The evaluation of plant-available sulphur in soils

Summary Examination of a range of naturally occurring calcium carbonates and calcareous soils has shown that insoluble sulphate associated with calcium carbonate may comprise an important fraction of soil sulphur. One soil contained as much as 93 per cent of its sulphur in this form. It seems likely that this sulphate occurs as a co-precipitated or co-crystallized impurity in the calcium carbonate.Most surface soils had only low capacity to adsorb sulphate and contained only small amounts of sulphur in this form. Two acid surface soils and many acid subsoils, however, adsorbed sulphate quite strongly and in some acid subsoil clays adsorbed sulphate made up an important fractions of the total sulphur.Sulphate adsorption was found to be negligible above pH 6.5 and adsorbed sulphate may be determined by aqueous extraction after increasing the pH above this value by addition of solid calcium carbonate. Adsorption of sulphate during acid extraction of soils can lead to low values in the determination of acid-soluble sulphates. Sulphate so adsorbed can be determined by a second extraction with water after the addition of solid calcium carbonate to increase the pH to a value greater than 6.5.     

Some factors influencing production of sulphate by oxidation of elemental sulphur and thiosulphate in upper horizons of spruce forest soils

Some factors influencing the oxidative activity of upper horizons of spruce forest soils (a mixture of fermentative and humus layers) toward intermediates of the oxidative part of the sulphur cycle were investigated. Preincubation of the soil with added cysteine, sulphide, elemental sulphur or thiosulphate was found to stimulate enzyme systems oxidating any of these compounds. Sulphite and sulphate were ineffective in this respect. The oxidation of elemental sulphur was stimulated by CaCO3, technical urea and high doses of superphosphate and potassium sulphate. It was inhibited by KH2PO4, pure urea, 40 % potassium salt, ammonium nitrate with calcium carbonate and the fertilizer NPK I. It proceeded at the highest rate at approximately 60 % capillary capacity (61 % of mass water content). Oxidation of thiosulphate was stimulated by KH2PO4, pure urea, superphosphate, potassium sulphate and only slightly by the fertilizer NPK I. It was inhibited by CaCO3, 40 % potassium salt and only slightly by ammonium nitrate with calcium carbonate. Potassium chloride, glucose and technical urea were without effect. The oxidation proceeded at the highest rate at 35 % maximal capillary capacity (48 % mass water content).     

Sodium in the mineral nutrition ofAvena Sativa

Summary In pot experiments with oats on sandy soil poor in sodium and potassium a study was made of the effect of the addition of Na₂SO₄ and K₂SO₄ on the mineral composition of the straw.The addition of sodium at 200 ppm Na significantly increased the phosphorus content of the straw and there was a slight further increase with 200 ppm Na plus 200 ppm K, but the phosphorus content never exceeded 0.13 per cent.Sodium and potassium caused a highly significant decrease in the silica content of the straw. Decreased lodging in soils inundated with sea water can therefore not be ascribed to an increase of silica content.The calcium and the cellulose contents of the straw were both significantly reduced by sodium and potassium.     

Effects of organic matter on sulphur oxidation in soil and influence of sulphur oxidation on soil nitrification

Summary The effects of wheat straw and pressed sugar beet pulp on sulphur oxidation were determined in a loam soil amended with 1% (w/w) elemental sulphur. Wheat straw stimulated the oxidation of elemental sulphur over the first 2 to 3 weeks of the incubation period, resulting in an increase in LiCl-extractable sulphate. After 4 to 7 weeks incubation however, the only significant increase in soil sulphate followed the 1% straw addition, while at week 7 sulphate concentrations in the 0.25% and 5.0% straw amended soils were lower than the control. Pressed sugar beet pulp (1% w/w) initially stimulated the oxidation of elemental sulphur in the soil, but by weeks 3 to 7 of the incubation period rates of oxidation in pulp-amended soils were lower than the control. Towards the end of the incubation period however, sulphate concentrations in the amended soils exceeded the control values, significantly so by week 11. The concentration of thiosulphate and tetrathionate also increased in soils receiving sugar beet pulp. Nitrification was inhibited in soils in which sulphur oxidation was actively occurring. Although possible alternatives are mentioned, such inhibition appears to result from a decrease in soil pH brought about by the oxidation of elemental sulphur to sulphuric acid.     

Sulphur oxidation by soil fungi including some species of mycorrhizae and wood-rotting basidiomycetes

Abstract The mycorrhizal fungi Amanita muscaria, Paxillus involutus, Hymenoscyphus ericae, Pisolithus tinctorius, Rhizopogon roseolus , and Suillus bovinus oxidized elemental sulphur to thiosulphate and sulphate in vitro. In some, but not all cases, tetrathionate was also formed. Limited oxidation of elemental sulphur by R. roseolus also occurred when growing in association with Pinus contorta in unsterilized peat. Although yeasts capable of oxidizing sulphur could not be isolated from a wide range of soils, a yeast-like fungus ( Monilia sp.) isolated from deciduous woodland soil oxidized elemental sulphur to sulphate, forming thiosulphate, but not tetrathionate. This fungus also oxidized tetrathionate to sulphate but showed only limited ability to oxidize thiosulphate to tetrathionate. Both Aspergillus niger and Trichoderma harzianum oxidized elemental sulphur in mixed culture with Mucor flavus . Larger amounts of sulphate were initially formed in mixed, compared to single culture; but by week 5 of the incubation period sulphate formation was greatest in single culture. The wood-rotting fungi, Hypholoma fasciculare and Phanerochaete velutina showed a limited ability to oxidize elemental sulphur in vitro but were incapable of oxidizing the element when growing as mycelial cords in non-sterilized soils. The relevance of these results to the possibility that fungi play a role in sulphur oxidation in soils is commented upon.     

Oxidation of reduced sulphur compounds by intact cells of Thiobacillus acidophilus

Oxidation of reduced sulphur compounds by Thiobacillus acidophilus was studied with cell suspensions from heterotrophic and mixotrophic chemostat cultures. Maximum substrate-dependent oxygen uptake rates and affinities observed with cell suspensions from mixotrophic cultures were higher than with heterotrophically grown cells. ph Optima for oxidation of sulphur compounds fell within the pH range for growth (pH 2–5), except for sulphite oxidation (optimum at pH 5.5). During oxidation of sulphide by cell suspensions, intermediary sulphur was formed. Tetrathionate was formed as an intermediate during aerobic incubation with thiosulphate and trithionate. Whether or not sulphite is an inter-mediate during sulphur compound oxidation by T. acidophilus remains unclear. Experiments with anaerobic cell suspensions of T. acidophilus revealed that trithionate metabolism was initiated by a hydrolytic cleavage yielding thiosulphate and sulphate. A hydrolytic cleavage was also implicated in the metabolism of tetrathionate. After anaerobic incubation of T. acidophilus with tetrathionate, the substrate was completely converted to equimolar amounts of thiosulphate, sulphur and sulphate. Sulphide- and sulphite oxidation were partly inhibited by the protonophore uncouplers 2,4-dinitrophenol (DNP) and carbonyl cyanide m-chlorophenylhydrazone (CCCP) and by the sulfhydryl-binding agent N-ethylmaleimide (NEM). Oxidation of elemental sulphur was completely inhibited by these compounds. Oxidation of thiosulphate, tetrathionate and trithionate was only slightly affected. The possible localization of the different enzyme systems involved in sulphur compound oxidation by T. acidophilus is discussed.     

Lead uptake from soils by perennial ryegrass and its relation to the supply of an essential element (sulphur)

Summary The lead status of 16 soils of England and Wales was studied by pot-culture and soil chemical procedures. Perennial ryegrass was grown on the soils, with and without added sulphur, in a controlled environment cabinet with carbonfiltered air. Plant-available lead comprised uptake in 4 successive harvests of tops plus that in roots at the final harvest. The concentration of lead in the tops of healthy plants, i.e. those with adequate sulphur, was lower than in the roots, e.g. at harvest 4 the means were 5.0 and 12.9 ppm, respectively. However, with sulphur-deficient plants the concentration of lead in the tops was often higher than in the roots, the means at harvest 4 being 16.3 and 13.0 ppm, respectively. The marked increases in the concentration of lead in the tops of sulphur-deficient plants coincided with decreases in dry-matter yield, but for any one soil the tops of such plants contained similar amounts of lead to those of healthy plants. The lead content of the tops was poorly correlated with soil lead whereas that of the roots, in terms of both concentration and total amount, was highly correlated. The amount of lead extracted by 0.5 M BaCl₂ or 0.05 M EDTA provided a slightly better assessment of availability than ‘total’ content or the amount extracted by 2.5 per cent acetic acid. The solutions of acetic acid, BaCl₂ and EDTA extracted, on average, 1.0, 16.3 and 32.7 per cent respectively, of the total lead in the soils. The greater replacement of lead by the Ba ion than by the H ion (acetic acid) is ascribed to valence and the similar radii of Pb⁺ and Ba⁺. It is concluded that in soil-grown ryegrass the roots restrict the movement of lead into the tops of high-yielding plants, but when growth is limited by sulphur deficiency the concentration in the tops increases markedly. re]19720922     

Sulphur mineralization and adsorption in soils

Summary Studies were conducted to determine the comparative sulphur mineralizing capacity of selected Malaysian and Iowan soils and to determine the amounts of available and adsorbed sulphate in a number of Malaysian soils. Results of the mineralization study indicated that more sulphur mineralised from Malaysian soils although their average contents of total sulphur were lower compared to Iowan Soils. For both sets of soils, significant correlations between contents of organic carbon and total sulphur existed indicating that most of the sulphur was in organic combination. Phosphate solution consistently extracted higher quantities of sulphate in comparison to chloride solution in the Malaysian surface soils implying that a portion of the sulphate existed in adsorbed form. Adsorption of sulphate in soils was found to be dependent on concentration of sulphate added and followed the Langmuir adsorption isotherm.     

Effect of industrial immissions with high sulphur dioxide content on thiobacilli and oxidative activity of spruce forest soils towards inorganic sulphur compounds

Effect of industrial immissions with high sulphur dioxide content on the upper horizons of spruce forest soils in NW Bohemia was investigated. The content of sulphates, oxidative activity towards sulphide, elemental sulphur, thiosulphate and sulphite, concentration and species representation of thiobacilli in horizons F, H and A in regions highly affected by immissions (two localities) and in regions relatively less influenced (three localities) were followed. In the affected areas the sulphur content in the soil was higher, the species representation of thiobacilli was similar and their concentration was higher, the ability of the soil to oxidize thiosulphate was inhibited and oxidation of elemental sulphur was stimulated. The oxidation of sulphide and sulphite was not significantly affected by the immissions. Changes caused by immissions could be observed only in horizons F and H and did not involve horizons A.     

Interactive effects of mycorrhization and elevated atmospheric CO2 on sulphur nutrition of young pedunculate oak (Quercus robur L.) trees

Pedunculate oak (Quercus robur L.) was germinated and grown at ambient CO₂ concentration and 650 μmol mol^?1 CO₂ in the presence and absence of the ectomycorrhizal fungus Laccaria laccata for a total of 22 weeks under nonlimiting nutrient conditions. Sulphate uptake, xylem loading and exudation were analysed in excised roots. Despite a relatively high affinity for sulphate (K_M= 1.6 mmol m^?3), the rates of sulphate uptake by excised lateral roots of mycorrhizal oak trees were low as compared to herbaceous plants. Rates of sulphate uptake were similar in mycorrhizal and non-mycorrhizal roots and were not affected by growth of the trees at elevated CO₂. However, the total uptake of sulphate per plant was enhanced by elevated CO₂ and further enhanced by elevated CO₂ and mycorrhization. Sulphate uptake seemed to be closely correlated with biomass accumulation under the conditions applied. The percentage of the sulphate taken up by mycorrhizal oak roots that was loaded into the xylem was an order of magnitude lower than previously observed for herbaceous plants. The rate of xylem loading was enhanced by mycorrhization and, in roots of mycorrhizal trees only, by growth at elevated CO₂. On a whole-plant basis this increase in xylem loading could only partially be explained by the increased growth of the trees. Elevated CO₂ and mycorrhization appeared to increase greatly the sulphate supply of the shoot at the level of xylem loading. For all treatments, calculated rates of sulphate exudation were significantly lower than the corresponding rates of xylem loading of sulphate. Radiolabelled sulphate loaded into the xylem therefore seems to be readily diluted by unlabelled sulphate during xylem transport. Allocation of reduced sulphur from oak leaves was studied by flap-feeding radiolabelled GSH to mature oak leaves. The rate of export of radioactivity from the fed leaves was 4–5 times higher in mycorrhizal oak trees grown at elevated CO₂ than in those grown at ambient CO₂. Export of radiolabel proceeded almost exclusively in a basipetal direction to the roots. From these experiments it can be concluded that, in mycorrhizal oak trees grown at elevated CO₂, the transport of sulphate to the shoot is increased at the level of xylem loading to enable increased sulphate reduction in the leaves. Increased sulphate reduction seems to be required for the enhanced allocation of reduced sulphur to the roots which is observed in trees grown at elevated CO₂. These changes in sulphate and reduced sulphur allocation may be a prerequisite for the positive effect of elevated CO₂ on growth of oak trees previously observed.     

Nitrogen and sulphur requirements of Colletotrichum inamdarii Lal

Summary Nitrogen and sulphur requirements ofColletotrichum inamdarii Lal isolated from the leaves ofCarissa carandas L. have been studied. DL-serine, L-asparagine and L-phenylalanine have been found to be of good nitrogen source followed by potassium nitrate, calcium nitrate, magnesium nitrate, DL-alanine, ammonium nitrate, glutamic acid, ammonium sulphate, DL-valine, aspartic acid, ammonium chloride, ammonium hydrogencarbonate, L-histidine and potassium nitrite. There was no growth in the absence of nitrogen.Sporulation was excellent on calcium nitrate and sodium nitrate, Very good on DL-serine, potassium nitrate, and magnesium nitrate. Good on L-asparagine, L-phenylalanine and ammonium oxalate. Fair on DL-alanine, DL-leucine, ammonium sulphate, DL-valine, ammonium chloride and L-histidine whereas poor on glutamic acid, aspartic acid, ammonium tartarate and ammonium nitrate. Few spores were observed on ammonium hydrogencarbonate but potassium nitrite did not show any sporulation.Amongst the sulphur compounds sodium bisulphate gave the best growth and good sporulation, followed by sodium thiosulphate, magnesium sulphate, ammonium sulphate and potassium sulphate. Thiourea gave negligible growth whereas it failed to grow on zinc sulphate and potassium persulphate.     

Sulphur oxidation by a Streptomyces sp. growing in a carbon-deficient medium and autoclaved soil

Streptomyces colonies, apparently all of the same species, were isolated from a range of soils using a polysulphide medium lacking an organic carbon source. Growth on this medium, and clearing of the otherwise white, opaque overlay, suggested that the organisms were capable of growing autotrophically. However, investigation of one of these isolates showed that it was unable to fix ¹⁴CO₂ and did not possess the enzyme ribulose bisphosphate carboxylase, showing that it was incapable of autotrophic growth. The isolate oxidized elemental sulphur, thiosulphate and tetrathionate to sulphate in vitro in carbon-deficient medium, and also oxidized elemental sulphur to sulphate when inoculated into autoclaved soil supplemented with sulphur. It also oxidized polysulphide when growing on Czapek Dox and plate count agars. The isolate can therefore grow heterotrophically in both carbon-rich media and in media lacking organic carbon — presumably by scavenging organic carbon from the laboratory atmosphere. The possible role of these organisms in sulphur oxidation in soils is commented upon.     

Studies of ‘Available’ and isotopically exchangeable sulphur in some North Queensland soils

Summary Using ³⁵S-sulphate, the specific activity of various sulphur fractions in some diverse North Queensland soils has been followed for up to 185 days in a glasshouse experiment. The sulphur extracted with 0.01 M calcium phosphate was from the same pool as that used by the test plants, and since near full recovery of added ³⁵SO₄ was obtained initially, this fraction is comparable to the L-value. On the other hand, 0.5 M NaHCO₃ removed some soil sulphur that was not available to the plants.Liming caused an initial increase in the phosphate extractable fraction, the sulphur seemingly being released from the NaHCO₃ extractable fraction, but decreased sulphate sorption also contributed to the increase in S uptake by the plants upon liming. re]19750507     

Effect of zinc,phosphorus and nitrogen on tryptophan concentration in rice grains grown on limed and unlimed soils

Summary The effects of Zn, P, N and CaCO₃ on tryptophan concentration in rice grain were studied in greenhouse at Haryana Agricultural University. Zinc application upto 20 ppm increased tryptophan concentration in rice grain. Zn-EDTA gave highest increase followed by ZnSO₄ and then ZnO. Liming at the rate of 4 and 8 per cent decreased tryptophan concentration significantly. Phosphorus application upto 100 ppm also decreased tryptophan significantly but Zn in combination with P increased tryptophan and overcame negative effect of P. Nitrogen application upto 120 ppm increased tryptophan concentration. There was positive interaction between Zn and N. Ammonium sulphate gave highest tryptophan followed by ammonium nitrate and then urea. The tryptophan concentration ranged between 766 ppm and 2011 ppm in paddy grain. The lowest tryptophan concentration was in the plants treated with 8 per cent lime in absence of added Zn and highest with 10 ppm Zn through Zn-EDTA. Department of Soils.     

Dynamics of oxidation of inorganic sulphur compounds in upper soil horizons of spruce forests

Dynamics of oxidation of inorganic sulphur compounds to sulphate by the soil of spruce forests was investigated. Sulphide, sulphite and thiosulphate are oxidized to sulphate at a maximal rate at the beginning of the reaction, oxidation of elemental sulphur exhibits a lag phase. Linear relationships between the amounts of the produced sulphate and concentrations of substrates in the soil could be detected. On the basis of this finding a method for comparison of the oxidative activity of various soils was proposed.     

ACTIVATION, INHIBITION AND AGGREGATION OF CHOLINE ACETYLTRANSFERASE (EC 2.3.1.6)

—Mercuric chloride, silver acetate and cupric sulphate (0·1 mm ) completely inhibited purified choline acetyltransferase from bovine caudate nuclei. At the same concentration cadmium chloride and zinc acetate gave a 50 per cent inhibition. Potassium and sodium salts more than doubled the enzymatic activity while creatinine hydrochloride more than tripled it. Guanidine hydrochloride was less effective than creatinine hydrochloride but more effective than KCl and NaCl. Sodium chloride and creatinine hydrochloride had a synergistic effect on the enzyme. When ammonium sulphate was used to fractionate the choline acetyltransferase that had been extracted from bovine caudate nuclei, the enzyme aggregated into different molecular sizes as determined by exclusion chromatography on Bio-gel A-1·5 m. The molecular weight of the largest aggregate was at least 10⁶ daltons. The initial tissue extract contained only one molecular species of ChAc as did a partially purified preparation in which ammonium sulphate was not used in the purification.     

Sulphur metabolism in Thiorhodaceae. II. stoichiometric relationship of CO2 fixation to oxidation of hydrogen sulphide and intracellular sulphur inChromatium okenii

Stoichiometry of sulphide and intracellular sulphur oxidation in connection with CO₂ fixation was studied inChromatium okenii. The equipment used was a special stirred cuvette with a rapid-sampling arrangement, which allowed short-time experiments with illuminated bacterial suspensions under anaerobic conditions. Turnover of the sulphur compounds is controlled by a linear CO₂ fixation rate which amounts to 0.069µmoles of CO₂/min mg of cell protein at light saturation. Van Niel's equations for bacterial photosynthesis could be confirmed for short periods under the condition that sulphate is produced during increase of intracellular sulphur; i.e., oxidation of sulphide and of intracellular sulphur do not occur consecutively but simultaneously. The full oxidation rate of intracellular sulphur starts after complete consumption of sulphide. The time during which sulphide is oxidized to intracellular sulphur amounts to 1/3–1/4 of the time necessary for the complete quantitative oxidation of the sulphide to sulphate.     

Salt uptake and salt tolerance by sunflower

Summary A normally grown crop of sunflower on red sandy loam soils was found to remove considerable quantities of chloride and sodium. On heavy clay soils with saline patches sunflower plants removed large quantities of sodium followed by chloride and sulphate. In view of its salt tolerance, it is suggested that intercropping or rotation with sunflower might help reduce soil salinity and improve soil conditions where salinity problems are coming up especially in heavy clay soils with low permeability. re]19720711     

Sulphur requirements of certain isolates ofAlternaria tenuis Auct

The sulphur nutrition of three isolates ofAlternaria tenuis Auct., isolated from the diseased leaves ofMangifera indica L.,Musa paradisiaca L. andPsidium guajava L., was studied. They were grown on the medium devoid of sulphur as well as on media containing various sources of sulphur viz., ammonium sulphate, sodium hyposulphite, sodium thiosulphate, magnesium sulphate, potassium sulphate, potassium metabisulphite, zinc sulphate and thiourea. Sodium hyposulphite, sodium thiosulphate, magnesium sulphate, potassium sulphate and zinc sulphate were generally found to be satisfactory sources for the growth of all the isolates under study. Poor growth of the different isolates was observed on the medium devoid of sulphur.     

Maximum Rate of Depolarization of Single Muscle Fiber in Normal and Low Sodium Solutions

The values of membrane action potentials and maximum depolarization rates of single muscle fibers in normal Tyrode solution and in low sodium solutions containing as little as 20 per cent of the sodium chloride were measured with intracellular microelectrodes. Under these conditions the membrane potential remains unchanged up to 36 per cent of [Na⁺]_out concentration, whereas the overshoot of the action potential varies linearly with the logarithm of the external sodium concentration. The maximum depolarization rate is a linear function of the external sodium concentration. The results obtained support the ionic theory for sodium and the independence principle for sodium current related to the external sodium concentration.