Mutual influence of copper and paraquat on their adsorption in soil

Paraquat and copper (Cu) are commonly used and detected in soil.Therefore,it is important to understand their mobility in the environment.In this study,the competitive effects of paraquat and Cu on their adsorption in five representative Chinese soils were investigated using batch adsorption equilibrium experiments and spectroscopic analysis.The results showed that the adsorption of paraquat in soil varied with soil type and was positively correlated with both soil cation exchange capacity and o...     

THE INTERACTION OF PARAQUAT (1: 1'-DIMETHYL 4:4'-DIPYRIDYLIUM DICHLORIDE) WITH MINERAL SOILS

Investigation of the adsorption of 1:1′-dimethyl 4:4′-dipyridylium (paraquat) dichloride by a range of soils, using a solution-equilibration technique, has shown that the adsorption is characterized by three factors: 1. Up to a limiting value, defined as the Strong Adsorption Capacity (SAC), the solution concentration of paraquat is reduced below the level of chemical detection by suspended soil: this strongly adsorbed paraquat is preferentially held against 0.1 to 2.0N solutions of ammonium ion. A range of strengths of adsorption probably exists within the strong adsorption range, but the greater part of the strongly adsorbed material is de-activated herbicidally; this accounts for the herbicidal de-activation of paraquat in soils. 2. Removal of soil organic matter by treatment with hydrogen peroxide usually does not greatly change the SAC. Strong adsorption of paraquat is primarily a property of clay minerals, and the presence of expanding lattice minerals is of particular importance. 3. For fortifications above the strong adsorption region, there is a region of weaker adsorption but the total adsorption capacities of soils at saturation are less than their cation exchange capacities for inorganic cations. Taken with the difficulty of displacement, this indicates that the adsorption of paraquat is strongly influenced by factors other than simple electrostatic interaction.     

土壤养分状况系统研究法在土壤肥力研究及测土施肥中的应用

土壤养分状况系统研究法应用美国国际农化中心的ASI联合浸提液(0.25mol/L NaHCO3-0.01mol/L EDTA-0.01mol/L NH4F)测定土壤中11种大、中、微量元素含量,结合土壤对营养元素的吸附研究和盆栽试验,判断土壤中存在的和潜在的养分限制因子,用以指导田间试验和施肥推荐。在全围17个省(市、自治区)范围内选取了140个土壤样品,应用该方法对土壤养分状况进行了研究。盆栽试验结果表明,土壤中氮、磷、钾、锌、硫、铜、硼、锰、钼、镁、钙和铁成为限制因子的土壤分别为137、126、84、68、45、37、36、34、28、25、20和17个。应用Cate和Nelson的方法估计出11种元素(钼除外)测定值在盆栽条件下的临界值。 应用在原取土地块安排的田间试验的资料估计出大田条件下应用ASI联合浸提液测定的土壤磷、钾含量的临界值分别为15mg/L和90mg/L。应用河北省玉田县试验和示范资料建立的计算机测土施肥模型综合考虑了土壤中各种营养元素的综合平衡和土壤对磷、钾的吸附固定能力。     

Long-term effects of bone char and lignocellulosic biochar-based soil amendments on phosphorus adsorption–desorption and crop yield in low-input acidic soils

Although the addition of biochar has been shown to reduce the phosphorus (P) adsorption capacity of soil, quantitative evidence of this has mainly been provided by incubation experiments and it is therefore essential to conduct long-term field trials to draw general conclusions. It is largely unknown whether bone char has a greater effect than lignocellulosic biochar on P adsorption–desorption processes and crop yield. The aim of this study was to determine the long-term (8 years) effect of bone char and biochar on P adsorption–desorption and crop yield in low-input acidic soils. The results showed that bone char decreased the maximum P adsorption capacity (Q_m) by 10% and increased the desorption capacity (D_s) by 150% compared with the control (i.e. without a soil amendment). The desorption ratio was highest for the bone char treatment (10.3%) and three times more than the control. Plant-available P was seven times greater under bone char than the control. There was no variation in adsorption–desorption characteristics, desorption ratio and plant-P available content between bone char and lignocellulosic biochar treatments. The average yield increment following the application of bone char and biochar was 1.7 and 1.4 Mg ha⁻¹ for maize and 1.8 and 1.9 Mg ha⁻¹ for soya bean, respectively. Despite the low application rate (4 t ha⁻¹ year⁻¹), these findings demonstrated that the long-term application of bone char and biochar-based amendments enhanced P availability in low-input cropping systems, mainly by altering the P adsorption and desorption capacity of soils.     

长期轮作与施肥对农田土壤磷素形态和吸持特性的影响

通过对黄土旱塬地区长期定位施肥(26a)条件下的不同轮作系统的土壤磷素形态和吸持参数的测定,研究了轮作和施肥对土壤磷素吸持特性和磷素形态的影响,以及土壤磷素吸持参数与磷素形态之间的关系。结果表明,长期轮作与施肥都可以减低土壤磷素的最大吸附量（Qm）,相对于其它轮作和连作,在氮磷（NP）施肥下,小麦-玉米-豌豆轮作可以减低土壤的Qm,在氮磷有机肥（NPM）施肥下,小麦-玉米轮作可以减低土壤的Qm。在施肥相同的条件下,小麦-玉米轮作和小麦-豌豆轮作可以显著增加土壤中各形态无机磷的含量,长期轮作比连作可以增加土壤中的有效磷养分,尤其对Ca2-P的提高效果更为显著。相关分析表明,Qm和磷吸持指数（PSI）与全磷（T-P）、Olsen-P、CaCl2-P、Ca2-P、Ca8-P、Fe-P、Ca10-P和有机磷呈极显著负相关（p＜0.01）,与闭蓄态磷（O-P）呈显著负相关（p＜0.05）,与Al-P关系不显著。土壤有机质（SOM）与Qm、PSI和磷最大缓冲能力（MBC）之间存在极显著负相关关系,与磷吸持饱和度（DPSS）存在显著正相关。通径系数和逐步回归分析表明,在石灰性黑垆土土壤的无机磷形态中,Ca2-P对Olsen-P的贡献最大。     

农田土壤重组有机碳平衡的研究

Considerable evidence that the soil organic matter （OM） level in agricultural soils will gradually over time reach an equilibrium state under certain bioclimatic conditions and for certain cropping systems has been accumulating. Although models or long-term experiments have been used, this research used physical fractionation procedure to attain an soil OM equilibrium value. To obtain soil OM equilibrium values in the heavy fraction, typical soils from three long-term field experiments at Fengqiu and Yingtan State Key Agro-Ecological Experimental Stations in China were studied using a simple density fractionation procedure and employing the Langmuir equation. Results for the fluvo-aquic soil with organic fertilizer treatments indicated that the soil OM equilibrium value in the heavy fraction was twofold more than that in the inorganic treatments; however, for the paddy soil developed on red soil the OM equilibrium value in the heavy fraction for both treatments was almost identical. It suggested that for fiuvo-aquic soils the increased potential of OM for the heavy fraction in the long run was larger for the organic than the inorganic fertilizer applications, whereas for paddy soils developed on red soils under the same conditions the present OM content in the heavy fraction was at or close to this equilibrium level for all treatments, and increased potential was very limited.     

Effects of plant residues and calcite amendments on soil sodicity

The effects of wheat, potato, sunflower, and rape residues and calcite were evaluated in soil that received sodic water. These materials were added to a sandy‐loam soil at a rate of 5%, after which the treated soils were incubated for 1 month at field‐capacity moisture and a temperature of 25°C–30°C. Column leaching experiments using treated soils were then conducted under saturated conditions using water with three sodium‐adsorption ratios (SAR) (0, 10, 40) with a constant ionic strength (50 mmol L^–1). The results indicated that the application of plant residues to soils caused an increase in cation‐exchange capacity and exchangeable cations. Leaching experiments indicated that the addition of plant amendments led to increased Na⁺ leaching and decrease in exchangeable‐sodium percentage (ESP). The ESP of the control soil, after leaching with solutions with an SAR of 10 and 40, increased significantly, but the level of sodification in soils treated with plant residue was lower. Such decreases of soil ESP were greatly affected by the type of plant residues, with the order of: potato‐treated soil > sunflower‐treated soil > rape‐treated soil > wheat‐treated soil > calcite‐treated soil > control soil.     

Influence of copper on the adsorption and desorption of paraquat, diquat, and difenzoquat in vineyard acid soils

Retention of the cationic herbicides paraquat (PQ), diquat (DQ), and difenzoquat (DFQ) in two vineyard soils with a different management history and retention capacity was examined. The influence of copper on the ability of the soils to retain the herbicides was determined by comparing the results of adsorption and desorption tests on untreated and Cu-enriched soil samples, and also on soils that were previously treated with EDTA to extract native copper. The three herbicides were strongly adsorbed by both soils. Soil 1 exhibited linear adsorption isotherms for PQ and DFQ with partition coefficients, KD, of 1.28 x 103 and 1.37 x 103 L kg-1, respectively, and a Freundlich-type isotherm for DQ with a linearized partition coefficient, KD*, of 1.01 x 103 L kg-1. On the other hand, soil 2 exhibited curved isotherms and smaller KD* values (viz. 106, 418, and 28 L kg-1 for PQ, DQ, and DFQ, respectively). Using EDTA to extract copper from the soils released new sites for the herbicides to bind. The three herbicides exhibited strong hysteresis in the adsorption-desorption process. Extracting copper decreased the percent desorption of PQ and DQ; on the other hand, it decreased the affinity of DFQ for the resulting vacant adsorption sites. Similarly, competitive adsorption tests with copper and the herbicides revealed that the metal was only capable of displacing DFQ from adsorption sites. The behavior of this herbicide in the soils was consistent with a specific adsorption model. The disparate behavior of the two soils toward the herbicides was a result of the adsorption sites in soil 1 being less extensively occupied than those of soil 2 in the adsorption tests. The effect of copper on the adsorption of DFQ in the two soils was acceptably reproduced by an adsorption model involving Coulombic and specific sorption with competition from the metal.     

Understanding the soil nitrogen cycle

Abstract. A quantitative knowledge of nitrogen cycle processes is required to design strategies for decreasing leakage of N from agriculture to the wider environment. However, it is remarkably difficult to make reliable measurements of many of the key processes under realistic field conditions. In impermeable soils hydrologically separated plots provide an invaluable method of measuring leaching and runoff. Estimates of nitrate leaching using porous ceramic cups agree well with lysimeter measurements on sandy soil but are suspect on more structured soils. Estimates of N₂O flux from soil are subject to great spatial heterogeneity; developing long path-length measuring techniques may overcome this problem.
¹⁵N labelling is valuable for assessing fertilizer N loss, forms of N left in soil and the fate of N from crop residues. The combination of experimental and modelling approaches can provide insights that are otherwise unattainable, including a basis for more precise advice on N fertilization.
Mineralization of soil organic matter and crop or animal residues provides much of the nitrate leached during winter under the climatic conditions of north-west Europe, because mineralization is poorly synchronized with crop N uptake. Maintenance of crop cover during winter can greatly decrease leaching but the long-term effects on the N cycle of winter cover crops or incorporating cereal straw are not yet clear.     

Experimental analysis of the effect of exotic and native plant species on the structure and function of soil microbial communities

Invasions of exotic plant species are among the most pervasive and important threats to natural ecosystems, however, the effects of plant invasions on soil processes and the soil biota have rarely been investigated. We grew two exotic and a native under-story plant species in the same mineral soil from a non-invaded forest stand in order to test whether observed differences in the field could be experimentally produced in the greenhouse. We characterized changes in the soil microbial community structure (as indexed by PLFAs) and function (as indexed by enzyme activities and SIR), as well as changes in potential nitrogen mineralization rates. We found that the invasion of two very dissimilar exotic species into the under-story of deciduous forests in eastern North America can rapidly cause changes in most of the studied soil properties. At the end of the three-month incubation, soils under the exotic species had significantly different PLFA, enzyme and SIR profiles than both initial soils and soils where native shrubs had been grown. We also observed a significant increase in pH and nitrification rates under one of the exotic plants. Such changes in the soil are potentially long-term (e.g. changes in soil pH) and are therefore likely to promote the re-invasion of these and other exotics. Both management of exotic plant invasions and the restoration of native communities must take into account exotic species effects on the soil.     

Transport of microorganisms through soil

Microorganisms migrating into and through soil from sources on the land surface may cause a serious threat to both ground and surface waters. It has been estimated that microorganisms can migrate significant distances in the field. Results from various studies suggested that preferential flow through macropores, worm holes, cracks, and fractures is the main reason for such observations. However, a quantitative representation of this phenomenon has not been provided. Microorganisms migrate through soil by advection and dispersion, while being subjected to effects of filtration, adsorption, desorption, growth, decay, sedimentation and chemotaxis. Both laboratory and field investigations have contributed important information on bacterial movement in soils. Qualitative comparisons are generally transferable from laboratory to field situations. Quantitative agreement is much more difficult to establish. Available mathematical modelling of microbial transport is limited in practical application because of the simplifying assumptions used in its development.     

Some factors affecting behaviour of boron in soil

It has been reported by many workers that various soil properties influence the retention of boron added to soils, but there is little infomration on the relative importance of these properties to boron retention and there is something controversial in the published results regarding the effects of different soil properties such as organic matter content, soil reaction, available calcium content and texture on boron retention (15). The present study was undertaken to obtain more detailed informations on the relationships between boron adsorption and different properties of soils, and on comparative contribution of soil constituents such as organic matter, sesquioxides and inorganic colloids to boron adsorption of soils. In Japan, boron deficiency symptoms of crops often appear in the fields of volcanic ash soils, and many experiments on boron application have been conducted to amend the boron deficiencies of the soils. It is considered that volcanic ash soils may have special characteristics concerning boron retention in comparison with nonvolcanic ash soils. In the present study, therefore, some volcanic ash soils were also taken as samples in addition to non-volcanic ash soils to confirm their speciality to boron retention.     

Heavy metal species,mobility and availability in soils

The ecological effects of heavy metals in soils are closely related to the content and speciation of the elements in the solid and liquid phases of soils. Methods for the determination of metal species in both phases are described and critically evaluated. In connection with the possible binding mechanisms of heavy metals in soils the concept of specific and non-specific adsorption is discussed. Recent results indicate that the adsorption of heavy metals on soil particles is not only restricted to the formation of surface complexes but can also take place in the interior of minerals. Diffusion processes of heavy metals into soil minerals are described for goethite. In order to assess metal mobility and availability in soils, the concentration and speciation of metals in the soil solution or in comparable aeqeous equilibrium solutions of soil samples and the transfer of metals from solid pools to the liquid phase and vice versa have to be assessed. Methods for the determination of the amount of plant available heavy metals are described and the associated problems discussed.     

Effect of long-term irrigation with untreated sewage effluents on soil properties and heavy metal adsorption of leptosols and vertisols in Central Mexico

The effect of long-term irrigation with untreated sewage effluents from Mexico City on soil properties and heavy metal adsorption behaviour of soils at Irrigation District 03 in the Mezquital Valley, Central Mexico, was studied. General soil parameters of 25 samples from Ap-horizons of Mollic Leptosols and Eutric Vertisols taken at sites which have been under irrigation for different periods of time were compared with samples from fields under rainfed agriculture. The adsorption of Pb, Cd, Cu and Zn was analysed in 8 selected samples by batch experiments. The long-term irrigation of soils with untreated sewage effluent has increased the contents of total (TOC) and dissolved (DOC) organic carbon in Ap-horizons of Leptosols and Vertisols, and diminished the contents of manganese oxides in Vertisols. This influences the heavy metal adsorption behaviour of both soils, since DOC enhances metal solubility at low loading rates and TOC improves metal adsorption capacities at high loading rates. The possibility of an increase in the chloride content in soils due to wastewater irrigation and its relation to higher Cd mobility are discussed, as is the importance of humus balance control through oriented management practices in order to minimize heavy metal mobility in soils, which have been under irrigation with wastewater during long periods.     

Movement of ammonium in paddy soils in Taiwan

The movement of ammonium due to diffusion in paddy soils in Taiwan was investigated in the laboratory. The movement of ammonium in flooded soils was inversely proportional to the concentration of ammonium in the soil solution, which was a function of the quantity of ammonium present, the content of solid matter in a unit volume of soil (bulk density), and the adsorptive property of soil. Although there was a considerable variation in the value of both the ammonium adsorption and bulk density of soils, the adsorptive property was more variable. Therefore, the adsorptive property seemed to be the most influencial factor on the movement of ammonium in flooded soils, where the property had a close relation to the cationexchange capacity.

The bulk density of flooded soils in the field could be reproduced in glass tubes under percolating condition in the laboratory. The values of bulk density determined on paddy soils after harvesting or on air-dry soils were considerably different from those in the flooded soils in the field. A simple determination method of bulk density was proposed for paddy soils.     

Pesticide adsorptivity of aged particulate matter arising from crop residue burns

Particulates (ashes) arising from the burning of crop residues are potentially effective adsorbents for pesticides in agricultural soils. To determine the long-term adsorptive sustainability of ashes, a wheat (Triticum aestivum L.) ash was aged under environmentally relevant conditions (in CaCl(2) solution at room temperature and pH 7) in soil extract for 1 month and in a soil (1% ash) for a period of up to 12 months. The aged ash and ash-amended soil were used to sorb diuron from water. The diuron sorption was also measured in the presence of atrazine as a competing pesticide. There was no observed microbial impact on the stability of the wheat ash in soil. All isotherms with the ash were nonlinear type-I curves, suggestive of the surface adsorption. On a unit mass basis, the ash in soil extract was 600-10000 times more effective than the soil in sorbing diuron. Adsorption of dissolved soil organic matter (DOM) during aging on the ash surfaces reduced the diuron adsorption by 50-60%. Surface competition from the atrazine adsorption also reduced the ash adsorption of diuron by 10-30%. A total of 55-67% reduction in diuron sorption by the ash-amended soil was observed. Due to its high initial adsorptivity, the ash fraction of the aged ash-amended soil contributed >50% to the total diuron sorption. Thus, the wheat ash aged in the soil remained highly effective in adsorbing diuron. As crop residues are frequently burned in the field, pesticides in agricultural soils may be highly immobilized due to the presence of ashes.     

Effect of the simultaneous addition of beta-cyclodextrin and the herbicide norflurazon on its adsorption and movement in soils

The effects of beta-cyclodextrin (BCD) on the sorption-desorption and transport processes of the herbicide norflurazon (NFL) in soils of different characteristics when both are applied simultaneously have been investigated. Adsorption-desorption studies of NFL on six soils of very different characteristics in the presence of BCD have been performed using a batch equilibration method and correlated to its mobility in homogeneous hand-packed soil columns. NFL determinations were undertaken by HPLC equipped with a diode array detector at a wavelength of 220 nm. BCD was also analyzed by HPLC with fluorimetric detection using a postcolumn reaction. The interaction of NFL with BCD yielded the formation of an inclusion complex in solution. When this complex is applied to soils, a large decrease in NFL adsorption capacity and an increase in its desorption were observed, due to the higher tendency of NFL-BCD complexes to remain in solution. The results obtained in adsorption and soil column experiments indicated that the influence of BCD on NFL mobility and availability depends on the different affinities of BCD to be sorbed on soils of different characteristics and on the concentration of BCD used. The lower the concentration of BCD added, the more tenaciously it adheres to the soil, and most of the BCD molecules would be adsorbed, providing a coating to soil particles that acts as a bridge between NFL and the soil surface, acting as an adsorbent and retarding the mobility of the herbicide. At higher concentrations of BCD, or in soils where its adsorption is very low, most of the BCD molecules are in the aqueous phase and NFL molecules tend to be complexed with BCD in solution, acting then as a solubilizing agent.     

The effects of biocidal treatments on metabolism in soil—V: A method for measuring soil biomass

A new method for the determination of biomass in soil is described. Soil is fumigated with CHCl₃ vapour, the CHCl₃ removed and the soil then incubated. The biomass is calculated from the difference between the amounts of CO₂ evolved during incubation by fumigated and unfumigated soil. The method was tested on a set of nine soils from long-term field experiments. The amounts of biomass C ha^?1 in the top 23 cm of soil from plots on the Broadbalk continuous wheat experiment were 530 kg (unmanured plot), 590 (plot receiving inorganic fertilizers) and 1160 (plot receiving farmyard manure). Soils that had been fallowed for 1 year contained less biomass than soils carrying a crop. A calcareous woodland soil contained 1960 kg biomass C ha^?1, and an unmanured soil under permanent grass 2020. The arable soils contained about 2% of their organic C in the biomass; uncultivated soils a little more—about 3%.     

Degradability of black carbon and its impact on trace gas fluxes and carbon turnover in paddy soils

Rice paddy soils are characterized by anoxic conditions, anaerobic carbon turnover, and significant emissions of the greenhouse gas methane. A main source for soil organic matter in paddy fields is the rice crop residue that is returned to fields if not burned. We investigated as an alternative treatment the amendment of rice paddies with rice residues that have been charred to black carbon. This treatment might avoid various negative side effects of traditional rice residue treatments. Although charred biomass is seen as almost recalcitrant, its impact on trace gas (CO₂, CH₄) production and emissions in paddy fields has not been studied. We quantified the degradation of black carbon produced from rice husks in four wetland soils in laboratory incubations. In two of the studied soils the addition of carbonised rice husks resulted in a transient increase in carbon mineralisation rates in comparison to control soils without organic matter addition. After almost three years, between 4.4% and 8.5% of the black carbon added was mineralised to CO₂ under aerobic and anaerobic conditions, respectively. The addition of untreated rice husks resulted in a strong increase in carbon mineralisation rates and in the same time period 77%-100% of the added rice husks were mineralised aerobically and 31%-54% anaerobically. The ¹³C-signatures of respired CO₂ gave a direct indication of black carbon mineralisation to CO_2. In field trials we quantified the impact of rice husk black carbon or untreated rice husks on soil respiration and methane emissions. The application of black carbon had no significant effect on soil respiration but significantly enhanced methane emissions in the first rice crop season. The additional methane released accounted for only 0.14% of black carbon added. If the same amount of organic carbon was added as untreated rice husks, 34% of the applied carbon was released as CO₂ and methane in the first season. Furthermore, the addition of fresh harvest residues to paddy fields resulted in a disproportionally high increase in methane emissions. Estimating the carbon budget of the different rice crop residue treatments indicated that charring of rice residues and adding the obtained black carbon to paddy fields instead of incorporating untreated harvest residues may reduce field methane emissions by as much as 80%. Hence, the production of black carbon from rice harvest residues could be a powerful strategy for mitigating greenhouse gas emissions from rice fields.     

Assessment of the influence of phosphate fertilizers on the microbial activity of pasture soils

The objective of the present work was to examine the effects of phosphate fertilizers on the microbial activity of pasture soils. Various microbial characteristics were measured using soils from an existing long-term phosphate fertilizer field trial and a short-term incubation experiment. The measurements included basal respiration, substrate induced respiration, inhibition of substrate-induced respiration by streptomycin sulphate (fungal activity) and actidione (bacterial activity) and microbial biomass C. The long-term field trials was initiated during 1985 to examine the effectiveness of different sources of phosphate fertilizers (single superphosphate, North Carolina phosphate rock, partially acidulated North Carolina phosphate rock, and diammonium phosphate) on pasture yield. The incubation experiment was conducted for 8 weeks using the same soil and the sources of phosphate fertilizers used in the field trial. In the incubation experiment the fertilizer addition caused an initial decrease in basal and substrate-induced respiration but had no effect on total microbial biomass. The initial decline in basal and substrate-induced respiration with the fertilizer addition was restored within 8 weeks after incubation. In the field experiment the fertilizer addtion had no significant effect on basal respiration but increased substrate-induced respiration and microbial biomass C. The short-term and the long-term effects of phosphate fertilizer addition on the microbial characteristies of the soils are discussed in relation to its effects on pH, salt concentration, and the nutrient status of the soils.