Reactive Phosphate Research Articles

Natural nutrient enrichment and algal responses in near pristine micro-estuaries and micro-outlets

Naturally-occurring pristine estuarine ecosystems are rare in modern environments due to anthropogenic encroachment. There are more than 100 outlets around the South African coast arising from streams flowing from small catchments close to the sea. Eight near natural systems were sampled seasonally over the period of a year to acquire baseline information on water quality and chlorophyll a status across a variety of algal guilds (benthic microalgae, phytoplankton and macroalgal cover). Albeit on a much smaller-scale, these systems represent natural surrogates of larger temporarily open/closed estuaries (TOCEs). Inorganic nutrients (ammonium, total oxidized nitrogen and soluble reactive phosphate), phytoplankton and microphytobenthos chlorophyll a, as well as macroagal percentage cover, were measured using standard methods. Algae showed a seasonal trend, with blooms of both micro- and macro-algae occurring during summer, with a dieback recorded in autumn. During summer, only one system had a phytoplankton peak in chlorophyll a above 20μgL−1, while the microphytobenthos concentrations in three of the systems were above 100mgm−2. Summer blooms of green filamentous macroalgae occurred in all four micro-outlets and in one micro-estuary. Using a linear mixed-effects modelling approach, significant drivers for algal growth related to temperature, nutrient conditions, light availability and water residence time, all of which are known to stimulate primary production. The results show that enrichment from natural sources display similar responses from primary producers to mesotrophic and/or eutrophic water bodies, with the exception that they revert to a natural state rather than continue into a degraded state as is the case in artificially enriched systems. This importantly demonstrates how larger temporarily/open closed estuaries, most of which are anthropogenically degraded, might have functioned under a former more balanced state. Some of these larger systems now respond to nutrient enrichment by exhibiting permanent cultural eutrophication.

Pools and solubility of soil phosphorus as affected by liming in long-term agricultural field experiments

Published laboratory studies suggest minimum solubility of soil phosphorus (P) in the pH range traditionally considered as the target for lime applications on agricultural land. However, the potential significance of these results for the timescale relevant in practical agriculture remains to demonstrate. We revisited four long-term (50–76years) agricultural lime experiments located on Quaternary deposits with topsoil texture ranging from silt loam to silty clay and initial pH between 5.0 and 6.0. Crop uptake data and desorption experiments in the laboratory indicated that liming enhanced the solubility of P added with fertiliser in the decades following the application of lime. An empirical mass-balance model demonstrated that changes in acetate-lactate extractable P (‘P-AL’), previously shown to be related to reactive phosphate adsorbed on soil mineral surfaces, was proportional to field P balances (fertiliser P – harvested P) and inversely proportional to the net proton load to the soil. Extraction data suggest that liming enhanced the incorporation of silica in non-crystalline sesquioxides, which in turn inhibited the conversion of fertiliser P into less extractable forms by migration of P to inside the oxides. Liming induced a lowering of the C/N ratio in one of the experiments, suggesting stimulated decomposition of soil organic matter. However, lime applications did not lead to a decline in the pool of soil organic P, as measured by the combustion method. Mass-balance considerations showed that changes in organic-matter input due to liming were unlikely to result in observable changes in the pool of soil organic P.

Hydrochemical controls on reservoir nutrient and phytoplankton dynamics under storms

Eutrophication and undesired algal blooms in surface water are common and have been linked to increasing nutrient loading. Effects of extreme events such as storms on reservoir nutrient and phytoplankton remain unclear. Here we carried out continuous high-frequency measurements in a long and narrow dam reservoir in southeast China during a storm period in June–July 2015. Our results show a strong nutrient-phytoplankton relationship as well as a very rapid response to storm runoff. We observed an increase in total suspended matter (TSM), ammonium (NH4-N), and dissolved reactive phosphate (DRP), with a sharp decline in chlorophyll-a (Chl-a) in the high flow periods. Afterward, Chl-a, total phytoplankton abundance and Cyanophyta fraction elevated gradually. Nitrate was diluted at first with increasing discharge before concentration increased, likely following a delayed input of groundwater. Physiochemical parameters and Chl-a were evenly distributed in the water column during the flooding period. However, 10% of NH4-N and 25% of DRP were removed in surface water (0–1m) when an algal bloom (Chl-a>30μgL−1) occurred 10days after peak discharge. Conversely, total particulate P (TPP) of surface water was 58% higher than in the deeper water. Dynamic factor analysis (DFA) revealed that TSM, NH4-N, DRP, total P and discharge significantly explain Chl-a variations following storms (Ceff=0.89). These findings highlight that the reservoir ecosystem was vulnerable to pulse input from storm runoff and the Cyanophyta bloom was likely fueled by phosphate and ammonium rather than nitrate.

Harmful Algae Bloom Occurrence in Urban Ponds: Relationship of Toxin Levels with Cell Density and Species Composition.

Retention ponds constructed within urban watershed areas of high density populations are common as a result of green infrastructure applications. Several urban ponds in the Northern Kentucky, USA area were monitored for algal community (algae and cyanobacteria) from October 2012 to September 2013. Many of the harmful algal blooms observed during this study were composed primarily of the cyanobacteria genus, Microcystis. No correlations were observed between basic water quality parameters (dissolved oxygen, pH, conductivity, temperature, nitrate and soluble reactive phosphate) and the presence of cyanobacteria and/or microcystin cyanobacterial toxin levels. Furthermore, levels of microcystin toxins did not always coincide with high Microcystis cell counts. Harmful algal blooms in small urban ponds are common which pose risk to human and ecological health due to proximity of dense human population including pets and wild animals. Because harmful algal blooms were detected throughout the year in this study, adaptation of universal guidelines for the design, construction and maintenance of urban ponds may be necessary to protect watershed aquatic ecosystems, and lower health risks from exposure to such harmful blooms.

Phytoplankton abundance in relation to the quality of the coastal water – Arabian Gulf, Saudi Arabia

Phytoplankton abundance in relation to some physicochemical characters of the costal water of Arabian Gulf (Saudi Arabia) was studied for one year. The sampling program included 15 locations in Dammam, Saihat, Al-Qatif, Al-Awamia and Safwa. Water samples were analyzed monthly for these parameters; temperature, pH, salinity, dissolved oxygen, nitrite, nitrate, ammonia, carbon dioxide, total chloride, reactive orthophosphate and total phosphorus and alkalinity, also phytoplankton communities were identified and Chlorophyll a was estimated. The results showed that, the high phytoplankton density attaining the maximum (190.3 × 104/m3) during May and June, and the minimum (10.4 × 104/m3) during November and December. Forty Five species belonging to 5 phytoplankton groups were recorded. Bacillariophyceae was the first dominant group forming 48% of the total phytoplankton communities (23 species). The dominant species of Bacillariophyceae were Pleurosigma strigosum, Pleurosigma elongatum, Lyrella clavata, Rhizosolenia shrubsolei, Cylindrotheca closterium, Nitzschia panduriform, Nitzschia longissimia, Amphora sp and Stephanopyxis. Dinophyceae was the second dominant group and formed 31% of the total phytoplankton communities (10 species); the dominant species were Ceratium fusus, Heterosigma sp, Ceratium furca, Prorocentrum triestium, Protoperidinium sp, Gyrodinium spirale, Noctiluca scintillans and Scrippsiella trochoidea. Cyanophyceae formed 13% (5 species) where Nostoc sp, Oscillatoria and Merismopedia sp were the dominant species. Chlorophyceae had 8% (6 species); Scendesmus sp., Chlorella sp., Chlamydomonas sp., Dunaliella salina and Nannochloropsis sp were the dominant species. The Euglinophyceae was rare only one species (Euglina sp). The relationship was positive between the phytoplankton, chlorophyll a and carbon dioxide while negative amongst dissolved oxygen and total nitrogen. This research indicated that the relation between water quality and phytoplankton organisms at the coast of Arabian Gulf (Saudi Arabia) was extremely overlapping and interdependent; any changes in the one component may significantly affect those of the other components.

Residue of Phosphorus Sources Broadcast and Applied on Rows in Forages during Off-Season Crops

This study aimed to evaluate the residual effect of phosphorus sources and application techniques in the intercropping of forages during off-season crops. The experimental design was randomized blocks in a 4 × 2 + 1 factorial, being four sources of phosphorus [Bayóvar Reactive Phosphate (BRP), Monoammonium Phosphate (MAP), Simple Superphosphate (SS) and Triple Superphosphate (TS)], two application techniques (broadcasting and on rows) and an additional without phosphorus. The experiment was conducted during the off-season crop. The residual effect of phosphorus fertilization increased the growth and the production of biomass of forage sorghum regarding broadcast SS and TS sources. The lowest P contents in the tissue of plants fertilized with SS and TS may be attributed to the diluting effect, as it achieved the highest production of biomass. The application of TS favored a greater dry matter production in Brachiaria brizantha cv. Piatã. At the depth 0.00-0.05 m, there was a higher P content with the application of BRP. However, the production of biomass was low, a factor that may be related to an overestimation of P bound to Ca by the Mehlich-1 extractor. Under cultivation conditions, broadcast SS and TS had a higher residual effect.

Phosphate fertilization strategies for soybean production after conversion of a degraded pastureland to a no-till cropping system

A considerable area of previously degraded pastureland in Brazil is appropriate for agricultural use, mostly for soybean cultivation. These degraded soils can be restored by establishing no-till systems which should protect the soil, enhance nutrient cycling, and be economically feasible. One of the main challenges when performing agricultural operations in these soils is soil phosphorus (P) status, due to the low levels and difficult management of this nutrient in highly weathered soils. This is mainly related to a lack of information regarding the best management strategy with respect to fertilizer sources and their placement and time of application. We hypothesized that applying P to the cover crop, rather than to the soybean furrow, is a better strategy for the production system, because it would improve P recycling and soil cover and guarantee better timing and operational efficiency in soybean sowing. A 4-year field trial examined the effect of P application (44kgPha−1year−1) using various P sources (RPR – Reactive Phosphate Rock, TP – Thermophosphate and TSP – Triple Superphosphate) at different times (black oat furrow or soybean furrow), on a sandy loam Oxisol of a degraded pastureland in Southern Brazil. A black oat (Avena strigosa Schreb) – soybean (Glycine max L. Merrill) cropping sequence was used for 4years after no-till establishment. Soil P content, plant nutrient uptake, black oat dry biomass yield, and soybean grain yield were assessed. Soil P content increased from 2.5 to 13.3mgdm−3 (0–0.20m depth) on average across all times and sources of P application after 4years. Different application times resulted in a residual P for black oat (when P was applied to soybean furrow) and soybean (when P was applied to black oat furrow). Soybean exhibited better use of residual P (based on nutrient uptake and grain yield) than black oat (based on effects on nutrient uptake and biomass yield). Black oat P uptake was positively correlated with soybean P uptake (r=0.71, p<0.01) and soybean yield (0.69, p<0.01). The use of the TSP source led to a greater P-use efficiency, which was about 67kg of black oat dry biomass for each kg of P applied to the black oat sowing furrow, and about 40kg of soybean grain for each kg of P applied to the sowing furrow of black oat or soybean. Compared to TSP, less soluble phosphate sources (RPR and TP) led to a two to three times lower P-use efficiency. Results suggest that, on a previously degraded sandy loam Oxisol, P application to cover crop boosts P recycling and improves soybean yield by improving soil cover, and increases operational efficiency at sowing, even at low soil P levels. The use of water-soluble P sources should be preferred over less-soluble sources for the application on cover crop furrow.

PHYSICO-CHEMICAL ASSESSMENT OF WATER SAMPLES COLLECTED FROM SOME SELECTED STREAMS AND RIVERS IN DISTRICT GILGIT, PAKISTAN

This study aims to provide information about the drinking water quality of two streams in Chakarkote Sai and Demote Sai and two rivers in Gilgit and Hunza. Parameters were tested including physical, and chemical. The physical parameters were temperature, pH, electric conductivity (EC), total dissolved solids (TDS), turbidity, dissolved oxygen (DO), ammonia (NH4),total nitrogen (TN), total phosphorus (TP) and reactive orthophosphate (PO4). The ranges of these parameters set by WHO and NEQs, as most of the Asian countries also follow the WHO standards. All the samples were tested in the EPA certified laboratory of biological sciences department Karakorum international university Gilgit Baltistan. The minimum and maximum values of temperature 15.2-18.4, PH 6.78-6.09, EC 109.3-297 µS, TDS 53.8-149 ppm, Turbidity 0.29-88.4 NTU, DO 7.1-8.9 mg/l, TN 5.63-7.13 mg/l, NH4 0.0106-0.0151 mg/l, TP 0.042-0.143mg/l, and PO4 0.0059-0.016 mg/l. Independent T test was applied separately for both streams and rivers to determine significant difference of water properties with respect to location wise. Water parameters like DO and TP were significantly, while temperature, PH, EC, TDS, turbidity, TN, NH4, PO4 were non-significant in streams and TDS, turbidity, DO and TN were significant, while temperature, PH, EC, NH4, TP, PO4 were non-significant in rivers according to area wise.

Investigation of acid hydrolysis reactions of polyphosphates and phytic acid in Bray and Mehlich III extracting solutions

Soil test phosphorus (STP) (Bray P-1, Mehlich III) was developed to predict the plant available P in agricultural soils in the USA. The acidic STP extracting solutions were intended to extract phosphate from alkaline earth metal-based solubility products and or adsorbed species on amorphous metal hydroxides or phyllosilicates in soils. However, the accuracy of STP in predicting plant available phosphate has often been questioned due to potential acid hydrolysis of poly- and organic-P in soils during the STP extraction. The objective of the study was to investigate the acid hydrolysis reaction of reference poly- and organic-P compounds (1.25–3.75 mM) in Bray and Mehlich III extraction solutions using spectrophotometric methods. The results showed that both tripolyphosphate and pyrophosphate readily underwent the acid hydrolysis reaction over 2 h, whereas phytic acid did not hydrolyze. The results suggest an overestimation of dissolved reactive phosphate from these polyphosphates should be considered when evaluating the STP data.

Reactive natural phosphate enriched with filter cake enhances soil P content and noni seedlings growth

ABSTRACTOne of the major challenges in crop production is increase efficiency of non-renewable P sources, or replace them with renewable sources. The objective of this study is to evaluate the effects of phosphorus (P) fertilization using reactive natural phosphate, filter cake, peat and biofertilizer on soil P content, foliar P content and growth of noni seedlings. The treatments were: control (without P fertilization); phosphorus; filter cake; phosphorus + filter cake; phosphorus + filter cake + peat; and phosphorus + filter cake + peat + biofertilizer. All treatments were replicated four times and arranged in a completely randomized design. The treatments phosphorus + filter cake; phosphorus + filter cake + peat; and phosphorus + filter cake + peat + biofertilizer increased phosphorus content in soil and in leaf, and the growth of noni seedlings. Our results indicates that natural reactive phosphate enriched with filter cake can be used as phosphate fertilizer on noni seedlings cultivation.

Coastal Acidification as Nutrients Over Enrichment Impact: A Case Study in Ambon Bay, Indonesia

Ambon Bay is a silled bay on Ambon Island consisting of two regions, Inner Ambon Bay (IAB) and Outer Ambon Bay (OAB) that are separated by shallow sill. Ambon bay and its surrounding have economically important ecosystem since the utilization for many activities. The bay is affected by anthropogenic impacts associated with urbanization, climate change, and nutrients over enrichment. The “deep water-rich nutrients” from Banda Sea that enter the bay during Southeast monsoon also contribute to this enrichment as well as the nutrients transport from the land. The high concentration of nutrients increases carbon dioxide level and promotes acidifications. There are literatures about nutrients over enrichment in Ambon Bay, however, little is known about coastal acidification as nutrients over enrichment impact. In order to study the effect of nutrients distribution on the acidity of Ambon Bay, the researchers measured pH and concentrations of nutrients {nitrate + nitrite (N+N) and Soluble Reactive Phosphate (SRP)} from water samples collected in 7 stations on both IAB and OAB during Southeast monsoon. The results showed that in surface water, nutrients concentrations is increased from May to June due to the “deep water flushing” occurrence on May and increased precipitations from May to June. From July to August, the nutrients concentrations on surface layer decreased, due to the decreased precipitations. In column and bottom water, the nutrients concentrations were increased from May to August. While the acidity have reverse pattern from the nutrients, when nutrient concentrations increased the acidity was decreased. From correlation test, pH was not significantly correlated with the concentrations of nutrients on surface water, but showed significantly correlated on column and bottom water. The results indicated that the distribution of nutrients on column and bottom water might be an important environmental factor affecting the acidification of the Ambon Bay in Southeast monsoon.

Impact of raking and bioturbation-mediated ecological manipulation on sediment-water phosphorus diagenesis: a mesocosm study supported with radioactive signature.

The study examined the impact of raking and fish bioturbation on modulating phosphorus (P) concentrations in the water and sediment under different trophic conditions. An outdoor experiment was set to monitor physicochemical and microbiological parameters of water and sediment influencing P diagenesis. A pilot study with radioactive 32P was also performed under the agency of raking and bacteria (Bacillus sp.). Raking was more effective in release of P under unfertilized conditions by significantly enhancing orthophosphate (35%) and soluble reactive phosphate (31.8%) over respective controls. Bioturbation increased total and available P in sediments significantly as compared to control. The rates of increase were higher in the unfertilized conditions (17.6-28.4% for total P and 12.2 to 23.2% for available P) than the fertilized ones (6.5-12.4% for total P and 9.1 to 15% for available P). The combined effects of raking and bioturbation on orthophosphate and soluble reactive phosphate were also stronger under unfertilized state (54.5 and 81.8%) than fertilized ones (50 and 70%). The tracer signature showed that coupled action of introduced bacteria and repeated raking resulted in 59.2, 23 and 16% higher counts of radioactive P than the treatments receiving raking once, repeated raking and bacteria inoculation, respectively. Raking alone or in sync with bioturbation exerted pronounced impact on P diagenesis through induction of coupled mineralization and nutrient release. It has significant implication for performing regular raking of fish-farm sediments and manipulation of bottom-grazing fish to regulate mineralization of organic matter and release of obnoxious gases from the system. Further, they synergistically can enhance the buffering capacity against organic overload and help to maintain aquatic ecosystem health.

Simulation on phosphorus release characteristics of Poyang Lake sediments under variable water levels and velocities

Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the disturbance intensity to sediments, which caused the increase of suspended solids (SS) concentration, total phosphorus (TP) concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well: when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4.86 mg/(md) at 0.4 m/s. The concentration of total dissolved phosphorous (TDP) and soluble reactive phosphate (SRP) both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.

Analysis of Chlorophyll-aCorrelation to Determine Nutrient Limitations in the Coastal Waters of the Bohai Sea, China

ABSTRACT Mao, X.; Kuang, C.; Gu, J.; Kolditz, O.; Chen, K.; Zhang, J.; Zhang, W., and Zhang, Y., 2017. Analysis of chlorophyll-a correlation to determine nutrient limitations in the coastal waters of the Bohai Sea, China. The coastal water of Qinhuangdao, a famous resort located in the NW of the Bohai Sea, China, suffered algal bloom for a consecutive 3 years by 2011, causing great economic loss. Based on measurements at 46 sampling points in the study's coastal area in May, August, and October 2011, the seasonal and spatial characteristics of the chemical indicators and chlorophyll-a (Chl-a) were analyzed. The chemical indicators for pH, chemical oxygen demand (COD), and reactive silicate (SiO3-Si) showed higher concentrations in the summer than in the spring and fall, whereas the nutrients of reactive phosphate (PO4-P) and dissolved inorganic nitrogen (DIN) presented complex seasonal characteristics under the combined influence of abundant nutrients from rivers and nutrient consumption by large algal bl...

Preservation of seawater samples for soluble reactive phosphate, nitrite, and nitrate plus nitrite analyses by the addition of sodium hydroxide

AbstractSeawater storage at ambient temperature is necessary when freezing facilities are unavailable for the preservation of samples collected for the determination of soluble reactive phosphate (SRP), nitrite ( ), and nitrate plus nitrite (N + N)—notably, during small boat operations. Here, we report that samples may be preserved at ambient temperature by the addition of NaOH at sampling to induce the precipitation of Mg(OH)2, and then returned to a shore base laboratory for further processing. In the laboratory, SRP, which has been sequestered in the precipitate, is analyzed by the MAGnesium‐induced co‐precipitation method. and N + N are quantitatively retained in the supernatant liquid and they are analyzed by the standard methods after a pH adjustment. The samples may be stored for up to at least 2 months and they yield concentrations that are indistinguishable from those in frozen samples. Internally added SRP, , and N + N to seawater samples can be recovered quantitatively after storage. This storage method also offers clear advantages over the preservation of samples at ambient temperature by the addition of HgCl2 as NaOH is a less toxic and less environmentally hazardous chemical and it does not interfere in the determination of N + N. It also allows low level SRP to be determined as part of the analytical routine as a pre‐concentration of SRP has been built into the storage scheme.

Structural aspects of nucleotide ligand binding by a bacterial 2H phosphoesterase.

The 2H phosphoesterase family contains enzymes with two His-X-Ser/Thr motifs in the active site. 2H enzymes are found in all kingdoms of life, sharing little sequence identity despite the conserved overall fold and active site. For many 2H enzymes, the physiological function is unknown. Here, we studied the structure of the 2H family member LigT from Escherichia coli both in the apo form and complexed with different active-site ligands, including ATP, 2′-AMP, 3′-AMP, phosphate, and NADP+. Comparisons to the well-characterized vertebrate myelin enzyme 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) highlight specific features of the catalytic cycle and substrate recognition in both enzymes. The role played by the helix α7, unique to CNPases within the 2H family, is apparently taken over by Arg130 in the bacterial enzyme. Other residues and loops lining the active site groove are likely to be important for RNA substrate binding. We visualized conformational changes related to ligand binding, as well as the position of the nucleophilic water molecule. We also present a low-resolution model of E. coli LigT bound to tRNA in solution, and provide a model for RNA binding by LigT, involving flexible loops lining the active site cavity. Taken together, our results both aid in understanding the common features of 2H family enzymes and help highlight the distinct features in the 2H family members, which must result in different reaction mechanisms. Unique aspects in different 2H family members can be observed in ligand recognition and binding, and in the coordination of the nucleophilic water molecule and the reactive phosphate moiety.

Indication of spatial variations in annual cycles of functional groups of planktonic ciliates to environmental change in marine ecosystems

The indication of spatial variations in annual cycles of functional groups of planktonic ciliates to environmental changes was studied in a bay, northern Yellow Sea. Samples were biweekly collected at five stations with different hydrographic conditions during a 1-year cycle. The second-stage-matrix-based multivariate approach was used to summarize the internal interactions of the ciliate functional groups among five stations during a 1-year period. The functional groups of the ciliates represented a clear spatial variation in annual cycle among five stations. Mantel analysis demonstrated that the spatial variation in annual cycles of the ciliate functional groups were significantly correlated with the changes nutrients (mainly soluble reactive phosphates and nitrates), alone or in combination with salinity among five stations. Based the results, it is suggested that the spatial variation in annual cycles of functional groups of planktonic ciliates may indicated the changes of hydrographic conditions.

Organomineral Phosphorus Fertilization in the Production of Corn, Soybean and Bean Cultivated in Succession

The use of organic waste in agriculture has been used aiming at greater productivity, decrease in the cost of production and sustainable use of resources. The present study aimed at evaluating the effect of phosphate fertilization with the maintenance of organomineral fertilizers, combining poultry manure and soluble or reactive phosphate, in the production of grains in corn culture and the residual effect for subsequent crops of beans and soybeans. The experiment was conducted in Sete Lagoas, MG, in 2015, using three fertilizers with sources of different phosphorus sources (triple super phosphate—STP, organomineral with STP and organomineral with Bayovar phosphate) applied at the doses of 65, 130, 195 and 260 kg·ha¯1 of P2O5 total, and compared to the control without phosphate fertilization. We evaluated the contents of foliar P, P accumulation in the grains, yields of corn grains, beans and soy, accumulated productivity and export of accumulated P of the three cultures. The three cultures assessed presented higher productivity when compared to the average of the factorial treatments that received phosphate fertilization relative to the control. Organomineral fertilizers increased grain production, obtaining average productivity equal to or greater than those obtained with the exclusive use of STP.

Ecological Study of the Rabigh Lagoon, Eastern Site of the Red Sea, Saudi Arabia with Special Reference to Eutrophication Index

Seasonal variation in plankton community structure (phytoplankton and zooplankton), chlorophyll a and some physico-chemical properties of Rabigh Lagoon were studied during 2015. The study area included seven sites situated between latitudes 22.9978° to 22.8519° and longitudes 38.8339° to 38.9616°E. The ecological parameters comprise some physical and chemical parameters as Temperature, Secchi Disc, pH, DO, S%, Nutrients “Nitrite, NO2-N; Nitrate, NO3-N; Ammonia, NH3-N; total nitrogen, T-N; Reactive phosphate, PO4-P and total phosphorus, T-P”. A total of 103 species belonging to five phytoplanktonic groups were identified. The most leadings group is Bacillariophyceae (45.05%) then Cyanophyceae (33.83%) followed by Dinophyceae (20.99%). On the other hand, Chrysophyceae (0.07%). and Chlorophyceae (0.05) are considered a rare group. Chlorophyll a showed almost the same pattern with the standing crops of the phytoplankton ranged between 12.33 μg l-1 during spring and a lowest value of 5.49 μg l-1 during summer. The most dominant group of zooplankton was Copepoda (89.00%) followed by Protista (7.30%) and Rotifera (3.70%). The maximum peak of Copepoda was recorded during all the investigation period except autumn. The Diversity Index fluctuated between 2.785 during autumn and 3.568 during summer. The calculating of trophic status index according to Secchi Disc methods was found to be better than chlorophyll a and total phosphorus methods. The analysis showed that Rabigh Khore is a mesotrophic ecosystem. Canonical correspondence analysis (CCA) was additionally completed to break down the relations between the physico- Chemical parameters and the plankton. It showed that the most important factors affecting plankton distribution.

Solubilization of Bay&amp;#243;var Natural Phosphate Rock under the Drain Effect of Calcium and Phosphorus at Two Levels of Acidity

Natural phosphate rock (NP) solubilization in soils is dependent on the soil pH and its power to remove or drain (sink effect) P and Ca of the solution that is in equilibrium with the NP. The aim of this work was to evaluate the effect of acidity and P- and Ca-sinks on the solubilization of bayovar reactive rock phosphate (a phosphorite). Samples of this NP in aqueous suspension were placed in a cassette (Slide-A-Lyzzer G2 Dialysis Cassette) compartment and immersed in a beaker containing 150 mL of an aqueous solution with pH adjusted at 4.5 or 6.0, where P- and Ca-sinks individually or in their combinations, were applied. The tested sinks were: Anionic Resin (AR); Cationic Resin (CR); Mixed Resin (MR: AR + CR); Goethite (Goe); Goe + AR; Goe + CR and one control (NP only) in five replicates. Beakers (experimental units) were shaken for 12 h daily, at 130 rpm, until completing 30 days of equilibrium. The suspensions were filtered to extract solution-P from the residue on the filter paper; the labile-P was extracted from this residue using 0.8 mol·L-1 NH4Cl in 2 mol·L-1 HCl and, finally, the remainder P in the same residue together with the filter paper were subjected to nitric-perchloric acid digestion, to determine the P-residual in the extract. Goe caused greater solubilization of the NP, indicating that this P-sink was more effective than AR, causing similar or greater solubilization than CR. AR and CR, in a similar way, significantly restricted the trait characteristic of Goe (p < 0.05), at both pH values, in the solubilization of NP. Although Goe generally caused greater solubilization of the NP, it also caused the lower formation of labile-P. The CR presented, in general, the highest contents of solution-P, thus it triggered solubilization of NP without the immobilization of the solution-P, unlike the one with the AR that adsorbs it. In the lower pH condition (4.5), the solubilization of NP tended to be higher than at pH 6.0, although in a little effective way, compared to the effects of the sinks.