Assessment of Arsenic and Selenium Concentration with Chlorophyll Contents of Sugar Beet (Beta vulgaris var.saccharifera) and Wheat (Triticum aestivum) Exposed to Municipal Sewage Sludge Doses

The present study was conducted to assess the suitability of sewage sludge amendment in soil for Beta vulgaris var. saccharifera (sugar beet) and Triticum aestivum (wheat) by evaluating the arsenic and selenium accumulation and physiological responses of plants grown at 10%, 25%, and 50% sewage sludge amendment rate. Sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently with higher accumulation in plant parts. The chlorophyll contents increased after the sewage sludge treatments except for 50%. The sewage sludge amendment led to a significant increase in arsenic and selenium concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency. The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake in the leaves and root concentrations of arsenic and selenium in plants as compared to those grown on unamended soil. Accumulation was more in roots than shoots and leaves for most of the heavy metals. Concentrations of arsenic and selenium were more than the permissible limits of national standards in the edible portion of sugar beet and wheat grown on different sewage sludge amendments ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet and wheat may not be a good option due to risk of contamination of arsenic and selenium.     

Influence of Amelioration of Strongly Acid Soils with Calcareous Materials and Sewage Sludge on Wheat Yield and Economic Results

Abstract

The amelioration of acid unproductive soils with various amendments may improve soil properties and increase crop yield. In this paper, the influence of several soil amendments (refuse sugar beet lime, calcium hydroxide, and municipal sewage sludge) on wheat yield and gross margin were studied in a three‐year (1995, 1996, 1997) field experiment, conducted in western Thessaly (Elassona area), central Greece. In order to evaluate soil amelioration from an economic point of view we estimated the profit that derives from soil amelioration for each year separately as well as for the whole period of the experiment. The results showed that sugar beet lime and sewage sludge at the rate 15 ton ha^?1 are preferable from an economic point of view compared to calcium hydroxide. This fact is supportive of all the efforts made to diffuse the use of quality by‐products for soil amelioration.     

Growth promotion of plants by plant growth-promoting rhizobacteria under greenhouse and two different field soil conditions

This study was conducted with sugar beet in greenhouse and field at two soil type with different organic matter (containing 2.4 and 15.9% OM, referred as the low- and high-OM soil) conditions in order to investigate seed inoculation of sugar beet, with five N₂-fixing and two phosphate solubilizing bacteria in comparison to control and mineral fertilizers (N and P) application. Three bacterial strains dissolved P; all bacterial strains fixed N₂ and significantly increased growth of sugar beet. In the greenhouse, inoculations with PGPR increased sugar beet root weight by 2.8-46.7% depending on the species. Leaf, root and sugar yield were increased by the bacterial inoculation by 15.5-20.8, 12.3-16.1, and 9.8-14.7%, respectively, in the experiment of low- and high-OM soil. Plant growth responses were variable and dependent on the inoculants strain, soil organic matter content, growing stage, harvest date and growth parameter evaluated. The effect of PGPR was greater at early growth stages than at the later. Effective Bacillus species, such as OSU-142, RC07 and M-13, Paenibacillus polymyxa RC05, Pseudomonas putida RC06 and Rhodobacter capsulatus RC04 may be used in organic and sustainable agriculture.     

Effects of organic and mineral amendments on available P and phosphatase activities in a degraded Mediterranean soil under short-term incubation experiment

The aim of this study was to determine the effects of mineral and organic-P-fertilizers on soil P availability, bacteria densities and phosphatase activities, in a degraded Mediterranean soil characterized by low level in soil organic matter and nutrients. A typical degraded Mediterranean soil, originating from a siliceous mineral parent material, was amended with different organic or mineral P-sources: aerobically digested sewage sludge (SS), with or without physico-chemical treatment by ferric chloride; sewage sludge compost (SSC); Na or K mineral P-salts (Pi-salts). All the amendments were carried out in order to provide soil with a P total quantity equivalent to 0.5 g P₂O₅/kg of soil. Bacterial density, phosphatase activities (i.e. acid (APH) and alkaline (BPH) phosphomonoesterases and phosphodiesterases), BPH/APH ratio, and available P (P Olsen) were measured after 25 and 87 days of incubation. Results showed that all the P-sources used to fertilize soil during this study resulted in significant increase in P concentration. However, different responses in phosphatase activities and bacterial densities were obtained with regards to the amendment applied to soil. Indeed, it appeared clearly that sewage sludge (SS) considerably stimulated soil biological activity, and more especially the different kinds of phosphatases involved in P mineralization and P turn-over. On the contrary, sewage sludge compost (SSC) as well as P-salts amendments did not affected these parameters in most cases. Results showed also that the incubation time influenced almost all the biological and chemical parameters investigated during this study. As a consequence, P availability was considerably improved in the amended soils between the two sampling dates.     

Density,metabolic activity,and identity of cultivable rhizosphere bacteria on Salix viminalis in disturbed arable and landfill soils

The objective of this study was to provide fundamental data for a subsequent selection of willow growth and soil remediation promoting bacterial strains. The rhizosphere of willows (Salix viminalis) was screened for cultivable bacteria with high enzymatic activity (proteolytic, pectolytic, cellulolytic, amylolytic) and production of siderophores at four test sites with broad spectrum of anthropogenic soil disturbance: sewage‐sludge application, impoverishment by unfavorable arable use, ash dumping, and household‐waste depositing. The density of bacteria in the rhizosphere ranged from 7.92 to 8.56 log₁₀ of colony‐forming units per gram dry weight of soil and varied in a site‐ and willow‐clone‐specific manner. Within the 240 bacterial strains, a high diversity of metabolic activities was observed but was rarely combined in one strain (1.2% having six and 5.8% having five out of seven metabolic activities, respectively). The majority of strains (79.2%) revealed just one or two metabolic activities. Most common was a combination of lipolytic, proteolytic activities, and siderophore production as found in 13.8% of the bacterial strains. The 50 strains with the highest metabolic activity belonged predominantly to the Gammaproteobacteria (66%), the others to Flavobacteria (18%), Betaproteobacteria (8%), Actinobacteria (4%), and Bacilli (4%). The highest portion of cultivable strains of rhizosphere bacteria with high metabolic activities belonged to the genera Pseudomonas, Serratia, and Flavobacterium. We hypothesize that these genera include strains that support willow growth and soil remediation. Therefore, the described strain collection from the rhizosphere of S. viminalis provides a valuable basis for a subsequent selection of these candidates for applications in improvement of site adaptation of plants or remediation of soils.     

Effect of N2‐fixing bacterial inoculations on yield of sugar beet and barley

Drawbacks of intensive farming practices and environmental costs of N fertilizers have renewed interest in bio‐fertilizers. This study was conducted in order to investigate the effectiveness of 7 N₂‐fixing bacterial isolates from various sources in sugar beet and barley production under field conditions in the higland plateau of Erzurum, Turkey (29° 55′ N and 41° 16′ E with an altitude of 1950 m) in 1999 and 2000. Seeds were inoculated with five bacterial strains of Bacillus; BA‐140, BA‐142, M‐3, M‐13, and M‐58, a strain of Burkholderia (BA‐7) and Pseudomonas (BA‐8). The bacterial strains had been demonstrated to grow in N‐free basal medium. The experiment also included applications of mineral nitrogen (N), phosphorous (P), and NP‐fertilizer as well as a control treatment without inoculation and fertilizer application. Two years of trials under field conditions showed that seed inoculation with bacterial strains significantly affected yield, yield components, and quality parameters both in sugar beet and barley. On an average of both years, seed inoculation of sugar beet with BA‐140, BA‐142, M‐58, BA‐7, BA‐8, M‐13, and M‐3 increased root yield by 13.0, 12.6, 10.5, 9.2, 8.1, 6.1, and 6.5% as compared to the control and sugar yield by 7.8, 6.3, 5.1, 4.0, 3.2, 2.3, and 5.3%, respectively. N, P, and NP applications, however, increased root yield up to 13.6, 5.3, and 21.4% and sugar yield by 6.1, 4.0, and 14.8%, respectively. Of the bacteria tested, BA‐140 and BA‐142 had yields equal to N application. All bacterial inoculations also gave higher seed and total biomass yields in barley than control plots. BA‐140 and BA‐142 were top yielding strains. In conclusion, bacterial seed inoculations especially with BA‐140 and BA‐142 may satisfy nitrogen requirements of sugar beet and barley under field conditions even in upland areas.     

The soil microbial community in a sewage-sludge-amended semi-arid grassland

Summary The value of sewage sludge for improving the fertility and productivity of a degraded semi-arid grassland soil was tested by quantifying and describing the effects of surface application of sewage sludge on soil chemical properties and the soil microbial community. Three surface application rates (22.5, 45, and 90 Mg sludge ha^–1) were tested over the course of two growing seasons. Most nutrient levels, including N, P, and K, increased linearly with increasing sludge application rates. Soil pH, however, declined linearly, from 7.8 to 7.4, with increasing sludge application rates. With the exception of Zn, heavy metals, including Cd, did not increase with the small decrease in pH or with increasing sludge application rates. Soil bacterial, fungal, and ammonium oxidizer populations increased linearly with increasing sludge application rates, and Streptomyces spp. populations remained relatively unchanged. The diversity of fungal groups declined initially with increasing sewage sludge rates but rebounded to near pretreatment levels under the low and intermediate application rates within 1 year. High fungal populations and low fungal diversity were related to the high nutrient contents provided by sludge amendment. Mucor spp. and Penicillium chrysogenum dominated the sludge-amended soils, and their densities in the treated soils in the first growing season were almost directly proportional to the sludge application rates. The improvement in soil fertility of a degraded semi-arid grassland due to sludge application was reflected in populations, diversity, and composition of the soil microbial community.The research reported here was conducted in cooperation with the USDI Bureau of Land Management which furnished funds and field study locations     

Changes in organic matter and enzymatic activity of an agricultural soil amended with metal‐contaminated sewage sludge compost

Abstract

The effect of organic amendment with sewage sludge composts of varying heavy metal content on the organic matter content and enzymatic activity of an agricultural soil supporting barley (Hordeum vulgare L.) or lettuce (Lactuca sativa L.) crops was studied. The organic amendments did not improved lettuce growth, the contaminated composts having a negative effect on yield. However, all organic amendments improved barley straw yields although they did not affect grain yields. The addition of the organic materials increased the total carbohydrate content of the soil although this content decreased with cultivation. There was a clearly observed effect of crop type and the degree of heavy metal contamination of the amendment on the most labile carbon (C) fractions (water‐soluble C, carbohydrates, and polyphenolics). In general, soil enzymatic activities were stimulated by addition of sewage sludge compost with low heavy metal content. The compost containing high level of cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) inhibited protease‐BAA activity with respect to the other composts. After cultivation, urease activity increased in soil amended with the high dose of composts, regardless their degree of metallic contamination. Both crop type and metallic contamination contained in the organic materials added influenced phosphatase and ß‐glucosidase activity.     

Potassium substitution by sodium in sugar beet (Beta vulgaris) nutrition on K‐fixing soils

Alluvial soils with illite and vermiculite clay minerals are highly potassium (K)‐fixing. Such soils have been reported to require a huge amount of K fertilization for optimum plant growth. For halophytic plants such as sugar beet, sodium (Na) can be an alternative to K under such conditions. This study was conducted to investigate the possible substitution of K by Na fertilization with reference to K‐fixing soils. Three soils, i.e., Kleinlinden (subsoil), Giessen (alluvial), and Trebur (alluvial), differing in K‐fixing capacities, were selected, and sugar beet plants were grown in Ahr pots with 15 kg soil pot^–1. Three treatments (no K and Na, K equal to K‐fixing capacity of soil, and Na equivalent to regular K fertilization) were applied. In a second experiment, containers (90 cm × 40 cm × 40 cm) were used with 170 kg Kleinlinden soil each, and one sugar beet plant per container was grown. In both experiments, plants were grown till beet maturity, and beets were analyzed for sucrose concentration and other quality parameters such as α‐amino nitrogen to calculate white‐sugar yield with the New Brunswick formula. The results showed that growth and quality of sugar beet were not affected by Na application, and ultimately there was no decrease in white‐sugar yield. Moreover, the soils with more K‐fixing capacity were more suitable for K substitution by Na. It is concluded that Na can substitute K in sugar beet nutrition to a high degree and soils with high K‐fixing capacity have more potential for this substitution.     

Effects of organic matter application on microbial biomass and available nutrients in various types of paddy soils

Abstract

The effect of the addition of bromacil (pesticide) or/and a sewage sludge on the urease, phosphatase and dehydrogenase activities of soil was studied. Urease and phosphatase activities increased initially with the addition of bromacil. This effect disappeared after 28 d of soil incubation. The increase in the urease and phosphatase activities caused by the addition of sewage sludge was more pronounced than that of bromacil. The combined addition of sewage sludge and bromacil also led to an increase in the activity of both hydrolases. Dehydrogenase activity was affected negatively by the addition of bromacil and positively by the sewage sludge addition. When sewage sludge and bromacil were added simultaneously, dehydrogenase activity was higher than when sewage sludge alone was added.     

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.     

Effects of microbial inoculants on phosphorus and potassium availability,bacterial community composition,and chili pepper growth in a calcareous soil: a greenhouse study

Purpose

Phosphorus (P) and potassium (K) are two important essential nutrient elements for plant growth and development but their availability is often limited in calcareous soils. The objective of this study was to determine the effects of applying microbial inoculants (MI, containing effective strains of Bacillus megaterium and Bacillus mucilaginous) on the availability of P and K, plant growth, and the bacterial community in calcareous soil.

Materials and methods

A greenhouse experiment was conducted to explore the effects of the addition of MI (control: without MI addition; treatment: with MI addition at the rate of 60 L ha^?1) on the concentrations of P and K in soil and plant, soil bacterial community diversity and composition, and chili pepper (Capsicum annuum L.) growth.

Results and discussion

The results showed that MI inoculation significantly increased the fruit yields by 28.5% (p?<?0.01), available P and K in the rhizosphere soil by 32.1% and 28.1% (p?<?0.05), and P and K accumulation in the whole plants by 40.9% and 40.2%, respectively (p?<?0.05). Moreover, high-throughput sequencing revealed that Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, and Gemmatimonadetes were the dominant phyla of soil bacteria. MI application did not significantly impact the diversity and composition of soil bacterial communities, but increased relative abundances of bacterial genera Flavobacterium responsible for promoting root development across growing stages (p?<?0.05), and changed the soil bacterial community structure associated closely with soil properties of available P, K, and pH in soil.

Conclusions

The application of MI improved the bioavailability of P and K and plant growth due to its impact on the soil bacterial community structure.

     

Effect of sewage sludge application to amelio‐rate iron deficiency of grain sorghum

Abstract

Recent research has indicated that land application of municipal sewage sludge to calcareous soils can be used to ameliorate iron (Fe) deficiency of grain sorghum [Sorghum bicolor (L.) Monech]. A greenhouse study was conducted to determine the response of grain sorghum grown on three different soils to application of sewage sludge. Sludge applied at rates of 0, 7.5, 15.0, and 25.0 g/kg soil did not completely ameliorate grain sorghum Fe deficiency. When FeEDDHA was soil applied, sewage sludge application significantly increased plant growth due to increases in soil phosphorus (P) availability. Application of sewage sludge at rates greater than 7.5 g/kg reduced dry matter production of grain sorghum in the FeEDDHA amended Orelia SC soil, the soil with the lowest total neutralizing potential. The decreases yield was possibly due to toxic levels of soil and plant copper (Cu) and zinc (Zn), and increased soil salinity.     

盐土改良肥对草甸盐土的改良效果和对甜菜经济效益的影响

[目的]研究甘肃省河西走廊盐土改良肥对草甸盐土改良效果和甜菜经济效益的影响,为该区甜菜产业可持续发展提供技术支撑。[方法]选择甘肃省酒泉市肃州区铧尖乡草甸盐土,采用田间试验方法开展研究。[结果]影响甜菜产量的原料依次是:盐土调控剂甜菜专用肥有机碳肥。盐土改良肥配方组合为:甜菜专用肥0.0586:盐土调控剂0.0623:有机碳肥0.8791。盐土改良肥施用量与草甸盐土孔隙度、团聚体、持水量、有机质、速效氮磷钾、甜菜农艺性状、经济性状和产量之间呈显著的正相关关系,与容重、pH值、全盐含量之间呈显著的负相关关系。经回归统计分析,盐土改良肥经济效益最佳施用量为39.64t/hm2,甜菜块根理论产量为96.68t/hm2。施用盐土改良肥与传统的抗盐丰盐碱土改良剂和沃丰隆盐碱土改良剂比较,施肥利润分别增加414.48,946.10%元/hm2。[结论]施用盐土改良肥,可以改善草甸盐土理化性质,提高酶活性和甜菜产量。     

Changes in Thermophilic Bacteria Population and Diversity during Composting of Coal Fly Ash and Sewage Sludge

The thermophilic bacteria in compost made from coal flyash-amended sewage sludge were isolated and identified using theBiolog system to investigate the effect of coal fly ash on thethermophilic decomposition of sewage sludge during composting. Atotal of 8 species of Bacillus were isolated from thecompost and Bacillus brevis was the dominant speciesduring the entire composting process. The present resultsdemonstrate that the Biolog system is a fast and simple methodfor identifying bacterial species in compost, provided thatoptimum conditions could be achieved for the Bacillusculture. Adding coal fly ash as an amendment did not change thedominant bacteria species during composting, but decreased thepopulation and diversity of thermophilic bacteria species due tothe high alkalinity and salinity. Fewer thermophilic bacteriawere detected in ash-amended sewage sludge compost than insludge compost. There was also reduced metabolic activityobserved in the ash-amended sludge compost from the data ofCO₂ evolution and weight loss. Although ash amendmentdemonstrated a negative effect on the population and diversityduring thermophilic phase, it did not cause any significanteffect on compost maturity.     

Reaktion der Zuckerrübe (Beta vulgaris var. altissima) auf die Kaliumdüngung – ein 20‐jähriger Feldversuch

Response of sugar beet ( Beta vulgaris var. altissima ) to potassium fertilization—a 20‐year field experiment A long‐term fertilizer experiment was performed to develop a K fertilization strategy to achieve highest extractable sugar yields (BZE). Sugar beet was grown in a crop rotation with wheat and barley on an alluvial soil (clayic silt) in Lower Saxony with annual recycling of straw and beet tops, respectively. Since 1983, the treatments were as follows: 1) K fertilization with 0, 29, 58, 87,174, and 524 kg K ha^–1 a^–1 corresponding to 0, 0.5, 1, 1.5, 3, and 9 times the average annual K removal by the marketable products of the crop rotation—since 1995, the two highest treatments (3 and 9 times the removal) received only 174 kg ha^–1 every third year; 2) K fertilization according to the average K removal, given each year (58 kg K ha^–1) or every third year (174 kg ha^–1) to sugar beet; 3) annual K fertilization of 87 kg K ha^–1 (1.5 times the removal) applied in autumn or spring, respectively; 4) annual K fertilization, applied as mineral fertilizer or as organic material (recycling of grain and straw or root and leaves); 5) application of 29 kg NaCl ha^–1 to sugar beet supplemental to a yearly application of 58 kg K ha^–1. Both root yield and soil concentration of lactate‐soluble K increased with K fertilization up to the highest K treatment. The extractable sugar content reached a maximum at a yearly application of 174 kg K ha^–1. Averaged over years, the extractable sugar yield (BZE) increased up to the highest K application. The time of K application (autumn or spring) and the source of K (mineral fertilizer or organic material) had no effect on BZE. An additional fertilization with NaCl increased BZE only slightly in single years. Low‐grade muriate of potash containing 33% K and 3% Na can thus be used. The economically optimal K‐fertilization rate was 174 kg K ha^–1 given once in the crop rotation to sugar beet. A soil K concentration of about 110 mg (kg soil)^–1 (lactate‐extractable K) is sufficient in this soil to achieve a high BZE.     

Isolation and identification of boron-accumulating bacteria from contaminated soils and active sludge

Abstract

High levels of boron are toxic to living organisms. The removal of boron from contaminated water is an important way of dealing with this environmental problem. For this purpose, we screened for bacteria that can absorb high levels of toxic boron from the environment. A range of boron-accumulating bacteria was isolated from boron-contaminated soil in Turkey, from uncontaminated soil in Tokyo, Japan, and from active sludge in Tokyo by semi-quantifying the boron accumulation of each single-cultured bacterium. Intracellular boron concentrations ranged from 0.3 to 1.36?nmol?g^?1 dry weight. Nineteen isolates identified by 16S rRNA gene sequence analysis were most closely related to the genera Bacillus, Variovorax, Pseudomonas, Shewanella, Mycobacterium and Rhodococcus. To our knowledge, this is the first study examining a wide range of bacterial strains in terms of boron accumulation.     

Evaluation of suppression of rhizomania disease by earthworm (Lumbricus terrestris L.) and its effects on soil microbial activity in different sugar beet cultivars

The ability of earthworm Lumbricus terrestris L. to suppress the multiplication of Beet necrotic yellow vein virus (BNYVV) transmitted by Polymyxa betae and its effects on soil microbial activity were investigated under controlled conditions. BNYVV-infested and a combination of earthworm with BNYVV-infested soil were compared to non-infested soils for their effects on plant and root weights and virus content of two different sugar beet cultivars by using partially resistant (cv. Leila) and susceptible (cv. Arosa) cultivars to the rhizomania disease. Soil testing with sugar beet baiting plants followed by enzyme-linked immunosorbent assay (ELISA) was used to diagnose virus. The results of the statistical analyses showed that total fresh plant and root weights were negatively correlated with BNYVV infection. Addition of L. terrestris significantly enhanced plant and root weights. The earthworm-added soils had higher microbial activity such as basal soil respiration and dehydrogenase activity. The presence of earthworms in the soil did not statistically suppress BNYVV infection (p < 0.05). Sugar beet production may be enhanced by using resistant cultivars with adding L. terrestris into soil where rhizomania is present.     

Determination of mobile heavy metal fraction in soil: Results of a pot experiment with sewage sludge

Abstract

The development of a method using a chelating resin to assess heavy metal mobility in soil and the first results obtained from a pot experiment with sewage sludge additions were studied. The resin was Chelex 100 with the calcium (Ca)‐form of the resin proving to be best suited for the extraction. The efficiency of recovery of the heavy metals from an aqueous solution ranged from 81.2% for cadmium (Cd) to 102% for copper (Cu) within 24 hours. For heavy metal extractions from a soil sample, a 96 hour extraction period was found to be optimum. The extracted heavy metal portion was comparable with the results obtained with an ammonium acetate (NH₄AOc) extraction. Total heavy metal contents in the substrate of the pot experiment did not show a significant influence due to the sewage sludge treatments, although considerable amounts of heavy metals were added by the sewage sludge. This effect can be both due to the incomplete recovery of heavy metals by an aqua regia extraction and leaching losses of these elements from the pots. Rape (Raphanus sativus L.) plants did not have any heavy metal contents which might indicate a high availability in soil, with the Cd and Cr contents in the rape biomass being partly lower in the sewage sludge‐treated pots than in the control plants; however, zinc (Zn) uptake slightly increased with increasing sewage sludge treatments. The Chelex 100 extraction procedure was correlated with Cd plant uptake, while the NH₄AOc extraction procedure was better related to the Zn uptake by rape plants.     

Effect of sewage sludge and sugarcane bagasse biochar on soil properties and sugar beet production

Recently, biochar has shown to be an alternative to waste disposal and a source of nutrients, acting as a soil amendment. The effects of two types of biochar on soil properties and sugar beet production as well as potential for carbon (C) sequestration were evaluated:biochar produced from sewage sludge (SB) and biochar produced from a 1:1 mixture of sewage sludge and sugarcane bagasse (MB). A greenhouse pot experiment was conducted using a sandy loam soil from the Brazilian savanna under treatments of MB applications at 2.5%, 5.0%, 7.5%, and 10.0%, SB application at 5.0%, and a conventional fertilization (CF) using lime and mineral fertilizers, with no fertilization as a control. After incubation for 45 d, seedlings were transplanted into each pot and cultivated for 55 d. Biochar characterization showed that pyrolysis reduced the biomass volume drastically, but concentrated the trace elements per unit of biochar weight. The MB treatments increased soil total C (by 27.8%) and pH (by 0.6), reduced the concentrations of nutrients, except for potassium (K), and chromium (Cr), and did not significantly alter lead (Pb) and cadmium (Cd) concentrations. Results of stable isotopes showed that all biochar treatments increased the total soil C stock and stability, suggesting a potential for application in C sequestration, and improved overall soil fertility. However, the biochar treatments also increased the concentrations of trace elements in the soil and plants. The sugar beet yields at 10.0% MB and 5.0% SB corresponded to 55% and 29% of the yield obtained in the CF treatment, respectively. These results may be due to biochar nutrients not being bioavailable when required by plants or to biochar nutrient adsorption.