Ground Phosphate Rock Research Articles

Fungi colonizing toxic acid soils in the dumping ground of the "Bełchatów" brown coal mine

The results of two years' studies on post-mining toxic acid soils of thc "Bełchatów" dumping grounds neutralized with chalk, ash, limestone, burnt lime, and ground phosphate rock are presented. The neutralization with ground phosphate rock and ash had the most favourable effect on the development of soil fungi.

Effect of sulphur added to phosphate rock on solubility and phytoavailability of phosphorus

Abstract For ground phosphate rock (GPR) to be applied as phosphorus fertilizer, the availability of phosphorus to plants needs to be improved. One possible way to achieve this is by adding sulphur, which will accelerate decomposition of phosphate in soil owing to the activation of microbiological processes. This study involved granulation of fertilizers composed of phosphate and sulphur mixed at 38:1 and 10:1 ratios and two analogous fertilizer variants but with added molasses as a source of organic carbon for sulphur bacteria. A small-scale industrial installation for production of multi-component fertilizers was used to make granular fertilizer by the compaction method. The granular fertilizers were then tested in an agricultural experiment. The fertilizer in which the phosphate to sulphur ratio was 10:1 produced better effects. Addition of molasses to the fertilizers did not improve their fertilizing capacity

Investigation of the Solubilities of Sulfated and Ground Phosphate Rock after Sulfation in H2SO4 Solution

In this study, the effects of temperature and acid concentration on the dissolution of the sulfated and ground after sulfation phosphate samples in sulfuric acid solution obtained after flue gas desulfurization were investigated and the results were compared for both samples. It was observed that the dissolution rate increased as the temperature and acid concentration increased during the dissolution of sulfated and ground after sulfation phosphate samples. It was shown that the dissolution reaction can be divided into two regions, with different rate controlling steps for both samples. The controlling step was determined as pseudo-first order reaction at low conversions and diffusion through the product (ash) layer at high conversions.

On-line XRF Analysis of Phosphate Materials at Various Stages of Processing

Potential applicability of X-ray fluorescence conveyor analyzer CON-X03 was demonstrated for the quantitative on-line measurement of P, S, Cl, K and Ca in several types of ground phosphate rock, phosphate fertilizers and intermediates at various stages of phosphate processing. In addition to the physical components required to perform on-line XRF measurements, the analyzer is equipped with special evacuated mini-chamber. Assessment of calibration quality for P, S, Cl, K and Ca was demonstrated on the basis of control samples and synthetic mixtures. The dynamic simulation of on-line measurements of ground N-P-K fertilizers continuous flow indicated a statistically acceptable correlation with laboratory chemical analyses (relative standard deviation for P is better than 2.0%, for S and K – better than 10% relative). Application of on-line conveyor XRF analyzer to industrial processing generates real-time feedback of elemental composition and quality of phosphates moving on the conveyor thus enables to automate control of the production processes.

Improvement of the solubility of rock phosphate by co-composting it with organic components

Abstract One possible way to improve the solubility of phosphate rock is by co-composting it with organic substances. Four variants of composts were made in a biomass composting bioreactor. Ground phosphate rock (GPR) and shredded barley straw, pine sawdust as well as beet pulp pellets were used as compost components. The four composts were different from one another in the type and amount of organic components. The composts were granulated in a pelleting press. Changes in the solubility of phosphorus were assessed via chemical analyses and P-recovery efficiency calculated from the data achieved in a pot experiment. Solubility of ground phosphate rock was increased resulting from co-composting with organic substances, which meant that bioavailability of phosphorus increased. All the tested composts were characterized by a higher ratio of ammonium citrate soluble phosphorus to total phosphorus than non-composted GPR. Co-composting GPR with all the tested organic components yielded better effects than composting it with straw alone. The four composts were characterized by a slow release of P, which justifies our expectation that they will produce residual effects in the years following their application.

The effect of co‐composted cabbage and ground phosphate rock on the early growth and P uptake of oilseed rape and perennial ryegrass

AbstractPhosphorus (P) availability to crops in organic systems can be a major issue, with the use of readily available forms often restricted. One product that can be used in organically managed systems, that is also relatively easily accessible to growers, is phosphate rock, although its solubility and therefore crop availability is often poor. One possible approach to improve this situation is co‐composting phosphate rock with selected organic waste materials. Various ratios of phosphate rock and cabbage (Brassica oleracea L.) residues were co‐composted and the products tested at different rates of application. The effects were assessed over 12 weeks using oilseed rape (Brassica napus L.) and perennial ryegrass (Lolium perenne L.) as bioassay crops in a pot experiment. At harvest, estimates of P derived from cabbage and phosphate rock for the lowest of two rates of compost were ≈ 2 and 10 mg P pot–1 for oilseed rape, compared to 5 and 2 mg P pot–1 for perennial ryegrass, respectively. Roots tended to have higher P concentrations than shoots. The crops showed differences in their abilities to access various P sources, with oilseed rape effectively taking P from phosphate rock, whereas perennial ryegrass was more effective at accessing cabbage‐derived P (the main substrate in the compost). Oilseed rape was able to take up 20% of the total P applied as phosphate rock, whereas perennial ryegrass took up less than 5% of the total P applied from this material. Both pre‐ and post‐application solubilisation/transformation mechanisms were involved in supplying plant‐available P. Quantifying the relative contribution from individual P sources remains problematic even within this relatively simple system.

Determination of the composition of ground phosphate rock by chemical and physicochemical methods of analysis

The composition of the phosphate-containing fraction of the ground phosphate rock from Polpino deposit was examined by chemical and physicochemical methods of analysis.

Nutrient uptake by grape in a Brazilian soil affected by rock biofertilizer

PK rock biofertilizers made from rocks and elemental sulphur inoculated with Acidithiobacillus improve yield of many short cycle plants similarly to soluble fertilizers. This study aims to evaluate the potential of PK rock biofertilizers for grape cultivation in the Brazilian San Francisco Valley. Three sources of P and K were compared: (a) soluble fertilizers, (b) biofertilizers plus elemental sulphur inoculated with Acidithiobacillus, and (c) ground phosphate and potash rocks, all at three application rates. A control treatment without P and K fertilization was added. Earthworm compound was applied as N source in all treatments. Grape (Vitis vinifera cv. Italia Pirovano) was cultivated in a dystrophic Planossol (medium texture) at the San Francisco River in the Brazilian Semiarid. P, K, Ca, Mg, S-SO 4 2and Fe concentrations were analyzed in grape leaves and fruits. The results showed adequate leaf contents of S-SO 4 2, K, and Fe with PK biofertilizer application plus earthworm compound, which indicates this may be alternative to soluble fertilizer for grape in soils with low available P and K.

Phosphorus uptake by cowpea plants from sparingly available or soluble sources as affected by nitrogen form and arbuscular‐mycorrhiza‐fungal inoculation

AbstractIn most plant species, nutrient uptake is facilitated upon root association with symbiotic arbuscular mycorrhizal (AM) fungi. The aim of the present experiment was to test how the form in which nitrogen (N) is supplied to the growth medium affects substrate pH, AM development, and contribution of the symbiosis to phosphorus (P) uptake from sparingly available or soluble resources. Cowpea (Vigna unguiculata L. Walp) plants inoculated or noninoculated with AM fungi (Glomus sp.) were grown in pots with a sand substrate supplied with nutrient solution. The nutrient solution was prepared either with a high or a low concentration of soluble P, and NO$ _3^- $‐N : NH$ _4^+ $‐N ratios of 9:1 or 5:5. The substrate supplied with low‐P nutrient solution was either or not additionally amended with ground rock phosphate. Despite a high level of root colonization, AM fungi used in the present study did not appear to increase plant availability of rock phosphate. It cannot be excluded that the ability of AM root systems to acquire P from sparingly available resources differs depending on the plant and fungal genotypes or environmental conditions. The absence from the growth substrate of P‐solubilizing microorganisms able to associate with AM mycelia might also have been a reason for this observation in our study. Increased supply of NH$ _4^+ $ relative to NO$ _3^- $ improved plant P availability from rock phosphate, but also had a negative effect on the extent of AM‐fungal root colonization, irrespective of the plant P‐nutritional status. Whether increasing levels of NH$ _4^+ $ can also negatively affect the functioning of the AM symbiosis in terms of plant element uptake, pathogen protection or soil‐structure stabilization deserves further investigation.

Physiological studies and comparative analysis of rock phosphate solubilization abilities of Actinomycetales originating from Moroccan phosphate mines and of Streptomyces lividans

Actinomycete strains originating from Moroccan phosphate mines (MPM) were selected for their ability to use the insoluble ground hydroxyapatite called rock phosphate (RP), present in their biotope, as sole phosphate (P) source. Physiological studies carried out with these strains and with the reference strains, Streptomyces lividans and Streptomyces griseus, demonstrated that all strains were able to grown in a synthetic minimal medium (SMM) containing either soluble (SP) or insoluble (RP) phosphate as sole P source. The MPM strains and S. griseus took up glucose much more actively and exhaustively than S. lividans, constituting more abundant glycogen reserves than the latter. All strains took up soluble P at comparable rates, storing it as polyphosphates. In SMM + RP, a sharp increase in the concentration of soluble P was detected in the culture broths of all MPM strains and S. griseus, at stationary phase, but not in that of S. lividans. The P peak detected in the supernatant of these strains correlated with the successive appearance of two compounds absorbing at 320 nm and 430 nm, respectively. These compounds are thought to be strong ion chelators involved in the destruction of the hydroxyapatite structure leading to soluble P release. The good growth of S. lividans in SMM + RP indicated that this strain was also able to release P from RP but consummed it as soon as it was released, unlike the other strains. Our study is expected to lead to the development of a novel type of slow release bio-phosphate fertilizer constituted by the association of the MPM strains and ground RP. This novel product would precisely supply plant needs and thus limit the pollution of the environment.

Nitrogen and carbon losses from dung storage in urban gardens of Niamey, Niger

Intensive vegetable production in urban and peri-urban agriculture (UPA) of West African cities is characterized by high nutrient inputs. However, little is known about nitrogen (N) and carbon (C) losses in these systems, in particular during the storage of manure, the main organic fertilizer in these systems. We therefore aimed at quantifying gaseous emissions of ammonia (NH3), nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) as well as leaching losses of C, N, phosphorus (P) and potassium (K) from animal manure stored in vegetable gardens of Niamey, Niger. During a first 3.5-month experiment in the hot dry season, cumulative gaseous N losses, measured with a closed-chamber system, were with 0.11 g kg−1 manure DM highest (P < 0.05) in the uncovered control treatment accounting for 1.8% of total manure N. Nitrogen losses decreased by 72% under plastic sheet roofing and by 50% under roofing + ground rock phosphate (RP) application at 333 g kg−1 manure DM. Carbon losses from manure amounted to 73 g kg−1 DM in the control and to 92 g kg−1 DM and 68 g kg−1 DM under roofing and under roofing + RP, respectively. In a second 3.5-month experiment conducted in the rainy season, C losses from the control were 164 g kg−1 manure DM and reduced to 77 and 65% of the control by roofing and roofing + RP, respectively. Leaching losses during the rainy season were only observed for the unroofed control and averaged 2.1 g C, 0.05 g N, 0.07 g P and 1.8 g K kg−1 manure DM.

Enhancing the agronomic effectiveness of natural phosphate rock with poultry manure: a way forward to sustainable crop production

Phosphorus inputs are required in highly weathered tropical soils for sustainable crop production. However, high cost and limited access to mineral P fertilizers limit their use by resource-poor farmers in West Africa. Direct application of finely ground phosphate rock (PR) is a promising alternative but low solubility of PR hampers its use. Co-application of PR with manure could be a low cost means of improving the solubility of natural PR and improve their agronomic effectiveness. Our objective was to quantitatively estimate the enhancement effect of poultry manure on P availability from low reactive PR (Togo phosphate rock) applied to highly weathered soils. We utilized two highly weathered soils from Ghana and Brazil for this greenhouse study. Using 32P isotopic tracers, the agronomic effectiveness of poultry-manure-amended Togo rock phosphate (TPR) was compared with partially acidulated Togo rock phosphate (PAPR) and triple superphosphate (TSP). Four rates of poultry manure: 0, low (30 mg P kg−1 soil), high (60 mg P kg−1 soil) and very high (120 mg P kg−1 soil) were, respectively, added to a constant amendment (60 mg P kg−1 soil) of the P sources and applied to each pot of 4 kg soil. A Randomized Complete Block Design was used for the greenhouse experiment and Maize (Zea mays L.) was used as a test crop. The plants were grown for 42 days after which the above ground biomass was harvested for analysis. Without poultry manure addition, the agronomic effectiveness, represented by the relative agronomic effectiveness (RAE) and proportion of P derived from fertilizer (% Pdff) was in the order TSP > PAPR > TPR = control (P0). In the presence of low rate poultry manure addition, the agronomic effectiveness followed the order TSP > PAPR = PR > P0. However, at the high and very high rates of poultry manure addition, no significant differences in agronomic effectiveness were observed among the P sources, suggesting that at this rate of poultry manure addition, PR was equally as effective as TSP. The study showed that direct application of PR co-applied with poultry manure at a 1:1 P ratio will be a viable option for P replenishment. Thus a combination of PR and poultry manure could be a cost-effective means of ensuring sustainable agricultural production in P-deficient, highly weathered tropical soils.

Plant- and microbial-based mechanisms to improve the agronomic effectiveness of phosphate rock: a review

Deficiency in plant-available phosphorus is considered to be a major limiting factor to food production in many agricultural soils. Mineral resources are necessary to restore soil phosphorus content. In regions where conventional fertilizers are not used due to cost limitations or to mitigate adverse environmental effects, local sources of phosphate rock are being increasingly recognized for potential use as alternative phosphorus fertilizers. The main obstacle associated with using directly applied ground phosphate rock is that the phosphate released is often unable to supply sufficient plant-available phosphorus for crop uptake. Plantand microbial-based mechanisms are low-cost, appropriate technologies to enhance the solubilization and increase the agronomic effectiveness of phosphate rock. Common mechanisms of phosphate rock dissolution including proton and organic acid production will be reviewed for both plants and microorganisms. This review will also address possibilities for future research directions and applications to agriculture, as well as highlight ongoing research at the University of Guelph, Guelph, Canada.

Factors Influencing the Dissolution of Phosphate Rock in a Range of High P‐Fixing Soils from Cameroon

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo‐Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)‐sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg−1 soil and incubated at 30°C for 85 days. Dissolution of the PRs was determined at various intervals using the ΔNaOH‐P method (the difference of the amount of P extracted by 0.5 M NaOH between the PR‐treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH‐(H2O)<5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH‐(H2O)>5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P=AtB. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.

Effect of Hydrochloric Acid on Leaching Behavior of Calcareous Phosphorites

The bulk of the world's phosphate reserves is located in sedimentary horizons that contain appreciable amounts of carbonate. During beneficiation of phosphate rocks, huge amounts of oversize phosphate rocks are rejected from crushers. This reject also mostly contains low tricalcium phosphate and high carbonate content. In this study, experiments have been carried out to reduce/eliminate carbonate content by leaching the ground phosphate rock with dilute hydrochloric acid solution. Effects of hydrochloric acid concentration, reaction time, temperature and liquid/solid ratio (vol./wt. basis) on the process have been studied. Under the reaction conditions, some of the apatite may be dissolved to form soluble monocalcium phosphate during the selective leaching. However, by specifying the pH of the process the lime milk can be used to recover the dissolved apatite. It has been observed that upon treatment of the ground rock with dilute hydrochloric acid, the P 2 O 5 percent can be raised up to the industrially acceptable level due to the selective reduction/elimination of calcium carbonate content of the sample, depending on the reaction conditions as well as nature and size of the raw phosphate particles used for analysis.

Selective leaching of calcareous phosphate rock in formic acid: Optimisation of operating conditions

Abstract In this study, formic acid was used to reduce the carbonate content of the ground phosphate rock. Effect of acid concentration, liquid/solid ratio (v/w), reaction time and temperature has been studied to get marketable and industrially acceptable phosphate grades. Depending on leaching conditions, it was found that the P2O5% could be raised by 30–35% along with corresponding reduction in CO2% up to 67–72% at a phosphate recovery of more than 70 wt.%.

Evaluation of Ground Phosphate Rocks for Growth and Yield of Maize (Zea mays) and Soybean (Glycine max) on a Tropical Alfisol in Nigeria

Experiments were conducted to study the best application time and the effects of P fertilizer sources on maize and soyabean production. The application times (AT) were one week before planting (1 WBP), at planting (AP), one week after planting (1 WAP) and 2 WAP. The P sources, PS (Ogun Rock Phosphate (ORP), 31.4% P2O5; Crystallizer (Cryst), 20.2% P2O5; Sokoto rock phosphate (SRP), 34.2% P2O5 and Single Super Phosphate (SSP), 18% P2O5) were applied at 50 kg/ha apart from the control. Maize was grown in the first experiment while soyabean was the test crop in the second and third experiments. No fertilizer was applied in the last experiment. In the first experiment, crop yields were highest when ORP, Cryst and SSP were applied 1 WAP while it was best at 2 WAP with the application of SRP. For the second experiment, crop yields were highest for Cryst and ORP applied 1 WBP and 1 WAP for SRP and SSP. Considering the effectiveness of the rock phosphate, ORP performed best in both the first and second experiments apart from SSP in the first experiment. The decreasing order of crop yield in the third experiment was Cryst > ORP > SRP and SSP even though there was no significant difference. Since significant differences could not be established for the P sources, times of application or for the residual effect, any of the RP could be used as P source and also for residual effect. Similarly, any of the times of P application was suitable for both crops

Study on structural characteristics of pillared clay modified phosphate fertilizers and its increase efficiency mechanism

Three types of new high-efficiency phosphate fertilizers were made when pillared clays at certain proportions were added into ground phosphate rock. Chemical analyses showed that their soluble phosphorus content decreased more than that of superphosphate. Pot experiment showed that, under equal weights, the new fertilizers increased their efficiency by a large margin over that of superphosphate. Researches on their structures by means of XRD, IR and EPR spectrum revealed that their crystal structures changed considerably, improving their activity and preventing the fixation of available phosphorus in the soil, and consequently, greatly improved the bioavailability and became the main cause of the increase of biomass.

Efficiency of indigenous ground phosphate rocks, organic fertilizer and their mixtures for maize performance in two Nigerian alfisols

Greenhouse experiments were conducted to evaluate main and residual effects of sole and combined applications of ground rock phosphates (GRP) and organic fertilizer, (OF) on maize performance in two Nigerian alfisols. A commercial OF (1.33% P 2 O 5 ), Ogun RP (31.00% P 2 O 5 ), Sokoto RP (36.10% P 5 O 2 ) and mixtures of OF with either ORP or SRP were used as “test” fertilizers while single super phosphate (SSP) was the “standard” P fertilizer. There were 7 fertilizer sources (OF, ORP, SRP, SSP, OF+ORP, OF+SRP and OF+SSP), each applied at 2 levels (25 and 50mg P 2 O 5 kg -1 ). The 14 treatments and the control were replicated 3 times in each of 2 soil types (a medium acid Oxic paleustalf, A, from Zaria and another low acid Typic paleustalf, B, from Ibadan), to give a total of 90 experimental pots arranged in completely randomised design (CRD). In the first cropping, the weakly acid soil, B produced taller maize plants (62.3cm) than the medium acid soil, A (60.3cm) after six weeks of growth. However, plants treated to 50mg P 2 O 5 kg -1 of OM+SRP were the tallest (66.3 cm) while the untreated ones were the shortest (55.1cm). In the second cropping, differences in height between plants given the various fertilizer treatments were recorded as early as the 3rd week of growth but there was no difference due to soil type even after five weeks. There was no difference in forage yield that could be attributed to the various fertilizer treatments in the first cropping. During the 2nd cropping, however, SRP, ORP and OF+ORP (at 25mg P 2 O 5 kg -1 ) as well as OF (at 50mg P 2 O 5 kg -1 ) treatments produced higher yields than the control. However, highest P uptake (about 23.5mg pot -1 ) was recorded by plants grown under the influence of OF and SSP fertilizer mixture, irrespective of the soil type. The lowest Relative Agronomic Efficiency (RAE) values estimated for the test fertilizer materials in the 1st cropping were 81.5 and 117.5% in soils A and B, respectively. The respective values for 2nd cropping were 78.3 and 62.0%. It was clear that the indigenous GRP, OF and their mixtures have great potentials as substitutes for the imported soluble P fertiliser sources in the medium and weakly acid alfisols. Key Words: Phosphate rocks; organic fertilizer; maize; Nigerian alfisols Moor J. Agric. Res. Vol.4(1) 2003: 1-7

Evaluation of Rape Response to Different Sources of Phosphate Rock in an Alkaline Soil

A greenhouse experiment was conducted to evaluate the agronomic effectiveness of one unground, as received from Tunisia, and eight finely ground phosphate rock (PR) sources from Syria, Kazakhstan, Jordan, Russia, Mali, Burkina Faso, Tanzania, and China as compared with TSP for rape grown on an alkaline soil (pH 7.7). The P rates applied were 0, 5, 10, 25, and 50 mg P kg−1. The rape was grown to maturity. The yield of rapeseed obtained with each P source was fitted to a linear function with P rate. The relative agronomic effectiveness (RAE) of each PR with respect to TSP was calculated as the ratio of the slopes of the response function. The results show that RAE ranged from 0 to 88%, depending on the reactivity of PR. RAE correlated highly with the solubility of all PR sources as measured by 2% citric acid (CA) (R2=0.947) in a semi-log function. When the unground, highly reactive PR was excluded in the correlation, R2 was increased to 0.957 with 2% CA. The correlation was also very high (R2=0.963) when the RAE of the unground PR was plotted against its solubility measured in the finely ground form along with other finely ground PR sources. Low-reactivity PR with 2% CA-soluble P as low as 2.5% P can be 50% as effective as TSP in increasing yield of rapeseed even in alkaline soils. Use of indigenous PR sources, especially high reactive, for rapeseed production is feasible in those countries where agricultural soils are alkaline.