Non-available Forms Research Articles

Immobilization of Heavy Metals in Biochar Derived from Biosolids: Effect of Temperature and Carrier Gas

Slow pyrolysis was carried out in biosolids under three different temperatures (400, 500 and 600 °C) and two different carrier gases (CO2 and N2) on a fluidized bed reactor. The total concentration, chemical fractionation, and plant availability of the heavy metals in biochar were assessed by standard methods. The total concentration of Fe, Zn, Cu, Mn, Cr, Ni and Pb increased with the conversion of biosolids to biochar and with increasing pyrolysis temperature. The community’s Bureau of Reference (BCR) sequential extraction identified the migration of metals from toxic and bioavailable to potentially stable available or non-available forms at higher pyrolysis temperatures. Diethylenetriamine penta-acetic acid (DTPA)-extractable metals (Cu, Zn, Cd, Cu, Fe and Pb) were significantly lower in biochar compared to biosolids. By replacing N2 with CO2, the total metal concentration of heavy metals was significantly different for Mn, Ni, Cd, Pb and As. There were larger amounts of metals in the residual and oxidizable fractions compared to when N2 was used as a carrier gas. Consequently, the biochar produced at higher temperatures (500 and 600 °C) in the N2 environment exhibited lower potential ecological risks than in CO2 environments (69.94 and 52.16, respectively, compared to values from 75.95 to 151.38 for biochars prepared in N2). Overall, the results suggest that the higher temperature biochar can support obtaining environmentally safe biochar and can be effective in attenuating the ecological risks of biosolids.

Global perspective of phosphate solubilizing microbes and phosphatase for improvement of soil, food and human health

Soil microbial flora has a pivotal role in the phyto-availability of phosphorus and other necessary minerals and nutrients. The primary class of Rhizobacteria involved in the solubilization of phosphate from non-available forms to available forms is Phosphate solubilizing bacteria (PSB). The application of Phosphate solubilizing bacteria increased phosphorus availability, which is one of the major factors responsible for the increase in the yield of crops. The phosphorus content is higher in the seeds than in the other plant parts; it helps plants in disease resistance and stress management such as winter rigors and improves the quality of fruits, vegetables, and cereal crops. Application of PSB as the biofertilizers positively affects the secretion of siderophores, nitrogen fixation, Indole acetic acid (IAA), 1-aminocylopropane-1-carboxylate (ACC) deaminase, chitinase, and protease. PSB can solubilize useful phosphate from rock phosphate and phosphate present in the combined state in lower to higher pH range (4 to 10), lower to a higher temperature (20 to 40 0C), and even in the higher salt ranges (0 to 7.5 % NaCl). Microbes help in the assimilation of phosphates and hydrocarbons by the secretions of different phosphatases such as monoesterase, diesterases, C-P lyase, and phosphatase and phytases. Using chemical P fertilizer in sustainable agricultural methods needs to be reduced. For this purpose, alternative and inexpensive technology are required so that plants can be provided with a sufficient amount of P. Phosphate solubilizing microbes can be an excellent option to replace chemical P fertilizers for improved agricultural production and soil fertility. The fertility of farm fields can be improved by using PSB as the bio-fertilizer and it will enhance the nutritional quality of plants and plant products which are directly or indirectly taken as food. Applying these microbes to soil/seeds makes good quality fruits and can help to fulfill the nutritional hunger of the world.

Induced changes of pyrolysis temperature on the physicochemical traits of sewage sludge and on the potential ecological risks

Biochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions. This study evaluates the induced effects of pyrolysis temperature on the physicochemical characteristics of sewage sludge (SS) biochar produced at 350 (SSB350), 450 (SSB450) and 600 (SSB600), based on the metal enrichment index, metal mobility index (MMI), and potential ecological risk index (PERI) of Cd, Cu, Pb, and Zn. Increased pyrolysis temperature reduced the biochar concentration of elements that are lost as volatile compounds (C, N, H, O, and S), while the concentration of stable aromatic carbon, ash, alkalinity, some macro (Ca, Mg, P2O5, and K2O) and micronutrients (Cu and Zn), and toxic elements such as Pb and Cd increased. Increasing the pyrolysis temperature is also important in the transformation of metals from toxic and available forms into more stable potentially available and non-available forms. Based on the individual potential ecological risk index, Cd in the SS and SSB450 were in the moderate and considerable contamination ranges, respectively. For all pyrolysis temperature biochar Cd was the highest metal contributor to the PERI. Despite this, the potential ecological risk index of the SS and SSBs was graded as low.

Alteration in root morphological and physiological traits of two maize cultivars in response to phosphorus deficiency

Phosphorus-efficient cultivars have an increased capacity to exploit the soil and/or to convert non-available forms of phosphorus (P) into available ones for root uptake. Preliminary field observations showed that nitrogen (N) inefficient maize cultivar ZD958 exhibited high tolerance to low P soil in the shoot performance than N-efficient cultivar XY335. However, it remains unknown whether ZD958 had a higher potential in acquiring sparsely soil P than XY335. In this study, three separate glasshouse experiments were carried out to explore the capacity of both cultivars in accessing soil P. The two cultivars grew for 40 days to evaluate functional root traits in soil columns (Expt.1) and for 20 days to examine root hair length in soil filled rhizoboxes (Expt.3) in a calcareous loamy soil amended with P (high P) or background soil (low P). The third experiment (Expt.2) cultured hydroponically the both cultivars for 15 days to determine the correlation between P uptake rate and P supply intensity. Results from Expt.1 showed that shoot P content of ZD958 was significantly higher than XY335. Higher capacity of the ZD958 to access soil P were not correlated with biomass allocation and root morphological traits, since ZD958 had a lower root mass ratio at two P supplies and a lower degree of total root length and root surface area at high P than XY335. Results from Expt.3 indicated that average root hair length was not associated with the improved P uptake by ZD958, since their root hair length remained the same under low P or high P supply. Therefore, changes in root morphological traits did not explain the improved P acquisition by ZD958 roots. Rhizosphere pH, malic acid concentration and acid phosphatase activity were similar between the two cultivars, while citric acid concentration was obviously higher in ZD958 than that in XY335 (Expt.1). These results suggested that the higher capacity of P acquisition by ZD958 might be attributed to the release more citric acids from roots. P uptake rate of ZD958 was significantly higher than XY335 with the solution P ranging from 12.5 to 250 μM (Expt. 2), indicating that the changes in P uptake rate largely explained the greater P acquisition by ZD958 than XY335. Taken together, ZD958 was identified as a P-efficient cultivar, with a better adaptation to low P environment by altering the exudation of citric acid and P uptake rate. The research findings highlight the importance of plant strategies in altering the root morphological and physiological traits for a better adaptation to the low P environment, and enhance our understanding of physiological mechanisms of plant P acquisition.

Correlation between High Carbohydrate Foods with Glycemic Index

High carbohydrate food has been perceived as a food with high glycemic index (GI). Meanwhile, the risks of diabetes are frequently associated with the GI carbohydrate based foods. Therefore, a comprehensive study based on the literature review regarding the relationship between high-carbohydrate food and the glycemic index needs to be conducted. High-carbohydrate foods can be grouped into the available carbohydrates type and non-available carbohydrates type. Food with available carbohydrates such as glucose, disaccharide, digestible oligosaccharides, and starch have positive correlation with the GI. The non-available forms of carbohydrates are hardly digested by the body, so they usually have low GI. The non-available carbohydrates foods are fructooligosaccharide (FOS) and galactooligosaccharide (GOS), raffinose, stachyose, and verbascose. High-carbohydrate foods can have low GI value due to complex carbohydrates or resistant starches. The type of carbohydrate can be turned into non-available due to chemical modification, processing, or interacting with other components. This information is necessary because recently, people have high awareness in choosing carbohydrate food. Not only the amount consumed, but also its carbohydrate content, types of carbohydrates, and how they are processed are important to be observed.

Effects of Soil Amendment on Potassium Fractions of Southwestern Nigerian Soils

ABSTRACTIncubation and pot experiments were done to determine the effect of poultry manure on soil potassium (K) fractions and soybean K concentration. Representative soils from southwestern Nigeria were used. The treatments applied consisted of five rates of manure (0, 2.5, 5.0, 7.5, and 10 t ha−1). The experiments were arranged in a completely randomized design with three replicates. Soybean (TGx 1448-2E) was grown for three consecutive cycles (7 weeks each), analyzed for K. Order of abundance of soil fractions in the soil was as follows: Total K > non-exchangeable K > mineral K > > 1 N (hydrochloric acid) HCl K > 1 N (nitric acid) HNO3K > available K > exchangeable K > water-soluble K. Most of the K is in nonavailable forms; and the exchangeable forms are less than non-exchangeable forms. Organic manure increased soil K fractions, but these increases could not be sustained with cycles of soybean growth due to crop uptake.

PAHs and potentially toxic elements in the fly ash and bed ash of biomass fired power plants

PAHs and heavy metal chemical fractions were determined in biomass ashes from four power plants that fired coconut, chicken, and wood wastes. All these ashes were alkaline (pH8.7–12.7). High unburned carbon in the fly ashes (8.3 to 16.9%) indicates incomplete combustion. The major chemical phases were SiO2 – CaO – K2O – MgO followed by Fe2O3>Al2O3>SO3>MnO, with an exception of higher P2O5 (5 – 8.8%) in chicken litter ash. SEM showed that the FAs have more angular particles, whereas BAs have fused and glassy particles. The contents of B (15– 205mg/kg), Cu (236 – 481mg/kg), Cd (13 – 23.2mg/kg), Ni (50 – 186mg/kg), and Zn (10 – 400mg/kg) were relatively higher in the ashes. Most of these elements (except B) were associated with metal oxide and silicates. B is the most mobile element and >75 % of B is present in the available forms. The total PAH content was comparatively lower (0.19 – 12.3mg/kg), except for wood ash (PAH 193mg/kg). These ashes have significant amount of plant nutrients and most of the potentially toxic elements are in non-available forms which supports their suitability for soil amendment.

Copper Dynamics in a Typic Hapludalf Under Rice-Wheat Cropping System After Twelve Years of Annual Lantana Camara L. Residue Incorporation

Long term effects of lantana (Lantana camera L.) residue and fertilizer application were studied on copper (Cu) fractions in a Typic Hapludalf under rice-wheat cropping at Palampur, India (32°6′N, 76°3′E). A partitioning of soil Cu revealed residual Cu and organically bound Cu as the most dominant fractions followed by Cu occluded by free oxides, specifically exchangeable Cu and soil solution and exchangeable Cu. Continuous incorporation of lantana after 12 years resulted in redistribution of Cu from non-available forms to readily and potentially available forms in soil. All the Cu fractions were positively interrelated amongst themselves and with grain yield and Cu uptake in rice and wheat crops. Specifically exchangeable Cu followed by organically bound Cu were the most important Cu fraction contributing towards grain yield and Cu uptake in rice and wheat crops.

Phosphate fertilization and phosphorus forms in an Oxisol under no-till

Under no-till phosphorus (P) accumulates in a few centimeters of the topsoil layer. Plant residues left on the soil surface release P and organic acids, which may improve P availability and fertilizer efficiency, including both soluble (such as triple super phosphate) and less soluble sources (such as reactive natural phosphates). In this study, soybean response to P fertilizer and P forms in the top 40 cm of an Oxisol were evaluated after surface application of different phosphates in a 5-year-old no-till system. Treatments consisted of 0 or 80 kg ha-1 of total P2O5 applied on the soil surface, both as natural reactive phosphate (NRP) or triple super phosphate (TSP). In addition, 80 kg ha-1 of P2O5 were applied to subplots, in furrows below and beside the soybean (Glycine max L.) seeds, in different combinations of NRP and TSP. Soil samples were taken before and after the soybean growth, down to 0.40 m and soil phosphorus was chemically fractionated. The responses to NRP were similar to TSP, with an increase in P reserves at greater depths, even in non-available forms, such as P-occluded. After the soybean harvest, P-occluded levels were lower at the surface layer, but an increase was observed in the soluble, organic and total P down to 40 cm. An improved P distribution in soil depth, especially regarding the soluble and organic forms, resulted in higher soybean yields, even when the phosphates were applied to the soil surface.

Eisenia fetida avoidance behavior as a tool for assessing the efficiency of remediation of Pb, Zn and Cd polluted soil

Remediation by means of soil leaching with ethylenediaminetetraacetic acid (EDTA) is capable of extracting the most labile soil fractions, leaving the residual metals in biologically non-available forms. We evaluated the feasibility of the standardized earthworm ( Eisenia fetida) avoidance test for assessing the efficiency of soil remediation of Pb, Zn and Cd polluted soil. Chemical extraction tests (six-step sequential extraction, toxicity characteristic leaching procedure, physiologically based extraction test, diethylenediaminepentaacetic acid extraction) indicated that the mobility, oral bioaccessibility and phytoavailability of Pb, Zn and Cd were consistently reduced. However, the avoidance test showed no significant avoidance of polluted soil in favor of that which had been remediated. Pb, Zn and Cd accumulation in E. fetida mirrored the decreasing pattern of metal potential bioavailability gained by leaching the soil with increasing EDTA concentrations. The calculated bioaccumulation factors indicated the possibility of underestimating the metal bioavailability in soil using chemical extraction tests.

Micronutrient fractionation and plant availability in bauxite-processing residue sand

Bauxite-processing residue must be disposed of in specifically designed facilities for long-term management. Consideration of alkalinity, salinity, sodium content, and poor nutritional status is essential for successful rehabilitation of residue disposal areas (RDA). The aim of this study was to examine the availability and distribution of the micronutrients, B, Cu, Fe, Mn, and Zn, in (i) fresh bauxite-processing residue sand (particle size >150 μm) with and without gypsum amendment, and (ii) aged residue sand from a 4-year-old rehabilitated RDA that had received past gypsum and fertiliser addition. Samples of fresh residue sand from India and Australia exhibited high alkalinity, high salinity, and sodicity. Gypsum addition significantly lowered pH, soluble Na, and alkalinity. Aged residue sand had low levels of all micronutrients, with low extractability for Zn and Mn followed by B, Cu, and Fe. Fractionation showed that 30–78% of Zn and Mn and 40–60% of B existed in non-available (residual) forms. The next most dominant fractions were the Fe and Mn oxide-bound and carbonate-bound fractions. Plant-available fractions (i.e. exchangeable and organically bound) contributed <1% of the total concentration. Total concentration was found to be a reliable indicator for Zn, Cu, and B extractability but not for DTPA-extractable forms of Fe and Mn. Leaf analysis of vegetation grown on aged residue sand indicated deficiencies of Mn and B. Results demonstrated that bauxite-processing residue sand contained very low levels of B, Mn, and Zn and these concentrations may be limiting to plant growth. Distribution of micronutrients among chemical pools was significantly influenced by pH, organic carbon, exchangeable Na, and alkalinity of residue. Nutrient management strategies that account for the characteristics of residue sand need to be developed for residue rehabilitation. Importantly, strategies to limit the conversion of nutrients to non-available forms are required to minimise micronutrient disorders.

Studies on phosphorus solubilizing activity of a strain of phosphobacteria isolated from chestnut type soil in China

A phosphorus solubilizing bacterium, designated phosphobacterium 9320-SD, was isolated from field soil in Tianjin, China. Cells of the phosphobacterium 9320-SD were gram-positive, rod shaped, and produced spores. When 9320-SD was inoculated into MPMLM, amended with powdered (insoluble) mineral phosphate as the single P source, and incubated at 30 °C, the release of soluble phosphorus increased with increasing amounts of added phosphates over the range of 0.12–4% (w/v). The maximal available phosphorus reached 12.01 mmol P/L after 7 days incubation. Furthermore, there was a direct positive correlation ( r = 0.9330) between the level of soluble phosphorus release and the concentration of viable bacteria. SEM study of the phosphate powder retrieved from the phosphobacterium 9320-SD cultured medium revealed the actual dissolution of phosphate from the mineral surface. Phosphobacterium 9320-SD had significant effect ( p < 0.05) on winter wheat total P and plant biomass under both pot and field conditions, although no obvious difference in plant height was found compared to the control. Taken together, these results demonstrate that phosphobacterium 9320-SD has the ability to convert non-available forms of phosphorus into plant-available forms, and therefore holds great potential for development as a biofertilizer to enhance soil fertility and promote plant growth.

Seasonal patterns of root-surface phosphatase activities in a Mediterranean shrubland. Responses to experimental warming and drought

Mediterranean ecosystems are water limited and the current general circulation Models (GCM) and ecophysiological models forecast a warming and a further increase of drought in the next decades. A stronger water stress can decrease the capacity for nutrient absorption by plants. We conducted a field experiment to simulate forecasted drought and warming in a Mediterranean calcareous shrubland to assess the performance of root-surface phosphatase activities of the dominant shrub Globularia alypum. These enzyme activities were higher in autumn and spring, when the climate conditions were optimal for plant activity, than in summer or winter, when there was either lack of water or cold temperatures. A decrease in soil moisture in drought plots decreased root-surface phosphatase activity (29% in summer and 25% in autumn). The decrease in root-surface phosphatase activity in drought plots coincided with a decrease in P leaf concentrations and P accumulation in aboveground biomass and loss of photosynthetic capacity of some dominant shrub species of this ecosystem, and with a tendency to increase total soil-P. These results suggest that the expected drier conditions in this Mediterranean shrubland in the next decades will slow down the P uptake by plants, thereby, diminishing the P contents in biomass and increasing total P contents in soil in non-available forms and that this can be, in part, attributable to a result of the decrease in root-surface phosphatase activity.

Fate of Nitrogen‐15 in a Long‐Term Nitrogen Rate Study: I. Interactions with Soil Nitrogen

A better understanding of how N management practices affect transformations and movement of fertilizer N may lead to more efficient N management. The objectives of this work were to determine how long‐term N fertilizer history in a continuous corn (Zea mays L.) production system affects (i) movement of fertilizer N through the soil profile and (ii) cycling of fertilizer N between available and nonavailable soil forms. Nitrogen‐15‐labeled ammonium nitrate (15NH415NO3) was applied at 0, 67, 134, 201, or 268 kg N ha−1 to subplots of long‐term N rate plots. Twenty to 55% of labeled N was converted into either organic or clay‐fixed forms during the first growing season, with the percentage decreasing with increasing N application rate. Significantly more N was released from nonavailable forms in plots where the historical N application rate had exceeded the long‐term optimum (186 kg ha−1) than in plots that received lower rates. Little fertilizer‐derived N leached from the profile during the first growing season, but losses did occur during the off‐season and subsequent growing season when N application rate was higher than the optimum. It was concluded that a history of excessive N application may decrease response of subsequent crops to fertilizer N due to greater release from nonavailable N forms, most likely as a result of increased mineralization of crop residues and recently formed soil organic N.

Co phytoavailability for tomato in amended calcareous soils

A plot study was conducted to assess changes in Co phytoavailability for a tomato cultivar grown on an agricultural soil (a Calcic Petrocalcid) amended with sewage sludge, under controlled conditions in South-eastern Spain. The experiment consisted of three main treatment blocks: (A) without organic fertilisation, (B) with addition of 60 t ha −1 and (C) 120 t ha −1 of sewage sludge. For each block (A, B, and C), four levels of Co (0, 50, 100 and 200 mg kg −1) were added, as CoCl 2. Diethylenetriaminepentaacetic acid, DTPA (0.005 M plus triethanolamine), ammonium acetate (1 N at pH 7), and water extractable fractions of the soils were analysed for all the plots. The time dependent Co accumulation in different parts (roots, stems, leaves, and fruits) of the tomato plants was studied. Soil Co seemed to be mainly in non-available forms, according to the low concentrations found in the water and ammonium acetate extracts, compared to DTPA. The gradient of Co accumulation in tomato plants was root > leaf > stem + branches > fruit, with a concentration in the edible parts ranging between 4 and 25 mg kg −1. The organic amendment enhanced the plant extraction of Co, this effect being more significant with time. Plant extraction efficiency decreased with increasing Co concentration in the soils. Co in fruit showed the best correlation with all the Co extraction pools in the soil.

Distribution of heavy metals among different bonding forms in tropical peat soils

Abstract The objective of this study is to analyze the characteristics of the macro- and micro-nutrient status of tropical peat soils under natural swamp forest and their changes after reclamation. We sampled peat soils from the coastal swamps in southern Thailand and southern Peninsular Malaysia. These soils were at varying stages of reclamation. Soil Fe, Mn, Zn, and Cu were sequentially divided into water soluble, Ca exchangeable, free-oxide-associated, weakly complexed, strongly complexed, carbonate-associated, and sulfide-associated extractable forms. Peat soils sampled in Malaysia were classified into Oligotrophic peat soils due to their low N, P, K, and Ca contents. The Ca, Mg, K, and Na contents did not change appreciably with the soil depth, though the Mn, Zn, and Cu contents decreased with the soil depth down to 30 cm and subsequently the decrease was negligible. Based on the analysis of the distribution of the metal forms, most of Cu and Fe occurred in strongly chelated and non-extractable forms. Average contents of water soluble and Ca exchangeable forms (intensity factor) of Mn, Zn, and Cu were 12, 4, and < 0.1 mg kg-1 of soils, respectively. In the case of fertilized soil (experimental field of MARDI), heavy metal contents of the surface soil were about 3 to 15 times as high as those of the subsoil. Most of the increment occurred in the weakly chelated, strongly chelated, or non-extractable forms, because the pH of the surface soil was higher than that of the subsoil. As the chelating effect of humic substances is likely to be pronounced for a high soil pH, heavy metals applied in fertilizers were changed into non-available forms. Adsorption strength of humic substances in peat for metal ions was as follows: Cu > Fe > Zn > Mn.

Trace metals in Valencia lake (Venezuela) sediments

An exploratory study of the trace metals Cd, Cu, Mn, Ni, Pb, and Zn in sediments of lake Valencia (Venezuela), South America, 10° 10′N, 68°68′W, gave the following results: (A) Total amounts of Cu, Ni, Pb, and Zn were within the normal range reported by the literature. (B) No consistent pattern of variation with depth was found. A and B could be taken as lack of evidence for contamination by Cu, Ni, Pb, and Zn of the studied sediments. Absence of Cu, Ni, Pb, and Zn pollution after more than 40 yr of anthropogenic discharges on this lake, was attributed mainly to the exploratory nature (limited sampling) of this work, together with some possible dilution effects due to the high CaCO3 content of these lake sediments. (C) Manganese was above normal values in most samples, but in absence of known anthropogenic sources of this metal, the results found could not be clearly ascribed to metal pollution. (D) Cadmium showed enrichment factors of 10 to 30 indicating pollution of the lake sediments by this metal (probably by urban effluents, runoff, and electroplating industries). (E) The proportion of exchangeable metals was nil in most cases. Exceptions (Ni and Mn) had very low exchangeable fractions (<1.22%). (F) The most abundant fraction (except for Mn) was the residual one (59.7–97.8% of total metal). Other fractions (carbonates, oxides, and organic) showed intermediate values. The general pattern was that the bulk of trace metals studied were present in non-mobile, slightly or non-reactive, poorly or non-available forms.

Some effects of cultivation and waterlogging on the availability of phosphorus in pasture soils

Compared with growth on undisturbed soil, uniform mixing of the surface 4 in. of pasture soils caused a decrease in the yield of subterranean clover grown in pot culture. This was shown to be due to lowered availability of the soil phosphorus and was probably brought about by sorption of the available phosphorus, which had accumulated at the soil surface, by the unsaturated subsurface soil. Short periods of waterlogging (1–2 days) also brought about lowered availability of soil phosphorus. This occurred both with undisturbed soil cores and with mixed soils, but was much more severe when the soil was mixed. The effect appeared to be due to the conversion of phosphate to non-available forms during the short period of anaerobic conditions. The phosphate sorption capacity of the soil was increased by the waterlogging treatment but decreased to its original value when the soil was air-dried.