Mitigating Iron Toxicity by Using Rock Phosphate to Improve Rice Productivity

Iron toxicity is a major constraint to rice production, particularly in highly weathered soils of inland valleys in Sub-Saharan Africa where the rice growing area is rapidly expanding. This study aimed to improve the productiveness of iron toxicity sensitive’s rice fields as well as in the unsensitive fields by using local phosphate fertilizers. Eighteen (18) rice genotypes were been assessed in a split plot design in two areas: without iron toxicity and with iron toxicity. NPK, NK, Rock Phosphate, Triple super phosphate, Calcined phosphate and Acidulated phosphate were used as fertilizers. Data collection was focused on agronomic traits and yield (g/m2). The best fertilizers in the area without iron toxicity were NPK (820.2 g/m2) and triple super phosphate (751.7 g/m2). In the iron toxicity area, the best yields were performed by NPK (785.5 g/m2) and raw calcined phosphate (698.3 g/m2). Yet, the Accessions 15, Accessions 225, Accessions 226 and Accessions 270 were rainfed rice genotypes while CC109 A, HB 46 and HB 62 were low-land/irrigated rice genotypes. NPK, NK and acidulated phosphate fertilizers alleviate the best, iron toxicity in both sensitive and unsensitive rice fields.

Mechanism of lead immobilization by oxalic acid-activated phosphate rocks

Lead （Pb） chemical fixation is an important environmental aspect for human health. Phosphate rocks （PRs） were utilized as an adsorbent to remove Pb from aqueous solution. Raw PRs and oxalic acid-activated PRs （APRs） were used to investigate the effect of chemical modification on the Pb-binding capacity in the pH range 2.0-5.0. The Pb adsorption rate of all treatments above pH 3.0 reached 90%. The Pb binding on PRs and APRs was pH-independent, except at pH 2.0 in activated treatments. The X-ray diffraction analysis confirmed that the raw PRs formed cerussite after reacting with the Pb solution, whereas the APRs formed pyromorphite. The Fourier Transform Infrared spectroscopy analysis indicated that carbonate （CO32-） in raw PRs and phosphate （PO43-） groups in APRs played an important role in the Pb-binding process. After adsorption, anomalous block-shaped particles were observed by scanning electron microscopy with energy dispersive spectroscopy. The X-ray photoelectron spectroscopy data further indicated that both chemical and physical reactions occurred during the adsorption process according to the binding energy. Because of lower solubility of pyromorphite compared to cerussite, the APRs are more effective in immobilizing Pb than that of PRs.

Phosphorus release from phosphate rock and iron phosphate by low-molecular-weight organic acids

Low-molecular-weight(LMW) organic acids widely exist in soils, particularly in the rhizosphere. A series of batch experiments were carried out to investigate the phosphorus release from rock phosphate and iron phosphate by low-molecular-weight organic acids. Results showed that citric acid had the highest capacity to solubilize P from both rock and iron phosphate. P solubilization from rock phosphate and iron phosphate resulted in net proton consumption. P release from rock phosphate was positively correlated with the p K _a values. P release from iron phosphate was positively correlated with Fe-organic acid stability constants except for aromatic acids, but was not correlated with p K _a. Increase in the concentrations of organic acids enhanced P solubilization from both rock and iron phosphate almost linearly. Addition of phenolic compounds further increased the P release from iron phosphate. Initial solution pH had much more substantial effect on P release from rock phosphate than from iron phosphate.

Phosphate rock reduces the bioavailability of heavy metals by influencing the bacterial communities during aerobic composting

Available information on the microbial mechanisms associated with heavy metal(HM)passivation during co-composting amended with phosphate rock(PR)remains limited.Thus,this study investigated the dynamic changes in bacterial communities and HM-fractions(Zn,Cu,Cd,Cr and Pb)during swine manure composting with maize straw,and ascertained the bacterial influence on HM-passivation.The results demonstrated that the addition of PR improved HM-passivation,especially for Zn and Cd,with their bioavailability factors(BFs)reduced by 247.41 and 176.25%,respectively.As for bacterial communities,the proportion of Firmicutes decreased,while the proportions of Proteobacteria,Bacteroidetes,DeinococcusThermus and Gemmatimonadetes increased in all treatments.PR significantly changed the primary bacterial phyla in the thermophilic phase.Bacteroidetes were the main bacterial component controlling the passivation of Zn,Cu and Cr,while Deinococcus-Thermus mainly regulated the mobility of Zn and Pb,and Proteobacteria only dominated the transformation among Cd-fractions.These results may provide a reference for the use of HM-passivation techniques during composting.

Rock Phosphate Solubilization Mechanisms of One Fungus and One Bacterium

Many microorganisms can dissolve the insoluble phosphates like apatite. However, the mechanisms are still not clear. This study was an attempt to investigate the mechanisms of rock phosphate solubiliza-tion by an Aspergillus 2TCiF2 and an Arthrobacter1TCRi7. The results indicated that the fungus produced a large amount of organic acids, mainly oxalic acid. The total quantity of the organic acids produced by the fungus was 550 times higher than that by the bacterium. Different organic acids had completely different capacities to solubilize the rock. Oxalic acid and citric acid had stronger capacity to dissolve the rock than malic acid, tartaric acid, lactic acid, acetic acid, malonic acid and succinic acid. The fungus solubilized the rock through excreting both proton and organic acids. The rock solubilization of the bacterium depended on only proton.

Removal of Lead,Copper,Zinc and Cadmium from Water Using Phosphate Rock

Removal of Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from aqueous solutions by sorption on a natural phosphate rock （FAP） was investigated. The effects of the contact time and initial metal concentration were examined in the batch method. The percentage sorption of heavy metals from solution ranges generally between 50% and 99%. The amount of sorbed metal ions follows the order Cu〉Pb〉Cd〉Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate. The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from polluted waters.

Physicochemical and Mineralogical Characterizations of Wastes Coming from Phosphate Ore Processing of Hahotoéand KpogaméMines

In the framework of various phosphates discharges valorization, we have realized physicochemical and mineralogical characterizations of these discharges. We have undertaken the physicochemical and mineralogical characterizations of this waste by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), thermal analysis and Atomic Emission Spectrometry Coupled to an Inductive Plasma Source. The results of these analyze show that phosphate sludge and screen rejects could be used in ceramics, in the manufacture of aggregates, in agriculture and other fields. On the other hand, rich magnetic waste could be used in heterogeneous photocatalysis in waste liquids treatment.

Effect of Lanthanum on Solubilization of Rock Phosphate in Liquid Culture by Aspergillus Niger and Penicillium Oxalicum

Rock phosphate (RP) is a low efficient P fertilizer when directly used in the soil. Phosphate-solubilizing microorganisms (PSMs) can solubilize RP in fermentation or soil condition. The effect of different concentration of lanthanum (La) on the solubilization of RP was investigated by two isolates of phosphate-solubilizing fungi (PSF) Aspergillus niger P39 and Penicillium oxalicum P66 in liquid culture. Experimental results show that relatively higher concentration of La in the culture solution inhibites fungal growth and delays RP solubilizing activity of two isolates. This inhibitory effect of La on RP solubilization varies with PSF (isolate P66 is more sensitive to La than P39 in this experiment). Comparing the pH value of culture media with soluble P content as affected by La application, only within individual isolate not different isolates the negatively significant relationship was observed.

Diversity of endophytic phosphate solubilising fungi associated with Pomatocalpa decipiens(Lindl.)J.J.Smith-an endangered orchid in Barbara forest of Odisha,India

Investigations were done to obtain potential phosphate solubilising strains from endophytic mycoflora isolated from the orchid,Pomatocalpa decipiens.928 endophytic phosphate solubilising fungal isolates were obtained from 2400 leaf segments(0.38%recovery)from rare epiphytic orchid Pomatocalpa decipiens present in the Barbara hills of Odisha(India).A number of isolates belonged to different genera such as Paecilomyces,Curvularia,Aspergillus,Cladosporium,Penicillium,Colletotrichum,while others,which were unidentified were classified as mycelia sterilia.Root sampling done from 25 different sites resulted in isolation of 20 endophytic phosphate solubilising fungal isolates from 300 segments(0.1%recovery).Aspergillus,Paecilomyces,Fusarium,Penicillium,and mycelia sterilia were mostly obtained.The qualitative and quantitative assessments of Phosphate(P)solubilisation were performed using TCP and Rock phosphate as P source for those strains.Aspergillus niger(leaf isolate)showed a maximum of 33.2 and 22.7%solubilisation in presence of TCP and Rock phosphate respectively whereas Aspergillus niger(Root isolate)showed a maximum of about 23.9%and 36.2%solubilisation in presence of TCP and Rock phosphate respectively.

Agronomic Suitability of Biologically Produced PARP as a Source of Phosphorus for Maize Production

Phosphorus (P) and Nitrogen (N) deficiencies are recognized as the major constraint of agricultural productivity in developing countries including Zambia. While N deficits can be restored at least in part through the application of crop residues and manure, the restoration of soil P can only be achieved by use of phosphate fertilizers which are unaffordable by the small scale farmers. The aim of the study was to assess the availability of P for crop use from rock phosphate (RP), partially acidulated by acid produced by sulfur oxidizing bacteria. The RP was obtained from Keren Mining Limited at Sinda district, Zambia;the Pyrite rock (iron sulfur) and bacteria culture were obtained Nampundwe mine dump. The pyrite and PR were ground and mixed with the bacterial culture to produce the Partially Acidulated Rock Phosphate (PARP). A pot experiment was set up in a CRB design in a greenhouse on four soil types with four treatments of: soil alone (control), soil with GRP, soil with PARP and soil with super single phosphate (SSP) replicated four times. The results showed that the plant height, biomass yield and P uptake across the different P sources showed significant differences (p < 0.01);particularly, the PARP and SSP were significantly higher than the both control and the GRP. A comparison of PARP and SSP within each soil based on both biomass yield and P uptake showed no significant difference between them. Despite the fact that the RAE values based on biomass yield were in most cases higher than those base on the P uptake, the trend was the same. On average the PARP was >90% effective within and across the four soils indicating that the PARP is reactive and suitable for direct application for crop production.

Rare Earth Element Geochemistry of Phosphatic Rocks in Neoproterozoic Ediacaran Doushantuo Formation in Hushan Section from the Yangtze Gorges Area, South China

Phosphatic rocks are widely distributed in Neoproterozoic Ediacaran Doushantuo Formation in Yangtze Gorges Area, South China. In this study, rare earth element geochemistry of eight phosphatic rock samples from the Hushan Section has been studied. All the samples display typical hat-shaped REE patterns, moderate negative Ce anomalies（Ce/Ce＊=0.55 to 0.67）, slightly positive Eu anomalies（Eu/Eu＊=1.05 to 1.22） and low Y/Ho ratios（38.2±5.6）. The hat-shaped REE patterns indicate diagenetic alteration of the primary REE signatures, which coincides with detrital siliciclastic sources of REE based on the Y/Ho ratios. The degree of Negative Ce anomalies and positive Eu anomalies may have recorded the redox features of diagenetic fluids, suggesting an anoxic environment during the phosphogenesis processes in Neoproterozoic Ediacaran Doushantuo Formation, South China. The geochemical comparison between the Lower Phosphorite Layer and Upper Phosphorite Layer at Hushan indicates a greater degree of diagenesis occurred in the Upper Layer than the Lower one. Besides the terrigenous sources of REE, organic materials could have also played a role on the REE characteristics.

Extraction of rare earth ions from phosphate leach solution using emulsion liquid membrane in concentrated nitric acid medium

It is very significant to recover rare earths （REs） from wet-process phosphoric acid, in terms of extraction rate and selectivity, the current carrier di（2-ethlhexly） phosphate （D2EHPA） out there is still inferior. Based on this question, our team modified D2EHPA to synthesize new extractants. This paper presents a comprehensive study on the extraction of rare earth ions （RE3＋） from phosphate leach solution using emulsion liquid membrane （ELM） in concentrated nitric acid medium. The ELM system is made up of （RO）2P（O）OPh-COOH as carrier, polyisocrotyl succinimide （T154） as surfactant, sulfonated kerosene as diluent, phosphoric acid （H3PO4） as stripping solution. Different chemical parameters such as type and concentration of carrier, surfactant, stripping solution, volume ratio of oil phase to internal phase, and volume ratio of emulsion ratio to external phase were analyzed. The extraction of RE^3＋ was evaluated by the yield of extraction. In addition, the demulsification process was also investigated. The proposed method of ELM using （RO）2P（O）OPh-COOH as carrier can he expected to provide an efficient, simplify operation, and facilitated method for extractine RE^3＋.

Mobilization and Acquisition of Sparingly Soluble P-Sources by Brassica Cultivars under P-Starved Environment I. Differential Growth Response,P-Efficiency Characteristics and P-Remobilization

Phosphorus （P） starvation is highly notorious for limiting plant growth around the globe. To combat P-starvation, plants constantly sense the changes in their environment, and elicit an elegant myriad of plastic responses and rescue strategies to enhance P-solublization and acquisition from bound soil P-forms. Relative growth responses, P-solublization and P- acquisition ability of 14 diverse Brassica cultivars grown with sparingly soluble P-sources （Rock-P （RP） and Ca3（PO4）2 （TCP）） were evaluated in a solution culture experiment. Cultivars showed considerable genetic diversity in terms of biomass accumulation, concentration and contents of P and Ca in shoots and roots, P-stress factor （PSF） and P use efficiency. Cultivars showed variable P-stress tolerance, and cultivars depicting low PSF and high P-efficiency values were better adaptable to P-starvation. In experiment 2, after initial feeding on optimum nutrition for 12 d after transplanting （DAT）, class-I （low P-tolerant （Oscar and Con-II）） and class-II （low P-sensitive （Gold Rush and RL-18）） cultivars were exposed to P-free environment for 25 d. All of the cultivars remobilized P from above ground parts to their roots during growth in P-free environment, the magnitude of which was variable in tested cultivars. P-concentrations （[P]s） at 37 DAT were higher in developing compared with developed leaves. Translocation of absorbed P from metabolically inactive to active sites in P- stressed plants may have helped class-I cultivars to establish a better rooting system, which provided a basis for enhanced P-utilization efficiency （PUE） and tolerance against P-stress. By supplying TCP and RP spatially separated from other nutrients in split root study, class-I cultivars were still able to mobilize RP and TCP more efficiently compared with class-II cultivars. To compare the growth behavior under P-stress, cultivars were grown in pots for 41 d after sowing, using a soil low in P （NaHCO3-extractable P = 3.97 mg/kg, Mehlich-III-extractable P = 6.13 mg/kg） with （＋P=60 mg P/kg soil） or without P addition （0P） in study 4. Tested cultivars showed genetic diversity in PUE, P-efficiency （PE）, P-efficiency ratio （PER） and PSF. P-stress markedly reduced biomass and plant P contents. Cultivars that produced higher root biomass accumulated higher total P-contents （r = 0.98＊＊）, which in turn was related negatively to PSF （r = -0.95＊＊） and positively to shoot and total biomass. PER and PE showed significant correlations with shoot P-contents and biomass. Cultivars depicting high PUE and PE, and low PSF values showed better growth behavior under low soil P-environment. Systematic analysis and deployment of the plant rescue traits underlying the nutrient acquisition, assimilation, utilization and remobilization under P-starvation will bring more sparingly soluble P into cropping systems and will help to scavenge more P from plant unavailable bound P reserves.

Phosphorus use efficiency and fertilizers:future opportunities for improvements

The continued supply of phosphate fertilizers that underpin global food production is an imminent crisis.The rock phosphate deposits on which the world depends are not only finite,but some are contaminated,and many are located in geopolitically unstable areas,meaning that fundamental changes will have to take place in order to maintain food production for a growing global population.No single solution exists,but a combination of approaches to phosphorus management is required not only to extend the lifespan of the remaining non-renewable rock phosphate reserves,but to result in a more efficient,sustainable phosphorus cycle.Solutions include improving the efficiency of fertilizer applications to agricultural land,alongside a better understanding of phosphorus cycling in soil-plant systems,and the interactions between soil physics,chemistry and biology,coupled with plant traits.Opportunities exist for the development of plants that can access different forms of soil phosphorus(e.g.,organic phosphorus)and that use internal phosphorus more efficiently.The development of different sources of phosphorus fertilizers are inevitably required given the finite nature of the rock phosphate supplies.Clear opportunities exist,and it is now important that a concerted effort to make advances in phosphorus use efficiency is prioritized.

Characteristics of mineralogical technology about medium-low grade bio-chip containing the rare earth dolomitic phosphorite in Xinhua,Zhijin,Guizhou

Using microscopic observation,chemical analysis,scanning electron microscopy,spectrum analysis and ICP-MS analysis,composition of rare earth bioclastic phosphate rock in Zhijin,China,was discussed.Using relevant statistical methods of particle size characteristics of phosphate rock and the mosaic relationship provided the relevant basic data of mineral processing.