Academic literature on the topic 'Phosphorus – Solubility'

The word vitamin was first used to mean ""the amine necessary for life"". • Vitamins are organic catalysts necessary for normal body functions, growth and healthy living. They are not synthesized in the human body and must be obtained externally. Vitamins are classified according to their fat and water solubility. Fat-soluble vitamins are vitamins A, D, E and K, and although they are essential for health, each of them has very important functions in the body. They have many biological activities such as vision, bone, coagulation and antioxidant effects. They are released, absorbed and transported (as chylomicrons) along with dietary fats. They are stored in the liver and fatty tissue and are eliminated more slowly than water-soluble vitamins. Vitamins A and D can accumulate in the body and cause toxic effects. Minerals are inorganic substances needed for the body to maintain its basic functions. These substances cannot be created directly by plants and animals and are taken from the soil. Minerals are divided into two groups: macrominerals and microminerals. Macrominerals are elements that should be taken in amounts greater than 100 mg daily. Calcium, phosphorus, magnesium, sodium, chlorine and potassium are macrominerals. Deficiency or excess intake of minerals can disrupt many biological functions and cause diseases. Sodium is a mineral that plays an important role in the body. Sodium, the main cation of extracellular fluid, is involved in functions such as transport of substances across the cell membrane, fluid-electrolyte balance, and regulation of blood pressure. Sodium levels in the body are kept under control by the functioning of the kidneys and the influence of hormones. Muscle contraction begins with an increase in intracellular calcium ion concentration. It is the most abundant element in the human body after calcium. It is a component of DNA and RNA. Phosphorus plays a role in the formation of bones and teeth and the repair of tissues and cells. It is found abundantly in water in nature, but rarely in plants, especially as sodium chloride and potassium chloride. It ensures that the fluids in the body are kept in balance.

Poverty alleviation in Sub-Saharan Africa is proportionally dependent on soil management. Low crop productivity has been linked to hunger and poverty as soil degradation is undeniably the cause. This chapter gives a general overview from major findings on how microbes could improve phosphate (P) levels in soils by enhancing its solubility. A cross-sectional study was under taken to highlight the role played by phosphate-solubilizing microbes—arbuscular mycorhizal fungi (AMF) and phosphate-solubilizing bacteria (PSB) in improving phosphate solubility. About 30–50% of phosphorus is organic which the plants could readily assimilate, while 50–70% is inorganic and inaccessible to plants. There are several mechanisms the plants utilize to optimize nutrient uptake from the root hairs to various parts of the plant to maximize crop production. The utilization of readily available minerals such as phosphate rock is known to play vital role in plant ecology and evolution, in checking drought stress, heavy metal toxicity, nutritional imbalances, plant pathogens, and salinity. Therefore, soil improvement using rock phosphate could potentially act in synergy with the phosphate-solubilizing microbes to boost phosphate levels in the soil. This could be a welcome development in low-income economies in the sub-Saharan Africa (SSA) to boost yield for profit maximization.

Phosphorus oxide for use as fertilizer is produced by using sulphuric acid to attack natural phosphates and this generates a byproduct essentially composed of hydrated calcium sulphate and known as phosphogypsum. The solubility of calcium sulphate, even in the natural rocks and soils containing gypsum, limits the utilisation of this material in slopes for linear works to a maximum calcium sulphate content of 20%. Other elements also appear in phosphogypsum that, in the event of solubilising, could contaminate the water in the surrounding area. In spite of all this, experience does exist with the use of phosphogypsum in experimental slopes designed to ascertain the possibility of storing this product in more areas capable of guaranteeing that the surroundings are not contaminated. This article reports on the characteristics of the Huelva phosphogypsum in terms of both composition and mechanical properties and the measures to be taken for its possible utilisation in roadwork fills.

During aerobic and anaerobic decomposition of plant and animal reside a complex aggregate of brown to dark coloured amorphous substances is obtained which is called as Humus. It includes humic substances and resynthesizes products of microorganisms. These products are stable and a part of the soil. Humus is categorised according to their molecular weights and solubility into humus, humic acids and fulvic acids. Humic substances are the organic material naturally present in soil. Humic substances positively effect’s soil quality and fertility by increasing its water holding capacity, stabilisation of soil structure, soil microbial activity, plant physiology. It also influence nutrient uptake and root architecture act like phytohormones for phosphorus acquisition, and improving plant adaptation to saline condition. Humus is the primary microhabitat for microorganism such as dictyostelids, myxomycetes, some species of protostelids, members of the genus Copromyxella etc. Other than that auxin like activity of Humic Substances has also been demonstrated in recent studies. The research suggested that it could be the main biological factor that exhibits positive effect on plant physiology. Based on that fertiliser factory also trying to produce are bio- stimulants, based on humic substances and other organic compounds.

Endophytic filamentous fungi from three genera, Trichoderma, Aspergillus and Penicillium, isolated from saffron corms, were tested in vitro for their ability to solubilize phosphorus from tricalcium phosphate and rock phosphate. When fungal strain filtrates were transferred into NBRIP medium amended with Ca3(PO4)2, Penicillium aeris showed the highest soluble phosphorus concentration, reaching 39.66 μg/ml after 5 days of incubation at 28°C, while the concentrations of soluble phosphorus in Trichoderma filtrates ranged from 18.33 to 29.4µg/ml, and those in Aspergillus filtrates ranged from 32,33 to 35,66µg/ml. The pH values decreased over time, reaching their lowest points of 3.38 and 3.57 after 196 hours of incubation in the culture filtrates of Aspergillus niger and Penicillium aeris, respectively. For rock phosphate solubilization, Trichoderma isolates, along with Aspergillus nomius, A. ochraceus, A. niger, Penicillium sp. and P. aeris, are among the most effective. This study highlights endophytic fungi's role in enhancing soil fertility and plant growth by solubilizing phosphates.

"The rhizosphere is a nutrient-rich and complex ecosystem known as the root zone of plants. It is known that this highly dynamic region, where various microorganisms such as bacteria, archaea, fungi, viruses, protistae, nematodes and invertebrates, as well as nematodes and invertebrates are abundant, is shaped by the interactions between soil, plants and organisms forming the rhizosphere. Primary metabolites (organic acids, carbohydrates and amino acids) and secondary metabolites (alkaloids, terpenoids, phenols, etc.) released by plant roots contribute greatly to the biodiversity of the rhizosphere. The (micro) organisms in the rhizosphere, most of which continue their development through plant secretions and signals, also contribute by binding free nitrogen from the atmosphere, solubilising phosphorus, transforming nitrogen, synthesising organic compounds such as vitamins and amino acids, increasing the solubility of minerals in the soil and promoting plant growth through the enzymes and hormones they produce. They also contribute indirectly to plant growth by aerating the soil, suppressing plant pathogens through their competitive properties and the antimicrobial compounds they produce, eliminating plant stressors such as heavy metals, toxic compounds or soil salinity, temperature and pH, and stimulating systemic resistance. Although some species have negative effects on plants by retaining minerals that limit plant growth or by competing with other species, the effects of rhizosphere organisms on plants, soil and living organisms are quite large. In this context, it is necessary to analyse the rhizosphere biota in detail and consider their possible interactions. Considering these interactions, which are important for the diversity of the rhizosphere, is often crucial for the success of management strategies such as bioremediation and biological control, which will increase yield and quality in production. For this reason, the study of rhizosphere diversity and the interactions between organisms living in this area is strategic for both crop production and environmental manipulation. In fact, taking solid steps to use the rhizosphere for sustainable agriculture, climate change and ecosystem stability is seen as a guarantee for our present and future."

Phosphogypsum is a waste product of processing phosphorous oxide into fertilizer. It is made up primarily of calcium sulfate hydrate and its possible use as a compressible material to form the core of fill is analyzed in Dapena et al. [1]. However, there are two aspects of phosphogypsum which may have an impact on environmental quality when it is used as fill. One, its solubility means that it could contaminate local water with soluble salts, particularly calcium sulfates. Two, it radioactivity may reach levels not permitted in the environment for phosphogypsum fill. This paper discusses studies made of the solubility of phosphogypsum and elements which appear in leachates and those carried out to determine any possible existing radioactive elements and their level of radioactivity. The pH of this phosphogypsum is acid, pH = 3.69. This results in an increase in calcium sulfate dihydrate solubility, which reaches 4 gr/l. In addition, phosphogypsum leachates (L/S =10) exceed the allowed limits to be accepted as landfill for the following elements: As, Cd, Cr, Se, F and SO3. Furthermore, as a result of radon-222 and the radon daughters Po-218, Pb-214, Bi-214 and Po-214, the radioactivity of the phosphogypsum studied is 68.1 pCi/gr, which is ten times the radioactivity of granite and five times that of miga sand, materials commonly used as road fill.

Application of limestone to a soil changes the (a) soil physical properties by encouraging granulation and improving tilth; (b) soil chemical properties by decreasing soil acidity, increasing availability of a number of essential plant nutrients, and decreasing levels of aluminum, iron, and manganese that potentially may be toxic; and (c) soil biological properties by improving conditions for micriobial organic matter decomposition with release of nitrogen, phosphorus, and sulfur for plant use, and by stimulating root development. Granulation Encouraged. Applying lime to soils improves soil physical conditions by encouraging granulation and crumb formation and aggregation. Tilth Improved. Tilth is the ability to work or cultivate a soil. By improving physical conditions with more granulation and crumb formation, soil tilth is improved. Lowering H+ Concentration (Acidity). When lime is applied to a soil, acidity is reduced and pH is raised. This is especially important in the humid regions where rainfall and other factors constantly make a soil more acid (explained in Chapter 9). Plant Nutrient Availability Increased. Liming a soil will increase availability of plant nutrients by (a) increasing Ca and Mg in the soil from added liming material; (b) adjusting soil to a higher pH so that N, P, K, S, and Mo are solubilized; and (c) reducing solubility of potentially toxic levels of Fe, Al, or Mn. Lowering of Potentially Toxic Levels of Al, Fe, and Mn. At very low soil pH, Al, Fe, and Mn are soluble and may be present in a high enough concentration to be toxic to plant growth. When lime is applied, the pH increases and these three elements become less soluble and less available for plants. Microbial Decomposition Enhanced. Soils that are limed provide conditions for active microbial decomposition of organic materials in soils, resulting in mineralization and release of N, P, and S in forms that plants can use. Liming also increases the amount of humus formed, thereby improving water infiltration and water-holding capacity. Furthermore, liming soils stimulates other types of biological transformations, such as nitrification, N-fixation, and S-oxidation, that improve plant growth. Deep Rooting Stimulated.

Abstract Nickel and electroless nickel (EN) coatings have found extensive use in caustic soda service. The corrosion resistance of the EN coatings depends on its phosphorus content, however, not in the trend expected. High phosphorus EN coatings have a poorer corrosion resistance in hot, concentrated NaOH than low and medium phosphorus EN coatings, which have a corrosion resistance comparable to nickel. The purpose of this research was to quantify the effect of phosphorus in EN coatings on its corrosion resistance in room temperature 50% NaOH. Electrochemical techniques were used to investigate the corrosion processes and X-ray Photoelectron Spectroscopy was used to characterize the surfaces of the coatings. Very low corrosion rates were measured (<2 μm/yr or less) for all coatings. It is proposed that the detrimental effect of phosphorus in EN coatings exposed to a concentrated caustic soda environment is due to the higher solubility of nickel phosphate relative to nickel hydroxide/oxide. This mechanism predicts an inverse relationship between the thickness of the corrosion protecting film on EN and its phosphorus content, which is consistent with experimental observations.

Abstract Aluminum and magnesium are prone to surface attack (dark stains) when exposed to aqueous alkaline conditions. Surface active phosphorus and other chemistries have been employed in the industry to passivate these surfaces and prevent staining. Phosphonate and phosphate chemistries have been shown to be effective in controlling surface corrosion. The current work explores alkyl phosphates and investigates how structure impacts the efficacy of the corrosion inhibition. Corrosion inhibition is related not only to the ability of the phosphate to interact with the nonferrous surface, but also the solubility of the additive in the formulation. Magnesium machining processes are further complicated by hydrogen evolution from the reaction of magnesium and high alkalinity water. The prevention of hydrogen evolution was also investigated. Performance was measured relative to industry phosphate and phosphonate controls.

Abstract In a 10 MPa class boiler system, (flow accelerated corrosion (FAC) occurs at the carbon steel feed water line between the de-aerator and the boiler at around 150 °C. FAC has an influence not only on the loss of metal, but also on the precipitation of iron oxide particles on the inside of the boiler tube for low solubility of iron ions at around 300 °C1 to make poor scale, where the efficiency of heat transfer rate between boiler water and fireside along the tube wall becomes worse. As a result of the poor scale, the metal temperature increases and the creep failure of the tube may occur. In this paper, it has become apparent that in the actual boiler system phosphoric ions prevent iron oxide from cohesion and adhesion on the inside of the tube where the precipitation of the iron oxide does not occur. Phosphate has an influence on higher pH of water and adds more negative zeta potential on the surface of the iron oxide particles in water compared to 2-aminomethanol (NH2CH2OH, MEA).

Municipal sewage sludge has a high concentration of phosphorus, which should be recovered because phosphorus is a limited natural resource. In this work, sewage sludge was co-fired with wood in a FBC boiler. The aim of the investigating was to study the solubility of phosphorus in the ashes, by leaching as an alternative to the phosphorous recovery method of using the ashes directly on farmlands. The fly ashes from the boiler’s secondary cyclone and bag filter were leached at various pH-values and the release of phosphorus was measured. Only acidic leaching was applied. The ashes precipitated with Al2(SO4)3 released nearly all phosphorus at a pH-value of 1, whereas the ashes precipitated with Fe2(SO4)3 did not release all phosphorus even at the very low pH of 0.5. The concentrations of phosphorous in the leachate must be compared with liquid phosphorus sources such as human urine or liquid animal manure used as fertilisers. This may result in that the leachate has to be processed further. A continuation of the work to investigate to what extent the leachate is contaminated with toxic trace elements is necessary.

Beneficial use of reclaimed wastewater (RW) and biosolids (BS) in soils is accompanied by large input of sewage-originated P. Prolonged application may result in P accumulation up to levelsBeneficial use of reclaimed wastewater (RW) and biosolids (BS) in soils is accompanied by large input of sewage-originated P. Prolonged application may result in P accumulation up to levels that impair plant nutrition, increase P loss, and promote eutrophication in downstream waters. This study aims to shed light on the RW- and BS-P forms in soils and to follow the processes that determine P reactivity, solubility, availability, and loss in RW and BS treated soils. The Technion group used sequential P extraction combined with measuring stable oxygen isotopic composition in phosphate (δ18OP) and with 31P-NMR studies to probe P speciation and transformations in soils irrigated with RW or fresh water (FW). The application of the δ18OP method to probe inorganic P (Pi) speciation and transformations in soils was developed through collaboration between the Technion and the UCSC groups. The method was used to trace Pi in water-, NaHCO3-, NaOH-, and HCl- P fractions in a calcareous clay soil (Acre, Israel) irrigated with RW or FW. The δ18OP signature changes during a month of incubation indicated biogeochemical processes. The water soluble Pi (WSPi) was affected by enzymatic activity yielding isotopic equilibrium with the water molecules in the soil solution. Further it interacted rapidly with the NaHCO3-Pi. The more stable Pi pools also exhibited isotopic alterations in the first two weeks after P application, likely related to microbial activity. Isotopic depletion which could result from organic P (PO) mineralization was followed by enrichment which may result from biologic discrimination in the uptake. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with RW. Specific P compounds were identified by the Technion group, using solution-state 31P-NMR in wastewater and in soil P extracts from Acre soils irrigated by RW and FW. Few identified PO compounds (e.g., D-glucose-6-phosphate) indicated coupled transformations of P and C in the wastewater. The RW soil retained higher P content, mainly in the labile fractions, but lower labile PO, than the FW soil; this and the fact that P species in the various soil extracts of the RW soil appear independent of P species in the RW are attributed to enhanced biological activity and P recycling in the RW soil. Consistent with that, both soils retained very similar P species in the soil pools. The HUJ group tested P stabilization to maximize the environmental safe application rates and the agronomic beneficial use of BS. Sequential P extraction indicated that the most reactive BS-P forms: WSP, membrane-P, and NaHCO3-P, were effectively stabilized by ferrous sulfate (FeSul), calcium oxide (CaO), or aluminum sulfate (alum). After applying the stabilized BS, or fresh BS (FBS), FBS compost (BSC), or P fertilizer (KH2PO4) to an alluvial soil, P availability was probed during 100 days of incubation. A plant-based bioassay indicated that P availability followed the order KH2PO4 >> alum-BS > BSC ≥ FBS > CaO-BS >> FeSul-BS. The WSPi concentration in soil increased following FBS or BSC application, and P mineralization further increased it during incubation. In contrast, the chemically stabilized BS reduced WSPi concentrations relative to the untreated soil. It was concluded that the chemically stabilized BS effectively controlled WSPi in the soil while still supplying P to support plant growth. Using the sequential extraction procedure the persistence of P availability in BS treated soils was shown to be of a long-term nature. 15 years after the last BS application to MN soils that were annually amended for 20 years by heavy rates of BS, about 25% of the added BS-P was found in the labile fractions. The UMN group further probed soil-P speciation in these soils by bulk and micro X-ray absorption near edge structure (XANES). This newly developed method was shown to be a powerful tool for P speciation in soils. In a control soil (no BS added), 54% of the total P was PO and it was mostly identified as phytic acid; 15% was identified as brushite and 26% as strengite. A corn crop BS amended soil included mostly P-Fe-peat complex, variscite and Al-P-peat complex but no Ca-P while in a BS-grass soil octacalcium phosphate was identified and o-phosphorylethanolamine or phytic acid was shown to dominate the PO fraction that impair plant nutrition, increase P loss, and promote eutrophication in downstream waters. This study aims to shed light on the RW- and BS-P forms in soils and to follow the processes that determine P reactivity, solubility, availability, and loss in RW and BS treated soils. The Technion group used sequential P extraction combined with measuring stable oxygen isotopic composition in phosphate (δ18OP) and with 31P-NMR studies to probe P speciation and transformations in soils irrigated with RW or fresh water (FW). The application of the δ18OP method to probe inorganic P (Pi) speciation and transformations in soils was developed through collaboration between the Technion and the UCSC groups. The method was used to trace Pi in water-, NaHCO3-, NaOH-, and HCl- P fractions in a calcareous clay soil (Acre, Israel) irrigated with RW or FW. The δ18OP signature changes during a month of incubation indicated biogeochemical processes. The water soluble Pi (WSPi) was affected by enzymatic activity yielding isotopic equilibrium with the water molecules in the soil solution. Further it interacted rapidly with the NaHCO3-Pi. The more stable Pi pools also exhibited isotopic alterations in the first two weeks after P application, likely related to microbial activity. Isotopic depletion which could result from organic P (PO) mineralization was followed by enrichment which may result from biologic discrimination in the uptake. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with RW. Specific P compounds were identified by the Technion group, using solution-state 31P-NMR in wastewater and in soil P extracts from Acre soils irrigated by RW and FW. Few identified PO compounds (e.g., D-glucose-6-phosphate) indicated coupled transformations of P and C in the wastewater. The RW soil retained higher P content, mainly in the labile fractions, but lower labile PO, than the FW soil; this and the fact that P species in the various soil extracts of the RW soil appear independent of P species in the RW are attributed to enhanced biological activity and P recycling in the RW soil. Consistent with that, both soils retained very similar P species in the soil pools. The HUJ group tested P stabilization to maximize the environmental safe application rates and the agronomic beneficial use of BS. Sequential P extraction indicated that the most reactive BS-P forms: WSP, membrane-P, and NaHCO3-P, were effectively stabilized by ferrous sulfate (FeSul), calcium oxide (CaO), or aluminum sulfate (alum). After applying the stabilized BS, or fresh BS (FBS), FBS compost (BSC), or P fertilizer (KH2PO4) to an alluvial soil, P availability was probed during 100 days of incubation. A plant-based bioassay indicated that P availability followed the order KH2PO4 >> alum-BS > BSC ≥ FBS > CaO-BS >> FeSul-BS. The WSPi concentration in soil increased following FBS or BSC application, and P mineralization further increased it during incubation. In contrast, the chemically stabilized BS reduced WSPi concentrations relative to the untreated soil. It was concluded that the chemically stabilized BS effectively controlled WSPi in the soil while still supplying P to support plant growth. Using the sequential extraction procedure the persistence of P availability in BS treated soils was shown to be of a long-term nature. 15 years after the last BS application to MN soils that were annually amended for 20 years by heavy rates of BS, about 25% of the added BS-P was found in the labile fractions. The UMN group further probed soil-P speciation in these soils by bulk and micro X-ray absorption near edge structure (XANES). This newly developed method was shown to be a powerful tool for P speciation in soils. In a control soil (no BS added), 54% of the total P was PO and it was mostly identified as phytic acid; 15% was identified as brushite and 26% as strengite. A corn crop BS amended soil included mostly P-Fe-peat complex, variscite and Al-P-peat complex but no Ca-P while in a BS-grass soil octacalcium phosphate was identified and o-phosphorylethanolamine or phytic acid was shown to dominate the PO fraction.

Soil microorganisms enhance the plant availability of phosphorus (P). This ability is related to the production of organic acids and the activity of phosphatases. It is assumed that the production of organic acids solubilize insoluble phosphate forms to usable form such as orthophosphate, increasing its potential availability to plants (Vázquez et al. 2000). Filamentous fungi such as Trichoderma sp. have advantages in acid soils presenting morphological and metabolic characteristics that make them promising organisms (Nahas, 1996; Vera et al, 2002). On the other hand, inoculation of soil with phosphate solubilizing fungi has been shown to increase yields in crops like maize and wheat (Singh and Reddy, 2011), beans (Wahid and Mehana, 2000), chickpea (Kapri and Tewari, 2010).

Rhizobia have been widely known by their capacity to form a symbiotic relationship with legumes and fix atmospheric nitrogen. Recently, however, rhizobia have shown to associate with plants in different botanical families. In this study, we aimed at elucidating the diversity of rhizobia associated to grasses, and determine their capabilities to solubilize phosphate in both lab and greenhouse experiments. Isolation of rhizobia was performed using rhizosphere from Brachiaria brizantha and B. decumbens and a promiscuous legume trap plant (i.e. Vigna unguiculata). Thirty days after inoculation of the trap plant, rhizobia were isolated from nodules using the conventional protocol, classified in basis on their phenotypic features, and molecularly grouped using Amplified Ribosomal DNA Restriction Analysis (ARDRA). Finally, phosphate solubilization assays and greenhouse experiments were carried out on representatives of each ARDRA cluster. The results showed that the diversity of rhizobia varied between both plant species, which suggests that plant exudates significantly determine the composition of the plant microbiome. Surprisingly, most of the isolated associated to B. brizantha rhizosphere exhibited typical attributes of slow-growing rhizobia, whereas rhizobia from B. decumbens displayed a mixed diversity including slow-, intermediate-, and fast-growing rhizobia. Sequencing of 16S rRNA of ARDRA representatives showed that most of the rhizobia isolated from B. brizantha belonged to the Mesorhizobium and Bradyrhizobium genera, while those isolated from B. decumbens were phylogenetically clustered into Rhizobium and Bradyrhizobium. The capability of the isolates to solubilize phosphate was studied using iron and calcium phosphate. We observed that overall Bradyrhizobium exhibited the highest ability to solubilize iron phosphate; by contrast, calcium phosphate was similarly solubilized within representatives of the three genera. In greenhouse experiments, we found that plants inoculated with isolated BT53, BD17 and BD21 exhibited a significantly higher content of phosphorus (p≤0.05). Additionally, dry weight was significantly higher in the treatment inoculated with BT16 isolate (p≤0.05). We conclude that 1) rhizobia is found associated with grasses, 2) plant genotype determines rhizobia diversity 3) rhizobia are able to solubilize phosphorus, and 4) they might be used to promote plant in different plant families. We further believe that further studies will reveal the true role of those old-known legume symbionts in development and growth of other important crops.

At the start of this project, fungi in the genus Trichoderma were known to be potent biocontrol agents, and their primary mechanism was considered to via direct effects upon the target fungi. Due in large part to the efforts of the two PIs, we now know that this view is far too limited; while Trichoderma spp. do indeed have direct effects on pathogenic fungi, they have very far reaching effects directly upon plants. Indeed, these fungi must be considered as opportunistic plant symbionts; they provide a number of benefits to plants and themselves are favored by large numbers of healthy roots. Research under this BARD grant has demonstrated that These fungi induce resistance mechanisms in plants. They increase root development and depth of rooting; Bradyrhizobium enhances this effect in soybean. They enhance uptake of plant nutrients. They have abilities to solubilize nutrients, such as oxidized metals and insoluble phosphorus compounds by a variety of different mechanisms and biochemicals. This is a marked expansion of our knowledge of the abilities of these organisms. This knowledge has direct implications for understanding of basic plant responses and abilities, and already is being used to improve plant productivity and reduce pollution of the environment.