Phosphate Reserves Research Articles

Looming Scarcity of Phosphate Rock and Intensification of Soil Phosphorus Research

In recent years, many researchers have claimed that world reserves of rock phosphate were getting depleted at an alarming rate, putting us on the path to scarcity of that essential resource within the next few decades. Others have claimed that such alarmist forecasts were frequent in the past and have always been proven unfounded, making it likely that the same will be true in the future. Both viewpoints are directly relevant to the level of funding devoted to research on the use of phosphate fertilizers. In this short essay, it is argued that information about future reserves of P or any other resource are impossible to predict, and therefore that the threat of a possible depletion of P reserves should not be used as a key motivation for an intensification of research on soil P. However, there are other, more compelling reasons, both geopolitical and environmental, to urgently step up our collective efforts to devise agricultural practices that make better use of P than is the case at the moment.

Explaining and mapping total phosphorus content in French topsoils

AbstractTotal phosphorus (TP) build‐up in agricultural soils represents both a threat to aquatic ecosystems and a valuable resource for future crop production, given the context of increasing food demand combined with the rapid depletion of the world's phosphate reserves. Therefore, it is crucially important (i) to identify the main factors controlling topsoil TP and (ii) to develop methods for mapping its spatial distribution. Multiple linear regression models were used with two distinct approaches to calculate TP and covariates linked to the P cycle. Firstly, covariates were selected from the Réseau de Mesures de la Qualité des Sols database, the French soil monitoring network, which consists of soil samples collected from 2158 sites on a 16‐km regular grid. Secondly, covariates were selected to map TP from spatially exhaustive datasets in France. The first approach explains 80% of variability in topsoil TP. The variables selected are linked to the autochthonous origin of P (parent material), to allochthonous origin (organic carbon and nitrogen contents) and to the retention capacity of soil (Al, Fe, Ca and clay contents). The predicted map obtained from the second approach provides a mean TP of 0.76 g/kg. This study demonstrates that creating national scale maps of TP, based on detailed soil sampling and many variables, is feasible and can be used to model the P cycle and P transfer processes. Such maps can be used in P erosion and transfer models over river basins, and therefore to predict P exports to surface waters.

Replace, reuse, recycle: improving the sustainable use of phosphorus by plants.

The 'phosphorus problem' has recently received strong interest with two distinct strands of importance. The first is that too much phosphorus (P) is entering into waste water, creating a significant economic and ecological problem. Secondly, while agricultural demand for phosphate fertilizer is increasing to maintain crop yields, rock phosphate reserves are rapidly declining. Unravelling the mechanisms by which plants sense, respond to, and acquire phosphate can address both problems, allowing the development of crop plants that are more efficient at acquiring and using limited amounts of phosphate while at the same time improving the potential of plants and other photosynthetic organisms for nutrient recapture and recycling from waste water. In this review, we attempt to synthesize these important but often disparate parts of the debate in a holistic fashion, since solutions to such a complex problem require integrated and multidisciplinary approaches that address both P supply and demand. Rapid progress has been made recently in our understanding of local and systemic signalling mechanisms for phosphate, and of expression and regulation of membrane proteins that take phosphate up from the environment and transport it within the plant. We discuss the current state of understanding of such mechanisms involved in sensing and responding to phosphate stress. We also discuss approaches to improve the P-use efficiency of crop plants and future direction for sustainable use of P, including use of photosynthetic organisms for recapture of P from waste waters.

Unmasking Novel Loci for Internal Phosphorus Utilization Efficiency in Rice Germplasm through Genome-Wide Association Analysis

Depletion of non-renewable rock phosphate reserves and phosphorus (P) fertilizer price increases has renewed interest in breeding P-efficient varieties. Internal P utilization efficiency (PUE) is of prime interest because there has been no progress to date in breeding for high PUE. We characterized the genotypic variation for PUE present within the rice gene pool by using a hydroponic system that assured equal plant P uptake, followed by mapping of loci controlling PUE via Genome-Wide Association Studies (GWAS). Loci associated with PUE were mapped on chromosomes 1, 4, 11 and 12. The highest PUE was associated with a minor indica-specific haplotype on chromosome 1 and a rare aus-specific haplotype on chromosome 11. Comparative variant and expression analysis for genes contained within the chromosome 1 haplotype identified high priority candidate genes. Differences in coding regions and expression patterns between genotypes of contrasting haplotypes, suggested functional alterations for two predicted nucleic acid-interacting proteins that are likely causative for the observed differences in PUE. The loci reported here are the first identified for PUE in any crop that is not confounded by differential P uptake among genotypes. Importantly, modern rice varieties lacked haplotypes associated with superior PUE, and would thus benefit from targeted introgressions of these loci from traditional donors to improve plant growth in phosphorus-limited cropping systems.

The acquisition of phosphate by higher plants: Effect of carboxylate release by the roots. A critical review.

AbstractPhosphorus is one of the most limiting macronutrients for plant productivity in agriculture worldwide. The main reasons are the limited rock phosphate reserves and the high affinity of phosphate (P) to the soil solid phase, restricting the P availability to the plant roots. Plants can adapt to soils low in available P by changing morphological or/and physiological root features. Morphological changes include the formation of longer root hairs and a higher root : shoot ratio both parameters increasing the root surface which provides the shoot with P. This may be successful if the P availability in soil, i.e., the P concentration of the soil solution is not extremely low (> 1–2 µM P). If the P concentration of the soil solution is lower, the diffusive flux to the root surface will be very low and may not satisfy the P demand of the shoots. Under these conditions plants have developed strategies to increase the rhizosphere soil solution concentration by secreting mobilizing agents. The most effective way of P mobilization is the release of di‐ and tricarboxylic acid anions, especially oxalate and citrate. Citrate can accumulate in the rhizosphere up to concentrations up to 80 µmol g−1 soil. Cluster root formation is an efficient way of carboxylate accumulation in the cluster root rhizosphere improving P mobilization. Cluster roots strongly improve the acquisition of the mobilized P. Considering a single root, around 80–90% of the mobilized P diffuses away from the root. From the rhizosphere of cluster roots, most of the mobilized P is taken up by the cluster roots. Both, the strong accumulation of carboxylates in and the effective P uptake from the cluster‐root rhizosphere are the basis of the unique ability of P acquisition by cluster root‐forming plants. Plants that do not form cluster roots, e.g., red clover, can also accumulate carboxylates in the rhizosphere. Red clover accumulates high quantities of citrate in the rhizosphere soil. Model calculations show that the release of citrate by red clover roots and its accumulation in the rhizosphere strongly improve P acquisition by this plant species in various soils. Similar results are obtained with alfalfa. In sugar beet, oxalate release can strongly contribute to P acquisition. In summary, P acquisition can be strongly improved by the release of carboxylates and should be taken as a challenge for basic and applied research.

Mineral Industry in Egypt – Part II Non-Metallic Commodities –Phosphate Rocks

Phosphorus is an essential element in the buildup of the human body and all other livings skeletons. The main source of phosphorus is the natural phosphate. About 95 percent of the produced phosphates are consumed in the agricultural sector as fertilizers and animal feed stocks. Most of the balance is converted into phosphoric acid and elemental phosphorus which are the raw materials for manufacturing various phosphate compounds. The world annual phosphate production in 2012 is around 217 million tons, and the global reserves amount to 67 billion tons. With the population increase, researchers estimate that the existing phosphate reserves cover the world needs of phosphates for more than 100 years to come. Egypt has about 4 percent of the world phosphate reserves (2.78 billion tons), and produces about 3 percent of the world phosphate production (about 6 million t/y). The present article covers different aspects of the Egyptian phosphate rocks. The phosphate deposits in Egypt lie between latitudes 23 ο 10 – 30 ο 50΄ N, whereas the payable zone lies between latitudes 24 ο 30΄ – 26 ο 50΄ N. They extend longitudinally from the Red Sea Coast to El Dakhla Oases. Geologically, the economic phosphate beds belong to the central facial zone of the Upper Senonian age (Upper Cretaceous and Lower Eocene) deposits. They cover the Red Sea Coast, Nile Valley, and Western Desert. The P2 O5 content ranges between 20 and 32 %. The gangue constituents are mainly carbonates, silica, and silicates (clays), depending on the region and locality. The phosphate ore is mined by open cast and/or underground mining. The underground mining is either long‐wall or room‐and‐pillar mining methods. Upgrading the phosphate rock is done through: crushing, screening, attrition scrubbing, desliming, and drying naturally or artificially. Flotation is a promising technique for the removal of all sorts of gangue minerals. This has been tested in laboratory and semi‐pilot scales.

Africa’s Last Colony

Africa’s Last Colony

Global Phosphorus Scarcity and Full-Scale P-Recovery Techniques: A Review

Phosphorus (P) is an essential element for all life on earth. However, natural P resources (phosphate rock) are depleting. The authors describe the current situation and a forecast for future phosphate production and reserves. The current depletion of phosphate reserves and the increasingly stringent discharge regulations have led to the development of various P-recovery techniques from wastewater. Existing full-scale P-recovery techniques from the liquid phase, sludge phase, and sludge ash are reviewed. Although the full-scale P-recovery techniques have been shown to be technologically feasible, the economical feasibility, legislation and national policies are the major reasons why these techniques are not yet operational worldwide.

Antiarrhythmic effect of uridine and uridine-5'-monophosphate in acute myocardial ischemia.

Experiments on rats with acute myocardial ischemia accompanied by early postocclusive arrhythmias have shown normalizing, energy-stabilizing, and antiarrhythmic effects of uridine and uridine-5'-monophosphate. The drugs decreased lactate and restored reserves of glycogen and creatine phosphate depleted by ischemia. Uridine and uridine-5'-monophosphate significantly decreased the severity of ventricular arrhythmias. Both drugs reduced the incidence and duration of fibrillation. Uridine -5'-monophosphate demonstrated most pronounced antifibrillatory effectiveness. We hypothesize that the antiarrhythmic effect of the drugs is determined by their capacity to activate energy metabolism.

Enhancing Geophysical Signals Through the Use of Savitzky-Golay filtering method

In the Sidi Chennane basin exploitation inclusions of sterile hardpan—so-called “derangements” — are hard to detect and interfere with phosphate extraction. A Schlumberger resistivity survey over an area of 50 hectares was carried out. The Savitzky-Golay filtering method was used as a tool for denoising the data.Savitzky-Golay (S-G) filters are one of the filters which can smoothen out the signal without much destroying its original properties. Despite their exceptional features, they were rarely used so far in the geophysical signal processing. The aim of this paper is the investigation of their properties in detail from the geoelectrical signal processing aspect. The experimental results indicate that S-G filter is better for denoising geoelectrical signal. Models of the geology were successfully obtained from Savitzky-Golay filtering method, which help mapping the phosphate deposit inclusions and the estimations of phosphate reserves were improved and better constrained.

How changing root system architecture can help tackle a reduction in soil phosphate (P) levels for better plant P acquisition.

The readily available global rock phosphate (P) reserves may run out within the next 50-130 years, causing soils to have a reduced P concentration which will affect plant P uptake. Using a combination of mathematical modelling and experimental data, we investigated potential plant-based options for optimizing crop P uptake in reduced soil P environments. By varying the P concentration within a well-mixed agricultural soil, for high and low P (35.5-12.5 mg L(-1) respectively using Olsen's P index), we investigated branching distributions within a wheat root system that maximize P uptake. Changing the root branching distribution from linear (evenly spaced branches) to strongly exponential (a greater number of branches at the top of the soil) improves P uptake by 142% for low-P soils when root mass is kept constant between simulations. This causes the roots to emerge earlier and mimics topsoil foraging. Manipulating root branching patterns, to maximize P uptake, is not enough on its own to overcome the drop in soil P from high to low P. Further mechanisms have to be considered to fully understand the impact of P reduction on plant development.

Feed the crop not the soil: rethinking phosphorus management in the food chain.

Society relies heavily on inorganic phosphorus (P) compounds throughout its food chain. This dependency is not only very inefficient and increasingly costly but is depleting finite global reserves of rock phosphate. It has also left a legacy of P accumulation in soils, sediments and wastes that is leaking into our surface waters and contributing to widespread eutrophication. We argue for a new, more precise but more challenging paradigm in P fertilizer management that seeks to develop more sustainable food chains that maintain P availability to crops and livestock but with reduced amounts of imported mineral P and improved soil function. This new strategy requires greater public awareness of the environmental consequences of dietary choice, better understanding of soil-plant-animal P dynamics, increased recovery of both used P and unutilized legacy soil P, and new innovative technologies to improve fertilizer P recovery. In combination, they are expected to deliver significant economic, environmental, and resource-protection gains, and contribute to future global P stewardship.

Establishment of Phosphorus Flow Model in Urban Area using Material Flow Analysis

Phosphorus (P) is an essential nutrient for all living organisms. P is mostly obtained from mined rock phosphate. However, existing rock phosphate reserves could be exhausted in the next 50‐100 years. As Korea is totally dependent on imported rock phosphate, we should seek for solution to overcome the P depletion by efficient use and recycling. For this, this study suggested a P flow model to identify the location and flow route of P in urban area based on traditional material flow analysis. The type of P entering the urban areas are fertilizer, food and feed. Each type of P is used in agriculture, human consumption and animal husbandry. After going through each process, P is moved to waste management facilities within food waste, excreta and sewage. Some portion of P in waste are buried, incinerated and discharged, which can be reservoir of P in the future.

Microbial mineralization of struvite: A promising process to overcome phosphate sequestering crisis

Due to extensive exploitation of non-renewable phosphate minerals, their natural reserves will exhaust very soon. This necessitates looking for alternatives and an efficient methodology through which indispensable phosphorus can be harvested back. The current study was undertaken to explore the potential of a metallophilic bacterium Enterobacter sp. EMB19 for the recovery of phosphorus as phosphate rich mineral. A very low phosphate concentration strategy was adopted. The process led to the mineralization of phosphorus as homogeneous struvite crystals. For each gram of Epsom salt added, the cells effectively mineralized about 20% of the salt into struvite. The effect of different inorganic sources, culture profile and plausible mechanism involved in crystal formation was also explored. The synthesized struvite crystals typically possessed a prismatic crystal habit. The characterization and identification of the crystals were done using single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), energy dispersive X-ray analysis (EDAX) and fourier transform infrared (FTIR). The thermal characteristics were studied using thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) processes. The synthesis of struvite by this bacterium seems to be a promising and viable strategy since it serves dual purpose (i) obtaining phosphorus and nitrogen rich fertilizer and (ii) conservation of natural phosphate reserves. This study is very significant in the sense that the process may be used for harvesting and synthesizing other valuable minerals. Also, it will provide new insights into phosphate biomineralization mechanisms.

The alternative respiratory pathway mediates carboxylate synthesis in white lupin cluster roots under phosphorus deprivation

Plant adaptations associated with a high efficiency of phosphorus (P) acquisition can be used to increase productivity and sustainability in a world with a growing population and decreasing rock phosphate reserves. White lupin (Lupinus albus) produces cluster roots that release carboxylates to efficiently mobilize P from P-sorbing soils. It has been hypothesized that an increase in the activity of the alternative oxidase (AOX) would allow for the mitochondrial oxidation of NAD(P)H produced during citrate synthesis in cluster roots at a developmental stage when there is a low demand for ATP. We used the oxygen-isotope fractionation technique to study the in vivo respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) in different root sections of white lupins grown hydroponically with and without P. In parallel, AOX protein levels and internal carboxylate concentrations were determined in cluster and non-cluster roots. Higher in vivo AOP activity was measured in cluster roots when malate and citrate concentrations were also high, thus confirming our hypothesis. AOX protein levels were not always correlated with in vivo AOP activity, suggesting post-translational regulation of AOX.

Determination of phosphorus availability in poultry

Optimising the supply of dietary phosphorus (P) to animals requires sound knowledge regarding the availability of P from feed raw materials. Different definitions of available P have been proposed and various approaches are in use to determine P availability. These differences make it difficult to compare published data and to compile comprehensive feeding tables for use in the industry. This is disadvantageous in regard to feeding costs and sustainable handling of the limited global phosphate reserves. Working Group No 2 (Nutrition) of the European Federation of Branches of WPSA has developed a standard protocol for determination of available P in broilers. It is based on precaecal P digestibility and the details of this proposed protocol are explained in the following paper. Unresolved questions in regard to the determination of available P are also addressed. Researchers are encouraged to implement this standard protocol in future P availability studies and to contribute to its further improvement.

Building future nuclear power fleets: The available uranium resources constraint

According to almost all forward-looking studies, the world′s energy consumption will increase in the future decades, mostly because of the growing world population and the long-term development of emerging countries. The effort to contain global warming makes it hard to exclude nuclear energy from the global energy mix.The availability of natural uranium resources is a major constraint in terms of meeting this demand. In line with the scenarios floated by various international organisations and taking into consideration only current uranium-consuming light water reactors technologies with slow neutrons, 4 to 7Mt of uranium could be consumed by 2050, namely, all identified or known resources barring uncertainties.Recovering uranium from seawater would guarantee a virtually infinite resource of nuclear fuel, but its technical and economic feasibility has yet to be demonstrated, and huge advances need to be achieved in this direction. According to different recent publications on phosphate reserves, the potential amount of uranium recoverable from phosphates can be estimated at around 4MtU. Furthermore, the production of uranium as a by-product of phosphate is determined by the world production of phosphoric acid. Uranium recovery as a by-product of phosphate rocks could be competitive for the moment, but limited at the most to 10ktU per year, i.e. less than 20% of current world demand. The only way to lift the constraint of phosphate capacity production is to produce uranium as a primary product of phosphates. Unfortunately, this solution is very unlikely due to its high unit cost.So, conventional uranium resources and unconventional resources, from seawater or phosphate rocks, are inadequate for expanded nuclear generating capacity required to combat global warming. Therefore we need to find more conventional uranium resources, in new deposits, or optimize the consumption by reprocessing/recycling spent nuclear fuel on a larger scale and deploy fast breeder reactors.

Extracellular phosphomannan as a phosphate reserve in the yeast Kuraishia capsulata

We have found that extracellular phosphomannan is the main phosphate reserve in the yeast Kuraishia capsulata, in contrast to other yeast species effectively absorbing Pi. Under nitrogen starvation, K. capsulata absorbed essentially all Pi from the medium containing 240mM glucose, 2.5mM MgSO4, and 11mM KH2PO4. Inorganic polyphosphate level in the cells was about 14% of the Pi absorbed. Most of the Pi (~60%) was found in the fraction of extracellular phosphomannan that can be used as a carbon and phosphorus source by this yeast in deficient media.

Peak phosphorus - peak food? The need to close the phosphorus cycle.

The peak in the world production of phosphorus has been predicted to occur in 2033, based on world reserves of rock phosphate (URR) reckoned at around 24,000 million tonnes (Mt), with around 18,000 Mt remaining. This figure was reckoned-up to 71,000 Mt, by the USGS, in 2012, but a production maximum during the present century is still highly probable. There are complex issues over what the demand will be for phosphorus in the future, as measured against a rising population (from 7 billion to over 9 billion in 2050), and a greater per capita demand for fertiliser to grow more grain, in part to feed animals and meet a rising demand for meat by a human species that is not merely more populous but more affluent. As a counterweight to this, we may expect that greater efficiencies in the use of phosphorus - including recycling from farms and of human and animal waste - will reduce the per capita demand for phosphate rock. The unseen game changer is peak oil, since phosphate is mined and recovered using machinery powered by liquid fuels refined from crude oil. Hence, peak oil and peak phosphorus might appear as conjoined twins. There is no unequivocal case that we can afford to ignore the likelihood of a supply-demand gap for phosphorus occurring sometime this century, and it would be perilous to do so.

Effects of Phosphorus Source, Phosphorus Rate, and Liming Rate on Growth and Quality of Verbena canadensis Britton ‘Homestead Purple’ and Lantana camara L. ‘New Gold’

Phosphate rock ores, rich in phosphorus (P), are mined in great quantities around the world for the production of P fertilizers. However, availability of phosphate reserves is in question due to decreasing global supplies. Therefore, application of alternative, renewable P sources is of interest. Poultry litter ash (PLA), a byproduct of bioenergy production, contains P concentrations comparable to conventional fertilizers. In this experiment, two P sources, PLA and superphosphate (SP), were compared at two P application rates and two liming rates as fertilizer sources for the production of two commonly-grown greenhouse crops (Verbena canadensis Britton ‘Homestead Purple’ and Lantana camara L.‘New Gold’). Application of PLA produced plants of comparable biomass and quality to those fertilized with SP. Increasing P application rate, across both P sources, increased total flower numbers 42 and 26% for verbena and lantana, respectively. Foliar P concentrations of verbena and lantana increased 27 and 62% for PLA-fertilized plants compared to SP. In addition, substrate pH increased 25% using PLA versus SP. Overall, PLA supplies adequate P fertility and does not reduce pH compared to the more water-soluble, rock phosphate based SP fertilizer.