Chemical speciation of Zn in acidic soils: suitable soil extractant for assessing Zn availability to maize (Zea mays L.)

Abstract

Chemical fractions of soil Zn namely: water soluble (WS), exchangeable (EX), Pb displaceable (Pb-disp.), acid soluble (AS), Mn oxide occluded (MnOX), organically bound (OB), amorphous Fe oxide occluded (AFeOX), crystalline Fe oxide occluded (CFeOX), residual (RES) were determined in 20 surface (0–15 cm) samples of acidic soils from the provinces of Uttarakhand and Uttar Pradesh, India. The chemical fractions of soil Zn in acidic soils were found to be in the following descending order of Zn concentration: RES > CFeOX > Pb-Disp. > AFeOX > MnOX > AS > OB > EX > WS. These soil samples were also extracted by: DTPA (pH 7.3), DTPA (pH 5.3), AB-DTPA (pH 7.6), Mehlich 3 (pH 2.0), Modified Olsen, 0.01 N CaCl₂, 1 M MgCl ₂ and ion exchange resins. Chemical fractions and the soil extractable content of Zn estimated by different soil extractants were significantly correlated with some general soil properties. Maize (cv. Pragati) plants were grown in these soils for 35 days after emergence and Zn uptake by plants was compared with the amount of Zn extracted by different soil extractants and chemical fractions of Zn. Among chemical fractions of soil Zn, Pb-displaceable and acid soluble chemical fractions of soil Zn showed a significant and positive correlation with Zn uptake by maize. Path coefficient analysis also revealed that the acid soluble Zn fraction showed the highest positive and direct effect on Zn uptake (P=0.960). Among different multinutrient soil extractants evaluated for their suitability to assess Zn availability in acidic soils, DTPA (pH=5.3) was most suitable soil extractant, as the quantity of soil Zn extracted by this extractant showed a significant and positive correlation with the dry matter yield, Zn concentration and uptake by maize plants.     

Trace elements extractable by 2-ketogluconic acid from soils and their relationship to plant contents

Summary Trace element levels extractable by 2-ketogluconic acid (2-KG), ammonium acetate, acetic acid, EDTA, and DTPA were determined in three different soils of the Tarves association. The 2-ketogluconic acid was derived from 2-litre batch cultures of a soil bacterium,Erwinia sp. Pasture grasses and clovers growing on these soils were also analysed. At the same pH, 2-KG extracted more Co, Ni and Zn and considerably more Fe, Ti and V than ammonium acetate. The quantities of Cu, Mn, Mo, Ni and Zn extracted by 2-KG from the three soils generally reflected, in a similar way to the other extractants, the contents of these elements in grasses and clovers growing on the soils.     

Effect of submergence on availability of certain plant nutrients in three Ultisol catenas

Soil samples from surface and sub-surface horizons in the well-drained and poorly-drained members of three soil catenas were incubated under submergence or at field capacity to study the effects of these incubation conditions and prior natural drainage on the solubility of four plant micro-nutrients. Iron, Mn, Zn and Cu were extracted by water using a 11 water:soil ratio. The four micronutrient metals were also extracted by DTPA solutions buffered at either pH 5.3 or pH 7.3 to compare the effectiveness of these two extractants under these incubation conditions with acid soils. Generally the extractability of the nutrients was much affected by the horizon (A, E or B) with A horizons having the greatest amounts of all nutrients and undergoing greater changes in water- and DTPA-extractability during incubation. Soil drainage class (wellvs. poorly drained) had few effects. Incubation moisture regime had major effects on water extractable Fe and Mn with lesser effects on Zn and Cu. Submerged soils generally had the greatest levels of water extractable nutrients, though rice uptake did not reflect this. DTPA at pH 5.3 extracted 2 to 3 times as much Fe, Mn, Zn and Cu as did DTPA at pH 7.3 and about 50 to 100 times as much as did water. Correlations between DTPA extractable nutrients and rice uptake were significant only for Fe and Cu and declined during incubation. The changes in all variables during incubation were complex, being related to soil properties such as organic matter content, pH and mineralogy as well as to incubation conditions.     

有机物料对滨海盐渍土重金属根际效应的影响Ⅱ.土壤内源铁形态分布

研究了排水条件下施用腐熟有机物料、种稻改良滨海盐渍土内源铁形态分布．结果表明,单淹水利于土中无定形氧化铁、络合态铁、有效态铁以及氧化铁活化度升高,并且络合态铁与有效态铁升高程度,低盐土壤显著;晶形氧化铁变化不明显,土中可能存在其它形态铁向晶形氧化铁转化．种稻不施有机物料,根际络合态铁和有效态铁富集;无定形氧化铁和晶形氧化铁亏缺．根际氧化铁活化度稍低于非根际．增施有机物料利于两种盐渍土根际内外铁形态向络合态铁和无定形氧化铁转化;有效态铁和氧化铁活化度提高,低盐土壤根际较明显     

Impact of the invasive polychaete Marenzelleria viridis on the biogeochemistry of sandy marine sediments

Strong correlations of soil total organic carbon (OC) with iron and aluminum phases reported frequently make it important to quantify these organic matter (OM) associations, but selective extractants sometimes contain OC. Soil nitrogen is often predominantly organic and might serve as a proxy for OM. We therefore investigated nitrogen associations with Fe and Al using several selective extractants that use reductive, complexation, and alkaline approaches. Total dissolved nitrogen (TDN) correlated strongly with extracted Fe and Al across seventeen samples, including highly- and weakly-weathered soils, iron-rich ultrabasic soils, podzolic, and volcanic soils. Typically a quarter to a third of total soil nitrogen was dissolved by the various extractions, though higher fractions (up to 60%) were found in spodic-horizon and volcanic surface-horizon samples. Similar proportions were found for OC, using three OC-free extractants, indicating that TDN provides a useful surrogate for assessing OM partitioning via extractants that contain OC. Use of TDN:metal ratios in extractant solutions allows estimation of extracted OM that could have been sorptively associated with metal oxide/hydroxides and poorly-crystalline aluminosilicates. These ratios were often high in extractions targeted at these adsorbents, and imply that usually most of the extracted TDN consists instead of organo–metal complexes. The dynamics of these complexes may have stronger control on accumulation/remobilization of soil OM than those of metal oxyhydroxides and poorly-crystalline aluminosilicates.     

The relationship between available molybdenum in soils of volcanic ash origin and the molybdenum content in red clover (Trifolium pratense,L) leaves

Summary The relationship between Mo content in red clover leaves and available Mo in two different soil series of volcanic ash origin (Iwate-san and Hizume soils) was studied.If results were treated separately for each soil series, positive single correlations were obtained between leaf Mo and soil Mo extracted by Grigg's pH 3.3, 0.55N ammonium oxalate method. Correlation between leaf Mo and soil Mo was not significant if data from both soil series were combined. This relationship appeared to be due to several factors. First, the recovery of added Mo was lower in Hizume soils than in Iwate-san soils. This tendency for Mo fixation was confirmed by a pot experiment. Second, the amount of Fe as free hydrous Fe oxides dissolved in the acidic ammonium oxalate extract was higher in Hizume soils than in Iwate-san soils. This was negatively correlated with leaf Mo content. Therefore, the multiple correlation and regression between leaf Mo of red clover and available Mo, free hydrous Fe oxides and Mo recovery of soils gave satisfactory results even if data from both soils were combined.However, in the two soils used in this study, extraction at pH 3.3 failed to give the highest yield of Mo. They were obtained at much lower pH even though the concentration of organic acid remained constant. This was particularly clear in Iwate-san soils. The acidic ammonium oxalate extraction procedure tends to underestimate soil Mo availability in these kinds of soils, especially in extraction of Iwate-san soils.     

A suitable extractant for assessing plant-available copper in different soils (peaty,red and alluvial)

Summary Relative efficiency of five chemical extractants for the extraction of available Cu in four different soils and its uptake by rice seedlings was studied in a pot culture experiment. The Cu extracted by 0.1N HCl showed significant relationship with plant uptake whereas the values for other extractants except 0.05M EDTA did not approach the level of significance. Among the soil properties studied, pH and CaCO₃ correlated negatively and organic matter and CEC positively with Cu uptake by rice plants.     

Evaluation of suitable extractant for available lead in soils

Summary Four extractants were used to extract Soil-Pb from alluvial soils and the amounts of Pb extracted was correlated with Pb concentration in wheat crop. Of all the reagents, the Grigg's reagent was found to extract maximum amount of Pb from soils and the N NH₄OAc the least. A highly significant correlation (r=0.295) was observed between Grigg's reagent extractable Pb and Pb concentration in wheat plants followed by ammonium acetate (r=0.238). While 0.02M EDTA did not show any significant correlation, a negative significant correlation was observed with 0.1N HCl. re]19750512     

Phosphorus status of some ethiopian soils

The capacity to sorb P varied among some Ethiopian soils. Volcanic ash soils sorbed the maximum P while Fluvisols and Regosols sorbed the least. Sorption of P was significantly correlated with exchangeable and extractable forms of Fe and Al as well as pH and organic matter. But is was not related to the clay content of the soils. The role of Al was more important than that of Fe even though more dithionite and oxalate extractable Fe than Al was found in all soils.     

Availability of iron,manganese, zinc and phosphorus in submerged sodic soil as affected by amendments during the growth period of rice crop

Summary Effect of amendments, gypsum (12.5 tonnes/ha), farmyard manure (30 tonnes/ha), rice husk (30 tonnes/ha) and also no amendment (control) on the availability of native Fe, Mn and P and applied Zn in a highly sodic soil during the growth period of rice crop under submerged conditions was studied in a field experiment. Soil samples were collected at 0, 30, 60 and 90 days of crop growth. Results showed that extractable Fe (1N NH₄OAC pH 3) and Mn (1N NH₄OAC pH 7) increased with submergence upto 60 days of crop growth but thereafter remained either constant or declined slightly. Application of farmyard manure and rice husk resulted in marked improvement of these elements over gypsum and control. Increases in extractable Mn (water soluble plus exchangeable) as a result of submergence and crop growth under different amendments were accompanied by corresponding decreases in easily reducible Mn content of the soil. Application of 40 kg zinc sulphate per hectare to rice crop could substantially raise the available Zn status (DTPA extractable) of the soil in gypsum and farmyard manure treated plots while the increase was only marginal in rice husk and control plots indicating greater fixation of applied Zn. Available P (0.5M NaHCO₃ pH 8.5) behaved quite differently and decreased in the following order with crop growth: gypsum>rice husk>farmyard manure>control.     

A common chemical extractant for estimating plant-available zinc in different soil types (peaty,red and alluvial)

Summary Relative efficiency of five chemical extractants for the extraction of available Zn in four different soils and its uptake by rice seedlings was studied in a pot culture experiment. The Zn extracted by dithizone-ammonium acetate showed a significant relationship with plant uptake whereas the values for other extractants except NH₄OAc (pH4.8) did not approach the level of significance. Among the soil properties studied, pH and CaCO₃ correlated negatively and organic matter and CEC positively with Zn uptake by rice plants.Contribution from the Soil Science and Agricultural Chemistry Dept., Banaras Hindu University, Varanasi-221005, India.Lecturer and Research Scholar of the Soil Science and Agricultural Chemistry Department, respectively.Lecturer and Research Scholar of the Soil Science and Agricultural Chemistry Department, respectively.     

有机物料对白浆土金属氧化物形态转化和迁移的影响及其肥力效应

通过土柱淋溶试验研究了牧草粉腐解物对白浆土Ｆｅ、Ｍｎ、Ａｌ氧化物形态转化及剖面迁移的影响及其对土壤Ｐ素形态转化和有效性的影响．结果表明,加有机物料淋溶使土壤ＤＴＰＡ提取态或有机络合Ｆｅ、Ｍｎ、Ａｌ氧化物含量显著上升;有效磷含量也极显著上升,主要在于铝磷和铁磷含量的增加;白浆层土壤中有效态磷及无机磷各形态均随着腐熟牧草粉用量的加大而极显著地升高,表层土壤中有效态磷、铝磷、铁磷的变化也与加入的腐熟牧草粉极显著正相关．土壤有效态磷、铝磷、铁磷与ＤＴＰＡ提取态和有机络合态Ｆｅ、Ｍｎ显著或极显著相关,但在表层土壤磷素各形态与ＤＴＰＡ及焦磷酸钠提取的Ａｌ呈极显著负相关,而白浆层却是极显著正相关．     

Phytoalexin production in lucerne roots inoculated withVerticillium albo-atrum

Summary Out of various soil and plant test methods tested for predicting response of rice to K application in soils of a rice growing valley region the Hanway and Heidal extractant neutralN NH₄ OAc turned out to be the best. The critical limit of extractable K was 160 ppm by the Hanway and Heidal extractant, and by the Bray's reagent 175 ppm. Critical K level in the rice plant is 0.4%. Correlations between the extractable K and K uptake were highly positive for various extractants: Hanway and Heidal, Morgan, Hunter and Pratt No. 2, Blanchet and Perigand and MacLean. Although majority of the soils of the region was Inceptisols followed by Alfisols and Vertisols, all soil types had a similar available nutrient status and a similar pattern in relative grain yields. K response was noticeable in Alfisols with respect to grain and straw yields. The grain P concentration in Vertisols, and straw K in Alfisols indicated the contribution of K towards the productivity of two soil groups.     

Potential errors caused by roots in analyses of rhizosphere soil

Roots contain high concentrations of many elements, and have the potential to interfere with measurements of chemical change in rhizosphere soil. To assess potential interferences, maize (Zea mays L.) roots (free of soil) and soil (free of roots) were extracted separately with several extractants commonly used to assess the status of soil nutrients. The maize roots were grown within filter envelopes which prevented direct contact with soil, but permitted passage of mineral nutrients and water from the adjacent soil. Water, ammonium acetate (pH 7), DTPA (pH 7.3), Morgan's solution (pH 4.8), and dilute HCl were used as extractants. Most elements were released readily into soluble forms from roots killed by freezing to lyse the cells. Significantly lower amounts were extracted from fresh roots, with the greatest differences between fresh and killed roots for the extractants H₂O and DTPA, which were the mildest in terms of acidity and salt concentration. Extraction of P from the fresh roots by H₂O and HCL was particularly low. Contamination of rhizosphere samples with root materials would almost certainly prevent the accurate measurement of water-soluble P, K, Mn, Zn, Cu, and Na in the slightly alkaline soil used in this experiment. Large errors would be likely also for P, Mn, and Cu extracted by ammonium acetate. The DTPA extractant is normally used only for micronutrient metals or heavy metals, and the small amounts of these elements released by roots should not contribute to significant error. With Morgan's solution, errors would likely be large only for P. Dilute HCl is a reasonably strong extractant for many elements in soil, and major errors from roots contained in rhizosphere samples are unlikely. The relatively high probability of errors in extractions of soluble elements from rhizosphere soil is unfortunate, because these elements are among the most readily available to plants and the most likely to be altered by the normal activities of roots.     

Effect of soil salinity on the electro-chemical and chemical kinetics of some plant nutrients in submerged soils

Summary The electro-chemical and chemical kinetics of six California rice soils were significantly influenced by the presence of salts up to an EC of 9 mmhos/cm in saturation extract (EC_e). Subsamples of each soil salinity treatment were incubated for periods up to 10 weeks after flooding. Most of the changes in Eh and pH values took place in the first 3–4 weeks after submergence. Salinity decreased pH values, but slightly increased the redox-potential. Both ammonification and nitrate reduction were significantly decreased, by increasing soil salinity. Salinity up to 9 mmhos/cm did not affect levels of Bray and Kurtz extractable P, but increased the water extractable Ca, Mg, K and Mn. In DTPA extract, salinity in incubated soils had no effect on Zn in 4 soils, but it decreased Fe in acid and neutral soils. Possible explanations for the electro-chemical and chemical kinetic changes due to flooding and salinity are discussed.     

Simultaneous extraction of soil phytoavailable cadmium,copper, and lead by chelating resin membrane

Cadmium, copper, and lead were extracted from suspensions of contaminated soils using metal chelating exchange resin membranes. Nine soils with widely varying properties and Cd, Cu and Pb levels were tested. Soil suspensions made up with 4 g in 40 mL deionized water were equilibrated with 5 cm² Ca-saturated Chelex exchange resin membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd, Cu and Pb of the soils were correlated with Cd, Cu, and Pb uptake by young wheat seedlings grown in these soils and compared with soil Cd, Cu, and Pb extracted by 0.1 M HCl, 0.01 M CaCl₂, and 0.005 M Diethylenetriamine pentaacetic acid (DTPA). The amounts of Cd, Cu and Pb extracted by the Ca-saturated Chelex membrane from all tested soils correlated well with those absorbed by young wheat seedlings. The Ca-saturated Chelex membrane extractable Cd, Cu and Pb of the soil had the strongest correlation with plant uptake Cd, Cu and Pb among the extraction methods we tested. It was demonstrated that the Ca-saturated Chelex membrane extraction is an appropriate method in simultaneously estimating Cd, Cu and Pb phytoavailability of soil and is applicable to a wide range of soils.     

Amelioration of growth reduction of lowland rice caused by a temporary loss of soil-water saturation

Decreases in nutrient availability after loss of soil-water saturation are significant constraints to productivity in lowland rainfed rice soils. The effectiveness of soil amendments like lime and straw in ameliorating these constraints are poorly understood. This pot experiment was conducted in Cambodia to investigate changes in soil chemical properties and nutrient uptake by rice after applying lime or straw to continuously flooded or intermittently flooded soil. In continuously flooded soils, exchangeable Al decreased to below 0.2 cmolc/kg. Liming (pH 6.5–6.8) the continuously flooded soil decreased the levels of acetate extractable Fe and P, plant P uptake and shoot dry matter, but had no effect on either Bray-1 or Olsen extractable P values. By contrast, the addition of straw (3.5 g dry straw/kg soil) increased Bray-1, Olsen, and acetate extractable P, plant P uptake, shoot P, and shoot dry matter. The non-amended soils became strongly acidic after loss of soil water saturation: extractable Al increased to 1.0 cmol_c/kg, a potentially harmful level for rice. By contrast, extractable P decreased markedly under loss of soil water saturation as did plant P uptake, shoot P, and shoot dry matter. With loss of soil water saturation, liming substantially depressed the levels of Al but it did not increase plant P uptake, shoot P, and shoot dry matter. Straw addition not only decreased extractable Al levels to well below 0.6 cmol_c/kg under loss of soil water saturation, but it also increased extractability of soil P, plant P uptake, shoot P, and shoot dry matter. Thus, in rainfed environments, the incorporation of straw may be more effective than liming to pH 6.8 for minimising the negative effects of temporary loss of soil-water saturation on P availability, P uptake, and growth of rice.     

土壤中铬的有效性与污染生态效应

本文研究了土壤中铬的有效性及其对水稻生长发育和吸收积累的影响,结果表明：０．０５ｍｏｌ／ＬＥＤＴＡ是土壤中有效态铬的较好提取剂;添加无机态Ｃｒ（Ⅲ）、Ｃｒ（Ⅳ）的盆栽土壤中有效态铬随时间延长而降低,在低添加浓度下,水稻根系中铬浓度随生长时间延长而增高,茎叶中铬含量则相反;铬对水稻的毒性和吸收积累明显受土壤性质的影响。     

The effects of flooding for rice culture on soil chemical properties and subsequent maize growth

Summary The effects of flooding and lowland rice culture on soil chemical properties and subsequent maize growth were investigated in two contrasting rice soils of S.E. Australia. The effects of incorporating rice straw, either during or after flooding were also studied. The experiment was conducted in a glasshouse with the use of large intact soil cores.Previous flooding markedly reduced maize growth, leaf P concentration and P uptake, despite the application of a large quantity of P fertilizer after drainage. Soil analyses showed that previous flooding increased the Langmuir sorption terms for maximum P sorption and bonding energy. The availability of P was more closely related to the bonding energy between soil and P than to the capacity of the soils to sorb P. The increases, in the P sorption parameters, were associated with decreases in the crystallinity of the free iron oxides as determined by their oxalate solubility. It was concluded that depressed P supply to maize sown in previously flooded soils was due to stronger P sorption by the drained soils, rather than to P immobilization during flooding.Rice plants grown during flooding reduced the amount of N available to the subsequent maize crop, but did not significantly affect P availability. Rice straw added during flooding did not affect subsequent maize growth, but when added after flooding caused microbial immobilization of N.Salts, Fe or Mn from previous flooding did not affect maize growth.     

不同典型地带性土壤氮素分布特征及其影响因素

在野外取样的基础上,研究中国不同典型地带性土壤各形态氮素分布特征及其影响因素.结果表明: 垂直地带性土壤中0.5 mol·L^-1 K₂SO₄提取的提取态总氮、提取态有机氮、吸附氨基酸随取样点海拔的增加而显著增加,且提取态总氮、提取态有机氮和吸附氨基酸平均值都大于水平地带性土壤;水平地带性土壤各形态氮含量随土壤类型的不同而差异显著.土壤吸附氨基酸含量是游离氨基酸的5倍,占提取态有机氮百分比为21.1%,表明吸附氨基酸可能作为土壤有机氮库的一种重要存在形态.相关分析结果表明,垂直地带性土壤中提取态总氮、提取态有机氮、铵态氮、氨基酸态氮均与有机质、全氮呈显著正相关(r=0.57～0.93,P<0.05),但与pH、硝态氮呈显著负相关(r=-0.37～-0.91,P<0.05);水平地带性土壤pH与提取态总氮、硝态氮、有机质、全氮、碱解氮及盐基离子(K⁺、Ca²⁺、Mg²⁺)呈显著正相关(r=0.36～0.85,P<0.05),与铵态氮、氨基酸态氮呈显著负相关(r=-0.39～-0.81,P<0.05).