Phosphorus Releasing Characteristics of Ogun Phosphate Rock Acidulated with Cashew Nutshell Liquid

The phosphorus (P) release characteristic of Ogun rock phosphate (OPR) acidulated with cashew nutshell liquid (CNSL), an industrial waste, was studied under laboratory conditions for ten weeks. The results showed that the acidulation of phosphate rock with cashew nutshell liquid at a ratio of 4 to 1 released the highest quantity of available P. There was a general increase in the amount of P extracted from the phosphate rock under the influence of cashew nutshell liquid and this was more spontaneous in alkaline media. The peak of phosphorus release occurred at the 56 days of incubation following a form of stoichiometric order. We found the use of the cashew nutshell liquid in this regard as a win-win approach to not only recycle a major waste of cashew processing industries, which will help to maintain a healthy environment, but to deploy the complementary use of this waste in crop production.     

Enhancement Effect of Water-Soluble Phosphorus on Agronomic Effectiveness of Phosphate Rocks

ABSTRACT

Direct application of phosphate rocks (PRs) with low/medium in reactivity has shown to be low in agronomic effectiveness for cereal crops. Presence of water-soluble P (WSP) in the vicinity of PR can significantly enhance the rooting system at the early stage of plant growth. This, in turn, can enable the plant to utilize the associated PR more effectively than the use of PR alone at planting. This report presents the results of several greenhouse experiments that show the granulated (WSP+PR) products by dry compaction process using different low-reactive PR sources were as effective as WSP fertilizers viz triple superphosphate (TSP) and monoammonium phosphate (MAP). The test plants were maize (30 days) and soybean and upland rice were grown to maturity on acid or neutral soils. Based on the results obtained a P ratio of 50:50 between WSP and PR is recommended for the granulated (WSP+PR) products that can achieve crop yields at the same levels as that with the WSP fertilizers.

Abbreviations: phosphate rock, PR; water-soluble P, WSP; dry-matter yield, DMY     

Agronomic Effectiveness of Cationic Phosphate Impurities Present in Superphosphate Fertilizers as Affected by Soil pH

Abstract

The general concept that low‐water‐soluble phosphorus (P) fertilizers should be more agronomically effective when applied to acidic soils was developed based on sources containing mainly calcium (Ca)‐P compounds, but it may not hold true for sources with different chemical composition. To obtain information related to this issue, two important iron (Fe)–potassium (K)–P compounds present in superphosphates [Fe₃KH₈(PO₄)₆ · 6H₂O, H8, and Fe₃KH₁₄(PO₄)₈ · 4H₂O, H14] were prepared and characterized. These P sources were used to provide 30 and 60 mg P kg^?1 as neutral ammonium citrate (NAC)+H₂O‐soluble P. Reagent‐grade monocalcium phosphate (MCP) was used as a standard P source with high water solubility with an additional rate of 120 mg P kg^?1 included. Also, mixtures of both Fe‐K‐P compounds and MCP were prepared to provide 0, 25, 50, 75, and 100% of the total P as MCP. All sources were applied to a clayey loamy acid soil (pH 5.3) classified as Rhodic Kanhapludult. The soil was incubated at two rates (0 and 10 g kg^?1) of lime, which resulted in pH 5.4 and 6.8. Upland rice was cultivated to maturity. The H14 compound confirmed to be a highly effective source of P for the rice plants at both soil pH, as opposed to the H8, which was poorly effective when applied alone. When mixed with water‐soluble P (WSP), the H8 was able to provide P to the plants with the maximum yield of upland rice reached with 54.8 and 80.5% of WSP for pH 5.4 and 6.8, respectively. The high agronomic performance of the H14 compound clearly indicates that this low‐water‐soluble P source cannot be deemed as ineffective at high soil pH.     

In Situ Acidulation of Rock Phosphate

This study was undertaken to study the impact of adding <75 μm elemental sulfur (ES) on P availability from a range of <250 μm ground rock phosphates (RP) namely; Minjingu (Mi) from Tanzania, Khouribga from Morocco (Mo) and Duchess (D) from Australia. Italian ryegrass (Lolium multiflorum, Thumpa tetraploid) grown in a glasshouse was used as the test crop and tops were harvested 5 times over 27 weeks. Co-granulating RP and 10.7% ES yielded 30–70% more ryegrass tops than RP alone, with the greatest effect with Mi. Fertilizer P recovery in the tops from the RP was 5.2% with D and 6.5% and 7.8% from Mi and Mo, respectively. ES addition increased this by 51% from Mo, 98% from D and 194% from Mi. Co-granulation of RP with ES has been shown to be an effective means of releasing plant available P to crops from RP with minimal fertilizer processing.     

Soil Lead Immobilization Using Phosphate Rock

Phosphate compounds of lead (Pb) are highly insoluble and their formation in contaminated soils would aid immobilization of Pb. The goal of the current research was to evaluate the immobilization of Pb by various treatments of phosphate rock on contaminated agricultural soils typical of Taiwan, and to determine the optimal amount of phosphate rock for use in field application. Samples of contaminated soil, each containing Pb concentrations ranging from 346 to 1873 mg kg^?1 were collected from arable land near a ceramic products manufacturing factory. Both batch immobilization experiments and in situ remediation were completed using phosphate rock additives. Results of the batch experiments demonstrate that the phosphate rock was effective in reducing Pb extractable by 0.1 M HCl, with a minimum reduction of 33–97% after 8 days of reaction, for initial Pb concentrations up to 1873 mg kg^?1. HCl-extractable Pb did not decrease after an additional 2-day reaction with a greater phosphate rock loading. It was also found that the reaction time had less effect on Pb immobilization than the amount of phosphate rock added. Results from in situ remediation experiments indicate that soil-extractable Pb was reduced by 93% (mean; range 85.2–97.2%), which is comparable with the results of the batch study. Additionally, the soil pH was increased from 6.25 (mean; range 5.96–6.76) to 7.2 (mean; range 6.92–7.53) after remediation. Based upon the HCl-extractable Pb content and the amount of phosphate rock added, various linear log-linear regression curves were obtained. These predictive equations have been used for field application. Our field results demonstrate that phosphate rocks have a potential to cost-effectively treat Pb-contaminated soils in Taiwan.     

Agronomic Evaluation of Calcined Crandallite from Three Brazilian Phosphate Deposits

Abstract

Samples from the weathering mantle containing crandallite of three Brazilian phosphate deposits, Tapira, Catalão, and Juquiá, were characterized, calcined, and agronomically evaluated. The calcination process increased total phosphorus (P) and neutral ammonium citrate soluble (NAC) P contents of all samples. The NAC solubility of original Tapira, Catalão, and Juquiá was about 5% of total P, whereas for calcined samples it was 54, 16, and 53%, respectively. In a greenhouse study, rates of P were applied at 0, 10, 20, 40, 80, and 120 mg P kg^?1 from the calcined materials and MCP (monocalcium phosphate) to an Ultisol cropped with upland and flooded rice for 65 days. The results showed that the calcined P samples increased dry‐matter yield and P uptake with increasing rates of P applied for both crops. Tapira and Juquiá were more effective for flooded than for upland rice. The calculated values of relative agronomic effectiveness of Tapira, Catalão, and Juquiá with respect to MCP were 57, 48, and 53% in dry‐matter yield for upland rice and 64, 50, and 69% for flooded rice, respectively.     

Agronomic Characteristics of Lettuce Grown with Monoammonium Phosphate in Sandy Soil

Information related to phosphate fertilization and coated phosphate fertilizer in lettuce (Lactuca sativa L.) is scarce. Thus, this study was carried out to evaluate the agronomic efficiency, production, and nutritional characteristics of coated monoammonium phosphate (MAP) in two subsequent crops with lettuce cv. Solaris. The experimental design was completely randomized (2 x 5 factorial experiment): two sources of phosphorus (P) (MAP and coated MAP), five applications (0; 75; 150; 300; and 600 mg phosphorus pentoxide (P₂O₅) kg^?1) with four replications. In the first crop, there was a greater accumulation of P in plants shoot with the application of coated MAP until 150 mg P₂O₅ kg^?1 dose, surpassed by MAP after this dose. On the second crop, fresh mass and the accumulation of P in the leaves were higher than the uncoated MAP. In both crops, the agronomic efficiency of P fertilization decreased with increase in the amount of phosphorus applied in lettuce cultivation.     

Differential Growth Response of Wheat Genotypes to Ammonium Phosphate and Rock Phosphate Phosphorus Sources

ABSTRACT

A solution culture experiment was conducted to determine the response of 15 wheat genotypes for growth, phosphorus (P) uptake, and P utilization efficiency, and their adaptability to P stress conditions using adequate [250 μM P in nutrient solution as ammonium phosphate (NH₄H₂PO₄)] and stress (powdered rock phosphate suspended in nutrient solution) P supply levels. Shoot dry matter (SDM) and total plant DM (shoot + root) and P uptake were generally higher for most genotypes in adequate P than stress P level treatment, but the opposite was true for root dry matter (RDM), root: shoot ratio (RSR), and root P uptake. Relative reduction in SDM due to P deficiency stress ranged from none to 54%. Genotypes Kohinoor 83, PB 85, Parvaz 94 and 4770 did not respond to P deficiency stress for SDM production, while genotypes FSD 83, Chakwal 86, Pasban 90, 4072, 4943, 5039, 6529-11, and 6544-6 were highly responsive to P application for SDM. Shoot P uptake in genotypes at adequate P level was about 3-times higher than those genotypes grown at stress P level. Differences in P concentration of shoot ranged between 2.00 to 3.06 mg P g^?1 in stress P level treatment, and had a significant positive correlation with P harvest index (PHI) (r = 0.558?, P < 0.05) and root efficiency ratio (RER) (r = 0.611?, P < 0.05) and negative correlation with P efficiency ratio (PER) (r = ?0.909??, P < 0.01). A significantly positive correlation of P utilization index (PUI) and SDM (r = 0.784??, P < 0.01) and non-significant negative correlation (r = ?0.483) of PUI with P concentration in shoot implies that wheat genotypes with higher PUI may be selected for P deficient milieu. Genotypes with higher PUI (>0.8 g mg^?1 P) in rook phosphate treatment were Inqlab-91, Pak-81, Lu 26s, Parvaz 94, 4072, 4770, 4943, and 5039. There was no interrelationship observed between shoot P uptake and P efficiency in stress P level treatment. However, highly significant and positive correlation (r = 0.720??, P < 0.01) between PHI and RER suggested that shoot P uptake depended upon root efficiency and it increased with the increase in P uptake per unit RDM. Consequently, this resulted in increased SDM which is evident from the significant positive correlation (r = 0.833??, P < 0.01) between SDM and shoot P uptake. In summary, the findings suggest that PUI and RER may be used for selecting P efficient wheat genotypes (e.g., 4072, 4770, 4943, Pak 81, and Inqlab 91) for dry matter production and P use.     

Phosphorus Fractions of Soils Treated with Phosphate Rock and Monocalcium Phosphate after Ryegrass Growth

Abstract

Excess EDDHA (ethylenediamine di(o‐hydroxyphenylacetic acid) ) had little effect on leaf concentrations of Fe in bush beans (Phaseolus vulgaris L. var Improved Tendergreen) when grown in nutrient solution at three pH values from 4.3 to 8.7. An excess of EDDHA 20 times that of Fe decreased yields slightly, but not as result of Fe deficiency. A resulting hypothesis is that chelated Fe can be transferred from chelating agent to uptake sites on roots without going in the ionic form through the solution around roots.     

微晶化磷矿粉的发酵活化效应

选用天然风化煤和pH 3.63的酒厂废弃物酒糟、MV菌剂为活化剂,与PB、PC微晶化磷矿粉在30℃下发酵研究对枸溶性磷的活化效果。结果表明,MV菌剂促进微晶磷矿粉有效P的溶解,且磷矿粉变细解磷效果增强;酒糟、风化煤促进微晶磷矿粉有效磷的溶解;MV菌条件下的酒糟、风化煤有利于微晶磷矿粉的活化,有效磷含量在25d达最高;酒糟对微晶磷矿粉的活化效应2∶1〉1∶1,25d枸溶性磷J6、J8、J2和J4分别比对照J净增长了1.63%,1.42%,1.32%及1.22%;MV菌条件下风化煤参与的发酵,25d处理F6、F8、F4和F2枸溶性磷分别比对照F增长了2.15%,2.13%,1.82%和1.77%。     

Influence of Ectomycorrhizal Hyphae on Phosphate Fractions and Dissolution of Phosphate Rock in Rhizosphere Soils of Pinus radiata

A study was conducted to determine the effect of ectomycorrhizal hyphae on phosphate rock dissolution and soil properties in the rhizosphere of one-year-old Pinus radiata D. Don seedlings established on an allophanic soil (Andosol) in the field. High and low ectomycorrhizal hyphal activities were produced in soils inside the lower compartments of rhizosphere study containers by using either 26 μm or < 10 μ m pore-size nylon mesh(es) at the interfaces between the lower and upper compartments. The meshes at the interfaces allowed (26 μm) or reduced (< 10 μ m) hyphae penetration into the lower compartment. Pairs of containers, one with 26 μ m mesh and the other with < 10 μ m mesh, were buried under Pinus radiata seedlings for 10 months in a forest plantation. The effect of ectomycorrhizal (ECM) hyphal activity on phosphate rock dissolution and soil properties was determined. The increased ECM hyphal activity induced increased soil acidification and promoted greater production of acid phosphatase enzyme, causing greater changes in phosphorus (P) fractions in the rhizosphere soils. The increased ECM hyphal activity also stimulated higher dissolution of phosphate rock and mobilization of soil organic P. The results suggest that ECM hyphal strand has a significant role in mobilizing low-solubility P forms and soil organic P for utilization by the tree.     

Compost Production from Olive Tree Pruning Wastes Enriched with Phosphate Rock

Olive production is increasing very fast in the last 20 years in Al-Jouf region, northern region of the Kingdom of Saudi Arabia. There are now more than 5 million olive trees in the productive stage. A huge amount of waste is produced annually from this sector, including pruning waste of olive trees and solid waste from olive oil mills of three-phase system. The waste of olive used to produce compost could be of safe disposal technique. Disposal of such waste is expensive and it causes some environmental hazards. Rock phosphate (RP), which is available in the same region, can be used to improve the nutrient value of the produced compost. In this experiment olive pruning waste was composted alone and in a mixture with different RP in two different ratios, namely 5% and 10%, on the dry weight basis of olive waste. Compost processing took place on plies for 8 months. Temperature and moisture were monitored daily while periodical samples were taken from all piles for testing pH, EC, C/N, and germination index. Composts in all treatments reached the theomorphic phase, which killed weed seeds and pathogens. The produced compost from all treatments fulfilled the requirements of maturity according to the California Compost Quality Council after 8 months of composting. In addition, the RP enhanced composting efficiency and improved the quality of the produced compost. Compost parameters met the standard requirements for the compost that was suitable for agriculture purposes with average values of pH ranging from (7.02–7.65) and EC (2.20–3.94 dS m^?1). Nutrient concentrations in the produced compost were N (1.28–1.79%), P (0.23–2.15%), and K (2.59–4.22%).     

微晶化磷矿粉的释磷特性及肥效机理

以有机材料为活化剂,用微晶化设备对磷矿粉进行活化处理,研究微晶活化后磷矿粉的物理特性、磷素释放动态及肥效.结果表明:微晶活化后磷矿粉的粒径整体变小,比表面积显著增大,磷素单次释放量和释放总量显著提高.施入土壤后,芦笋合格产品支数、单支质量和总产量较普通磷矿粉处理分别提高了2.61％,7.94％和9.64％;施用磷矿粉还可以增加土壤有效磷含量,提高土壤pH值,并促进芦笋对磷素的吸收,其中微晶化磷矿粉处理增加幅度明显高于普通磷矿粉处理.微晶化磷矿粉增量施用后,增产效果与普通过磷酸钙处理相当.     

Mycorrhiza Effect on Maize P Uptake from Phosphate Rock and Superphosphate

Low available phosphorus (P) is a serious constraint for crop production in acidic tropical soils. Economical yields in these environments require application of large amounts of costly nitrogen (N) and P fertilizers. Although phosphate rock (PR) has been proposed as a less expensive P source, the slow P release to the soil limits its use for annual crops. The objective of this work was to examine the effect of inoculating a nonsterile acidic soil with vesicular arbuscular mycorrhizal (VAM) Gigaspora margarita on PR dissolution and P uptake by aluminum (Al)–tolerant maize inbreds. Three maize inbreds from CIMMYT, at Cali, Colombia, ranked as Al‐tolerant and one local breed ranked as Al‐susceptible were seeded in 4‐kg pots filled with a soil of pH 4.1 and 2.5 mg kg^?1 available P. Inoculants (Gigaspora margarita and indigenous VAM), P fertilizer (Riecito phosphate rock and triple superphosphate), and the four inbreds were arrainged in a factorial design (2 × 2 × 4) with four replications. Plants were harvested 35 days after seeding, and P was determined in shoots. Four 2.5‐cm‐diameter soil cores were obtained from each pot to determine root length (two cores), root colonization (one core), and available P (one core). The inoculation with Gigaspora margarita caused a reduction in root length but better root colonization, 55% increase in P uptake, and 27% increase in shoot growth. When PR was used as fertilizer, plant growth was reduced in both roots and shoots. However, when PR was used in the presence of Gigaspora margarita, inbreds had 13% longer roots and shoot growth was the same as shoots fertilized with triple superphosphate. Our data suggest that inbreds exhibit different abilities to acquire P from PR under the influence of Gigaspora margarita fungi.     

磷矿粉超微细化对磷有效性的影响

以含P2O528.97%的同一胶磷矿制备的3种细度磷矿粉为供试材料.采用2%柠檬酸连续浸提的方法,研究了细度和厩肥发酵对磷矿粉释磷效果的影响.结果发现,连续3次浸提的枸溶性磷,细化磷矿粉PR2(400目)和细化磷矿粉PR3(800目)均较普通磷矿粉PR1(100目)提高,达显著水平(p>0.05),细度高的磷矿粉释磷快;磷矿粉与牛粪1:2混合发酵3周后,PR1、PR2、PR3的枸溶性磷含量分别达到发酵前的1.42倍、1.65倍和1.56倍,发酵后PR3的枸溶性磷含量达到未发酵普通磷矿粉PR1的2倍,显示了两种技术结合的累加效应;增加厩肥比例对等质量的磷矿粉活化效果好.     

Comparison of Prewashing Procedures for the Assessment of Phosphate Rock Dissolution in Soils

When evaluating phosphate rock (PR) dissolution, previous to the extraction with sodium hydroxide (NaOH), dry soil samples with PR were extracted with three solutions to remove exchangeable and solution calcium (Ca) [sodium chloride (NaCl) 1 M, buffered NaCl with ethylenediaminetetraacetic acid (EDTA) (NaCl–EDTA), and NaCl buffered at pH 7 with triethanolamine (TEA) (NaCl–TEA)] for comparison with the extraction of soil samples without any prewash. In acidic soils, up to 51% of applied P was recovered during the NaCl extraction because of the high exchangeable acidity released during the extraction. In soils with exchangeable Ca>2 cmol₍₊₎kg^?1, high EDTA quantities also promoted PR dissolution. The NaCl–TEA solution efficiently removed Ca, avoiding PR dissolution and P retention by calcium hydroxide [Ca(OH)₂] during the NaOH extraction. Thus, when evaluating PR dissolution we recommend the use of NaCl–TEA to remove Ca. We also recommend the same procedure when applying the Chang and Jackson fractionation to calcareous soils and soils submitted to PR application.     

Extraction and Analysis of Soil Solution of Phosphate Rock and Acid Treated Soil

Abstract

Increasing basic phosphate rock (PR) rates and acid loads were applied to an acidic sandy soil in a laboratory experiment. ‘Total’ amounts of potentially toxic elements in the soil and PR samples were determined by inductively coupled plasma (ICP) spectrometry after acidic, microwave digestion. Soil solution was extracted from wet soil by centrifugation with a speed corresponding to the suction power exerted by plants at the conventional wilting point. Addition of PR generally decreased rather than increased metal concentrations in the soil solution because of its pH elevating, immobilizing effect. Except for Pb, the extreme acid treatment compensated for the immobilizing effect of PR. Release of Cd (expressed as soil solution concentration in percentage of the total amount in soil+PR) was generally highest among elements at every treatment, and Cr was the least mobile metal. The one‐time, high rate of PR application did not make a direct environmental risk probable.     

细菌溶磷作用与磷矿粉伴生性重金属元素的释放

以4株溶磷细菌和5种磷矿粉为材料,对细菌溶磷作用与磷矿粉伴生性重金属元素释放间的关系进行了研究。结果表明,溶磷细菌在促进磷矿粉中磷溶出的同时,还促进了磷矿粉中伴生性重金属的释放,在测定的6种伴生性金属元素(Zn、Pb、Cu、Co、Ni、Cd)中,Zn最容易随细菌溶磷作用而释放,最多可占该磷矿粉中总Zn量的97.0%,Pb和Cd随细菌溶磷释放率皆低于10%;细菌溶磷作用强度与磷矿粉中各伴生性重金属释放量间的关系因磷矿粉产地和伴生性重金属种类而异。细菌作用于湖南石门磷矿粉和四川马边磷矿粉的溶磷量与Zn、Cu、Co、Ni释放量间(四川马边磷矿粉中Co除外)正相关,但未达到显著水平(r=0.50~0.95,P>0.05),但在溶解贵州开阳磷矿粉时,Zn、Co、Ni的释放量都与溶磷量显著正相关(r>0.88,P<0.05)。     

In Situ Digestion of Rock Phosphates to Mobilize Plant-Available Phosphate for Organic Farming

Sustainable phosphorous (P) management is a key problem in organic farming. In situ digestion of naturally occurring rock phosphates (RPs) may be a solution. This would require the application of fertilizers consisting primarily of RP mixed with elemental sulfur (S). Through microbial action, the S is oxidized into sulfuric acid, which then transforms the RP into soluble, plant-available forms. By means of an incubation experiment, this study characterized the in situ digestion of RP and revealed how it is influenced by temperature and microbial action. When either S alone or S together with RP (SP) was added to soil that had been inoculated with S-oxidizing microorganisms, the soil pH decreased rapidly from about 7.3 to 3.2 over 12 weeks of incubation. In soil that had not been inoculated with of S-oxidizing microorganisms, the pH of the soil treated either with S or with SP decreased only slightly. The pH of the inoculated soil to which either S or SP had been added decreased more rapidly at 30 °C than at 23.8 °C during the first 4 weeks. The oxidation rate in inoculated soil was much greater than in noninoculated soil and greater at 30 °C than at 23.8 °C. The S oxidation rate in inoculated soil was significantly greater in the SP treatment than in the S treatment both at 23.8 °C and at 30 °C. After incubation, the amounts of water-soluble P and of CAL P (calcium-acetate-lactate–extracted P) were large only in the SP treatment in inoculated soil.     

Effectiveness of Chloride Compared to 3,4-Dimethylpyrazole Phosphate on Nitrification Inhibition in Soil

Microbial oxidation of ammonium to nitrate may impose dangers to ecosystem functioning through soil and atmosphere contamination with end products or intermediate gases. A wide range of chemicals can inhibit nitrification under soil and laboratory conditions. In the present study, the effectiveness of chloride compared to 3,4-dimethylpyrazole phosphate (DMPP) as a standard nitrification inhibitor was evaluated. The results showed that DMPP (especially with double concentrations) inhibited nitrification for a longer time, until the end of incubation period. Chloride in the form of ammonium chloride (NH₄Cl) or potassium chloride (KCl) also significantly inhibited nitrification compared to the control during the 7-week incubation period. This inhibition was positively correlated with applied chloride concentrations in soil. During a 5-week incubation period, the strongest concentration (500 mg/kg soil) showed more inhibition than concentrations of 250 or 100 mg/kg soil, particularly when compared to control. The results suggest that beside commercial nitrification inhibitors, chloride can significantly inhibit microbial nitrification in soil. Therefore, when chloride is not a soil problem, the chloride form of nitrogen fertilizers (e.g., ammonium chloride) could be a proper nitrogen fertilizer.