Effect of soil amendments on fractionation of Selenium‐enriched soil

Abstract

This study was to determine the effect of soil amendments on the fractionation of selenium (Se) using incubation experiments under simulated upland and flooded conditions. The treatments were as follows: 1) control [soil + sodium selenite (Na₂SeO₃) (1 mg Se kg^‐1)]; 2) control + calcium carbonate (CaCO₃) (5 g kg^‐1); 3) control + alfalfa (40 g kg^‐1); and 4) control + CaCO₃ (5 g kg^‐1) + alfalfa (40 g kg^‐1). After a 90‐day incubation, soil was sampled and fractionated into five fractions: 1) potassium sulfate (K₂SO₄)‐soluble fraction (available to plants); 2) potassium dihydrogen phosphate (KH₂PO₄)‐exchangeable fraction (potentially available); 3) ammonium hydroxide (NH₃H₂O)‐soluble fraction (potentially available); 4) hydrochloric acid (HCl)‐extractable fraction (unavailable); and 5) residual fraction (unavailable). Compared with the control, CaCO₃ increased the K₂SO₄ fraction at the expense of the NH₃H₂O fraction. Alfalfa increased both the K₂SO₄ and residual fractions but reduced the KH₂PO₄ and NH₃H₂O fractions. The CaCO₃‐alfalfa treatment had a similar effect to the alfalfa treatment alone. The comparison between the upland and flooded conditions showed that the flooded condition generally increased the residual fraction and decreased the potentially‐available fractions. In general, CaCO₃ was a better amendment because it not only increased the available fraction but also maintained the potentially available fractions at a high level. The application of Na₂SeO₃ and use of appropriate soil amendments can improve Se availability in soil.     

Simultaneous determination of soil aluminum,ammonium‐ and nitrate‐nitrogen using 1 M potassium chloride extraction

Abstract

Determination of soil aluminum (Al), ammonium‐nitrogen (NH₄‐N), and nitrate‐nitrogen (NO₃‐N) is often needed from the same soil samples for lime and fertilizer recommendations, but Al has to be extracted and quantified separately from NH₄‐N and NO₃‐N according to present methods. The objective of this study was to develop a reliable method for simultaneous analyses of soil Al, NH₄‐N and NO₃‐N using a Flow Injection Autoanalyzer. Thirty‐five soil samples from different locations with wide ranges of extractable Al, NH₄‐N and NO₃‐N were selected for this study. Aluminum, NH₄‐N and NO₃‐N were extracted by both 1 M and 2 M potassium chloride (KCl), and quantified using a LACHAT Flow Injection Autoanalyzer simultaneously and separately. One molar KCl was found to be a suitable extractant for all three compounds when compared to 2 M KCl. The 1 M KCl extract proposed could aid in decreasing the costs associated with simultaneous NH₄‐N, NO₃‐N, and Al analyses. Results of those three compounds analyzed simultaneously were not statistically different from those analyzed separately in 1 M KCl solution. This new procedure of simultaneous determination of NH₄‐N, NO₃‐N, and Al increases efficiency and reduces cost for soil test laboratories and laboratory users.     

Impact of soil fumigation practices on soil nematodes and microbial biomass

This study was designed to understand the impact of methyl bromide (MB) (CHaBr) and its alternatives on both free-living and root-knot nematodes in the soil. A randomized complete block experiment with six treatments and 4 replicates (each replicate in a separate greenhouse) was established in Qingzhou, Shandong Province, China. In addition to MB and untreated control (CK) treatments there were four alternative soil fumigation practices including MB virtually impermeable films (VIF), metam sodium (MS), MS VIF and soil solarization combined with selected biological control agents (SS BCA). Two tomato (Lycopersicum esculentum Mill.) cultivars, cv. Maofen-802 from the Xian Institute of Vegetable Science, China, and cv. AF179 Brillante from the Israeli Hazera Quality Seeds, were selected as test crops. The results indicated that Rhabditidae was the most dominant population with percentage abundance as high as 85% of the total number of identified free-living nematodes, followed by that of Cephalobidae. Methyl bromide and its alternatives except for the non-chemical SS BCA treatment controlled the target pest, root-knot nematodes. Also, the impact of the three chemical alternatives on free-living nematode number and functional group abundance was similar to the impact associated with a typical methyl bromide application. Chemical fumigation practices, especially that with MB, significantly reduced the number of nematodes in the soil and simultaneously significantly reduced the number of nematode genera thereby reducing nematode diversity. All the four soil chemical fumigation activities decreased soil microbial biomass and had an obvious initial impact on microorganism biomass. Furthermore, both plant-parasitic and fungivore nematodes were positively correlated with soil microbial biomass.     

Ecotoxicological assessment of nickel pollution of soil and water environments adjacent to soddy–podzolic soil

The indicators of functioning of soil microorganisms in soddy–podzolic soil contaminated with Ni compounds show different ranges of soil ecotoxicity. A halving of soil microorganisms' nitrogen-fixing activity has been shown in slightly acidic soddy–podzolic cultivated soil with a Ni concentration of 150 mg/kg and for noncultivated acidic soils with a Ni concentration 100 mg/kg. The reduction of denitrification activity in cultivated soil has been observed with a Ni concentration of 500 mg/kg, and in uncultivated soil it has been observed at a Ni dose of 100 mg/kg. The inhibition of soil respiration in slightly acidic soil occurred only at the highest dose of Ni, 1000 mg/kg, while in the acidic soil it took place at 300 mg/kg. Biotesting based on bacterial luminescence can be used for determination of soil pollution with heavy metals such as Ni, as well as for the assessment of the toxicity of aqueous environments in contact with contaminated soils.     

Effects of concentrated application of soil conditioners on soil–air permeability and absorption of nitrogen by young peach trees

ABSTRACT

To study the effects of concentrated application of two soil conditioners, two-year-old peach trees (Prunus persica L.‘Chunmei’) were selected to test the soil air permeability, ¹⁵N absorption and the growth of trees. The experiment comprised three treatments involved concentrated applying either polyacrylamide (treatment I) or Agri-SC (a proprietary soil conditioner, treatment II) at the bottom of each pit or neither of the two (treatment III). And then the whole pit was back-filled with soil. Neither digging a hole nor use of soil conditioners as the control (CK). The results showed that volumetric oxygen content in gases in 5–10 cm soil layer upon concentrated application layer was significantly higher in treatments I and II than that in CK. Soil volumetric water content upon concentrated application layer was higher in treatments I and II than that in CK. Compared with CK, no matter root activity, leaf area, leaf chlorophyll content, or leaf net photosynthesis rate in treatments I and II increased in August and October, which promoted the growth of new shoots and the stem. Compared with CK, the leaf superoxide dismutase activity increased 31.24%, 22.66% and 4.74%, Guaiacol peroxidase increased 21.88%, 13.25% and 3.39%, Catalase increased 11.80%, 7.92% and 1.24% respectively in treatments I, II and III in October. As a result, values of the total roots surface area, total root volume, number of root tips, dry matter accumulation, and organ nitrogen content were markedly higher in treatments I and II than that in CK. And the ¹⁵N utilization rate significantly increased 24.22% and 10.40% respectively in treatments I and II. The result suggested that concentrated application of soil conditioners formed a rhizosphere water storage and breathable layer that not only stores moisture but is also permeable to air. That, in turn, promotes plant growth, increases the nitrogen use efficiency.     

Have you checked for charcoal? Assessment of soil condition using soil organic carbon

Soil condition is commonly assessed by using soil organic carbon (SOC) as an indicator; however, a large proportion of the world's soils can contain charcoal, a biologically‐inert form of organic carbon. We investigated whether the presence of charcoal in soil could lead to an inaccurate assessment of soil condition when using SOC as an indicator. We sampled topsoil in a south‐east Australian catchment affected by severe fires in 2003. Samples (n = 100) were analysed for two SOC fractions: (i) total SOC (t‐SOC, loss on ignition), which included charcoal, and (ii) biologically‐active SOC (a‐SOC, persulphate‐oxidation), which did not contain charcoal. Using novel (boosted regression trees) and traditional (linear regression) modelling methods we compared the relative importance of abiotic (slope, aspect, elevation and soil texture) and biotic (land use and vegetation structure) factors as predictors of t‐SOC and a‐SOC concentration. A major difference between the two response variables was less relative importance of land use as a predictor when using t‐SOC as a response variable. Therefore, ignoring the presence of charcoal would have led to an under‐estimation of the effect of land‐use conversion on the biologically‐available SOC fraction. The presence of charcoal has important ramifications for routine assessments of soil condition given that (i) SOC is a commonly used indicator and charcoal and biologically‐active SOC differ in their effects on soil properties, (ii) fires historically occur on a large area of land, (iii) charcoal is a long‐lasting consequence of fires and (iv) charcoal can account for a large proportion of SOC and yet be unnoticed during sample preparation.     

Extraction of humic-β-glucosidase fractions from soil

Humic compounds with -glucosidase activity were extracted from soil using tetrasodium pyrophosphate as extracting solution. Mixture of soil samples with 0.01 M pyrophosphate in a ratio of 1:5 (w/v), adjustment to pH 7.0–7.3, extraction for 18 h with reciprocating agitation, and bacteriological filtration after centrifugation were the optimum conditions for extraction of the -glucosidase complexes. Otherwise, experimental conditions for extraction indicated that the concentration and pH of pyrophosphate were the factors with the most influence on enzymatic extraction yields. The results indicated that the -glucosidase was extracellular and associated with soil humates.     

The effects of biocidal treatments on metabolism in soil—IV. The decomposition of fumigated organisms in soil

To calculate the biomass from the size of the flush that follows fumigation, the fraction (k) of the killed biomass C that is respired as CO₂ must be known. This was measured for a range of organisms: two yeasts Succharomyces cerevisiae and Candida utilis), two fungi (Cylindrocarpon sp. and Penicillium chrysogenum), an actinomycete (Streptomyces clavuligerus), seven bacteria (Aerobacter aerogenes, Bacillus subtilis, Clostridium histolyticum, Escherichia coli, Microccus lysodeikticus, Pseudomonas fluorescens and Nitrosomonas europaea) and a soil invertebrate (Lumbricus terrestris). The organisms were mixed with soil and fumigated; the consumption of O₂, evolution of CO₂ and mineralization of N were then measured under the standard conditions used to measure the flush. Control values obtained with fumigated soil alone were deducted, assuming that the added organisms did not cause a priming action. Taking all the organisms together, 50·0 ± 8·2% of the C originally present was mineralized in the 10 days following fumigation, giving a mean value of 0·5 for k.Experiments with earthworms showed that fumigation with CHCl₃ did not appreciably increase the amounts of C and N mineralized from organisms that were already dead and that k was independent of the amount of organism added.From a consideration of the results in this and in the preceding three papers, it is concluded that the flush following fumigation can be used to give a rough measure of the amount of biomass in a soil.     

Effects of multiple soil conditioners on a mine site acid sulfate soil for vetiver growth

A pot experiment was conducted to investigate the effects of various soil treatments on the growth of vetiver grass ( Vetiveria zizanioides (L.) Nash) with the objective of formulating appropriate soil media for use in sulfide-bearing mined areas. An acidic mine site acid sulfate soil (pH 2.8) was treated with different soil conditioner formula including hydrated lime, red mud (bauxite residues), zeolitic rock powder, biosolids and a compound fertilizer. Soils treated with red mud and hydrated lime corrected soil acidity and reduced or eliminated metal toxicity enabling the establishment of vetiver grass.Although over-liming affected growth, some seedlings of vetiver survived the initial strong alkaline conditions. Addition of appropriate amounts of zeolitic rock powder also enhanced growth, but over-application caused detrimental effects. In this experiment, soil medium with the best growth performance of vetiver was 50 g of red mud, 10 g of lime, 30 g of zeolitic rock powder and 30 g of biosolids with 2 000 g of mine soils (100% survival rate with the greatest biomass and number of new shoots), but adding a chemical fertilizer to this media adversely impacted plant growth. In addition, a high application rate of biosolids resulted in poorer growth of vetiver, compared to a moderate application rate.     

Evaluation of agronomic effectiveness of phosphate rocks for aluminum‐tolerant soybean cultivar

Abstract

The effect of liming on the agronomic effectiveness of three phosphate rocks (PRs) Pesca and Huila from Colombia and Sechura from Peru as compared with TSP was evaluated in a greenhouse experiment for an Al‐tolerant soybean cultivar grown on an acid Ultisol. On both unlimed (pH 4.4) and limed (pH 5.0) soils, the agronomic effectiveness of P sources in terms of increasing seed yield followed the order of TSP > Sechura PR > Huila PR > Pesca PR > check, an order similar to that of solubility of P sources. Liming slightly decreased the effectiveness of Pesca PR, whereas liming had no effect on Huila PR. A significant increase in agronomic effectiveness was observed upon liming for Sechura PR and TSP. Soil‐available P as extracted by the Pi method was closely related to the amount of N fixed by soybean crop that, in turn, was related to the soybean seed yield. Values of relative agronomic effectiveness (RAE) of PRs with respect to TSP were calculated by assuming the check = 0% and TSP = 100%. On unlimed soil, the RAE values of PRs were: Pesca PR = 31%, Huila PR = 42%, Sechura PR = 84%. On the limed soil, the RAE values were: Pesca PR = 8%, Huila PR = 24%, Sechura PR = 66%. It can be concluded that the use of PR with respect to that of TSP for soybean crop is more favorable in the unlimed soil than in the limed soil, provided that the soybean plant is relatively Al‐tolerant.     

Calcium‐induced modification of aluminum toxicity in sorghum genotypes

Effects of calcium (1, 2 and 5 mM) and aluminum (0, 15 and 45 μM) on growth and internal nutrient concentrations were examined with 12 sorghum genotypes (Sorghum bicolor (L.) Moench) in a nutrient solution experiment with a factorial design. At 1 (or 2) mM Ca the severity of root damage induced by Al well reflected the genotypical variation in growth response to Al toxicity. Severity of Al‐induced root damage slightly decreased with increasing Ca level. Moreover, Ca at 5 mM amplified the Mg deficiency induced by Al, as seen from both heavier deficiency symptoms and lower internal Mg concentrations. Under conditions of Al stress at a high Ca supply, induced Mg deficiency apparently predominated the genotypical differentiation in growth response to Al toxicity. An antagonism between Al‐ and Ca ions for uptake was hardly found with the sorghum genotypes. However, the genotypes differed in Ca efficiency, a characteristic which may be relevant in assessing their sensitivity to Mg deficiency.     

Effect of aluminum modification of rice straw–based biochar on arsenate adsorption

Journal of Soils and Sediments - To evaluate the adsorption capacity of aluminum-modified biochars for arsenate (As(V)) and the effect of the biochars on As(V) adsorption by acidic Ultisols. Rice...     

Simulation of soil–blade interaction for sandy soil using advanced 3D finite element analysis

In this paper a finite element investigation of the tillage of dry sandy soil, using the hypoplastic constitutive material model, is described. In most earth moving machinery, such as bulldozers or tillage tools, the working tool is a blade. Hence for tillage systems, accurately predicting the forces acting on the blade is of prime importance in helping to enhance productivity. The initial conditions, such as blade geometry or soil type, and operating conditions, such as cutting speed and cutting depth, have been shown experimentally to have a great effect on machine productivity. Experimental studies give valuable insights but can be expensive and may be limited to certain cutting speeds and depths. Results are also highly dependent on the accuracy of the measuring devices. However with increasing computational power and the development of more sophisticated material models, finite element analysis shows more promise in analyzing the factors affecting soil–blade interaction. Most of the available finite element studies in the literature are two-dimensional or if three-dimensional (3D), are limited to a certain blade displacement depending on the element distortion limit before the solution has convergence problems. In this study, a 3D finite element analysis of soil–blade interaction was carried out based on predefined horizontal and vertical failure surfaces, to investigate the behavior of the soil–blade interface and study the effect of blade-cutting width and lateral boundary width on predicted forces. Sandy soil was considered in this study and modeled using the hypoplastic constitutive model implemented in a commercial finite code, ‘ABAQUS’. Results reveal the validity of the concept of predefined failure surfaces in simulating soil–blade interaction and the significant effect of blade-cutting width, lateral boundary width and soil swelling on cutting forces.     

Snow cover and soil moisture controls of freeze–thaw-related soil gas fluxes from a typical semi-arid grassland soil: a laboratory experiment

In situ field measurements as well as targeted laboratory studies have shown that freeze–thaw cycles (FTCs) affect soil trace gas fluxes. However, most of past laboratory studies adjusted soil moisture before soil freezing, thereby neglecting that snow cover or water from melting snow may modify effects of FTCs on soil trace gas fluxes. In the present laboratory study with a typical semi-arid grassland soil, three different soil moisture levels (32 %, 41 %, and 50 % WFPS) were established (a) prior to soil freezing or (b) by adding fresh snow to the soil surface after freezing to simulate field conditions and the effect of the melting snow on CO₂, CH₄, and N₂O fluxes during FTCs more realistically. Our results showed that adjusting soil moisture by watering before soil freezing resulted in significantly different cumulative fluxes of CH₄, CO₂, and N₂O throughout three FTCs as compared to the snow cover treatment, especially at a relatively high soil moisture level of 50 % WFPS. An increase of N₂O emissions was observed during thawing for both treatments. However, in the watering treatment, this increase was highest in the first thawing cycle and decreased in successive cycles, while in the snow cover treatment, a repetition of the FTCs resulted in a further increase of N₂O emissions. These differences might be partly due to the different soil water dynamics during FTCs in the two treatments. CO₂ emissions were a function of soil moisture, with emissions being largest at 50 % WFPS and smallest at 32 % WFPS. The largest N₂O emissions were observed at WFPS values around 50 %, whereas there were only small or negligible N₂O emissions from soil with relatively low soil water content, which indicates that a threshold value of soil moisture might exist that triggers N₂O peaks during thawing.     

Spatial variation of soil test phosphorus and potassium,oxalate‐extractable iron and aluminum,phosphorus‐retention index,and organic carbon content in soils of Western Australia

Abstract

Spatial variation of bicarbonate soil test phosphorus (P) and bicarbonate soil test potassium (K) was studied by measuring soil test values for 40 individual soil samples collected from random locations within eight uniform 100 m by 100 m field sites in south‐western Australia. In addition, for five of the sites, spatial variation of the three P sorption indices (ammonium oxalate extractable iron, ammonium oxalate extractable aluminum, and the P retention index) and of organic carbon (C) was measured for 20 individual soils samples. Spatial variation was found to be large, with coefficient of variation (CV) exceeding 20% in most cases, and 50% in some cases. It is therefore essential to collect an adequate number of soil samples from uniform areas in paddocks in order to provide a representative composite sample to measure the soil properties.     

Role of root cation‐exchange capacity in differential aluminum tolerance of lotus species

Three experiments were conducted in which roots of two species of Lotus were immersed for up to 40 min in complete nutrient solutions containing 6, 15 or 25 μM Al. The two species tested were L. pedunculatus cv. Grasslands Maku (Al‐tolerant) and L. corniculatus cv. Maitland (Al‐sensitive). There was an initial rapid (< 5 min) decrease in solution Al at 25 μM Al. The effect was less marked with solution Al ≤ 15 μM. The decrease in solution Al was greater in the Al‐sensitive Maitland than in the Al‐tolerant Grasslands Maku, particularly when expressed on the basis of root fresh mass and root length. Root cation‐exchange capacity (CEC) was lower in Grasslands Maku than in Maitland, viz. 23.9 vs 36.5 mmol kg^‐1 dry mass. Maitland roots removed more Al from solution than did those of Maku on the basis of total exchange capacity.

We propose a mechanism of Al tolerance on the basis of the results of this study and of other published information, viz. that differential Al tolerance results from differences in root CEC. Aluminum‐tolerant genotypes have roots with low CEC, and high Al activities (> 20 μM in the case of Grasslands Maku) are required to precipitate the relatively highly methylated pectins associated with low CEC. In contrast, relatively low activities of Al would precipitate the pectins in plants with roots of high CEC. This would decrease the protective capacity of the pectins, enabling the toxic, monomeric Al ions to come in contact with a number of Al‐sensitive compounds or processes in the cell wall, plasmalemma, or cell cytoplasm.     

Do elevated soil concentrations of metals affect the diversity and activity of soil invertebrates in the long‐term?

This study aimed to elucidate the response of diversity and activity of soil invertebrates to elevated soil metal concentrations that were a result of sewage sludge application. Field sampling of soil invertebrates was carried out from 2002 to 2004 at an experimental site established in 1982 to test the effects on crop production of metal contamination from sewage sludge applications with elevated concentrations of zinc (Zn), copper (Cu) and nickel (Ni) with certain treatments exceeding the current UK statutory limits for the safe use of sludge on land. At metal concentrations within the limits, none of the invertebrates sampled showed adverse effects on their abundance or overall community diversity (from Shannon–Weiner index). At concentrations above the limits, individual taxa showed sensitivity to different metals, but overall diversity was not affected. Earthworm abundance was significantly reduced at total Cu concentrations at and above 176 mg kg^?1, while nematode and enchytraeid abundances were sensitive to Cu and high Zn concentrations. Correspondingly, litter decomposition was lower in Zn and Cu treatments although there was no direct relationship between decomposition and soil invertebrate abundance or diversity. Such enduring changes in both soil biodiversity and biological activity around the current UK regulatory limits warrant further investigation to determine whether they indicate detrimental damage to soil functioning over the long‐term.     

Extraction of β-glucosidase activity from PEA field soil

Brown compounds with β-glucosidase activity were extracted from a cultivated soil in 0.1 m phosphate buffer (pH 7), 0.3 m KCl and 10 mm EDTA. A curvilinear relationship of the Langmuir type was observed between the solution volume and β-glucosidase activity of the extract. The results indicated the β-glucosidase was extracellular and was adsorbed on the surfaces of soil particles by ionic bonds. The preparation was treated with protamine sulfate and its enzymatic properties were investigated. The activity of the preparation was optimal at pH 5.4 and was lost after 10 min at 80°C. The extract hydrolyzed p-nitrophenyl β-glucoside(100), phenyl β-glucoside(19), salicin(8), amygdalin(33), cellobiose(52) and gentiobiose(55) (relative activities shown in parentheses). But, the extract had no effect on methyl β-glucoside and phlorizin. The substrate specificity and optimum pH of the enzymatic activity of the soil extract was similar to those of β-glucosidases from various fungi.     

Use of diffusion for automated nttrogen‐15 analysis of soil extracts

Abstract

Studies to evaluate the use of diffusion for automated ¹⁵N analysis of inorganic N in soil extracts showed that serious error can arise from use of the Devarda's alloy recommended for steam distillations and that the error can be avoided by using a commercial product of higher purity. These studies showed that serious error can also arise when NO₃ ^‐‐N is diffused following NH₄ ⁺‐N and that separate diffusions should be performed for NH₄ ⁺‐N and (NH₄ ⁺ + NO₃‐)‐N. Other work demonstrated that the plastic specimen containers employed for diffusion can be reused if acid‐washed, that diffusions can be performed using either light or heavy MgO without ignition to decompose carbonate, and that labeled NO₂‐is completely removed from soil extracts by treatment with sulfamic acid before diffusion. A comparison of ¹⁵N analyses by steam distillation and diffusion using extracts from two soils revealed better agreement for the soil having a lower content of organic matter. Substantial differences in analyses by the two techniques for the soil having a higher organic‐matter content were attributed to enzymatic conversions of inorganic N during the 6‐d diffusion period.