Soil tests for available copper and zinc in soils of Western Nigeria

Four soil tests for copper and zinc were evaluated for their ability to predict Cu and Zn uptake by oats (Avena sativa, L., Lodi var.) grown on 28 soils from Western Nigeria. Statistical analyses showed that EDTA was a better extractant for predicting Cu uptake than was DTPA, 0.1 N -HCl or 1 N -HCl. Copper uptake was more strongly correlated with inorganic soil fractions than with organic matter and was not significantly affected by soil pH. The best prediction of Zn uptake was provided by a combination of 0.1 N -HCl extractable Zn, pH, organic matter and the silt plus clay fraction in a multiple regression analysis. All four extractants predicted plant Zn uptake better on soils of pH less than 6.0 than on soils of pH greater than 6.0. A significant amount of Cu and Zn in the soils appeared to be associated with sesquioxides, part of which was available for plant use.     

Comparison of chemical tests for estimation of the availability of soil zinc

Tests for determining the availability of soil Zn were evaluated by simple and multiple correlation analysis. The soil tests included total Zn, and Zn extractable from soil by 0.2 M MgSO₄, 0.1 N HCl or dithizone. In simple correlation analyses, each of the tests correlated significantly with the uptake of soil Zn by maize (Zea mays L.) plants grown in the glasshouse. The predictions were improved significantly with all tests by the inclusion of one or more of the soil variables, pH and clay and organic matter contents, in multiple correlation analyses. The plant uptake of soil Zn could best be predicted from a multiple regression equation which included soil pH and logarithmic functions of 0.1 N HCl-extractable Zn and soil clay content as the independent variables.     

Availability of Cu,Zn and Mn in soils: I.—Influence of soil pH,organic matter,and extractable phosphorus

Samples from Ap horizons of 36 cultivated Wisconsin fields were tested for concurrent availability of Cu, Zn and Mn. The effects of soil pH, organic matter, and available P were evaluated by using four chemical extract ants. Oats were used as the test crop and were grown using a self-watering pot-culture technique in a plant-growth room. The divergent soils had the following averages: pH, 6–4; organic matter, 2–6%; available P, 37 ppm; total Cu, 20 ppm; total Zn, 35 ppm; and total Mn, 631 ppm. Concentrations of the micronutrient elements in plants and soils were determined by atomic absorption spectrophotometer. NPK fertilisation resulted in greater plant uptake of Cu, Zn and Mn. Significant interactions between the soil properties and the different chemical fractions influenced the plant uptake of each micro-element; interactions between Cu, Zn and Mn in the same chemical fraction also influenced their individual uptake. Copper uptake was best predicted by inclusion particularly of soil pH, or the same chemical fractions of Zn and Mn in the regression equation; Zn uptake by inclusion of soil organic matter and available P, Mn uptake, or the chemical fractions of Cu and Mn; and Mn uptake by inclusion of available P, Cu chemical fraction, or Zn uptake in the equation. The extractants N ammonium acetate (pH 7) 10 · 01 M EDTA and 0·1 N -HCI show promise in soil tests for the simultaneous availability of Cu, Zn and Mn.     

A comparison of various extractants for the estimation of extractable zinc in cacao-growing soils of south-western Nigeria

Forty-six soil samples from cacao plantations located in South-western Nigeria were analysed for extractable zinc by four methods, namely, ammonium acetate, dilute hydrochloric acid, magnesium chloride and diethylenetriamine pentaacetic acid (DPTA). Guinea corn (sorghum) was grown as a test crop. Relations among soil test methods, plant zinc uptake, and soil properties were examined by simple and multiple correlation analyses. The Zn extracted was in the following order: 1.0N NH₄OAc>0.1N HCl>2N MgCl₂>0.005M DTPA. The only correlation between extracts that was significant at the 5% level was between NH₄OAc and DTPA extractable Zn. No soil properties except iron and aluminium oxide were significantly correlated with soil test values. Silt, clay and silt plus clay were correlated at 5, 5 and 1% respectively with Zn uptake, but pH was not. Zinc uptake by the plant was more closely correlated with 2N MgCl₂ extractable Zn (r=+0.389) than with 1N NH₄OAc extractable Zn (r=+0.291); 0.1N HCl extractable Zn (r=+0.079); or with DTPA extractable Zn (r=+0.220). The best prediction of uptake by plants was observed in multiple regression analyses involving combination of MgCl₂ extractable Zn, pH, organic matter, and silt plus clay fraction (r=+0.601).     

Availability of Cu,Zn and Mn in Soils: III.—Predictability of plant uptake

The influence of various chemical soil fractions Of Cu, Zn and Mn in conjunction with plant uptake of any one or two of the elements on the variability of plant uptake of one of them was evaluated by correlation and regression analyses. Plant and soil data were obtained from divergent Wisconsin soils. Inclusion of Zn uptake and the HCl-or EDTA-extractable soil Cu fraction in the regression equation resulted in very high predictability of Cu uptake by oats. High predictability of Zn uptake was likewise realized by using the Mg(NO₃)₂ or DTP A soil Zn fraction along with plant Cu uptake as determinants. Manganese uptake was best predicted by using plant Zn uptake and Mg (NO₃)₂-rextractable soil Mn as predictors. The extractant N ammonium acetate (pH 7)/0·01 M EDTA showed promise as a reliable soil test for predicting the concurrent plant availability of Cu, Zn and Mn in Wisconsin soils.     

海藻多糖与有机物料对烟草青枯病的防控效果

为探究海藻多糖与其他有机物料混合使用对烟草青枯病的防控效果,以烤烟品种NC102为试验材料进行田间试验,设置不同用量海藻多糖与微生物菌肥、草木灰、贝壳粉、生物炭等有机物料的组合处理,分析了不同处理对烟草农艺性状和经济性状、土壤理化性质、烤后烟叶化学成分的影响,以及土壤理化性质与烟草青枯病发病率和病情指数的相关性。结果表明,与对照相比,海藻多糖与有机物料的施用普遍促进了团棵期和旺长期的烟株生长发育,提高了土壤pH和有机质含量,降低了烟草青枯病的发病率和病情指数;烤后烟叶经济性状和主要化学成分也有不同程度的提升。Pearson相关性分析表明,土壤有机质含量和pH与青枯病发病率和病情指数之间存在极显著的负相关关系。500倍海藻多糖稀释液在50~100 mL/株的范围内,用量越高,效果越好;组合处理中草木灰+海藻多糖75 mL/株处理效果最好。通过增加海藻多糖和有机物料,调节土壤pH或增加土壤有机质含量有助于控制青枯病的发生。     

Identification of copper binding sites in soil organic matter through chemical modifications and 13C CP-MAS NMR spectroscopy

Metal binding to an organic peat soil was probed by paramagnetic doping with copper, chemical modifications of the organic matter in the soil, and 13C CP-MAS NMR spin lattice relaxation rate measurements. Carboxyl and hydroxyl functional groups were determined to be most significant in copper uptake by the unmodified soil. Esterification and acetylation of the soil showed that metal binding by carbohydrate structures occurs independently of other functional groups and may even induce a pseudochelation phenomenon. Sorption isotherms corroborate the importance of carbohydrate structures in metal binding. These results suggest that environmental modeling of metal binding and retention in soils should incorporate estimates of the distributions of all functional groups in the soil organic matter (e.g. aliphatic, carbohydrate, phenolic, carboxyl) and their relative binding strengths.     

Removal of copper from contaminated soil by use of poly(amidoamine) dendrimers

This study characterizes poly(amidoamine) (PAMAM) dendrimers of various generations and terminal functional groups for removal of copper(II) in a sandy soil. Effects of dendrimer dose, generation number, pH, terminal functional groups, and ionic strength on the removal efficiency were investigated through a series of column tests. Over 90% of copper initially sorbed in the soil was removed by use of approximately 66 bed volumes of 0.10% (w/w) of a generation 4.5 dendrimer with carboxylate terminal groups at pH 6.0. On the basis of equal equivalent dose, dendrimers of lower generation removed more copper. Lowering pH enhanced copper removal for all dendrimers tested. In contrast, types of terminal groups (carboxylate, amine, or hydroxyl) showed a modest effect on the removal efficiency. Results from a sequential extraction procedure suggested that dendrimers removed primarily exchangeable and carbonate-bound copper. The residual copper in treated soil is predominantly bound with soil organic matter (SOM), which is much less available physical-chemically or biologically. Spent dendrimers were recovered through nanofiltration with a commercially available nanofilter. Upon acid regeneration, recovered dendrimers were reused and performed as well as the virgin dendrimers. The dendrimers may be used as reusable, high-capacity extracting agents for in situ removal of heavy metals from contaminated soils.     

The sorption of iodide by soils as influenced by equilibrium conditions and soil properties

The sorption of iodide was reduced when soil was dried before equilibration with an iodide solution. With undried soils, sorption continued for > 48 h, maximum sorption occurred at pH values < 5 but a secondary sorption peak occurred at pH 8.5 to 9.0, particularly with a soil containing a high level of organic matter. Temperature had only a small effect on sorption over the range 10 to 35 °C. Maximum values for the sorption of iodide by two surface soils (0 to 10cm) at pH 6.6 to 6.8, assessed with a soil: solution ratio of 1:10, an equilibrium time of 40 h and at room temperature, were 25 and 6 fig I/g soil, respectively. The amounts of iodide sorbed by these soils, and by soils taken from successive 10 cm layers to a depth of 40 cm at the same two sites, were closely related to the contents of organic matter in the soils but not to contents of iron or aluminium oxides or of clay. Treatment of the surface soils with hydrogen peroxide to destroy organic matter greatly reduced the sorption of iodide at the pH of about 5.5 that resulted from the treatment. The removal of iron and aluminium oxides with Tamm reagent also resulted in a marked reduction in sorption at pH < 5. The results indicate that sorption was due in part to soil organic matter and in part to iron and/or aluminium oxides. At pH > 6, organic matter appeared to be the major sorbing constituent but under more acid conditions the oxides appeared to be increasingly important.     

Uptake of copper,nickel and zinc by crops growing in contaminated soils

A series of three replicated pot trials is reported in which various crops were grown in soils having enhanced concentrations of copper, nickel and zinc. Concentrations of these elements in the tops of plants harvested at their most sensitive stage were compared with ‘total’ and ‘extractable’ concentrations in soil and with concentrations in soil solutions. There was little difference between the relationships of ‘total’ and ‘extractable’ soil metal and concentrations in plant tissue. In general, the correlation between concentrations of metals in soils and plants was unpredictable. Plants differed in their efficiency of uptake of elements; lettuce assimilated more than the other crops tested (barley, rape and ryegrass). Similarly, soil concentrations of the elements required to achieve toxic thresholds in plant tops increased in the order lettuce, ryegrass, rape and barley. Measurements made with conventional extractants of copper, nickel and zinc in soils can be of value in predicting plant uptake and hence toxicity, only if appropriate calibration curves plotting extractable soil metal against plant uptake are at hand for the particular soils and plants under consideration. Mild extracts are more sensitive to the soil properties, especially pH value, which determine plant uptake and results with metals in soil solution were promising, especially for zinc. Nevertheless, soil analyses for copper, nickel and zinc are not always closely associated with their likely toxicity to crops.     

重庆植烟土壤有效养分含量及其影响因素

为了明确重庆烟区土壤速效养分含量的主要影响因子,采用典型相关分析的方法研究了海拔高度、耕层厚度、pH、有机质等对土壤有效养分含量的影响。结果显示,重庆部分烟区土壤酸化严重,速效氮、磷、钾含量丰富,除有效硼、钼和水溶性氯外其他中微量元素含量均为丰富或很丰富。典型相关分析显示,土壤碱解氮、有效铜、有效锌、有效铁、有效硼含量随有机质的增加而增加;土壤速效钾和有效锌含量随海拔升高而增加;土壤pH的降低将导致有效磷、有效铁含量的降低,交换性钙含量的增加;土壤交换性镁等养分含量随耕层厚度的增加而增加。因此,生产上应着重解决土壤酸化、有机质低、耕层浅等问题,并合理布局植烟区域,以提供烟草产质量形成的适宜环境。     

Modeling kinetics of Cu and Zn release from soils

Kinetics of Cu and Zn release from soil particles was studied using two surface soils with a stirred-flow method. Different solution pH, dissolved organic matter (DOM) concentrations, and flow rates were tested in this study. A model for kinetics controlled sorption/desorption reactions between soils and solutions was globally fit to all experimental data simultaneously. Results were compared to a model that assumes local instantaneous equilibrium. We obtained one unique set of model parameters applicable to different pH, dissolved organic carbon (DOC), and flow conditions. We included DOM complexation of copper ions, which decreased their sorption. The effect of pH was included by assuming proton competition with metal ions for binding sites on soil particles. These results provide the basis for developing predictive models for metal release from soil particles to surface waters and soil solution.     

Zinc,copper and nickel concentrations in ryegrass grown on sewage sludge-contaminated soils of different pH

Sewage sludges containing high concentrations of zinc, copper and nickel were added separately to samples of two soils, a silty clay loam and a sandy loam, on which pH levels between 4.5 and 7.5 had been established; there were also treatments with sludge of low metal content or no-sludge. Soil-sludge mixtures were either continuously cropped with ryegrass or kept uncropped in pots in the glasshouse for 6 months. Zinc and nickel concentrations in 0.1 μM calcium chloride extracts of soils from the cropped pots and in solutions displaced from the fallow pots decreased with increasing pH over the range tested, but copper concentrations remained steady above pH 5.5; individual metal concentrations in ryegrass tops followed the same pattern with pH as those in extracted solutions. Squared correlation coefficients (R⁷) between shoot metal concentrations and concentrations of metals in EDTA, DPTA or calcium chloride extracts or displaced solutions, when taken over all soil, pH and sludge treatments, were >0.60 (P<0.001). Ryegrass yield reductions occurred on soils contaminated with each of the three metal sludges when soil pH was 5.5 or below.     

Understanding the effects of soil characteristics on phytotoxicity and bioavailability of nickel using speciation models

Acidity (pH) has been realized to be the most important soil characteristic that modulates bioavailability of heavy metals by affecting both the chemical speciation of metals in soil and the metal binding to the active sites on biota. In this work, we show that besides soil pH, metal bioavailability also depends to a certain extent on the type of soil. A better understanding of the role of soil type in regulating metal availability can be achieved with the analysis of soil composition and with calculations using chemical speciation models. Results of pot experiments, in which three different soils were spiked with nickel, show that the EC50 of total nickel in decreasing the biomass production of oats varies widely (0.7-22.5 mmol kg(-1) soil, more than 30 times). pH (4.7-7.0) is the most important factor, explaining up to a factor of 14 difference of nickel bioavailability in the soils. The remaining variation is caused by other differences in soil composition (soil type). The bioavailability and toxicity of nickel in the organic matter-rich soil studied is less than half of that in the sandy and clay soil studied at a similar pH. The chemical calculations using a multi-surface speciation model show that soil organic matter binds Ni much stronger than clay silicates and iron (hydr)oxides within the acidic pH range, which supports the experimental findings. In all three soils, the EC50 of Ni expressed in terms of Ni in 0.01 M CaCl2 soil extraction is rather stable (24-58 microM), suggesting the possibility to use this extraction as an estimation of metal availability in soil.     

Empirical models of cadmium accumulation in maize,rye grass and soya bean plants

Linear regression of published values for soil parameters and cadmium concentrations in plant tissues offers the opportunity to develop uptake coefficients that can be applied in a wide range of circumstances. A widespread literature search was performed which identified publications from the last 20 years containing information on cadmium uptake by maize and rye grass plants. After discarding experiments with inadequate data or parameters, 10 and eight papers were chosen for maize and rye grass respectively to develop linear models that related pH and cadmium concentration in the growth media (soil in pots or nutrient solution) to cadmium concentration in maize or rye grass plants (excluding roots). Cadmium concentrations in both maize and rye grass were positively correlated with soil cadmium concentration, and in the case of maize negatively correlated with soil pH. They were also negatively correlated with the product of soil cadmium concentration and soil pH, demonstrating that at high soil cadmium concentration a high soil pH reduced plant cadmium concentration. A further model of data generated from one experiment with soya beans demonstrated that other factors, such as soil temperature, can have a major influence on uptake. Copyright © 2004 Society of Chemical Industry     

烟田掺沙对土壤理化性质与烤烟养分积累的影响

为解决植烟水稻土质地黏重、烤烟生长发育受阻的问题,以云南玉溪烤烟5年连作的水稻土为研究对象,通过掺沙改变土壤粒级组成,研究土壤水稳性团聚体组成、理化指标、酶活性以及烤烟养分吸收与干物质积累情况,并分析了其相关性。结果表明,与未掺沙处理比较,掺沙30%、60%后砂粒含量分别显著增加了44.55%、58.59%（p<0.05）,黏粒、粉砂粒含量随掺沙量的增加而降低。掺沙后,<0.25 mm粒级团聚体含量显著降低（p<0.05）,大团聚体含量增加,土壤团聚体稳定性大小为掺沙30%>掺沙60%>不掺沙;土壤pH、过氧化氢酶活性增加,有机质、速效钾等主要养分含量降低,掺沙30%后土壤蔗糖酶、酸性磷酸酶活性分别比不掺沙处理显著提高了20.42%、268.69%（p<0.05）;烟株干物质、氮磷钾元素累积量均增加,其中掺沙30%时增幅最大,并且干物质和养分累积量也最高。Pearson相关分析与冗余分析表明,土壤机械组成对土壤性状和养分累积的影响显著,多数生长指标、土壤pH、过氧化氢酶活性与砂粒含量极显著正相关（p<0.01）,与黏粒、粉砂粒含量极显著负相关（p<0.01）,土壤团聚体稳定性与砂粒含量正相关。综上,本试验中水稻土掺沙比例为30%为宜,此比例掺沙可以明显改善土壤结构,改良土壤质量,阻滞土壤酸化,增加烟株对养分的吸收,促进烟株生长。     

Surface complexation of copper(II) on soil particles: EPR and XAFS studies

The interactions of transition metals with natural systems play an important role in the mobility and the bioavailability of these metals in soils. In this study, the adsorption of copper(II) onto natural soil particles was studied as a function of pH and metal concentration. The retention capacity of soil particles was determined at pH 6.2 to be equal to 6.7 mg of copper/g of solid. The Langmuir and Freundlich isotherm equations were then used to describe the partitioning behavior of the system at different pH values. A combination of EPR, extended X-ray absorption fine structure (EXAFS), and X-ray absorption near-edge structure (XANES) spectroscopies was used to probe the Cu atomic environment at the soil particles/aqueous interface. The spectroscopic study revealed that copper(II) ions are held in inner-sphere surface complexes. It also revealed that Cu was in an octahedral coordination with first-shell oxygen atoms. A weak tetragonal distortion was pointed out due to the Jahn-Teller effect, with a mean Cu-Oequatorial bond distance of 1.96 A and a Cu-Oaxial bond distance of 2.06 A. A detailed analysis of the spectroscopic data suggested that Cu(II) was bonded to organic matter coated onto the mineral fraction of soil particles.     

Interactions between soil and fertiliser in the supply of nitrogen to ryegrass grown on 21 soils

Perennial ryegrass (Lolium perenne L.) was grown in pots on 21 UK soils, both with and without fertiliser N. The fertiliser N was applied in six equal applications of ¹⁵N-labelled ammonium nitrate, each at the rate of 120 mg N per pot. The first application was mixed thoroughly with the soil, while subsequent applications were made in solution to the soil surface, after each of the first five of the six harvests of herbage. In the absence of fertiliser N, the proportion of the total soil N taken up by the plants, including stubble and roots at the sixth harvest, varied between 1.5 and 4.0%. In the presence of fertiliser N, the proportion varied between 2.1 and 4.7%. The apparent recovery of the fertiliser N was calculated from the difference between the amounts of N in the plants that received fertiliser N and in those that did not, expressed as a percentage of the amount applied. The actual recovery of the applied fertiliser N was determined by analysis of the plant material for ¹⁵N. With all soils at the first harvest, the apparent recovery was greater than the actual recovery. When calculated over all six harvests, apparent recovery of the total amount of fertiliser N was generally close to the actual recovery. This difference from the first harvest probably reflected (i) a reduction in the extent of turnover between fertiliser N and soil N when the fertiliser N was applied to the surface and (ii) a virtually complete uptake of available soil N by the end of the experiment, in both the absence and presence of fertiliser N. Differences between the 21 soils in actual recovery were not closely related, either positively or negatively, to a range of measured soil properties. A mean of 17.2% of the labelled fertiliser N was retained in the soil (excluding visible roots) at the end of the experiment. The lowest retention (6.2%) occurred with the soil which had the lowest contents of organic matter and silt plus clay but, with the other soils, the extent of retention varied only between 14.7 and 22.0% of that applied, and was not closely related to contents of total organic matter or macro-organic matter, or to the C:N ratio of the whole soil or the macro-organic matter.     

郴州植烟土壤pH空间分布及影响因素初探

为探明郴州植烟土壤酸碱度状况,于2015年在郴州烟区采集土壤样品1055个,利用多元统计学和地统计学方法分析了郴州植烟土壤pH值空间变异及其影响因素。结果表明:郴州植烟土壤pH均值为7.00,变幅为4.47~8.14,pH值小于5.5的植烟土壤占10.91%,pH值大于7.0的植烟土壤占62.37%;各县植烟土壤pH均值在5.58 ~ 7.26。植烟土壤pH值空间结构为指数模型,空间变异主要由人为因素决定（如使用石灰和钙镁磷肥等）,空间分布呈现西南高、东北低的格局。偏最小二乘回归的分析结果表明,交换性钙、粉粒、全磷、全氮、有机质、碱解氮、阳离子交换量（CEC）和交换性镁是影响植烟土壤pH值的主要因素,8项指标对植烟土壤pH值的累计解释能力达65.2%,其中以交换性钙的变量投影重要性值（VIP,Variable Importance Plot）最大;这8项指标对土壤pH值表现为正效应,土壤pH值与交换性钙、全磷、全氮、有机质、碱解氮、阳离子交换量等符合线性加平台模型,与土壤粉砂粒（0.02~0.002 mm）符合线性模型。      

Solid-solution partitioning of organic matter in soils as influenced by an increase in pH or Ca concentration

Organic matter is an important component of soil with regard to the binding of contaminants. Hence, the partitioning of organic matter influences the partitioning of soil contaminants. The partitioning of organic matter is, among other factors, influenced by the ionic composition and ionic strength of the soil solution. This study focuses on the behavior of organic matter after a change in the ionic composition of the soil solution, particularly in Ca concentration and pH. Different amounts of Ca(NO3)2 and NaOH were added to soil suspensions. The dissolved organic carbon (DOC) concentration increased with increasing pH (addition of NaOH), whereas an increase in Ca (addition of Ca(NO3)2) had the opposite effect. A stronger increase in DOC was observed if a single dose of NaOH was added, compared to a gradual addition of the same amount of NaOH. Cation binding by organic matter in the supernatant was calculated using the NICA-Donnan model. The log DOC concentration appeared to be correlated to the Donnan potential, calculated under the assumption that all DOC equals humic acid. This correlation was found for all eight neutral to acidic soils used in this study, although the slopes and elevations of the regression lines varied. The slope varied by a factor of 2 and the elevation appeared to be strongly influenced by the DOC concentration in the untreated soils, which is related to the total organic matter in the soil. Finally, we predicted the Donnan potential on the basis of an extraction of untreated soil with 0.03 M NaNO3, and the total additions of Ca(NO3)2 and NaOH. Comparison of these predictions with speciation calculations in solution showed a good correlation, indicating that a combination of one batch experiment and the presented calculation procedure can provide good estimations of DOC concentrations after addition of chemicals.