at the coastal site. For spring harvest, there were no yield benefits of RCG/legume intercropping compared with RCG monoculture. However, intercropping might be more beneficial in a two‐harvest system.     

Phytoextraction of Risk Elements by Willow and Poplar Trees

To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4–2.0 mg Cd.kg^?1, 78–313 mg Zn.kg^?1, 21.3–118 mg Cu.kg^?1). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg^?1, 909 mg Zn.kg^?1, and 17.7 mg Cu.kg^?1) compared to Populus clones (maximum 2.06 mg Cd.kg^?1, 463 mg Zn.kg^?1, and 11.8 mg Cu.kg^?1). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.     

Impact of chelator-induced phytoextraction of cadmium on yield and ionic uptake of maize

Enhanced phytoextraction uses soil chelators to increase the bioavailability of heavy metals. This study tested the effectiveness of ethylenediaminetetraacetic acid (EDTA) and citric acid in enhancing cadmium (Cd) phytoextraction and their effects on the growth, yield, and ionic uptake of maize (Zea mays). Maize seeds of two cultivars were sown in pots treated with 15 (Cd₁₅) or 30 mg Cd kg^?1 soil (Cd₃₀). EDTA and citric acid at 0.5 g kg^?1 each were applied 2 weeks after germination. Results demonstrated that the growth, yield per plant, and total grain weight were reduced by exposure to Cd. EDTA increased the uptake of Cd in shoots, roots, and grains of both maize varieties. Citric acid did not enhance the uptake of Cd, rather it ameliorated the toxicity of Cd, as shown by increased shoot and root length and biomass. Cadmium toxicity reduced the number of grains, rather than the grain size. The maize cultivar Sahiwal-2002 extracted 1.6% and 3.6% of Cd from soil in both Cd+ EDTA treatments. Hence, our study implies that maize can be used to successfully phytoremediate Cd from soil using EDTA, without reducing plant biomass or yield.     

Improving the Agronomy of Alyssum murale for Extensive Phytomining: A Five-Year Field Study

Large ultramafic areas exist in Albania, which could be suitable for phytomining with native Alyssum murale. We undertook a five-year field experiment on an ultramafic Vertisol, aimed at optimizing a low-cost Ni-phytoextraction crop of A. murale which is adapted to the Balkans. The following aspects were studied on 18-m² plots in natural conditions: the effect of (i) plant phenology and element distribution, (ii) plant nutrition and fertilization, (iii) plant cover and weed control and (iv), planting technique (natural cover vs. sown crop). The optimal harvest time was set at the mid-flowering stage when Ni concentration and biomass yield were highest. The application of N, P, and K fertilizers, and especially a split 100-kg ha^?1 N application, increased the density of A. murale against all other species. It significantly increased shoot yield, without reducing Ni concentration. In natural stands, the control of graminaceous weeds required the use of an anti-monocots herbicide. However, after the optimization of fertilization and harvest time, weed control procured little benefit. Finally, cropping sown A. murale was more efficient than enhancing native stands and gave higher biomass and phytoextraction yields; biomass yields progressively improved from 0.3 to 9.0 t ha^?1 and phytoextracted Ni increased from 1.7 to 105 kg ha^?1.     

Effect of wastewater sludge on growth and heavy metal bioaccumulation of two Salix species

Fast-growing tree species, such as willows, can benefit from sludge application. While sludges are good fertilizers, they may contain heavy metals which could reduce productivity and cause environment risks. The aims of the present research were to: i) determine the biomass production of Salix discolor Mühl. and Salix viminalis L. when supplied with various amounts of dried and pelleted sludge and ii) assess the uptake and accumulation of heavy metals. Trials were carried out using unrooted cuttings that were planted in large plastic pots containing sandy soil and grown outdoors for a 20-week period. Five doses of sludge were applied: the equivalents of 0 (T0), 40 (T1), 80 (T2), 120 (T3), 160 (T4) and 200 (T5) kg “available” N ha^-1. Trees which received the highest dosage of sludge showed the best growth. Stem biomass was significantly greater for S. viminalis which had received sludge treatments. The relationship between the total biomass yield Y (g) and the rate of fertilization X (equivalent to kg of “available” nitrogen provided per hectare) is linear. Regression equations of predicted biomass production were established as follows: S. discolor, Y=28.36+0.56X and S. viminalis, Y=39.95+0.64X. For both species, the greatest stem biomass per g of N applied was produced with treatment 4 and 5. Amounts of nitrogen per leaf area (N/LA) and per dry leaf mass (N/DL) were higher for S. viminalis. The metal transfer coefficient did not vary between the species but was significantly different for Cd and Zn. Plants were able to absorb Cd and Zn, but were less able to absorb Ni, Hg, Cu, and Pb. It was concluded that the dried and pelleted sludge is a good fertilizer. S. discolor and particularly S. viminalis can be used as filters for the purification of wastewater sludge as well as for biomass production purposes. R F Huettl Section editor     

Impact of Compost on Metals Phytostabilization Potential of Two Halophytes Species

Phytostabilization of heavy metals in contaminated soils should be subject to two conditions, the first is the choice plant must be able to stabilize heavy metals in soil, the second is the plant material which produced from the phytostabilization process must be safe and useful to avoid overload on environmental system. A field experiment was conducted out to evaluate the phytostabilization potential of two halophytes species (Atriplex lentiformis and Atriplex undulata). Compost at rates of 0, 15 and 30 ton ha^?1 was used to examine its role in plant growth and heavy metals uptake. The high rate of compost (30 ton ha^?1) decreased zinc (Zn) concentrations in the leaves of A. lentiformis and A. undulata by 15.8 and 13.0%, while lead (Pb) in the leaves decreased by 37.6 and 35.2% respectively. Despite the extremely high total heavy metals concentrations in the studied soil, plants of Atriplex were able to grow and maintain shoots metals content below the toxic level and the produced plant materials had a high nutritive value compared to the conventional forage crops. Phosphorus (P) and chloride (Cl) in the roots of Atriplex plants play important function in heavy metals phytostabilization mechanism by the two halophytes plants.