Variation in the incidence of H2-oxidizing chemolithotrophic bacteria in rice grown under different cultivation conditions

Summary The incidence of H₂-oxidizing chemolithotrophic bacteria associated with rice grown under continuous wetland, upland, and rainfed wetland conditions was studied by¹⁴C-autoradiographic technique in a neutral soil at IRRI (Maahas) and an acid rainfed wetland soil (Luisiana).In Maahas soil, H₂-oxidizing chemolithotrophic bacteria were not detected in the endorhizosphere, rhizosphere, and nonrhizosphere soil of rice grown under dryland conditions. Under continuously flooded conditions a very large population of these bacteria were found in the endorhizosphere but not in the oxidized and reduced soil.A very low population of these bacteria were found in the endorhizosphere and basal culm of rice grown under rainfed wetland conditions at Luisiana. Bacteria isolated from Maahas wetland rice and inoculated to rice seedling planted in Luisiana soil failed to establish.Both Maahas and Luisiana soils consumed externally supplied H₂ and produced H₂ and CH₄ almost at the same rate when they were amended with rice straw or sucrose. This paper discusses possible causes of variation in the number of these bacteria and their distribution in rice grown under different cultural and soil conditions.     

The supply of soluble phosphorus to the wheat plant from inorganic soil phosphorus

Summary Pots containing a slightly acid, red-brown soil were maintained at three moisture levels, in half the pots wheat was grown and in the remainder there was no plant growth. Fractionation of the soil phosphorus showed the aluminium phosphates fraction to be the main source of plant-available phosphorus, but at the same time the growth of the plants reduced the significant increase in iron phosphates which occurred during the period in the no-wheat pots. The plant roots compete with the iron phosphates for the soluble phosphate released from the aluminium phosphates fraction.     

Effect of flooding and cropping on the changes in the inorganic phosphate fractions in some rice soils

Summary Greenhouse experiments were conducted to evaluate the significance to flooded rice of the various forms of inorganic soil phosphate on Aborlan, Luisiana and Pili soils with and without phosphate. Changes in the various inorganic soil phosphate fractions with time under cropped and uncropped conditions were measured. Results showed that the iron phosphate fraction was the most important source of phosphate to the rice plant. It was also evident that phosphate added to the soils was slowly converted into the iron phosphate form. Transformation of soil phosphate seemed to be greatly affected by the presence of plant roots. Changes in the phosphate fractions were marked in the cropped soils.Data presented in this paper form part of Ph.D. dissertation submitted by the first author to the University of the Philippines, College of Agriculture, Los Banos, The Philippines.Professor of Agr. Chemistry, Dept. of Agr. Chemistry, Univ, of the Philippines, College of Agriculture.Rice Agronomist, Univ. of Agr. Sciences, Regional Research Station, Mandaya, Mysore, India.     

Porewater oxidation,dissolved phosphate and the iron curtain

The process of dissolved phosphate removal from aqueous solution, which occurs during oxidation of soluble ferrous compounds to insoluble ferric forms, was examined in soils of two tidal freshwater marshes. Sites of amorphous iron deposition and sorption or co-precipitation of phosphate were found to be in surface soils and along creekbanks, where both ion diffusion and porewater advection move dissolved iron and phosphate from reduced to oxidized regions. Profiles of extractable iron and total phosphorus from creekbank and interior soils were consistent with hypothesized differences between a high and a low marsh. Porewater concentrations of dissolved phosphate were higher in creekbank soils of the high marsh, compared with water actually discharging from the creekbank during tidal exposure. We propose that an iron curtain of ferric hydroxides functions as a barrier to diffusive and advective movement of dissolved phosphate along surfaces of tidal freshwater marshes, and has important implications for the distribution and availability of phosphorus in other types of wetlands and aqueous systems.     

Phosphorus transformations from rock phosphates in acid soils and measures for increasing their efficiency for growing rice (Oryza sativa L.)

Summary Laboratory incubation experiments showed that addition of rock phosphate to P-deficient acid red and laterite soils resulted in an increase in Al–P or/and Fe–P, with a consequent decrease in Ca–P during 15 days, of moist aerobic incubation. The transformations of P from Gafsa, Jordan, North Carolina and Florida rock phosphates were more than those from Tennessee, Missouri and Udaipur. Studies with North Carolina, Gafsa, and Udaipur rock phosphates showed that application of the former two to moist aerobic P-deficient acid soils 2 weeks prior to flooding and transplanting rice gave higher content of Al–P, Fe–P and Bray-P, compared to when these were applied at flooding. The grain yields obtained with the former two treatments were also at par with that obtained with the addition of superphosphate at comparable rate (100 ppm) of P application, compared to when the, rock phosphates were applied at flooding, where the grain yields were lower than the superphosphate treatment, indicating that some of these rock phosphates could be made as efficient as superphosphate for growing rice on acid soils by their application to moist aerobic soil, 2–3 weeks prior to flooding and transplanting rice and thus conserve some amount of sulphur required for the manufacture of water soluble phosphates.     

Changes in organic phosphorus composition in boreal forest humus soils: the role of iron and aluminium

Organic phosphorus (P) is an important component of boreal forest humus soils, and its concentration has been found to be closely related to the concentration of iron (Fe) and aluminium (Al). We used solution and solid state ³¹P NMR spectroscopy on humus soils to characterize organic P along two groundwater recharge and discharge gradients in Fennoscandian boreal forest, which are also P sorption gradients due to differences in aluminium (Al) and iron (Fe) concentration in the humus. The composition of organic P changed sharply along the gradients. Phosphate diesters and their degradation products, as well as polyphosphates, were proportionally more abundant in low Al and Fe sites, whereas phosphate monoesters such as myo-, scyllo- and unknown inositol phosphates dominated in high Al and Fe soils. The concentration of inositol phosphates, but not that of diesters, was positively related to Al and Fe concentration in the humus soil. Overall, in high Al and Fe sites the composition of organic P seemed to be closely associated with stabilization processes, whereas in low Al and Fe sites it more closely reflected inputs of organic P, given the dominance of diesters which are generally assumed to constitute the bulk of organic P inputs to the soil. These gradients encompass the broad variation in soil properties detected in the wider Fennoscandian boreal forest landscape, as such our findings provide insight into the factors controlling P biogeochemistry in the region but should be of relevance to boreal forests elsewhere.     

Effectiveness of some iron phosphates as sources of phosphorus for plants

Summary Two well-characterized crystalline ferric phosphates, two colloidal ferric phosphates, and fluorapatite were tested under greenhouse conditions as sources of phosphorus for corn over a 3-cropping period. The selected compounds are representative of those expected to form in soils as reaction products from more soluble phosphate fertilizers.Strengite, FePO₄·2H₂O, was completely unavailable in acid soils and gave only a slight phosphorus response on soils limed to pH 7.6. Uptake of P from hydrogen ammonium ferric phosphate, H₈NH₄Fe₃(PO₄)₈·6H₂O, was approximately 70 per cent that from MCP, and increased with cropping.The colloidal ferric phosphates were approximately 78 per cent as available as MCP and became more available with liming and cropping. In the soil limed to pH 6.5, their effectiveness increased from 47 per cent that of MCP in the first crop to 100 per cent as effective by the third crop.Fluorapatite, included as an insoluble calcium phosphate source, was completely unavailable.     

Effects of vesicular-arbuscular mycorrhiza on the availability of iron phosphates to plants

Summary The effect of inoculation with a mycorrhizal fungus on the growth of subterranean clover and of ryegrass was measured using three sources of phosphorus with different solubilities. These were (in order of decreasing solubility): potassium dihydrogen phosphate, colloidal iron phosphate and crystalline iron phosphate. Mycorrhizal infection increased growth more for subterranean clover than for ryegrass for all sources of phosphorus. For both species the greatest benefit from mycorrhizal inoculation was obtained with the least soluble source of iron phosphate. It is suggested that the mycorrhizas were able to explore the soil more thoroughly and hence were able to locate and use the point sources of phosphorus in the insoluble iron phosphates.     

Effect of algal growth on the availability of phosphorus,iron and manganese in rice soils

Summary Laboratory experiments were conducted to study the effect of algal growth on the change of (I) pH, (II) available phosphorus and (III) solubility of iron and manganese content in five waterlogged alluvial rice soils of West Bengal, India. The results showed that the algal growth initially caused an increase in the soil pH, which later declined to the original value in some of the soils. The available phosphorus content decreased upto 90 days of their growth and began to increase towards the later period of incubation. The drastic fall of water soluble plus exchaneable manganese content of the soils due to algal growth was accompanied by similar increase in reducible manganese content. No appreciable change in water soluble plus exchangeable ferrous iron content was encountered but theN-NH₄OAC(pH 3) extractable iron due to algal growth progressively decreased with the progress of the incubation period.     

Reducing phosphorus release from paddy soils by a fly ash-gypsum mixture

A mixture of fly ash and phospho-gypsum (50:50, wtwt(-1)) was selected to study its potential to supply Ca and Si to rice while reducing B toxicity. We expected that the high Ca content in this mixture might convert water-soluble P to less soluble forms and thereby reduce the loss of soil P to surface runoff. The mixture was applied at rates of 0, 20, 40, and 60 Mgha(-1) in two paddy soils of contrasting textures (silt loam in Yehari and loamy sand in Daegok). The mixture significantly reduced water-soluble phosphate (W-P) in the surface soils by shifting from W-P and iron bound-P (Fe-P) to calcium bound-P (Ca-P) and aluminum bound-P (Al-P) during rice cultivation in both soils. Lancaster and Mehlich 3 extractable P increased significantly with application rate due to high contents of P and Si in the mixture. Mixtures of fly ash and phospho-gypsum should reduce P loss from rice paddy soils and increase soil fertility.     

Inorganic transformation of applied phosphorus in brackishwater fish pond soil under different water salinity levels

Transformation of applied phosphorus in a brackishwater fish pond soil was studied under different water salinity levels, as occurring in such ponds, in presence and in absence of added organic matter. Added phosphorus was found to disappear rapidly from the water phase with some variations under different water salinities. The amount of added phosphorus in saloid-bound form increased with increase in water salinity but the same in Bray's (No. 2) extractable form showed a reverse trend. Applied phosphorus was transformed mostly into insoluble calcium phosphate form which increased with increase in water salinity. Transformation was intermediate into iron phosphate and the least into aluminium phosphate form. Application of organic matter reduced the fixation of added phosphorus into the iron phosphate form during the initial period of study and thus increased availability of phosphorus both in water as well as soil phases.This work formed a part of a thesis submitted for the Degree of Doctor of Philosophy to Bidhan Chandra Agricultural University, West Bengal in 1978This work formed a part of a thesis submitted for the Degree of Doctor of Philosophy to Bidhan Chandra Agricultural University, West Bengal in 1978     

一株新的溶磷草生欧文氏菌的分离、鉴定及其溶磷效果的初步研究

从湖南、湖北、云南等地磷矿开采场的土壤样品中筛选到一株溶磷能力较强的菌株P21,结合生理生化指标和16S rDNA序列分析鉴定其属于草生欧文氏菌菠萝变种(Erwinia herbicola var.ananas).该菌能溶解磷酸三钙、羟基磷灰石、磷酸铁、磷酸锌,其中对磷酸三钙和羟基磷灰石的每升液体培养基溶磷量(P2O5)分别高达1206.20mg、529.67mg.溶磷菌草生欧文氏菌菠萝变种P21对产地不同的8种磷矿石溶解能力不同,对云南晋宁和昆阳、四川雅安、江苏锦屏等地磷矿石有较强的溶解能力,每升液体培养基溶磷量分别为96.64mg、78.46mg、67.07mg、65.24mg,对其它产地的磷矿石溶解能力较差.实验表明,培养液的pH下降与溶磷菌P21的溶磷量无直接关系.     

Studies on the nutrition of forage legumes

Summary Surface samples of six Ontario soils were selected to provide a range in pH, texture and carbonate content. Phosphorus was added to the soil samples at the rate of 200, and 2000 pounds. P₂O₅ per acre and the inorganic phosphates associated with aluminum (Al-P), iron (Fe-P) and calcium (Ca-P) were analysed 15, 30, and 335 days after treatment. Samples of the check soils were leached with the equivalent of 7 litres of soil-percolated water and then analysed for phosphate fractions. In 5 soils with added phosphorus the Al-P fraction increased at both rates of added phosphorus, Fe-P increased only at the higher rate of added phosphorus and Ca-P did not increase at either rate. In the sixth soil (69.9% CaCO₃ equivalent) Ca-P increased at both rates of added phosphorus, but proportionately less than the water-soluble phosphorus. These changes in phosphorus values existed relatively unchanged for 335 days after the addition of phosphorus. Leaching generally removed phosphorus from all phosphorus fraction. At or below pH 7.1 (soil paste) the Al-P decreased proportionately more than the Fe-P and Ca-P. Above pH 7.1 the Ca-P decreased proportionately more than the other two fractions upon leaching.Contribution from Dept. of Soil Science, O.A.C., Guelph, Canada. Part of thesis submitted by junior author to the Graduate School, University of Toronto, in partial fulfilment of the requirements for the M.S.A. degree.     

Sources and bioavailability of phosphorus fractions in freshwaters: a British perspective

This paper seeks a perspective on the forms of phosphorus which promote aquatic eutrophication, with the particular quest of establishing their sources. A short background traces the development of understanding of nutrient enrichment and the suppositions about the relative contributions of agriculture, sewage and detergent residues. Most aquatic systems, and their primary producers, are naturally deficient in biologically-available phosphorus. Aquatic plants have evolved very efficient phosphorus uptake mechanisms. The biomass responses to an increase in the supply of phosphorus are stoichiometrically predictable. The most bioavailable forms of phosphorus are in solution, as orthophosphate ions, or are readily soluble or elutable from loose combinations. Ready bioavailability coincides well with what is measurable as molybdate-reactive (MRP) or soluble-reactive phosphorus (SRP). Most other forms, including phosphates of the alkaline earth metals, aluminium and iron are scarcely available at all. Orthophosphate ions sorbed to metal oxides and hydroxides are normally not biologically available either, except through weak dissociation ('desorption'). The production of alkaline phosphatase provides organisms with an additional mechanism for accelerating the sequestration of phosphate from organic compounds. Bioavailable phosphate is liberated when redox- or alkali-sensitive metal hydroxides dissolve but these processes are minor contributors to the biological responses to nutrient enrichment. Most of the familiar eutrophication is attributable to the widespread application of secondary sewage treatment methods to the wastes emanating from a burgeoning and increasingly urbanised human population. The use of polyphosphate-based detergents, now in decline, has contributed to the problem. In aquatic systems, the additional phosphorus raises the biological supportive capacity, sometimes to the capacity of the next limiting factor (carbon, light, hydraulic retention or of another nutrient). At high orthophosphate loadings, the straight stoichiometric yield relationship between biomass yield and phosphorus a vailability is lost. Movements of phosphorus and its recycling within aquatic systems do not prevent the slow gravitation of phosphorus to the bottom substrata. The phosphorus retentivity of sediments depends upon their chemical composition. While oxide-hydroxide binding capacity in the surface sediments persists, they act as a sink for phosphorus and a control on further cycling. Iron-rich and clay-rich sediments perform best in these conditions; calcareous sediments least so. Eutrophication may lead to the exhaustion of sediment P-binding capacity. Non-sorbed phosphate is readily recyclable if primary producers have access to it. Recycling is most rapid in shallow waters (where sediment disturbance, by flow, by wind action and through bioturbation, is frequent and least in deep ventilated sediments. The contributions of phosphorus from catchments are assessed. The slow rate of weathering of (mostly apatitic) minerals, the role of chemical binding in soils and the incorporation and retentivity bv forested terrestrial ecosystems each contribute to the minimisation of phosphorus leakage to drainage waters. Palaeolimnological and experimental evidence confirms that clearance of land and ploughing its surface weakens the phosphorus retentivity of catchments. The phosphorus transferred from arable land to drainage remains dominated by sorbed fractions which are scarcely bioavailable. Some forms of intensive market gardening or concentrated stock rearing may mobilise phosphates to drainage but it is deduced that drainage from agricultural land is not commonly a major source of readily bioavailable phosphorus in water. Careful budgeting of the phosphates in run-off from over-fertilised soils may nevertheless show that a proportionately small loss of bioavailable phosphorus can still be highly significant in promoting aquatic plant production. The bioavailable-phosphorus (BAP) load achieving the OECD threshold of lake eutrophy (35 mg P m(-3)) is calculated to be equivalent to a terrestrial loss rate of approximately 17.5 kg BAP km(-2) year(-1)), or only 1-2% of a typical fertiliser application. The output is shown to be comparable with the P yield from secondary treatment of the sewage produced by a resident population of 30-44 persons km(-2). With tertiary treatment, the equivalence is with approximately 200 persons km(-2).     

Effects of liming on phosphate availability in acid soils

Summary The critical factors involved in the plant-soil-phosphorus-lime interaction are outlined and discussed. Conflicting reports suggest that the prior liming of highly weathered acid soils can result in an increase, a decrease, or no change in the availability of applied phosphate. Adsorption of phosphate by amphoteric soil surfaces generally decreases slowly as the pH is raised from 4.0 to 7.0. However, in soils initially high in exchangeable Al³⁺, liming results in the formation of new, highly active, phosphate adsorbing surfaces as the Al³⁺ ions precipitate as insoluble polymeric hydroxy-Al cation species. Thus, if an acid soil is reacted with lime and then phosphate, without intervening air drying, liming can increase phosphate adsorption. If the same limed soil is air dried before reaction with phosphate (e.g. adsorption isotherm studies), liming decreases phosphate adsorption. Apparently, air drying alters the surface characteristics of recently limed soils, probably by promoting the crystallization of the hydroxy-Al cation polymers as gibbsite.An important phenomenon, which is often overlooked, is that liming can increase phosphate availability by stimulating mineralization of soil organic phosphorus. However, at high soil pH values, the precipitation of insoluble calcium phosphates can decrease phosphate availability. Since Al toxicity is characterised by the inhibition of the uptake, translocation and utilization of phosphate by plants, liming often increases the utilization of soil phosphate by plants through amelioration of Al toxicity.When making lime recommendations or interpreting the data collected from lime-phosphate experiments, it is important to consider all the complex interacting soil and plant factors involved.     

A critical review on the role of mycorrhizal fungi in the uptake of phosphorus by plants

The beneficial effects of mycorrhizae on plant growth have often been related to the increase in the uptake of immobile nutrients, especially phosphorus (P). In this review the mechanisms for the increase in the uptake of P by mycorrhizae and the sources of soil P for mycorrhizal and non-mycorrhizal plants are examined.Various mechanisms have been suggested for the increase in the uptake of P by mycorrhizal plants. These include: exploration of larger soil volume; faster movement of P into mycorrhizal hyphae; and solubilization of soil phosphorus. Exploration of larger soil volume by mycorrhizal plants is achieved by decreasing the distance that P ions must diffuse to plant roots and by increasing the surface area for absorption. Faster movement of P into mycorrhizal hyphae is achieved by increasing the affinity for P ions and by decreasing the threshold concentration required for absorption of P. Solubilization of soil P is achieved by the release of organic acids and phosphatase enzymes. Mycorrhizal plants have been shown to increase the uptake of poorly soluble P sources, such as iron and aluminium phosphate and rock phosphates. However, studies in which the soil P has been labelled with radioactive ³²P indicated that both mycorrhizal and non-mycorrhizal plants utilized the similarly labelled P sources in soil.     

The use of P32 in studies on the uptake of phosphorus by plants

Summary A fertilizer experiment with calcium phosphates labelled with P³² was carried out in pots with barley as a test plant. By determining the ratio of P³² in fertilizer and plant phosphorus after more than 7 weeks the content of exchangeable phosphate in the soil could be calculated. The results of the calculation were independent of the amount of phosphate added providing it was soluble.     

Phosphate solubilization potential and stress tolerance of Eupenicillium parvum from tea soil

Eupenicillium parvum was recorded for first time during isolation of phosphate-solubilizing microorganisms from the tea rhizosphere. The fungus developed a phosphate solubilization zone on modified Pikovskaya agar, supplemented with tricalcium phosphate. Quantitative estimation of phosphate solubilization in Pikovskaya broth showed high solubilization of tricalcium phosphate and aluminium phosphate. The fungus also solubilized North Carolina rock phosphate and Mussoorie rock phosphate, and exhibited high levels of tolerance against desiccation, acidity, salinity, aluminium, and iron. Solubilization of inorganic phosphates by the fungus was also observed under high stress levels of aluminium, iron, and desiccation, though the significant decline in phosphate solubilization was marked in the presence of aluminium than iron. The fungal isolate showed 100 % identity with E. parvum strain NRRL 2095 ITS 1, 5.8S rRNA gene and ITS 2, complete sequence; and 28S rRNA gene, partial sequence.     

Phosphate adsorption on bottom sediments of the Rio de la Plata

A study of the phosphate adsorption onto the bottom sediments of the Rio de la Plata has been made with the aim to understand the dynamics of this compound in the fluvio-marine system. Previous to the chemical analysis of the phosphate content, an extraction of the different adsorbed phosphate fractions have been made. In addition to phosphate, calcium, iron and aluminium in the sediment samples were determined. The phosphate is associated to the fine fractions of the sediments and good correlations with Al and Fe content in the bottom sediments were found. There is a relative decrease of the adsorbed phosphate on the bottom sediment in the areas where the influence of the marine water is more conspicuous; it is explained by the pH increase of the estuary waters due to the mixture with the marine waters. A hypothesis about the role of the ionic strength and the pH on the phosphate adsorption process is suggested.     

Effect of phosphorus and zinc on the growth and phosphorus,zinc, copper,iron and manganese nutrition of rice

Summary A greenhouse experiment was conducted to study the effect of phosphorus and zinc application, in three lowland alluvial rice soils (Haplustalf) on the growth of rice and the concentration of phosphorus, zinc, copper, iron and manganese in shoots and roots. The results showed that application of phosphorus and zinc significantly increased the dry matter yield of shoots, grains and roots. Application of phosphorus caused a decrease in the concentration of zinc, copper, iron and manganese both in shoots and roots. Application of zinc also similarly lowered the concentration of phosphorus, copper and iron, but increased that of manganese in shoots and roots. The decrease in the concentration of the elements in the shoots was not due to dilution effect or to the reduced rate of translocation of the elements from the roots to tops. This has been attributed more to the changes in the availability of the elements in soil resulting from the application of phosphorus and zinc.