Amounts and mineralization of organic phosphorus compounds and derivatives in some surface soils of bangladesh

Concentrations of a few organic phosphorus compounds and their hydrolysis products have been determined in a number of Bangladesh soils. The amounts of DNA and its derivatives, inositol penta- and hexaphosphates, ranged from 0.16 to 1.30, and 18.5 to 130.0 ppm, respectively. The hydrolysis products of phospholipids such as choline, ethanolamine and glycerophosphate ranged from 0.36 to 3.29, 0.28 to 2.52 and 0.20 to 1.05 ppm, respectively. Multiple correlation suggested that pH, organic matter, organic phosphorus and total phosphorus were collectively related to the amounts of different organic phosphorus fractions in soil samples. Individually, DNA and its derivatives were found to be significantly related to total phosphorus and inositol penta- and hexaphosphates to organic phosphorus. Choline was significantly related to organic matter, organic phosphorus and total phosphorus; ethanolamine to organic matter and total phosphorus; and glycerophosphate to organic phosphorus.Moisture and lime promoted progressive mineralization of organic phosphorus with time. Potassium dihydrogen phosphate, glucose and ammonium sulphate showed rapid initial and final mineralization. In contrast, the application of compost caused an initial luxury immobilization followed by a marked increase in mineralization with time. Maximum mineralization was observed when ammonium sulphate was added to samples in submerged conditions. The least mineralization occurred when lime was added to samples at 50% of field moisture capacity.     

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.     

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.     

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.     

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.     

Tillage, mineralization and leaching: phosphate

Phosphate is usually the limiting nutrient for the formation of algal blooms in freshwater bodies, so tillage practices must minimize phosphate losses by leaching and surface run-off from cultivated land. Mineral soils usually contain 30–70% of their phosphate in organic forms, and both organic and inorganic phosphate are found in the soil solution. Some organic phosphates, notably the inositol phosphates, are as strongly sorbed by soil as inorganic phosphates, and this decreases their susceptibility to mineralization. The strength with which both categories are sorbed lessens the risk of their being leached as solutes but makes it more likely that they will be carried from the soil on colloidal or particulate matter, and the greatest losses of phosphate from the soil usually occur by surface run-off and erosion. Recent studies at Rothamsted have, however, shown substantial concentrations of phosphate in drainage from plots that have long received more phosphate as fertilizer than is removed in crops. These losses probably occurred because preferential water flow carried the phosphate rapidly from the surface soil to the field drains. For lessening losses of phosphate by leaching and run-off, the prime requirement of tillage is that it should encourage flows of water through the soil that help it to retain phosphate. Primary and secondary tillage should ensure that the surface roughness and porosity of the top-soil encourage the flow of water into the soil matrix where it will move relatively slowly and allow phosphate to be sorbed, thereby avoiding problems from run-off and preferential flow. Inversion tillage can be useful for lessening the loss of phosphate by run-off and erosion. Secondary tillage could be used to decrease the size of the aggregates and increase the surface area for sorption. Although tillage will increase the mineralization of organic phosphate, pulses of mineralization are unlikely to be so rapid or to lead to such large losses as with nitrate. The strength with which phosphate is sorbed also lessens the problem. As with nitrate, the key to managing phosphate is basically good husbandry.     

CHARACTERIZATION OF THE INOSITOL PENTA- AND HEXAPHOSPHATE FRACTIONS OF A NUMBER OF CANADIAN AND SCOTTISH SOILS

The nature of the inositol pentaphosphate and hexaphosphate isomers in a number of contrasting Canadian and Scottish soils has been examined. The mixed esters were extracted from the soil with alkali and separated from other soil phosphates by anion-exchange chromatography using HCOONH₄ as eluent. The composition of the mixture was established by anion-exchange chromatography using a gradient of HC1 as eluent, followed by paper chromatography of the esters thus separated, and by paper chromatography of the hydrolysis products. Esters of myo- and scylloinositol together constituted more than 90 per cent of the mixture in most cases. Relatively small amounts of dl-inositol and neoinositol were detected in hydrolysates and it was estimated that esters of these cyclitols did not exceed 10 per cent and 1 per cent, respectively, of the total. The ratio of myo-+dl-inositol hexaphosphates to scylloinositol hexaphosphate ranged from 1.1 to 2.7 in the Canadian soils and 1.8 to 4.6 in the Scottish soils. The ratio of hexaphosphates to pentaphosphates ranged from 0.9 to 2.4 in the Canadian soils and 3.0 to 4.3 in the Scottish soils. The three soils with the highest pH values contained relatively large amounts of scyllo- relative to myoinositol hexaphosphate, but one very acid soil also contained a high proportion of this isomer and no consistent relationship was noted between the constitution of the inositol polyphosphate fraction and any other soil property.     

STABILITY OF FERRIC PHOSPHATES

Essentially congruent dissolution of colloidal ferric phosphate, metastrengite, and strengite was observed at pH 1.5 during 25 days. In contrast, preferential release of P to solution was obtained at pH 6.0. Dialysis of dried preparations of these three materials against hydrous ferric oxide gel (Fe gel) resulted in the loss of 9.0, 3.0, and 0.4 per cent of total P, respectively, during 20 days. A wet preparation of colloidal ferric phosphate released 17 per cent of total P during the same time. During dialysis, all ferric phosphates assumed a brownish colour. Electron microscopy revealed the presence of an appreciable quantity of short-range order material surrounding crystals of strengite following dialysis. These observations, coupled with the decrease in type ratio, demonstrate that an Fe gel coating forms on the ferric phosphates during dialysis. The results are discussed in terms of the likely stability of ferric phosphates in soils.     

GENESIS, MINERALOGY, AND RELATED PROPERTIES OF WEST INDIAN SOILS

The Montserrat series is one of the most fertile of tropical soils. Substantial amounts of exchangeable K, available P, and favourable organic matter content and distribution contribute to its unique properties. P occurs in amounts ranging from 0.4 to 0.6 per cent, about 75 per cent of which is inorganic with Fe phosphates making up the bulk. Truog's reagent almost quantitatively extracts Ca phosphate and Bray's and Olsen's reagents extract mainly Al phosphate. Exchangeable K is derived from glauconite. High exchangeable Ca and Mg contents derived from weathering of carbonates impart a favourable pH to the soil for plant growth. Exceptional structural stability to 120 cm depth is associated with high free iron oxide, organic matter, and Ca contents. The outstanding feature in mineral weathering is the rapid transformation of glauconite through vermiculite to kaolinite and the formation of goethite. Considerable interlayering occurs between vermiculite with sesquioxide coatings and mica-vermiculite interlayers. Much of this weathering occurs in the calcareous, oxidized, friable parent rock. The features of the Montserrat series described above substantiate its classification as a Brown Earth (Mollisol).     

温度和土壤类型对氮素矿化的影响

采用短期(15 d)室内好气培养方法,研究我因东部三类主要旱地土壤(黑土、潮土和红壤)有机氮矿化对温度(15～30°C)的响应及其影响因素.结果表明,土壤累积净矿化氮量的顺序为黑土>潮土>红壤,其中高有机质土壤大于低有机质土壤.黑土累积净矿化氮量随温度升高而增加,但潮土和红壤在25℃以上表现出持平和下降趋势.土壤矿质氮...     

上海土壤磷的吸附特性及缓冲性能的研究

本文以上海土壤为对象,研究选定了土壤磷等温吸附试验条件为:水土比10,平衡时间6天,控温25℃,磷加入量为100,200,400,600μgP/g土,溶液基质为0.01M CaCl₂。磷缓冲能力试验条件为:平衡时间2天,磷加入量为20,40,100,200μgP/g土。根据Freundlich, Tempkin和Langmuir方程计算的土壤吸附指标与土壤类型及土壤性质有密切关系,是土壤磷素肥力的重要指标。反映土壤缓冲能力的“磷肥指标”与土壤有机质、粘粒、活性铝及pH值相关较好。上海几种主要土壤中以青紫泥的最大吸附量(X_m),0.2ppm P吸附量和“磷肥指标”为最高,其次为青黄土,沟干泥和黄泥头,最小为夹沙泥。应用磷吸附指标与“磷肥指标”来预测土壤需磷量,初步试验是可行的,但实际应用还需进一步试验研究。     

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.     

Inositol phosphate esters in some surface soils of Bangladesh

Concentrations of inositol mono-, di- and tri-, tetra-, penta- and hexaphosphate ranged from 5.0 to 12.5, 10.0 to 27.6, 20.0 to 45.0, 22.5 to 64.6, and 20.0 to 275.4 ppm, respectively, in samples of soils that were poorly drained and mostly derived from alluvium. Multiple correlation suggested that the amounts of esters of inositol phosphate other than inositol monophosphate were significantly correlated with organic phosphorus, total phosphorus, organic carbon, total nitrogen, inositol phospate, clay, exchangeable iron and aluminium, and pH. Individually, inositol hexa-, penta-, and di- and triphosphates were significantly correlated with organic phosphorus, total phosphorus, organic carbon, total nitrogen, inositol phosphate, and exchangeable iron and aluminium; inositol tetraphosphate with organic carbon, total nitrogen, inositol phosphate, and exchangeable iron and aluminium; inositol monophosphate with none.     

我国磷矿磷肥中镉的含量及其对生态环境影响的评价

本文收集了全国36个矿区67个磷矿标本和全国30个主要磷肥厂的磷肥样品,对其含镉量进行了分析和评价。67个磷矿含镉量范围为0.1-571mg kg^-1Cd,平均为15.3±74mg kg^-1。如果除去广西等四个贮量较小但含镉较高的矿区,其余矿区磷矿平均含镉为0.98mg kg^-1Cd。30个磷肥样品平均含镉0.60±0.63mg kg^-1Cd,变幅为0.1-2.93mg kg^-1。其中普钙平均为0.75±0.65mg kg^-1Cd,钙镁磷肥为0.11±0.03mg kg^-1Cd。热法磷肥在生产过程中含镉量因挥发而降低。根据我国磷肥通常用量和作物吸镉特点,认为长期施用国产磷肥,不至产生污染环境问题。     

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.     

有机质、全氮和可矿化氮在反映土壤供氮能力方面的意义

用 2 5个表层土壤样品和 6个土壤 3 6个不同层次的土壤样品研究了可矿化氮与有机质、全氮的关系。可矿化氮由通气培养法测定。研究结果表明 ,不论表层土壤或不同层次剖面土壤中的可矿化氮都与有机质、全氮高度正相关。但是由于可矿化氮与有机质、全氮有自相关存在 ,他们之间的相关有一定的不真实性。而且 ,土壤的可矿化氮并不与全氮或有机质成正比 ,可矿化氮与有机质或全氮的比值因土壤而不同 ,差别很大。特别重要的是 ,可矿化氮对有机质或全氮的比率几乎在一条直线上 ,它们之间的相关性明显高于可矿化氮与有机质或全氮的关系。这些结果显示 ,矿化氮的数量取决于有机质和全氮中的可矿化部分 ,而不是其总量。土壤剖面中累积的硝态氮数量低时 ,作物的吸氮量与可矿化氮的关系远较与有机质或全氮的关系密切 ,更证明了测定可矿化氮有其特定意义 ,有机质、全氮的测定并不能代替可矿化氮的测定。     

合成磷源在石灰性潮土中的有效性及氮肥形态对其的影响

采用盆栽试验的方法研究了几种人工合成磷源在两种质地土壤中的有效性及不同氮肥形态对它们有效性影响的机理。研究结果表明 :几种合成磷酸盐在轻壤质和轻粘质潮土中的生物有效性的大小顺序分别为 :磷酸二钙 (DCP) >磷酸八钙 (OCP) >磷酸铝 (Al P) >磷酸铁 (Fe P) >氟磷灰石 (FA)和DCP >Al P >OCP >Fe P >FA。几种人工合成磷源在两种质地土壤中的有效性与土壤中相应形态无机磷的有效性相一致。它们在轻粘质潮土中的生物有效性明显受氮肥形态的影响。配施NH 4 N和CO(NH2 ) 2 时 ,Al P和FA的有效性比配施NO-3 N明显提高。配施NO-3 N可以明显提高Fe P的有效性。它们在配施不同氮肥形态下的生物有效性与不同氮肥形态处理下的根际pH变化密切相关。     

pH对土壤吸持磷酸根的影响及其原因

本文选择了浙江、江苏15个性质变化范围较大的土壤样品,研究在两种支持电解质、不同pH条件下对磷酸根的吸持反应。结果表明,加碱提高强酸性土壤的pH值,导致交换性铝的水解和羟基铝聚合物的生成,增加对磷的吸持。磷酸根同酸性土壤的反应,可促进交换性铝的水解,释放出H⁺,降低体系的pH。在CaCl₂介质中,当pH>6时,可能有磷酸钙类盐形成,使溶液中磷浓度显著降低。有机质对土壤吸持磷有重要影响。在低pH下有机质通过与Al³⁺形成络合物,阻碍溶液中A1³⁺的水解,并与磷酸根竞争羟基铝化合物表面的反应点位,从而降低酸性土壤对磷酸根的吸附量。     

四川盆地土壤中微量元素的含量分布及其有效性的研究

四川盆地是一个古老的农业区,但其土壤中的微量元素,尚未曾作过专门研究。本文研究了四川盆地土壤中微量元素硼、锌、铜、锰、铁的含量分布状况和影响其有效性的某些因子。结果表明:各元素的总含量较高,但有效硼的含量很低,有效锌和锰的含量在多数土壤中亦较低,有效铜和铁的含量却较丰富。土壤中各微量元素的含量因土而异,其有效性受pH和有机质含量的影响,各有效态微量元素的含量均是pH<7的高,而pH>7则低,且与有机质含量呈显著正相关关系。水稻土中各有效态微量元素(除硼以外)的含量一般高于同母质发育的旱地。