CONTENT OF INOSITOL PHOSPHATES IN SOME ENGLISH AND NIGERIAN SOILS

The mono-, di-, tri-, tetra-, penta-, and hexaphosphates of inositpl accounted for between 11·2 and 30·4 per cent of the organic P in three English and four Nigerian soils. M yoinositol hexaphosphate was the component present in greatest amount in all soils. The lower esters (mono-, di-, and triphosphates) accounted for less than 3 per cent of the organic P in all soils, with the lowest amounts in the soils from Nigeria. For the penta- and hexaphosphates the ratio of myo- plus dl- isomers to scyll oinositol varied from 2·9 to over 10, the highest ratio occurring in the soils from Nigeria. Examination of the techniques showed that they gave approximately correct estimates of the inositol phosphates. The organic P in soil which was not estimated as inositol phosphate occurred in other forms.     

CONTENT OF INOSITOL PENTA- AND HEXAPHOSPHATES IN SOME CANADIAN SOILS

The combined amounts of inositol penta- and hexaphosphates in a number of Canadian soils of differing origin have been measured. The esters were precipitated as barium salts from alkali extracts and purified by anion-exchange chromatography; their identity was confirmed by paper-partition chromatography. An alternative method involving precipitation of the esters as ferric salts in acid medium was found to give much lower values, probably because of incomplete precipitation. Values for eighteen surface soils ranged from 20 to 71 and for twelve subsoils from 18 to 43 ppm P. The amounts found were related to the contents of both total phosphate and total organic phosphate, and accounted, on average, for 6 per cent of the former and 17 per cent of the latter. A correlation of +0.67 (P < 0.01) was found with orthophosphate retention capacity but correlations with soil N and C contents were poor. Amounts of the esters were higher in forest soils than in grassland soils.     

Inositol penta- and hexaphosphate content of some cocoa soils in Ghana

The inositol penta- and hexaphosphate content of some typical cocoa soils in Ghana was measured by anion exchange chromatography with HCOONH₄ as eluant. The values which ranged from 6 to 35 ppm P (average 18 ± 8 ppm P) and accounted for 6% to 40% (average 14%) of the organic phosphorus are within those ranges reported for Canadian, Nigerian, but much lower than those for Scottish soils. The penta- and hexaphosphate content of the soil significantly correlated with total P, organic P, organic C, total N, Fe and P retention capacity. Incubation of soil for 11 weeks did not alter the inositol penta- and hexaphosphate content of the soil. Inorganic P adsorption could be decreased by adding inositol hexaphosphate. These data support the suggestion that a role of the esters in nutrition of crops is probably through the indirect effect of blocking of retention sites and agents which would otherwise be free to bind inorganic phosphorus.     

SOME EFFECTS OF FERTILIZERS AND FARMYARD MANURE ON THE ORGANIC PHOSPHORUS IN SOILS

The amounts of P applied cumulatively to a neutral arable soil (pH 7.1–7. in 0.01M CaCl₂) at Rothamsted, as farmyard manure, alone or with superphosphate, which were converted to organic P in 100 years ranged from 18 to 44 μg P/g of soil (0–23 cm). Superphosphate alone (3300 kg P/ha) slightly lessened the total organic P in the soil. Neither farmyard manure nor super-phosphate significantly changed the amounts (38 to 42 μg P/g) of inositol penta- and hexaphosphate in these soils. In the surface layers (0–7.5 cm) of soils from permanent grassland at Rothamsted, superphosphate (3370kg P/ha) increased organic P by 134 μg P/g at pH 4.5 and 19 μg P/g at pH 6.5, about 6 and 1 per cent respectively of the P remaining from superphosphate applied cumulatively since 1858. In the sub-surface layers (7.5–23 cm) superphosphate increased organic P by 93 μg P/g at pH 4.5 and 62 μg P/g at pH 6.2, about 18 and 10 per cent respectively of the P remaining from superphosphate. The sum of inositol penta- and hexaphosphates accounted for 32 per cent at pH 4.5 and 21 per cent at pH 6.5 of the increases in organic P in the surface layers and 45 per cent and 26 per cent in the sub-surface layers at pH 4.5 and 6.5 respectively. Superphosphate (1260–2100 kg P/ha) applied intermittently or cumulatively increased total organic P by 19 to 52 μg P/g and inositol penta- and hexaphosphates by 13 to 17 μg P/g in acid tea soils (pH 3.2–3.4) from Georgia, U.S.S.R. Rock phosphate (510–1020kg P/ha) applied cumulatively had no effect on either the total organic P or the inositol P in acid tea soils (PH 3.6–3.7) from Ceylon.     

The influence of rhizosphere microflora on the availability of 32P-myoinositol hexaphosphate phosphorus to wheat

Experiments with wheat grown in nutrient solution and in a sandy soil showed that ³²P activity, supplied as ³²P-myoinositol hexaphosphate (IH ³²P), was translocated to the tops of aseptic plants. The proportion of the added ³²P activity recovered in the tops of solution grown plants was influenced by the concentration of IH ³²P, decreasing from 8 per cent with 10 μg P/ml to 0.4 per cent with 0.2 μg P/ml.With concentrations of IH ³²P equivalent to 0.2 parts/10⁶ P, inoculation of the root zone of soil grown plants with soil bacterial isolates shown to possess phytase activity, or with a mixed rhizosphere flora had no effect on the incorporation of ³²P into the wheat plants. It is considered unlikely, with the concentration of inositol hexaphosphates normally present in soil solution, that soil microflora will increase the dephosphorylation of these compounds at root surfaces above the activity due to plant enzymes.     

OCCURRENCE OF INOSITOL PHOSPHATES AND OTHER ORGANIC PHOSPHATE COMPONENTS IN AN ORGANIC COMPLEX

A calcareous organic soil was extracted by shaking with Na⁺-resin suspended in 0·2M acetyl acetone at pH 8·3. Fractionation of the fulvic acid on Sephadex G 25 gave (a) a high molecular-weight component which contained inositol tetraand hexa-phosphates and a sugar phosphate; (b) low molecular-weight components which included the mono-, di-, and triphosphate esters of inositol and two sugar phosphates, but no free inositol phosphates. Inositol phosphates and sugar phosphates accounted for 30·2 per cent and 16·6 per cent of the soil organic P respectively. Our evidence indicates that these phosphate esters exist in an organic complex.     

The chemical nature of organic phosphorus that accumulates in fertilized soils of a temperate pasture as determined by solution 31P NMR spectroscopy

Inefficiency of fertilizer phosphorus (P) use in grazing systems is often associated with the accumulation of inorganic and organic P in fertilized soil. However, the chemical nature of the accumulated organic P remains poorly understood. The aim of this study was to use solution ³¹P nuclear magnetic resonance (NMR) spectroscopy on sodium hydroxide–ethylenediaminetetraacetic acid (NaOH‐EDTA) extracts to identify the chemical nature of organic P in soils from a medium‐term (13 years) permanent pasture field experiment. This included an unfertilized pasture (P0), and treatments designed to maintain soil P fertility at near ‘optimum' (P1) and ‘supra‐optimum' (P2) levels for pasture growth; pastures at all levels of soil P fertility were continuously grazed with either a moderate or high stocking rate (SR09 and SR18). Approximately 20% of the fertilizer P added to pastures was recovered as organic P in NaOH‐EDTA extracts at the P1 level of soil P fertility in the 0–10 cm soil layer, and the majority (≈ 65%) of this was detected as the broad phosphomonoester signal. In addition, several specific forms of phosphomonoesters (myo‐ and scyllo‐inositol hexakisphosphate, α‐ and β‐glycerophosphate, and RNA mononucleotides) and phosphodiesters were detected across all soils but at low concentrations. This study shows that phosphate fertilization of pastures primarily results in the accumulation of complex forms of phosphomonoesters rather than that of specific forms of recognizable biomolecules (e.g ., myo‐inositol hexakisphosphate).     

SULPHUR, CARBON, AND NITROGEN CONTENTS OF ORGANIC FRACTIONS FROM ACETYLACETONE EXTRACTS OF SOILS

Ultrasonic dispersion of acid-pretreated soils in aqueous acetylacetone at pH 8, and at a solvent: soil ratio of about 45: I, extracted from 61 to 97 per cent of the organic sulphur from five Scottish soils. Narrowing the ratio to about 9:1 reduced the proportion extracted but was more convenient for the subsequent isolation of the organic components. Gel permeation chromatography of the extracts yielded materials containing from 14 to 60 per cent of the soil organic sulphur. Most of the soils gave four distinct fractions which contained from 21 to 38 per cent carbon, 0.2 to 2.1 per cent nitrogen, and 0.1 to 0.8 per cent sulphur. There was no consistent similarity between corresponding fractions of the various soils. Considerable amounts of iron and aluminium were extracted, presumably incorporated in organic complexes. Since they were obtained under very mild conditions, the fractions should provide useful starting materials for qualitative investigations on the nature of soil organic sulphur.     

THE NATURE OF ALKALI-SOLUBLE SOIL ORGANIC PHOSPHATES

Fractionation of the phosphates in a sodium hydroxide extract of an arable soil has shown the presence of a number of esters of a type not previously detected in soils. These included several mono-phosphorylated carboxylic acids with C to P ratios of approximately 7 or 8 to I and two esters each containing glycerol, myoinositol, chiroinositol and an unidentified component. Another ester, probably containing two phosphate groups, was also detected but was not completely separated from other compounds containing no P. These esters constituted only approximately 3 per cent of the total soil organic P but considerable losses of organic P occurred during the extraction and isolation procedures. The amounts of the inositol phosphates, nucleoside phosphates, and inorganic pyrophosphate in the extract were also measured.     

Quantification and bioavailability of scyllo-inositol hexakisphosphate in pasture soils

The recent identification of scyllo-inositol hexakisphosphate in alkaline soil extracts by solution ³¹P NMR spectroscopy allowed us to investigate this compound in soils by re-analyzing spectra from two previously published studies. Concentrations of scyllo-inositol hexakisphosphate in 29 temperate pasture soils from England and Wales ranged between 11 and 130 mg P kg⁻¹ soil and accounted for between 4 and 15% of the soil organic phosphorus. The ratio of scyllo-inositol hexakisphosphate to myo-inositol hexakisphosphate ranged between 0.29 and 0.79. In a 10 month pot experiment with six grassland soils from New Zealand, growth of pine seedlings (Pinus radiata D. Don) decreased scyllo-inositol hexakisphosphate concentrations by between 10 and 46%. Growth of ryegrass (Lolium perenne L.) decreased scyllo-inositol hexakisphosphate in three low-nutrient soils by 5-21%, but increased it in three other soils by 11-16%. We conclude that scyllo-inositol hexakisphosphate is an important component of soil organic phosphorus with potential ecological significance.     

The use of gas‐liquid chromatography to determine the proportions of inositol isomers present as pentakis‐ and hexakisphosphates in alkaline extracts of soils

Abstract

A method for determining the relative proportions of inositol isomers present in soil as their pentakis‐ and hexakisphosphate derivatives (IP₅ + IP₆) is presented. The method involves determination of the isomers as their hexakis‐O‐acetyl derivatives by gas‐liquid chromatography. The only isomers detected in extracts of 4 soils were chiro‐inositol, neo‐inositol, myo‐inositol and soyllo‐to‐inositol. Little variation in the relative proportions of the isomers was found between the 4 soils but the relative proportion of the neo‐isomer was considerably greater than previously published estimates. The method also makes possible the estimation of the (IP₅ + IP₆) fraction, using anion‐exchange chromatography on a aliquot of the extract.     

CLAY MINERAL DISTRIBUTION AND ORIGIN IN THE SOIL TYPES OF ISRAEL

The mineralogical composition of clays (< 2μm) in representative profiles of all soil types of Israel was investigated. The soils were classified according to their clay mineral assemblages into three groups. I. Montmorillonitic soils. Montmorillonite is the dominant mineral and exceeds 65 per cent of the total minerals found; each of the other minerals comprises less than 15 per cent. 2. Montmorillonitic-kaolinitic soils. The soil clay fractions contain 50-60 per cent montmorillonite and 15-25 per cent kaolinite, generally adding up to more than 75 per cent of the clay fraction. 3. Montmorillonitic-calcitic soils. The clays contain more than 10 per cent calcite. Montmorillonite is the dominant clay mineral (except for one soil type, mountain rendzina, where calcite is dominant). The first and second assemblages are typical of the soils of the Mediterranean zone, whereas the soils of the desert zone are characterized by the third assemblage. The origin of montmorillonite, kaolinite, and illite, the three main clay minerals, was found to be detritic, as was the origin of palygorskite which was mainly found in the calcite rich soils of the desert zone. The cation exchange capacity of montmorillonite seems to be higher under higher precipitation. Montmorillonite content and cation exchange capacity of the clays were found to be highly correlated. The carbonate content of the clay fraction and the amount of carbonate in the soil were also highly correlated.     

THE REACTION OF FLUORIDE WITH SOILS AND SOIL MINERALS

The reaction of sodium fluoride solution with soils and soil minerals at constant pH has been assessed as a possible single-value characteristic in the classification of soils, particularly those containing significant amounts of poorly ordered inorganic material. A suitable method involves reaction of the soil or clay at 25°C with 0·85 M sodium fluoride at pH 6·8, the amount of OH^? released after 25 min being taken as the single-value characteristic. There was a statistically significant correlation between the amount of OH^? released and the amount of alumina extracted with cold 5 per cent sodium carbonate solution from both freely drained and poorly drained Scottish soils. The multiple correlation coefficients were improved for freely drained soils by including the dithionite-extracted ferric oxide and the silica soluble in 5 per cent sodium carbonate solution. The procedure is not suitable for surface soils, because of interference by organic matter, or for carbonate-containing soils unless carbonate is removed.     

Organic phosphorus speciation and pedogenesis: analysis by solution 31P nuclear magnetic resonance spectroscopy

Changes in phosphorus (P) during soil development are central to the understanding of labile P for plant productivity and soil P management. We used NaOH‐EDTA extraction with ³¹P nuclear magnetic resonance spectroscopy (³¹P NMR), sequential P fractionation, and general soil chemical characterization to better our understanding of P dynamics within two chronosequences (Manawatu and Reefton) and one Basalt maturity sequence under original native vegetation. With time, orthophosphate and orthophosphate monoesters tended to increase with organic C to a maximum of about two‐thirds of NaOH‐EDTA‐extractable P in young soils (16 000 years in the Reefton chronosequence), but gradually declined thereafter to about one‐third of NaOH‐EDTA‐extractable P in the oldest soils (130 000 years old). This coincided with a depletion of P from primary minerals (e.g. apatite) and readily available P for plant production. This depletion of inorganic P resulted in a greater reliance on organic P cycling via mineralization, hence the depletion of the normally recalcitrant monoester‐P pool. Concomitantly, the build‐up of labile P species (diesters and pyrophosphate) and scyllo‐ over myo‐inositol hexakisphosphate occurred as soils developed, and might be attributed to microbial activity, including scavenging for P. This work highlights the importance of organic P cycling during pedogenesis.     

有机肥料和土壤中的有机磷对水稻的营养效果

本文对三种有机肥料和二种土壤的肌醇六磷酸磷含量和有机磷进行了测定和分组,通过无菌溶液培养,比较了肌醇六磷酸磷与无机磷在等磷量的条件下对水稻的营养效果.结果表明:猪、鸡粪中有机磷的形态主要是以肌醇六磷酸钙镁盐为主,而土壤和牛粪是以肌醇六磷酸铁的形式为主.肌醇六磷酸磷对水稻的营养效果明显优于无机磷.磷的分组结果表明:猪、鸡粪中有机磷以活性和中等活性有机磷为主,而土壤则以稳定性有机磷为主,牛粪介于二者之间.因此,猪、鸡粪中有机磷的有效性高于牛粪,而以土壤中的有机磷为最低.     

A COMPARISON OF THE SORPTION OF INORGANIC ORTHOPHOSPHATE AND INOSITOL HEXAPHOSPHATE BY SIX ACID SOILS

A comparison has been made of the sorption of inorganic orthophosphate and inositol hexaphosphate by six acidic surface soils from arable land in north-east Scotland. The sorption of inorganic P increased with increasing quantities added and tended towards a maximum, but was never complete. In contrast, the organic P was completely sorbed up to an added quantity which varied with the soil, and above this level the absolute sorption decreased, probably due to the formation of soluble complexes involving iron and aluminium. The sorption sites were apparently the same for the two P forms and, particularly at high levels of addition, the organic P depressed the sorption of inorganic P. Inorganic P did not depress the sorption-of organic P, which was preferentially adsorbed. The results help to explain the extreme stability of inositol hexaphosphate in these soils.     

CHANGES IN THE CHEMICAL NATURE OF SOIL ORGANIC PHOSPHATE DURING PEDOGENESIS

In two chronosequences of soils, total organic phosphate (P₀) accumulated rapidly during the first 50 years of soil development, when organic matter increased and pH decreased. The rate of P₀ accumulation then declined with age of soil until a ‘steady state’ was reached. The amounts of phospholipid, inositol phosphates and humic acid—P₀ followed the same trends as the total P₀. Parent materials and very young soils contained largely citric acid-soluble P₀, but after less than 50 years, surface horizons accumulated sufficient organic matter to complex a considerable proportion of the P₀. An upper limit of 20–5 per cent citric acid-soluble P₀ and 70–80 per cent NaOH-soluble P₀ was attained within 50 years of soil formation in the surface layers, and this slowly extended down the profile so that, after 10000 years, the soil had 20 per cent citric acid soluble-P₀ and 70 per cent NaOH-soluble P₀ to a depth of 1 m.     

The comparative plant availability of 32P myo‐inositol hexaphospha.te and KH2 32PO4 added to soils

Abstract

The comparative availability to Lolivm perenne of ³²P myo‐inositol hexaphosphate (IH³²P) and KH₂ ³²PO. added to soil could be determined unequivocally from the ³²P count of leaf material even when dry matter yields and total P content were not significantly different from the control.

IH³²P was equivalent to KH₂ ³²PO₄. in a soil with a low P retention at 200 p.p.m. P but not at 20 p.p.m. P. IH ³²P was totally unavailable in two soils with high P retention at 200 p.p.m. and 20 p.p.m. P, whereas uptake of KH₂ ³²PO₄. was observed in each instance.     

THE VOLATILISATION, FROM SOILS AND MIXTURES OF SOIL COMPONENTS, OF IODINE ADDED AS POTASSIUM IODIDE

Iodine, as potassium iodide in solution, was added to samples of 24 surface soils, 15 subsoils and 16 mixtures of sand with other materials representing soil components, at 10 μg iodine/g soil. The extent of volatilisation of the added iodine was measured after 30 days' exposure in a well-ventilated room. With many of the surface soils volatilisation was negligible although with an acid sandy podsol it amounted to 57 per cent of the iodine added. Eleven of the subsoils induced volatilisation amounting to > 10 per cent of that added. With sand alone, having a pH of 5.7, volatilisation amounted to 100 per cent, and with the mixtures it ranged from nil to 100 per cent. Organic matter reduced volatilisation, probably by retaining the iodine in bound form. Montmorillonite, kaolinite and ferric oxide also reduced volatilisation in comparison with sand alone, but had less effect than did organic matter. Calcium carbonate, although in general reducing volatilisation, probably through its influence on pH and hence on retention by other materials, caused no reduction when added to sand alone.     

AVAILABILITY OF POTASSIUM TO RYEGRASS FROM SCOTTISH SOILS I.

Scottish soils were cropped with two sowings of perennial ryegrass (Lolium perenne, cv, Dutch Barenza) in the glasshouse, without addition of potassium, until growth virtually ceased. Potassium uptake and the corresponding changes in soil K properties were examined. Uptake of K correlated well over the entire cropping period with the initially labile K predicted from the Q/I isotherms of the soils, although K uptake was at least a factor of 1.9 greater than the initially labile K. The Q/I isotherms were similar for soils from the same series, and the form of the lower part remained virtually unchanged during intensive cropping. The equilibrium activity ratio, AR₀, of soil K measured in 0.01 M calcium chloride was reduced in all soils to a narrow range close to a mean value of 3 × 10 ^?4 M^1/2. Drying-and-wetting fresh soil samples severely depleted of ryegrass-available K raised their K status. The increases were negatively correlated with the percentage K saturation of the fresh depleted soils, and a K saturation of 1.4 per cent must apparently be left in the fresh cropped soils for no K to be released. Freezing-and-thawing did not affect the K status of these soils.