Repeated Bray‐2 extractions of an Inceptisol and an Andisol

Abstract

Bray‐2 extractable phosphorus (Bray2‐P) is commonly used to measure plant‐available P in soil. The pool size of extractable P in the residual soil should be reduced after extraction. Phosphorus, once released with the Bray‐2 solution, is resorbed by the soil during the extraction‐filtration period. If P resorption is large, the Bray2‐P concentration is underestimated. The P absorption coefficient and composition of inorganic P [calcium (Ca)‐P, aluminum (Al)‐P, and iron (Fe)‐P] probably affect the Bray2‐P concentration. We investigated the effect of repeated Bray‐2 extractions on the Bray2‐P concentrations in relation to the P absorption coefficient and Ca‐P, Al‐P, and Fe‐P concentrations in two soils (an Inceptisol and an Andisol), which markedly differ in the P absorption coefficient. Test soil samples were the initial soil (S0) and soils after the 1st to 4th extractions (S1‐S4) for the Inceptisol, and S0, S1‐S4, and S7 for the Andisol. The Bray2‐P, Ca‐P, Al‐P, and Fe‐P concentrations in the S0 were 260, 75, 338, and 536 mg kg^‐1 in the Inceptisol, and 217, 31, 972, and 354 mg kg^‐1 in the Andisol, respectively. All of the extractable P concentrations in the Inceptisol decreased with increasing numbers of extractions, and the Bray2‐P, Ca‐P, Al‐P, and Fe‐P concentrations in the S4 were 5.3, 21, 5.7, and 30% of those in the S0, respectively. On the other hand in the Andisol, the Bray2‐P, Ca‐P, and Fe‐P concentrations did not decrease in the S1 and S2 compared with those in the S0, although the Al‐P concentration decreased with increasing numbers of extractions. The Bray2‐P, Ca‐P, Al‐P, and Fe‐P concentrations in the S7 were 23, 71, 16, and 79% of those in the S0, respectively. The P absorption coefficient in the S0 was higher in the Andisol (7,703 mg kg^‐1) than in the Inceptisol (1,582 mg kg^‐1), and it decreased with increasing numbers of extractions in both soils. The P absorption coefficient in the S7 Andisol was 51% of that in the S0, while the P absorption coefficient in the S4 Inceptisol was 24% of that in the S0. The results suggest that Presorption affects the efficiency of extraction with the Bray‐2 solution, and the composition of Ca‐P, Al‐P, and Fe‐P fractions. The Bray2‐P concentration in soil with high P absorption coefficient is underestimated due to P resorption.     

Ecotoxicological testing of sediments and dredged material: an overlooked opportunity?

Purpose

Basing decisions for the management of contaminated sediments on ecotoxicological data is still often met with skepticism by European stakeholders. These concerns are discussed as they pertain to bioassays to show how ecotoxicological data may provide added value for the sustainable management of sediment in aquatic systems.

Materials and methods

Five “concerns” are selected that are often raised by stakeholders. The ecotoxicological practice is discussed in light of the knowledge gained in recent decades and compared with chemical sediment analysis and chemical data.

Results and discussion

Common assumptions such as a higher uncertainty of biotest results for sediments compared to chemical analyses are not supported by interlaboratory comparisons. Some confusion also arises, because the meaning of biotest data is often misunderstood, questioning their significance in light of a limited number of organisms and altered test conditions in the lab. Because biotest results describe a sediment property, they should not be directly equated with an impact upon the biological community. To identify a hazard, however, the possibility of false-negative results due to the presence of contaminants that are not analyzed but are toxic is lower.

Conclusions

The cost of increased investment in ecotoxicological tests is, in our view, small compared with that of making false-negative assessments of sediment/dredged material that can ultimately have long-term environmental costs. As such, we conclude that ecotoxicological testing is an opportunity for sediment management decision-making that warrants more attention and confidence in Europe.

     

Removal of Cyanide and Zinc–Cyanide Complex by an Ion-Exchange Process

Removal efficiencies of cyanide and a zinc–cyanide complex in solutions were studied by using an ion-exchange process at pH 10.0 and 12.0. An anion-exchange resin, AMBERLITE® IRA-402 Cl, was used to perform packed bed continuous experiments. For the initial 200 mg/l cyanide solution, the packed bed gave a cyanide effluent concentration of 0.2 mg/l at 80 bed volumes for both pH 10.0 and 12.0. Comparatively, in the mixture of 200 mg/l cyanide and 100 mg/l zinc, packed bed volumes were obtained as 80 and 90 at pH 10.0 and 12.0, respectively, to have 0.2 mg/l cyanide effluent concentrations. The packed beds were exhausted at 250 and 400 bed volumes for cyanide and zinc–cyanide complex solutions, respectively. Speciation calculations in Zn(II)/cyanide/OH^? were used to interpret the results. The exchange capacities of the resin were determined as ～1.2 and ～0.9 meq/ml resin for cyanide and zinc–cyanide complex solutions, respectively, and were independent of pH in the studied pH range.     

Comparison of Laboratory Methods and an In Situ Method for Estimating Nitrogen Mineralization in an Irrigated Silt‐Loam Soil

Abstract

Nitrogen (N) mineralization makes a considerable contribution to crop‐available N and is difficult to estimate. Reliable methods for measuring N mineralization are needed to produce data sets for developing N‐mineralization models, as a component in fertilizer recommendation algorithms, and to assess the effect of management practices on N mineralization. Numerous methods are available for estimating N mineralization. Laboratory methods are relatively easy but may not reflect conditions in the field, and field methods are usually labor‐intensive. A study was conducted to compare N‐mineralization estimates using anaerobic and aerobic laboratory methods and an in situ field method for the 0‐ to 15‐cm depth of a silt loam soil under irrigated corn (Zea mays L.). Mineralization estimates were also compared to N mineralization based on crop N content. Estimates of N mineralization were 101 kg ha^?1 for the anaerobic laboratory method, 284 kg ha^?1 for the aerobic laboratory method, and 134 kg ha^?1 for the in situ field method. The in situ field method provided a reasonable estimate of N mineralization (0 to 15 cm) when compared to the estimate of mineralized N (root zone) based on crop N content (215 kg ha^?1). The in situ field method can be used to measure N mineralization during the growing season and for comparing N mineralization among management practices.     

Removal of Hydrophobic Volatile Organic Compounds in an Integrated Process Coupling Absorption and Biodegradation—Selection of an Organic Liquid Phase

Since usual processes involve water as absorbent, they appear not always really efficient for the treatment of hydrophobic volatile organic compound (VOC). Recently, absorption and biodegradation coupling in a two-phase partitioning bioreactor (TPPB) proved to be a promising technology for hydrophobic compound treatment. The choice of the organic phase, the non-aqueous phase liquid (NAPL) is based on various parameters involved in both steps of the process, hydrophobic VOC absorption in a gas?Cliquid contactor, and biodegradation in the TPPB. VOC solubility and diffusivity in the selected NAPL, as well as NAPL viscosity, seems to be the main parameters during the absorption step, while biocompatibility, namely the absence of toxic effect of the NAPL towards microorganisms, non-biodegradability and VOC partition coefficient between NAPL and water were revealed as the key factors during the biodegradation step. The screening of the various NAPL available in the literature highlighted two families of compounds matching the required conditions for the proposed integrated process, silicone oils and ionic liquids.     

Effect of an anionic surfactant on hydraulic conductivities of sodium- and calcium-saturated soils

The effect of sodium dodecylbenzenesulfonate （SDBS）, an anionic surfactant used widely in household products and industrial processes, on saturated hydraulic conductivities （Ksat） of an Anthrosol saturated with sodium （Na-soil） or calcium （Ca-soil） was analyzed in a laboratory experiment using the constant head method, and adsorption and dispersion experiments were also conducted to infer the possible mechanisms of Ksat fluctuations. The results showed that SDBS was more intensely adsorbed in the Ca-soil than in the Na-soil. With an increase in the SDBS concentration, the stability of the Na-soil suspensions decreased when the SDBS concentration was less than 1.2 mmol L^-1 and then above this concentration, increased markedly, while the stability of the Ca-soil suspensions increased gradually at all SDBS concentrations studied. With an increase in the SDBS concentration, the Ksat of the Na-soil increased, which resulted mainly from the increase of water channels in the soil because of the coagulation of the soil particles, while the Ksat of Ca-soil decreased mainly on account of the clogging of partial water channels by precipitated Ca（DBS）2 and the fine soil particles generated.     

Effect of cycloheximide on N2O and NO3– production in a forest and an agricultural soil

The present work aims at evaluating the effect of cycloheximide at concentrations of between 0.5 and 5mgg^–1 on N₂O and NO₃ ^– production in two slightly alkaline soils, sampled from deciduous woodland and arable cultivation. In the first experiment, peptone was used as the “inducing substrate” for heterotrophic activity, and soil was incubated with cycloheximide (at different concentrations) and/or acetylene (1mll^–1) to block induced eukaryotic protein synthesis and ammonia monooxygenase activity, respectively. Peptone addition stimulated N₂O and NO₃ ^– production significantly in woodland soil, whereas arable soil showed no significant N₂O emissions and low NO₃ ^– production. Low cycloheximide concentrations drastically reduced N₂O emissions in woodland soil, suggesting a potential role of fungi in N₂O emissions. However, acetylene was equally effective in blocking N₂O emissions and part of NO₃ ^– production, so that a possible role of ammonia monooxygenase in an organic-inorganic pathway of N nitrification in fungal metabolism can be hypothesized. A second experiment was carried out on the woodland soil to check if low cycloheximide concentrations had non-target biocidal effects on soil microorganisms. Attention was focused on the range of concentrations which had reduced N₂O emission in the woodland soil. The results suggested that at concentrations of cycloheximide between 0.5 and 2mgg^–1 any biocidal effect on microbial biomass was negligible in the first 48h; therefore only selective inhibition of protein synthesis could be expected. The whole nitrifier population seemed to be particularly sensitive to cycloheximide concentrations higher than 2.5mgg^–1. Received: 4 July 1997     

Phosphorus Fractionation in Soils and Wastewater Sorbent Materials as an Indicator of Material Specific and Storage‐Dependant Availability

Abstract

Wastewater treatment with reactive filters and recycling the phosphorus (P)‐saturated materials as fertilizers in plant production is a suitable concept for a sustainable society. The objective of the present study was to evaluate the ability of the Hedley P fractionation scheme to separate different P fractions, including inorganic and organic P, in soils and sorbent materials used to reduce the P content of waste water. An additional aim was to determine changes in P fractions after storage for 8 months under different humidity regimes. This was to evaluate whether extractability of P is dependent on storage conditions between sorption of P and the subsequent use of the sorbent materials as P fertilizers. This study is the first one showing that in sorbent materials used for treatment of wastewater, the Hedley fractionation scheme separated Ca phosphates in the HC1 extract from Al and Fe phosphates in the NaOH extract. The different fractions could also be used to characterize soils of different origins, to separate liming treatments, and to approximately document soil P fertility, but could not assess differences in soil P status caused by different P fertilization in a single year. No significant influence of moisture regimes during storage on resin‐exchangeable P was detected. This increases the suitability of the studied sorbent materials for recycling P from wastewater to agricultural crops, because it indicates that plant availability of sorbed P does not change drasticaIly during the studied storage conditions.     

Soil Algal Colonization and Its Ecological Role in an Environment Polluted by Past Zn�CPb Mining and Smelting Activity

The research was carried out around dumps made at the beginning of twentieth century linked to Zn?CPb ore mining of deposits of Mississippi Valley type in Southern Poland. Soil algae communities were investigated near spoil dumps rich in Zn, Pb, Fe, Cd, and Tl. In algal crusts, Chlorophyta and Cyanophyta occur in filament forms such as Stichococcus bacillaris, Stichococcus chlorelloides, S. cf. fragilis, and Cylindrocapsa sp. The algal crusts form aggregates containing metal-bearing minerals and algal organic material. The development of the crusts occur on sandy-clayey soils poor in water and highly enriched in heavy metals (up to 68,800 mg kg^?1 for Zn, 85,060 mg kg^?1 for Pb, 369 mg kg^?1 for Cd and 355 mg kg^?1 for Tl). Algal-crust formation is an important initial stage which facilitates vascular plant succession and topsoil formation. The results of investigation of algal material with ESEM are presented and the mineral phases in the top soil layer based on the XRD and EDS are described. The results indicate the presence of secondary labile minerals of lead, e.g., anglesite and plumbojarosite and minerals of Zn, e.g., smithsonite and minrecordite.     

Self-generated microbial population or cultured microflora – an important criterion toward development of an effective and economically viable road map for organic soil management

Huge depletion of soil microflora under conventional farming practice has become the primary contributory factor toward the present depletion of soil and crop productivity. Reconstitution of soil microbial dynamics has been identified as the only way out, but there has been a debate regarding the most effective pathway for soil rejuvenation i.e. whether to create the environment for natural proliferation or opt for inoculation of laboratory generated microbes. In this respect, a study was undertaken at Maud T.E. (Assam) under FAO-CFC-TBI Project, where bio-fertilizer (microbial inoculant, MI), vermicompost (organic food source, OF), vermicompost + bio-fertilizer (OF+MI), and Novcom compost (representing self-generated native microflora in the order of 10¹⁶c.f.u. along with organic food source, SNM); were taken as treatments for a yield target of 1500 kg made tea/ha. The highest crop yield (1500 kg ha^?1) along with high and consistent soil quality development was noted under SNM treatment; while MI influenced lowest yield (1268 kg ha^?1) and minimal soil response. Addition of the organic food source with cultured microbes (MI+OF) was found to improve crop performance (1427 kg ha^?1), but with 7.60 times higher cost (Rs. 39.97 kg^?1 made tea). Economic viability study indicated that except SNM, all other treatments were vulnerable toward crop loss or market downfall.     

Effects of Rice Husk Ash and Bagasse Ash on Phosphorus Adsorption and Desorption in an Alkaline Soil under Wheat–Rice System

Rice husk ash (RHA) and bagasse ash (BA) are available in large quantities in South Asian countries growing rice and sugarcane. Land application of RHA and BA is likely to influence chemistry of soil phosphorus (P) and thereby P adsorption and desorption. Laboratory studies were carried out to investigate the short-term and long-term effects of RHA and BA application on P adsorption and desorption in an alkaline soil under a wheat–rice system. Addition of RHA or BA (10 Mg ha^?1) resulted in a significant decrease in P adsorption compared to the control. The decrease in P adsorption was lower when RHA and BA were applied to either rice or wheat as compared with when applied to both the crops. The BA was more effective in reducing P adsorption than RHA because of its greater P concentration. Fresh addition of RHA and BA at 1% (dry-weight basis) showed a small effect on P adsorption as compared to their long-term application. The Frendulich isotherm equation gave better fit with the experimental data than the Langmuir equation and is reliable to describe the P quantity/intensity relationships of this soil as affected by the additions of RHA and BA. The P-adsorption capacities (revealed from the Langmuir isotherms) of the unamended control, RHA, and BA (applied to both wheat and rice) were 256, 313, and 385 mg kg^?1, respectively; the corresponding bonding energies for the three treatments are 0.0085, 0.0041, and 0.0026 L kg^?1, respectively. Desorption of P was minimum in the control plots and maximum with BA followed by RHA, especially when applied to both the crops.     

Effect of mulch rates and tillage systems on infiltrability and other soil physical properties of an Oxisol in Paraná, Brazil

A 7-year-old tillage trial, comprising conventional tillage (CT), minimum tillage (MT) and no-tillage (NT), was chosen to study the relative importance of controlled mulch rates and soil physical properties such as bulk density, pore volume and hydraulic conductivity upon infiltrability. Infiltration measurements were carried out with a portable rainfall simulator. Mulch consisted of soya bean residues.Soil physical analysis showed higher bulk densities in the top 20 cm under NT, whereas CT, and to a lesser extent MT, led to the development of a plough pan in 20–30 cm depth. At the same time, compaction brought about a decrease in macropores and an increase in micropores. Total porosity ranged between 56.6% and 66.4%. Hydraulic conductivity did not differ significantly between tillage systems, and overall conductivity values were very high.The main factor influencing infiltrability was the formation of a surface seal depending on the degree of soil cover by mulch, irrespective of tillage system. For all 3 tillage systems, a 100% soil cover led to the complete infiltration of a 60-mm rainfall, whereas only 20% of the applied rain infiltrated when the soil was bare and the surface completely sealed. Plant residues of 4–6 t ha⁻¹ are proposed, as the minimum amount of mulch needed to reduce runoff and erosion effectively.     

Carbon and nitrogen turnover in response to warming and nitrogen addition during early stages of forest litter decomposition—an incubation experiment

Purpose

Little is known about the interactive effects of temperature, nitrogen (N) supply, litter quality, and decomposition time on the turnover of carbon (C) and N of forest litter. The objective of this study was to investigate the interactive effects of warming, N addition and tree species on the turnover of C and N during the early decomposition stage of litters in a temperate forest.

Materials and methods

A 12-week laboratory incubation experiment was carried out. The leaf litters including two types of broadleaf litters (Quercus mongolica and Tilia amurensis), a needle litter (Pinus koraiensis), and a mixed litter of them were collected from a broad-leaved Korean pine mixed forest ecosystem in northeastern China in September 2009. Nine treatments were conducted using three temperatures (15, 25, and 35 °C) combined with three doses of N addition (equal to 0, 75, and 150 kg?·?ha^?1?a^?1, respectively, as NH₄NO₃).

Results and discussion

After 12 weeks of incubation, the mass loss ranged between 12 and 35 %. The broadleaf litters had greater mass loss and cumulative CO₂–C emission than the needle litter. Temperature and N availability interacted to affect litter mass loss and decomposition rate. The dissolved organic carbon (DOC) and nitrogen (DON) concentrations in litter leachate varied widely with litter types. DOC increased significantly with increased temperature but decreased significantly with increased N availability. DON increased significantly with increased N availability but showed a higher level at the moderate decomposition temperature. The amounts of CO₂ and N₂O emission were significantly higher at 25 °C than those at 15 and 35 °C, and were significantly increased by the N addition.

Conclusions

The present study indicated relatively intricate temperature and N addition effects on C and N cycling during early stages of litter decomposition, implying that future increases in temperature and N deposition will directly affect C and N cycling in broad-leaved Korean pine mixed forest ecosystem, and may indirectly influence the ecosystem composition, productivity, and functioning in NE China. It is, therefore, important to understand the interactive effects of biotic and abiotic factors on litter decomposition in field conditions in order to assess and predict future ecosystem responses to environmental changes in NE China.     

Switchgrass from North Dakota – an adaptable and promising energy crop for northern regions of Europe

Searching for novel energy crops, an interest in C4-type plant switchgrass (SWG) has increased worldwide. The present research was aimed to study SWG genetic resources for most important agrobiological traits with a view of extending the range of energy plants in the Nemoral zone of Europe. SWG was studied for the peculiarities of developmental stages, winter hardiness, and dry matter (DM) yield. SWG regrowth in spring started one month later compared to the reed canary grass (variety ‘Chiefton’). All investigated genotypes matured seeds in the second half of September. The most winter-hardy SWG accessions (0–20% winter damage) were the majority of wild ecotypes and the variety ‘Dacotah’ from North Dakota (2–4 hardiness zone) as well as the variety ‘Summer’ from South Nebraska (4, 5 hardiness zone). Ecotypes from North Dakota exhibited a high breeding potential and prospects in Northern regions of Europe due to genotypic variation of winter hardiness trait. The varieties ‘Alamo’, ‘Falcon’, ‘Grenville’, ‘Shawnee’, and ‘Trailblazer’ that originated from warmer climate zones (6–9 hardiness zone) were heavily damaged or completely killed. The worst overwinter survival of plants was recorded after the first winter. DM yield was estimated at two regimens of cutting. When grass was cut once at seed maturity stage, DM yield in the first harvest year was 249 g per plant, in the second harvest year 349 g per plant, and in the third harvest year 493 g per plant. When grass was cut twice per season (at the beginning of anthesis and after regrowth of aftermath), DM yield was significantly lower: in the first harvest year the DM yield was 203 g per plant (18.4% less), in the second harvest year 182 g per plant (47.9% less), and in the third harvest year 272 g per plant (44.7% less).     

Which uncertainty? Using expert elicitation and expected value of information to design an adaptive program

Natural resource management is plagued with uncertainty of many kinds, but not all uncertainties are equally important to resolve. The promise of adaptive management is that learning in the short-term will improve management in the long-term; that promise is best kept if the focus of learning is on those uncertainties that most impede achievement of management objectives. In this context, an existing tool of decision analysis, the expected value of perfect information (EVPI), is particularly valuable in identifying the most important uncertainties. Expert elicitation can be used to develop preliminary predictions of management response under a series of hypotheses, as well as prior weights for those hypotheses, and the EVPI can be used to determine how much management could improve if uncertainty was resolved. These methods were applied to management of whooping cranes (Grus americana), an endangered migratory bird that is being reintroduced in several places in North America. The Eastern Migratory Population of whooping cranes had exhibited almost no successful reproduction through 2009. Several dozen hypotheses can be advanced to explain this failure, and many of them lead to very different management responses. An expert panel articulated the hypotheses, provided prior weights for them, developed potential management strategies, and made predictions about the response of the population to each strategy under each hypothesis. Multi-criteria decision analysis identified a preferred strategy in the face of uncertainty, and analysis of the expected value of information identified how informative each strategy could be. These results provide the foundation for design of an adaptive management program.     

Is there an impact of climate change on soil carbon contents in England and Wales?

It is not yet clear how soils are responding to a warming climate. A major study using the National Soil Inventory (NSI) of England and Wales reported large declines in soil carbon concentration across 11 land uses between 1978 and 2003 and concluded there was a link to climate change. However, a second, almost contemporary study, recorded no significant changes, raising the possibility that the reported declines were caused by changes in land use and management rather than by climate change. We have used ‘space‐for‐time’ substitution on the data from the initial NSI study, combined with changes in rainfall and temperature over the survey period, to determine the extent to which the declines in soil carbon observed in the second NSI study could be predicted from changes in climate. For organo‐mineral and mineral soils, little (0–5%) of the observed decline in carbon concentration can be predicted from changes in climate. In contrast, 9–22% of the changes reported for organic soils in semi‐natural habitats are consistent with changes in temperature and rainfall between the two NSI surveys. We also found that carbon concentration in organic soils in semi‐natural habitats declines as temperatures exceed 7°C, mirroring independent observations for the decline in bog and dense shrub moor vegetation as temperatures rise above 7°C, and raising the possibility that climate change may influence soil carbon indirectly by changing vegetation cover, and hence litter quality.     

Is CO2 evolution in saline soils affected by an osmotic effect and calcium carbonate?

Salt-affected soils are widespread, particularly in arid climates, but information on nutrient dynamics and carbon dioxide (CO₂) efflux from salt-affected soils is scarce. Four laboratory incubation experiments were conducted with three soils. To determine the influence of calcium carbonate (CaCO₃) on respiration in saline and non-saline soils, a loamy sand (6.3% clay) was left unamended or amended with NaCl to obtain an electrical conductivity (EC) of 1.0 dS?m^?1 in a 1:5 soil/water extract. Powdered CaCO₃ at rates of 0%, 0.5%, 1.0%, 2.5%, 5.0% and 10.0% (w/w) and 0.25-2 mm mature wheat residue at 0% and 2% (w/w) were then added. Cumulative CO₂-C emission from the salt amended and unamended soils was not affected by CaCO₃ addition. To investigate the effect of EC on microbial activity, soil respiration was measured after amending a sandy loam (18.8% clay) and a silt loam (22.5% clay) with varying amount of NaCl to obtain an EC_1:5 of 1.0–8.0 dS?m^?1 and 2.5 g glucose C?kg^?1 soil. Soil respiration was reduced by more than 50% at EC_1:5?≥?5.0 dS?m^?1. In a further experiment, salinity up to an EC_1:5 of 5.0 dS?m^?1 was developed in the silt loam with NaCl or CaCl₂. No differences in respiration at a given EC were obtained between the two salts, indicating that Na and Ca did not differ in toxicity to microbial activity. The effect of different addition rates (0.25–2.0%) of mature wheat residue on the response of respiration to salinity was investigated by adding NaCl to the silt loam to obtain an EC_1:5 of 2.0 and 4.0 dS?m^?1. The clearest difference between salinity levels was with 2% residue rate. At a given salinity level, the modelled decomposition constant ‘k’ increased with increasing residue addition rate up to 1% and then remained constant. Particulate organic carbon left after decomposition from the added wheat residues was negatively correlated with cumulative respiration but positively correlated with EC. Inorganic N (NH ₄ ⁺ -N and NO ₃ ^? -N) and resin P significantly decreased with increasing salinity. Resin P was significantly decreased by addition of CaCl₂ and CaCO₃.