Water-soluble Phosphorus Research Articles

Differential stimulation and suppression of phytoplankton growth by ammonium enrichment in eutrophic hardwater lakes over 16 years

AbstractPrevious research suggests that fertilization of surface waters with chemically reduced nitrogen (N), including ammonium (NH4+), may either enhance or suppress phytoplankton growth. To identify the factors influencing the net effect of NH4+, we fertilized natural phytoplankton assemblages from two eutrophic hardwater lakes with growth‐saturating concentrations of NH4Cl in 241 incubation experiments conducted biweekly May–August during 1996–2011. Phytoplankton biomass (as chlorophyll a) was significantly (p < 0.05) altered in fertilized trials relative to controls after 72 h in 44.8% of experiments, with a marked rise in both spring suppression and summer stimulation of assemblages over 16 yr, as revealed by generalized additive models (GAMs). Binomial GAMs were used to compare contemporaneous changes in physico‐chemical (temperature, Secchi depth, pH, nutrients; 19.5% deviance explained) and biological parameters (phytoplankton community composition; 40.0% deviance explained) to results from fertilization experiments. Models revealed that that the likelihood of growth suppression by NH4+ increased with abundance of diatoms, cryptophytes, and unicellular cyanobacteria, particularly when water temperatures and soluble reactive phosphorus (SRP) concentrations were low. In contrast, phytoplankton was often stimulated by NH4+ when chlorophytes and non‐N2‐fixing cyanobacteria were abundant, and temperatures and SRP concentrations were high. Progressive intensification of NH4+ effects over 16 yr reflects changes in both spring (cooler water, increased diatoms and cryptophytes) and summer lake conditions (more chlorophytes, earlier cyanobacteria blooms), suggesting that the seasonal effects of NH4+ will vary with future climate change and modes of N enrichment.

Corroles at the Real Solid-Liquid Interface: In Situ STM Investigation of a Water-Soluble Corrole Layer Deposited onto Au(111).

Corrole derivatives have been recently employed in many applications at the solid-liquid interface. Therefore, the structural arrangement of the molecular layers in direct contact with the liquid is of fundamental interest. We investigated in solution the deposition of molecular layers of the previously prepared water-soluble phosphorus complex of a 2-sulfonato-10-(4-sulfonatophenyl)-5,15-dimesitylcorrole [see synthesis in our previous paper, M. Naitana et al., Chem. Eur. J. 2017, 23, 905-916]. The layer formation of P corroles onto the Au(111) surface was monitored by STM in situ, that is, with the substrate immersed in the solution. Marked differences in the morphology between the organic layer formed on the substrate and that deposited after solvent evaporation (drop casting) are reported. In particular, the coating of gold was more effective and stable in the presence of liquid. Preservation of functionality of the corrole molecules after adsorption was verified. This result validates the relevance of corrole layers at the solid-liquid interface to exploit the peculiar properties of these molecules in real-world applications.

Phytoplankton species interactions and invasion by Ceratium furcoides are influenced by extreme drought and water-hyacinth removal in a shallow tropical reservoir

This study explored the interactions of phytoplankton species during the invasion of Ceratium furcoides and the environmental variables that contributed to its establishment and ecological success in a shallow eutrophic reservoir (Garcas Reservoir, southeast Brazil), which has been monitored monthly for 20 years (1997–2017). The Ceratium furcoides invasion in September 2014 was preceded by disturbance events (macrophyte removal and a historical drought period), which disrupted the dominance of cyanobacteria by modifying resource availability (high water transparency and soluble reactive phosphorus concentrations) and recruiting other species. Ceratium blooms at the water surface were preceded by high abundance near the bottom, suggesting the importance of the propagule bank. However, the pattern of Ceratium-Microcystis coexistence that is usually recorded in temperate lakes was not observed. Instead, Ceratium replaced Cylindrospermopsis raciborskii in mixing periods with high light and nitrogen availabilities, significantly influencing the abundance of Trachelomonas spp. Flagellated forms became dominant in the Garcas Reservoir, due to the higher water transparency and relatively lower water-column stability, and alternative states between Ceratium-Trachelomonas in mixing periods and Microcystis-Cryptomonas in stratified periods have been repeated. Since then, cyanobacterial dominance ceased, and the “skillful” Ceratium apparently has come to stay, influencing interactions among phytoplankton species.

Phosphorus Utilization Efficiency and Yield Responses of Drip Irrigated Cotton under Plastic Film Mulching to Three Types of Water Soluble Phosphorus Fertilizers

Phosphorus Utilization Efficiency and Yield Responses of Drip Irrigated Cotton under Plastic Film Mulching to Three Types of Water Soluble Phosphorus Fertilizers

Phosphorus saturation and superficial fertilizer application as key parameters to assess the risk of diffuse phosphorus losses from agricultural soils in Brazil

In Brazil, a steady increase in phosphorus (P) fertilizer application and agricultural intensification has been reported for recent decades. The concomitant P accumulation in soils potentially threatens surface water bodies with eutrophication through diffuse P losses. Here, we demonstrated the applicability of a soil type-independent approach for estimating the degree of P saturation (DPS; a risk parameter of P loss) by a standard method of water-soluble phosphorus (WSP) for two major soil types (Oxisols, Entisols) of the São Francisco catchment in Brazil. Subsequently, soil Mehlich-1P (M1P) levels recommended by Brazilian agricultural institutions were transformed into DPS values. Recommended M1P values for optimal agronomic production corresponded to DPS values below critical thresholds of high risks of P losses (DPS=80%) for major crops of the catchment. Higher risks of reaching critical DPS values due to P accumulation were found for Entisols due to their total sorption capacities being only half those of Oxisols. For complementary information on soil mineralogy and its influence on P sorption and P binding forms, Fourier transformation infrared (FTIR) spectroscopic analyses were executed. FTIR analyses suggested the occurrence of the clay minerals palygorskite and sepiolite in some of the analyzed Entisols and the formation of crandallite as the soil specific P binding form in the investigated Oxisols. Palygorskite and sepiolite can enhance P solubility and hence the risk of P losses. In contrast, the reshaping of superphosphate grains into crandallite may explain the chemical processes leading to previously observed low dissolved P concentrations in surface runoff from Oxisols. To prevent high risk of P losses, we recommend avoiding superficial fertilizer application and establishing environmental thresholds for soil M1P based on DPS. These measures could help to prevent eutrophication of naturally oligotrophic surface waters, and subsequent adverse effects on biodiversity and ecosystem function.

Effects of an Aluminum Sulfate and Ferric Chloride Blend on Poultry Litter Characteristics in Vitro

Previous studies have applied various concentrations of aluminum sulfate and ferric chloride separately to poultry litter to reduce environmental pollution and increase chicken productivity. In the present study, we investigated the effect of using a blend of these 2 chemicals under 5 different treatments: control (no addition), 50 + 50, 25 + 50, 50 + 25, and 25 + 25 g/kg of litter, which consisted of fresh chicken manure (1 kg) and sawdust (4 kg) thoroughly mixed in a 70 × 47 × 43 cm box. NH3 and CO2 volatilizations, pH, electrical conductivity (EC) and moisture content of the poultry litter were assessed weekly up to 6 wk and in the case of total and water-soluble nutrients they were assessed after 1 and 42 d. The control treatment had higher NH3 and CO2 volatilizations than the treated litter throughout the experiment. EC and pH showed an inverse relationship, whereby the control treatment had high pH and low EC values and the treated litter had low pH and high EC values. After 42 d, nitrogen levels were significantly reduced in the control treatment, whereas the 50 + 50 g/kg treatment had the highest content. Conversely, water-soluble phosphorus levels were much lower in the treated poultry litter after 1 and 42 d. A higher ferric chloride concentration (25 + 50 g/kg) in the blend was more effective than a higher aluminum sulfate concentration (50 + 25 g/kg). These findings demonstrate that a combination of aluminum sulfate and ferric chloride may be a useful amendment for reducing NH3 and CO2 volatilizations, pH, and moisture content of poultry litter, which will help in improving poultry productivity, pollution control, and poultry litter fertilizer usage.

Factors that drive zooplankton diversity in Neo-Tropical Savannah shallow lakes

Abstract Zooplankton is an important community in aquatic ecosystems due to its linkage between primary producers and secondary consumers also playing a key role in cycling of organic materials. Aim: Therefore, our objective was to evaluate the effects of physicochemical variables of the water on the diversity of zooplankton community in seven tropical shallow lakes of Brazilian savannah. Methods Zooplankton samples were taken using a bucket and filtered 200 L by a 64 µm-mesh-plankton-net, and preserved for subsequent identification. Water temperature, dissolved oxygen, pH, electrical conductivity, turbidity, chlorophyll-a, ammonium, nitrate, nitrite, total phosphorus, and soluble reactive phosphorus were measured. Results The turbidity (decreases the temperature, luminosity and the system productivity) and ammonium (increases the toxicity) values were the major factors responsible for structuring the zooplankton community. On the other hand, also nitrogen and phosphorus (increase the productivity) are limiting in savannah lentic systems for the zooplankton. The higher α diversity was positively associated with aquatic macrophytes (increase of niches and refuge), whereas lakes with geographic proximity increase the similarity in species composition, decreasing the β diversity. Conclusions We conclude that the deterministic processes (niche theory), due to species have different ecological requirements, are different responses to environmental gradients and increase the diversity in heterogenic lentic systems.

Modification of chemical properties, Cu fractionation and enzymatic activities in an acid vineyard soil amended with winery wastes: A field study

The effects of adding two winery wastes, perlite waste (PW) and bentonite waste (BW), to an acid vineyard soil were assessed using some chemical and biological soil properties in a field study that lasted 18 months. The addition of PW (up to 81 Mg ha−1) had neither significant nor permanent effects on soil characteristics such as the pH, organic matter content or nutrient concentrations, the amounts of copper or zinc, or the electrical conductivity. Moreover, no persistent negative effects were found on the enzymatic activities after PW application. In contrast, soil that was amended with up to 71 Mg BW ha−1 showed increases in its soil pH values, exchangeable potassium and water soluble potassium and phosphorus contents. In addition, it caused significant increases in the electrical conductivity and water-soluble Cu. In addition, the phosphomonoesterase enzymatic activity decreased significantly (up to 28%) in response to the amendment with 71 Mg BW ha−1. These results showed that adding BW and PW to the soil may be a good agronomic practice for recycling these types of wastes. However, in the case of PW, its use as a soil amendment must be performed with caution to control its possible harmful effects.

Effectiveness of combined application of Kodjari phosphate rock, water soluble phosphorus fertilizer and manure in a Ferric Lixisol in the centre west of Burkina Faso

ABSTRACTIncreasing soil phosphorus and organic matter content for crop production while reducing the cost of production are required to facilitate the achievement of green revolution in Africa. Field and pot experiments were laid out during 2012 and 2013 to assess the effects of combined application of Kodjari phosphate rock (PR) and water soluble phosphorus on sorghum yields, P uptake and Lixisol characteristics in the centre west of Burkina Faso. Five P fertilizers treatments (zero P, 100% TSP (triple super phosphate), 100% PR, 50% PR + 50% TSP, 75% PR + 25% TSP) and two cow manure treatments (zero, 5 t ha−1) were tested. In field experiment, 50% PR + 50% TSP was as effective as 100% TSP in increasing sorghum yield above the control by 30% in 2012 and 50% in 2013 and P uptake by 30% in both years. Manure had an additive effect on phosphorus fertilizers in increasing sorghum yields and P uptake. In pot experiment, increases of Ca uptake, soil pH and microbial P were observed with the application of 50% PR + 50% TSP. Our results suggest that formulation of fertilizer combining phosphate rock and mineral P would improve sorghum yields and income of smallholders.

The degree of phosphorus saturation of agricultural soils in Germany: Current and future risk of diffuse P loss and implications for soil P management in Europe

Decades of intensive agricultural production with excessive application of P fertilizer have resulted in the accumulation of P in soils, threatening water bodies in most industrialized countries with eutrophication. In our study, we elucidated the risk of P loss of German agricultural soils by transforming provided monitoring data of plant-available P determined by the calcium-acetate-lactate (PCAL) and double-lactate method (PDL) into the degree of phosphorus saturation (DPS). As water-soluble phosphorus (WSP) is correlated to DPS, we derived a pedotransfer function (PTF) between PCAL and WSP for different soil types. Considering all soils together resulted in WSP=0.1918×PCAL (R2=0.80, n=54). Subsequently, risk parameters DPS and EPC0 were calculated from PCAL and PDL monitoring data (n>337,000) by using the determined PTF and soil type-independent correlations with WSP, as published in an earlier study. Calculated DPS values from monitoring data indicated high risks of dissolved P loss for >76% of German arable soils. Recent suggestions by the Association of German Agricultural Analytical and Research Institutes (VDLUFA) to reduce recommended PCAL levels are crucial for the reduction of P loss risks in the future. The accuracy of predicted DPS and EPC0 values by CAL and other methods used in Europe to estimate plant-available P is limited by the soil type-dependency of these methods. Consequently, we recommend considering WSP as an agri-environmental soil P test across Europe. Our results indicate that a WSP level in soils can be defined that constitutes a reasonable compromise between the securing of agronomic production and the fulfillment of environmental goals.

A Highly Emissive Water-Soluble Phosphorus Corrole.

The synthesis, spectroscopic, and optical properties of the water-soluble phosphorus complex of a 2-sulfonato-10-(4-sulfonatophenyl)-5,15-dimesitylcorrole have been investigated. The compound was prepared by adopting a novel strategy for the corrole sulfonation, leading to the regioselective isomer in an almost quantitative yield. The phosphorus coordination has a key role in determining the corrole substitution pattern, limiting the formation of poly-substituted species, which affected the reaction of the corrole free base. The resulting complex shows excellent optical properties in terms of emission quantum yield, also in polar protic solvents, including water. 31 P NMR spectroscopy in CD3 OD indicates that the P sulfonate complex has been isolated in a hexacoordinated geometry with two different ligands (L1=-OH, L2=-OCH3 ), and it is prone to axial ligand exchange with methanol, with no evidence of intermediate pentacoordinated species. The morphological characterization of thin layers of the P corrole deposited onto an Au(111) surface showed that the addition of an intermediate layer of reduced graphene oxide allows for a better control of corrole aggregation, inducing also transformation of the Au(111) reconstructed surface.

Efficiency of Phosphatases in Mobilization of Native Phosphorus Fractions Under Different Vegetation

The efficiency of acid and alkaline phosphatase toward hydrolysis of different P fractions was studied under fallow, rhizosphere and non-rhizosphere soils of crops, trees and grasses from Aridisol, and forest rhizosphere and non-rhizosphere soils of Inceptisol. Native P of soil was fractioned into four different pools: water-soluble inorganic phosphorus (Pi) and organic phosphorus (Po), NaHCO3 (0.5 M)-extractable Pi and Po, NaOH (0.1 M)-extractable Pi and Po, HCl (1.0 M)-extractable Pi and Po and residual P after digestion to H2O2:H2SO4 (1:4). The decrease in different Po fractions due to the action of both acid and alkaline phosphatase showed 41.3–86.7 % of water-soluble fraction, 50–84.1 % of NaHCO3 fraction, 14.6–25.9 % of NaOH fraction and 8.0–19.2 % of HC1 fraction was hydrolyzed under different vegetation. The rate of organic phosphorus hydrolysis by acid and alkaline phosphatase was initially rapid followed by a gradual declining rate, which was constant after 8 h onwards for acid phosphatase and after 9 h onward till 24 h for alkaline phosphatase. At initial stage (<4 h), the rate of hydrolysis by acid phosphatase was almost doubled than alkaline phosphatase. The result indicates that acid phosphatase was 8.8–13.8 % more efficient as compared to the alkaline phosphatase toward hydrolysis of different soil P fractions, while the residual P fractions were hydrolyzed 17.3 % more by alkaline phosphatase than acid phosphatase. Among the different P fractions, the residual P was most resistant and water soluble and NaHCO3-P was most susceptible to phosphatase enzymes.

Layer-by-layer self-assembly of bisdendrons: An unprecedented route to multilayer thin films

We present an unprecedented route to fabricate multilayer thin films by single component layer-by-layer molecular self-assembly. Tailored water-soluble phosphorus bisdendrons were obtained via core to core assembling of two dendrons bearing anionic groups at one end and quaternizable amino groups at the other end. Adsorption of a 1st bisdendron monolayer on a charged substrate followed by sequential quaternization/deposition of a 2nd layer leads to a stepwise growth of multilayers. By this way, homogeneous multilayer thin films were successfully constructed as confirmed by spectroscopic and microscopic analysis.

Assessing the Contribution of the Environmental Parameters to Eutrophication with the Use of the "PaD" and "PaD2" Methods in a Hypereutrophic Lake.

Lake Pamvotis (Greece) is a shallow hypereutrophic lake with a natural tendency to eutrophication. Several restoration measures were applied, but with no long-term success. To examine the causes for this an Artificial Neural Network (ANN) was created in order to simulate the chlorophyll-a (Chl-a) levels and to investigate the role of the associated environmental parameters. The ANN managed to simulate with good correlation the simulated Chl-a and can be considered as a reliable predictor. The relative importance of the environmental parameters to the simulated Chl-a was calculated with the use of the “Partial Derivatives” (“PaD”) sensitivity method. The water temperature (WT) and soluble reactive phosphorus (SRP) had the highest relative importance, with values of 50% and 17%, respectively. The synergistic effect of the paired parameters was calculated with the use of the “PaD2” algorithm. The SRP-WT paired parameter was the most influential, with a relative contribution of 22%. The ANN showed that Lake Pamvotis is prone to suffer the effects of climatic change, because of the major contribution of WT. The ANN also revealed that combined nutrients reduction would improve water quality status. The ANN findings can act as an advisory tool regarding any restoration efforts.

Effects of Organic Acids on Availability of Phosphate and Growth of Corn in Phosphate and Salts Accumulated Soil

Accumulated Phosphate can be released by ligand exchange reaction of organic acids. The objective of this study was to evaluate effects of the organic acids on the availability of phosphate and the growth of crop in phosphate and salts accumulated soil. Soil samples were collected from farmer’s plastic film house. Available phosphate and electrical conductivity of soil were 3,005 mg kg -1 and 16.63 dS m -1 which were 6 and 8 times higher than the optimum range of soil for crop growth, respectively. Corns were cultivated in pots for 2 months. Treatments were no treatment (control), phosphate fertilizer (P), citric acid (CA) 1, 5, 10 mM, and oxalic acid (OA) 1, 5, 10 mM. Water soluble phosphorus, available phosphate, corn growth and uptake were determined after cultivation. Results showed that organic acids increased water soluble phosphorus and available phosphate. For the level of 10 mM, the order of effectiveness of organic acids for water soluble P was citric acid (44%) > oxalic acid (32%). Height and dry weight of corns were increased significantly by the treatment of citric acid 1 and 5 mM. Also, corn absorbed more phosphorus, nitrogen, potassium, calcium and magnesium in the treatment of citric acid 1 mM than these of other treatments. Even though phosphate availability of soil was enhanced by addition of citric acid 10 mM, the growth of corns decreased because high concentration of citric acid caused salt damage by increasement of electrical conductivity. Thus, the citric acid of 1 mM has the potential to improve the availability of phosphate and the healthy growth of corns.

Estimating Streambank Phosphorus Loads at the Watershed Scale with Uncertainty Analysis Approach

AbstractStreambank nutrient loading rates are a growing concern within many watersheds. Only a few studies exist on streambank soil chemistry and phosphorus (P) concentrations, spatial distributions in watersheds, and P loading rates with a consideration of the potential uncertainty associated with the estimates. More so, limited studies compare streambank P loading for streams within similar watersheds and with similar land use and management. The objectives of this research included (1) quantifying the magnitude and spatial distribution of soil pH, electrical conductivity (EC), total P concentration, dissolved P concentration, and the degree of P saturation of streambanks in a watershed; (2) quantifying whether water-soluble phosphorus (WSP) and total phosphorus (TP) loads entering the stream from streambanks are significant based on a combined mass balance and uncertainty analysis approach; and (3) contrasting streambank P concentrations and loadings between two similar streams: Spavinaw Creek (SC) ver...

The Release of Phosphorus from Sediment to Lake Water Induced by Cyanobacterial Blooms and Phosphorus Removal by Cell Harvesting

ABSTRACTTo investigate the influence of cyanobacterial blooms on phosphorus release across the sediment-water interface and the repair mechanisms of internal phosphorus by harvesting of cyanobacteria, a series of laboratory-based experiments were conducted. Microcystis aeruginosa was cultured in phosphorus-free BG11 medium containing sediments from different eutrophic water bodies. The culture solution was removed and the same volume of phosphorus-free BG11 medium was put into the system until the M. aeruginosa had died. Cyanobacterial density, pH and different phosphorus forms in culture solution and sediments after culturing M. aeruginosa were determined. The results showed that cyanobacterial blooms stimulated phosphorus release from the sediment to the overlying water for the sediment in the eutrophic water body. Phosphorus released from the sediment was assimilated by M. aeruginosa and no increase in water-soluble phosphorus was observed. Cyanobacterial blooms caused sharp increases in different phosphorus fractions of sediment with the exception of the phosphorite-type (Ca10-P). Cyanobacterial blooms decomposed iron minerals in the sediment yet there was no clear evidence to demonstrate a positive correlation between water-soluble phosphorus in the overlying water and iron bound phosphorus (Fe-P) in the sediment. These results indicated that harvesting of cyanobacteria might be a suitable method to eradicate cyanobacterial blooms and to limit phosphorus pollution under controlled external nutrient loads.

Evaluation of phosphorus distribution and bioavailability in sediments of a subtropical wetland reserve in southeast China

The phosphorus (P) fractions and bioavailable P in the sediments from the Quanzhou Bay Estuarine Wetland Nature Reserve were investigated using chemical extraction methods for the first time to study the distribution and bioavailability of P in the reserve sediments. A hypothesis was presented suggesting that the bioavailable P in the sediments could be evaluated using the P fractions. The total phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), non-apatite phosphorus (NAIP), and apatite phosphorus (AP) contents in the sediments were in the ranges of 303.87–761.59mgkg−1, 201.22–577.66mgkg−1, 75.83–179.16mgkg−1, 28.86–277.90mgkg−1, and 127.36–289.94mgkg−1, respectively. The water soluble phosphorus (WSP), readily desorbable phosphorus (RDP), algal available phosphorus (AAP), and NaHCO3 extractable phosphorus (Olsen-P) contents in the sediments were in the ranges of 0.58–357.17mgkg−1, 80.77–586.75mgkg−1, 1.09–24.12mgkg−1, and 54.96–676.82mgkg−1, respectively. The correlation analysis results showed that the NAIP was the major component of the bioavailable P and that the impact of the AP on the bioavailable phosphorus may be minimal. Due to the low TP content in the sediments of the Quanzhou Bay Estuarine Wetland Nature Reserve, the potential pollution risks of P in the sediments may not be very high. The results also show that the bioavailable P concentrations in the sediments of the Quanzhou Bay Estuarine Wetland Nature Reserve could not be evaluated by measuring the P fractions and that the hypothesis was untenable.

Regional distribution and temporal changes in density and biomass of Didymosphenia geminata in two Mediterranean river basins

This study aimed to strengthen the knowledge of Didymosphenia geminata distribution in Spain, and to determine which environmental variables were related to its regional distribution and temporal changes in growth and production in two Ebro River tributary basins (Iregua and Najerilla¸ La Rioja Region). Living cells of D. geminata were present in 40% of the studied sites of both basins but only four of the sites developed massive growths. The diatom is widely distributed only in mountain areas of both basins (above 690 masl), which have low average annual air temperature (8.27 ± 0.28 oC) and low water Soluble Reactive Phosphorus (SRP) concentration (average value 0.024 ± 0.007 ppm). Massive growths occur in sites with high light intensity, hydrological regulation of river flow and the lowest measured SRP concentrations (below 0.018 ppm SRP). We carried out an intensive spatio-temporal survey in the Lumbreras River (Iregua basin), where the first massive growth was detected in La Rioja Region. The highest cell densities (1.6 × 105 cells cm−2) and biomass values (480 gDWm−2) were recorded in late summer. An increase in solar radiation and slight rise in water temperature were associated with an increase in biomass over time, but always in waters with low SRP concentration, the key factor that enhances massive growth development. The alteration of the natural streamflow in the Lumbreras River by the Pajares Reservoir and the fact that water is discharged from the hypolimnion (which decreases the summer river water temperature) are important factors in understanding why D. geminata shows such an increase in biomass in a Mediterranean river. This paper provides new insights into the importance of different factors controlling D. geminata massive proliferations in the Mediterranean climate zone, where it is assumed that the species should not develop such massive growths, compared to temperate zones where the majority of previous studies have been carried out. We suggest that changing the reservoir management strategy would be a very important contribution to the control of such significant developments.

Phosphate-solubility and phosphatase activity in Gangetic alluvial soil as influenced by organophosphate insecticide residues

An experiment was conducted under laboratory conditions to investigate the effect of four organophosphate insecticides, viz. monocrotophos, profenophos, quinalphos and triazophos at their field application rates (0.75, 1.0, 0.5 and 0.6kga.i.ha−1, respectively), on the growth and activities of phosphate solubilizing microorganisms in relation to availability of insoluble phosphates in the Gangetic alluvial soil of West Bengal, India. The proliferation of phosphate solubilizing microorganisms was highly induced with profenophos (38.3%), while monocrotophos exerted maximum stimulation (20.8%) towards the solubility of insoluble phosphates in soil. The phosphatase activities of the soil (both acid phosphatase and alkaline phosphatase) were significantly increased due to the incorporation of the insecticides in general, and the augmentation was more pronounced with quinalphos (43.1%) followed by profenophos (27.6%) for acid phosphatase, and with monocrotophos (25.2%) followed by profenophos (16.1%) for alkaline phosphatase activity in soil. The total phosphorus was highly retained by triazophos (19.9%) followed by monocrotophos (16.5%), while incorporation of triazophos and quinalphos manifested greater availability of water soluble phosphorus in soil.