Phosphorus Dynamics

Zr-Pillared K10 (Zr-K10) was synthesized by using Montmorillonite K10 clay. Zr-pillared K10 based superabsorbent (Zr-PILC-SA) was synthesized by using Zr-pillared-montmorillonite K10 via graft copolymerization reaction of acrylic acid (AA). After preparation of the films of hydrogels of Zr-pillared K10, swelling studies were performed in distilled water and different pH values at room temperature to investigate swelling behavior of pillared clay based superabsorbent films. It was also obtained that Zr-K10 based superabsorbent was pH dependent and showed a reversible swelling behavior. The swelling behavior of Zr-K10-SA was increasing by decreasing amount of Zr-K10 in the hydrogel. SEM, FTIR and XRD analysis were conducted for further characterization of the Zr-PILC-SA. FTIR analyses lead to ester formation between Zr-K10 and SA. XRD revealed the morphology of the superabsorbent was exfoliated and the layers of clay dispersed on the composite.

Superabsorbents hydrogel were prepared by using Zr pillared-montmorillonite KSF by graft copolymerization reaction of acrylic acid (AA). Swelling behavior of pillared clay based superabsorbent films in distilled water and different pH values were investigated at room temperature. It was also obtained that pillared clay based superabsorbents were pH dependent and showed a reversible swelling behavior. Water absorbency of pillared clay based superabsorbent (PILC-SA) was increased by decreasing pillared clay amount in the network of the superabsorbents. SEM and XRD analysis were conducted for further characterization of the PILC-SA. XRD revealed the basal spacing of the pillared clays before and after in-situ incorporation indicating that the morphology of the superabsorbent was exfoliated and the layers of clay dispersed on the composite.

Superabsorbents hydrogel were prepared by using Zr pillared- montmorillonite KSF by graft copolymerization reaction of acrylic acid (AA).  Swelling behavior of pillared clay based superabsorbent films in distilled water and different pH values were investigated at room temperature. It was also obtained that pillared clay based superabsorbents were pH dependent and showed a reversible swelling behavior. Water absorbency of pillared clay based superabsorbent (PILC-SA) was increased by decreasing pillared clay amount in the network of the superabsorbents. SEM and XRD analysis were conducted for further characterization of the PILC-SA. XRD revealed the basal spacing of the pillared clays before and after in-situ incorporation indicating that the morphology of the superabsorbent was exfoliated and the layers of clay dispersed on the composite. 

Zr- Pillared K10 (Zr-K10) was synthesized by using Montmorillonite K10 clay. Zr- pillared K10 based superabsorbent (Zr-PILC-SA) was synthesized by using Zr- pillared- montmorillonite K10 via graft copolymerization reaction of acrylic acid (AA). After preparation of the films of hydrogels of Zr- pillared K10, swelling studies were performed in distilled water and different pH values at room temperature to investigate swelling behavior of pillared clay based superabsorbent films. It was also obtained that Zr-K10 based superabsorbent was pH dependent and showed a reversible swelling behavior. The swelling behavior of Zr-K10-SA was increasing by decreasing amount of Zr-K10 in the hydrogel. SEM, FTIR and XRD analysis were conducted for further characterization of the Zr-PILC-SA. FTIR analyses lead to ester formation between Zr-K10 and SA. XRD revealed the morphology of the superabsorbent was exfoliated and the layers of clay dispersed on the composite.  

The southeast subtropical Pacific Ocean was sampled along a zonal transect between the coasts of Chile and Easter Island. This remote area of the world's ocean presents strong gradients in physical (e.g., temperature, density and light), chemical (e.g., salinity and nutrient concentrations) and microbiological (e.g., cell abundances, biomass and specific growth rates) properties. The goal of this study was to describe the phosphorus (P) dynamics in three main ecosystems along this transect: the upwelling regime off the northern Chilean coast, the oligotrophic area associated with the southeast subtropical Pacific gyre and the transitional area in between these two biomes. We found that inorganic phosphate (Pi) concentrations were high and turnover times were long (>210 nmol l À1 and >31 d, respectively) in the upper water column, along the entire transect. Pi uptake rates in the gyre were low (euphotic layer integrated rates were 0.26 mmol m À2 d À1 in the gyre and 1.28 mmol m À2 d À1 in the upwelling region), yet not only driven by decreases in particle mass or cell abundance (particulate P-and cell-normalized Pi uptake rates in the euphotic layer were $1-4 times and $3-15 times lower in the gyre than in the upwelling, respectively). However these Pi uptake rates were at or near the maximum Pi uptake velocity (i.e., uptake rates in Pi amended samples were not significantly different from those at ambient concentration: 1.5 and 23.7 nmol l À1 d À1 at 50% PAR in the gyre and upwelling, respectively). Despite the apparent Pi replete conditions, selected dissolved organic P (DOP) compounds were readily hydrolyzed. Nucleotides were the most bioavailable of the DOP substrates tested. Microbes actively assimilated adenosine-5 0triphosphate (ATP) leading to Pi and adenosine incorporation as well as Pi release to the environment. The southeast subtropical Pacific Ocean is a Pi-sufficient environment, yet DOP hydrolytic processes are maintained and contribute to P-cycling across the wide range of environmental conditions present in this ecosystem.

Phosphorus (P) is an essential element for phytoplankton growth, and in recent years our understanding of P use based on kinetics has been overturned with new knowledge of the complexity of P utilization. However, much of this knowledge is based on culture studies with individual species. Our objective was to measure the effect of dissolved inorganic P (DIP) concentrations on DIP uptake rates by phytoplankton, in the context of seasonal phytoplankton succession in a large monomictic, DIP-depauperate lake. We demonstrated an inverse relationship between surface DIP concentration and DIP uptake rate, with substantially higher uptake rates occurring under thermally stratified, DIP-depauperate conditions. The combination of surface water DIP concentration and water temperature explained 50.3% of the variation in uptake rates. DIP concentration explained the majority of variation, with a concentration of 4.75 µg DIP l -1 appearing to be a transition between low-and high-affinity uptake. Variability below 4.75 µg DIP l -1 was further explained by water temperature. High-affinity DIP uptake was most common when Cyanobacteria dominated the phytoplankton assemblage. We validated our field results by conducting a DIP starvation study on an isolate of a dominant cyanobacterium, Cylindrospermopsis raciborskii. High-affinity uptake was demonstrated as the culture became progressively starved of P. Our findings indicate that rapid DIP scavenging via high-affinity uptake is advantageous under DIP-depauperate conditions during the summer-stratification period. It may also contribute to the switch from diatom/cryptophyte/chlorophyte dominance to cyanobacterial dominance in summer. This study also has implications for phytoplankton-nutrient models, which typically do not incorporate high-affinity P uptake.

Natural polymer-based hydrogels are of great interest to research community owing to their inherent characters of environment friendliness and biodegradability. Current work aims to synthesize lignosulfonate grafted sodium acrylate hydrogel (LS-g-SAH) and investigate its application in urea release behaviour. The hydrogel has been characterized by different techniques. The release kinetics has been analyzed by using a UV-visible spectrophotometer. The optimized composition of lignosulfonate, KPS, and N,N'-MBA has shown the highest water absorbency of 560 g g-1 in distilled water. The equilibrium swollen LS-g-SAH 12 hydrogel has slowly released 60% of loaded urea in 24 h and followed first-order release kinetics. Soil treatment with hydrogel has shown a significant effect in reducing the water evaporation rate. It also improved the seed germination and average height of wheatgrass. The synthesized LS-g-SAH is, thus, expected to have potential application in modern sustainable agriculture.

The southeast subtropical Pacific Ocean was sampled along a zonal transect between the coasts of Chile and Easter Island. This remote area of the world's ocean presents strong gradients in physical (e.g., temperature, density and light), chemical (e.g., salinity and nutrient concentrations) and microbiological (e.g., cell abundances, biomass and specific growth rates) properties. The goal of this study was to describe the phosphorus (P) dynamics in three main ecosystems along this transect: the upwelling regime off the northern Chilean coast, the oligotrophic area associated with the southeast subtropical Pacific gyre and the transitional area in between these two biomes. We found that inorganic phosphate (Pi) concentrations were high and turnover times were long (>210 nmol l À1 and >31 d, respectively) in the upper water column, along the entire transect. Pi uptake rates in the gyre were low (euphotic layer integrated rates were 0.26 mmol m À2 d À1 in the gyre and 1.28 mmol m À2 d À1 in the upwelling region), yet not only driven by decreases in particle mass or cell abundance (particulate P-and cell-normalized Pi uptake rates in the euphotic layer were $1-4 times and $3-15 times lower in the gyre than in the upwelling, respectively). However these Pi uptake rates were at or near the maximum Pi uptake velocity (i.e., uptake rates in Pi amended samples were not significantly different from those at ambient concentration: 1.5 and 23.7 nmol l À1 d À1 at 50% PAR in the gyre and upwelling, respectively). Despite the apparent Pi replete conditions, selected dissolved organic P (DOP) compounds were readily hydrolyzed. Nucleotides were the most bioavailable of the DOP substrates tested. Microbes actively assimilated adenosine-5 0triphosphate (ATP) leading to Pi and adenosine incorporation as well as Pi release to the environment. The southeast subtropical Pacific Ocean is a Pi-sufficient environment, yet DOP hydrolytic processes are maintained and contribute to P-cycling across the wide range of environmental conditions present in this ecosystem.

Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the performance of alternative monitoring strategies in streams under contrasting climate-driven flow regimes. We compared a set of paired streams draining lowland microcatchments under temperate climate and stable discharge conditions (Denmark) and under subtropical climate and flashy conditions (Uruguay). We applied two alternative nutrient sampling programs (high-frequency composite sampling and low-frequency instantaneous-grab sampling) and estimated the contribution derived from point and diffuse sources fitting a source apportionment model. We expected to detect a pattern of higher total and particulate phosphorus export from diffuse sources in streams in Uruguay streams, mostly as a consequence of higher variability in flow regime (higher flashiness). Contrarily, we found a higher contribution of dissolved P in flashy streams. We did not find a notably poorer performance of the low-frequency sampling program to estimate P exports in flashy streams compared to the less variable streams. We also found signs of interaction between climate/hydrology and land use intensity, in particular in the presence of point sources of P, leading to a bias towards underestimation of P in hydrologically stable streams and overestimation of P in flashy streams. Based on our findings, we suggest that the evaluation and use of more accurate monitoring methods, such as automatized flow-proportional water samplers and automatized bankside analyzers, should be prioritized whenever logistically possible. However, it seems particularly relevant in currently flashy systems and also in systems where climate change predictions suggest an increase in stream flashiness.

Slow release fertiliser (SRF) is one of the important materials, which provides benefit to the green chemistry and green chemical engineering in the agricultural applications. Various modifications on porous materials and super-adsorbent based composites have been developed to act as the host for fertilisers including nitrogen- based fertilisers. In this work, a scheme of organic nitrogen compound, methenamine, was used as the SRF compound and in order to increase the effectivity of the releasing nitrogen, immobilisation of the compound in montmorillonite clays has been conducted. Methenamine immobilised montmorillonite at varied methenamine contents (20 mmol/g; 50 mmol/g and 100 mmol/g) was prepared using intercalation process by employing microwave irradiation method. Study on the change of crystallinity and chemical structure of the composite was performed by x-ray diffraction (XRD) analysis, gas sorption analyser, and electronic microscope analysis. The kinetic study of the nitr...

A major problem for 21st century agriculture is the prospect of P scarcity. Adsorption of PO 4 on the soil's solid phase is the primary mechanism regulating P availability. Release of citrate by roots is generally thought to increase the availability of P, which in turn improves P acquisition by plants. However, the interaction between citrate and PO 4 remains poorly understood in soils and conflicting results are found in the literature. Here modeling is used to investigate the effects of citrate adsorption on P availability in a chromic cambisol, a luvisol and two ferralsols over a range of soil pH values. The effect of different levels of exchangeable Ca, soil organic C (SOC), dissolved organic C (DOC) and PO 4 fertilization were also tested in order to cover a wider range of environmental conditions. Results showed that the competition of citrate for PO 4 binding sites was not the only mechanism regulating P availability. Citrate adsorption can also increase PO 4 adsorption through electrostatic interactions with adsorbed Ca 2+ ions and actively reduce P availability. More precisely, it was found that the addition of 10 lmol citrate kg À1 soil decreased P availability in both chromic cambisol and luvisol. The same trend was predicted by the model with 100 lmol of citrate kg À1 soil in the chromic cambisol, whereas available P was found to increase in the luvisol. In contrast, the addition of citrate at these two concentrations always increased P availability in the two ferralsols. Increasing exchangeable Ca further decreased P availability in the chromic cambisol and luvisol, while it further increased available P in ferralsols. Additional sensitivity tests showed that DOC concentration had little influence on these results. In contrast, increasing SOC concentration massively counteracted the deleterious influence of citrate in chromic cambisol, while the effect was amplified in luvisol. In ferralsols, it was mainly observed that the increase of SOC further promoted P availability. To conclude, it was found that citrate can either increase or decrease P availability in soil, depending mainly on the occurrence of 2:1 clay minerals and on the concentrations of citrate, adsorbed Ca, and soil organic C. Special attention should, therefore, be given to possible adverse effects of rhizosphere management for improved P nutrition.

In the permanent experimental site, started in 1988, in the farm of Soils and Water Department, Assiut University, ground corn stover and ground clover straw (CR) were incorporated in the surface (0.00-0.25 m) soil layer at an average rates of 5.45 ton fed-1 year-1 and 3.71 ton fed-1 year-1 , respectively. Six rates of fertilizer P fertilization (0, 100, 200, 300, 400, and 500 kg superphosphate fed-1) were also applied each season. The results showed that the amount of Olsen's Pt required to give the maximum P uptake in grains was equal to 46.8 and 51.4 ppm P in P fertilization management without crop residues (-CR) and with crop residues (+CR), respectively. In both P fertilization managements (-CR and +CR), P application significantly (p≤0.05) and curvilinearly increased the dry matter accumulation and grain yield of corn plants. The P apparent balances showed that in both P fertilization managements (with and without CR), P fertilization rate of 62 kg P2O5 fed-1 (400 kg SP fed-1 each growth season) and higher were more than the requirements of corn-clover cropping system, and resulted in accumulation of P in soil. Phosphorous adsorption in the surface layer of soil treated with all levels of mineral P fertilizer appeared to be decreased with incorporation of crop residues into soil

The southeast subtropical Pacific Ocean was sampled along a zonal transect between the coasts of Chile and Easter Island. This remote area of the world's ocean presents strong gradients in physical (e.g., temperature, density and light), chemical (e.g., salinity and nutrient concentrations) and microbiological (e.g., cell abundances, biomass and specific growth rates) properties. The goal of this study was to describe the phosphorus (P) dynamics in three main ecosystems along this transect: the upwelling regime off the northern Chilean coast, the oligotrophic area associated with the southeast subtropical Pacific gyre and the transitional area in between these two biomes. We found that inorganic phosphate (Pi) concentrations were high and turnover times were long (>210 nmol l À1 and >31 d, respectively) in the upper water column, along the entire transect. Pi uptake rates in the gyre were low (euphotic layer integrated rates were 0.26 mmol m À2 d À1 in the gyre and 1.28 mmol m À2 d À1 in the upwelling region), yet not only driven by decreases in particle mass or cell abundance (particulate P-and cell-normalized Pi uptake rates in the euphotic layer were $1-4 times and $3-15 times lower in the gyre than in the upwelling, respectively). However these Pi uptake rates were at or near the maximum Pi uptake velocity (i.e., uptake rates in Pi amended samples were not significantly different from those at ambient concentration: 1.5 and 23.7 nmol l À1 d À1 at 50% PAR in the gyre and upwelling, respectively). Despite the apparent Pi replete conditions, selected dissolved organic P (DOP) compounds were readily hydrolyzed. Nucleotides were the most bioavailable of the DOP substrates tested. Microbes actively assimilated adenosine-5 0triphosphate (ATP) leading to Pi and adenosine incorporation as well as Pi release to the environment. The southeast subtropical Pacific Ocean is a Pi-sufficient environment, yet DOP hydrolytic processes are maintained and contribute to P-cycling across the wide range of environmental conditions present in this ecosystem.

Dissolved inorganic phosphate (henceforth referred to as P i) is an essential nutrient for growth and metabolic functioning (e.g., nucleic acids, lipids, energy-transferring molecules) of living organisms, including marine microbial communities. P i can be limiting for growth in many lakes and in some oligotrophic areas of the world ocean, where nanomolar concentrations are measured (Björkman et al. 2000; Wu et al. 2000; Moutin et al. 2002; Van Den Broeck et al. 2004). Measuring P i uptake fluxes through different compartments of planktonic communities permits both to determine the main actors responsible for the bulk P fluxes and to assess the taxon-specific response of aquatic microorganisms to fluctuating P i concentrations. This approach was developed primarily using size fractionation with different membrane porosities (e.g.,

Slow release fertiliser (SRF) is one of the important materials, which provides benefit to the green chemistry and green chemical engineering in the agricultural applications. Various modifications on porous materials and super-adsorbent based composites have been developed to act as the host for fertilisers including nitrogen- based fertilisers. In this work, a scheme of organic nitrogen compound, methenamine, was used as the SRF compound and in order to increase the effectivity of the releasing nitrogen, immobilisation of the compound in montmorillonite clays has been conducted. Methenamine immobilised montmorillonite at varied methenamine contents (20 mmol/g; 50 mmol/g and 100 mmol/g) was prepared using intercalation process by employing microwave irradiation method. Study on the change of crystallinity and chemical structure of the composite was performed by x-ray diffraction (XRD) analysis, gas sorption analyser, and electronic microscope analysis. The kinetic study of the nitr...

Introduction: Laguna Cartagena (LC), a wetland in Lajas, Puerto Rico, has been negatively impacted by nutrients, mainly phosphorus run-off from agricultural activities until the end of sugar cane cultivation in the late 1900s.  This led to P concentration remain high at hypereutrophic state that was irremediable even after a 5-fold reduction in source water nutrient concentration. Objective: The main goal of this research paper is to apply two different mathematical approaches to assess the eutrophication level of a wetland in Puerto Rico. Method:   Grey Cluster Method (GCM) was used to classify LC’s eutrophic state by applying the International and Chinese trophic standards and two parameters, total phosphorous (TP) and total nitrogen (TN).  Mean TP and TN from LC consolidated bottom substrate and flocculence samples were used to classify LC.  To address whether LC can recover, soluble reactive phosphorus (SRP) and TP from LC inlet, outlet and center water samples were used to mode...

Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the performance of alternative monitoring strategies in streams under contrasting climate-driven flow regimes. We compared a set of paired streams draining lowland microcatchments under temperate climate and stable discharge conditions (Denmark) and under subtropical climate and flashy conditions (Uruguay). We applied two alternative nutrient sampling programs (high-frequency composite sampling and low-frequency instantaneous-grab sampling) and estimated the contribution derived from point and diffuse sources fitting a source apportionment model. We expected to detect a pattern of higher total and particulate phosphorus export from diffuse sources in streams in Uruguay streams, mostly as a consequence of higher variability in flow regime (higher flashiness). Contrarily, we found a higher contribution of dissolved P in flashy streams. We did not find a notably poorer performance of the low-frequency sampling program to estimate P exports in flashy streams compared to the less variable streams. We also found signs of interaction between climate/hydrology and land use intensity, in particular in the presence of point sources of P, leading to a bias towards underestimation of P in hydrologically stable streams and overestimation of P in flashy streams. Based on our findings, we suggest that the evaluation and use of more accurate monitoring methods, such as automatized flow-proportional water samplers and automatized bankside analyzers, should be prioritized whenever logistically possible. However, it seems particularly relevant in currently flashy systems and also in systems where climate change predictions suggest an increase in stream flashiness.

Introduction: Laguna Cartagena (LC), a wetland in Lajas, Puerto Rico, has been negatively impacted by nutrients, mainly phosphorus run-off from agricultural activities until the end of sugar cane cultivation in the late 1900s.  This led to P concentration remain high at hypereutrophic state that was irremediable even after a 5-fold reduction in source water nutrient concentration. Objective: The main goal of this research paper is to apply two different mathematical approaches to assess the eutrophication level of a wetland in Puerto Rico. Method:   Grey Cluster Method (GCM) was used to classify LC’s eutrophic state by applying the International and Chinese trophic standards and two parameters, total phosphorous (TP) and total nitrogen (TN).  Mean TP and TN from LC consolidated bottom substrate and flocculence samples were used to classify LC.  To address whether LC can recover, soluble reactive phosphorus (SRP) and TP from LC inlet, outlet and center water samples were used to mode...

Relative to areas under canopy, the soils in forest gaps receive more irradiance and rainfall (snowfall); this change in microclimate induced by forest gaps may influence the release of carbon (C) and nutrients during litter decomposition. However, great uncertainty remains about the effects of forest gaps on litter decomposition. In this study, we incubated foliar litters from six tree and shrub species in forest gaps and canopy plots and measured the release of C, nitrogen (N) and phosphorus (P) in different snow cover periods in an alpine forest from 2012 to 2016. We found that N was retained by 24-46% but that P was immediately released during an early stage of decomposition. However, forest gaps decreased litter N retention, resulting in more N and P being released from decomposing litters for certain species (i.e., larch, birch and willow litters). Moreover, the release of C and nutrients during litter decomposition stimulated by forest gaps was primarily driven by warmer soil temperature in this high-altitude forest. We conclude that gap formation during forest regeneration may accelerate C turnover and nutrient cycling and that this stimulation might be regulated by the litter species in this seasonally snow-covered forest.

Relative to areas under canopy, the soils in forest gaps receive more irradiance and rainfall (snowfall); this change in microclimate induced by forest gaps may influence the release of carbon (C) and nutrients during litter decomposition. However, great uncertainty remains about the effects of forest gaps on litter decomposition. In this study, we incubated foliar litters from six tree and shrub species in forest gaps and canopy plots and measured the release of C, nitrogen (N) and phosphorus (P) in different snow cover periods in an alpine forest from 2012 to 2016. We found that N was retained by 24-46% but that P was immediately released during an early stage of decomposition. However, forest gaps decreased litter N retention, resulting in more N and P being released from decomposing litters for certain species (i.e., larch, birch and willow litters). Moreover, the release of C and nutrients during litter decomposition stimulated by forest gaps was primarily driven by warmer soil temperature in this high-altitude forest. We conclude that gap formation during forest regeneration may accelerate C turnover and nutrient cycling and that this stimulation might be regulated by the litter species in this seasonally snow-covered forest.

Background and aims The characterisation of plant-available phosphorus (P) pools and the assessment of the microbial community in the rhizosheath of cover crops can improve our understanding of plant–microbe interactions and P availability. Methods Mustard (Sinapis alba), phacelia (Phacelia tanacetifolia) and buckwheat (Fagopyrum esculentum) were grown as cover crops before soybean (Glycine max) in an on-farm experiment on a soil low in available P in southwest Germany. The cycling of P through the cover crop biomass and the enzyme-availability of organic P (Porg) pools in the cover crop rhizosheath were characterised. The soil microbial community (PLFA), activity (acid and alkaline phosphomonoesterase, as well as phosphodiesterase), and microbial P were assessed. The abundance of 16S-rRNA and phoD, coding for alkaline phosphomonoesterase in bacteria, were quantified using real-time qPCR. Results Mustard contained the greatest amount of P in its large biomass. In the rhizosheath of ...

Use of innovative nano clay polymer composite (NCPC) superabsorbent was explored particularly to ameliorate moisture stress condition under rainfed ecosystem. NCPC were synthesized by polymerization reaction with 10% acrylic acid, acrylamide, 0.9% ammonium per sulphate as initiator, 0.12% N, N′methylene bis acrylamide loaded with 10% kaolinite clay at 65C reaction temperature in presence of inert nitrogen gas. The water sorption was found maximum (131.25 g H2O/g NCPC) when kaolinite clay was modified by hot water FYM extract irrespective of amount of loaded phosphorus in NCPC (treatment 15 & 16) as compared to pure clay 90.04 g H2O/g NCPC without any modification (T14). The average water desorption pattern was also found to be conducive when clay was modified by hot water FYM extract. The rate kinetics for water sorption and desorption was studied under different innovative modified NCPC. The present study revealed that when NCPC added in alluvial soil it helps to maintain soil mois...

Atomic force microscopy (AFM) was applied to small clay particles of illite/smectite from North Sea Jurassic rock, which is the most important source rock for North Sea oil. The clay is dispersed in water and a drop is then dried on graphite or mica. The images show flat particles with areas from 1000 to 30000 nm 2 and sides of equal length. Details of the surface topography of the illite/smectite particles can be imaged and it is possible to resolve both the distance between unit-cells (0.51 nm) and the distance between oxygen atoms (0.3 nm). Systematic thickness measurements show that the particles are 2 to 4 nm thick on average. The measurements also showed that the material contains 1 nm thick single silicate 2: l layers. Information about the thickness, size and surface structure of mixed layers of illite/smectite can provide new insight into their formation.

Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of P from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the performance of alternative monitoring strategies in streams under contrasting climate-driven flow regimes. We compared a set of paired streams draining lowland micro-catchments under temperate climate and stable discharge conditions (Denmark) and under sub-tropical climate and flashy conditions (Uruguay). We applied two alternative nutrient sampling programs (high frequency composite sampling and low frequency instantaneous-grab sampling) and estimated the contribution derived from point and diffuse sources fitting a source apportionment model. We expected to detect a pattern of higher total and particulate phosphorus export from diffuse sources in streams in Uruguay streams, mostly as a consequence of hig...

Water sorption capacity is an important characteristic for nano clay composite (NCC) super absorbents especially when used under rainfed condition. The Zn coated nano clay composite cross-linked polyacrylamides polymers were synthesized by polymerization reaction with 10% acrylic acid, acrylamide, 0.9% ammonium persulphate as initiator, 0.12% N, N/ methyl biscrylate as cross linker loaded with 8% benitonite clay and 10 % Zn citrate at 650C reaction temperature. The water absorbency of product had 165.7 g/g in tap water, 183.0 g/g in distilled water and 74.3 g/g in 1% NaCl solution. Water-holding capacity of the soil with NCC was 8.5% more as compared to original soil.

Superabsorbent polymers are used in agriculture for the purpose of increasing water use efficiency in arid and semiarid regions. In this research two kinds of superabsorbent polymers, Super AB A200 and Herbosorb were used on sandy soils of Karkhe Noor river bank near Hamidieh. The effect of 5 concentration levels of 0.3, 0.6, 0.8, 2 and 4 grams per kilogram of soil in 3 replications was studied on the parameters of soil moisture characteristic curve using RETC program and Rosetta database. It was observed that fitting of the data to the RETC model was better compared to Rosetta. Statistical analysis of the research results show that for sandy soils in these experiments there was a significant difference at one percent level for all the polymers used and the control treatment at suctions of 0.3, 1, 3, 5 and 15 bars. On the other hand for the different concentration levels of 4, 2, 0.8, 0.6 and 0.3 g/kg soil, volumetric soil moisture content showed a significant difference at one percent level. Among the superabsorbents used A200 with application rate of 4 g/kg soil resulted in the highest effect. Soil available water for plant use showed an increase compared to the control treatment. It was finally concluded that the application of 4 gram Super AB A200 and Herbosorb per kilogram soil increased soil available water about 350 and 320 percent respectively.

Conservation agricultural practices has received wide acceptance among the farmers in Indo Gangetic Plains (IGPs) of India as it ensures efficient land utilization, improves soil fertility and provide additional income (Sharma and Sharma, 2004; Meena et al., 2015). According to FAO (2008), conservation agriculture (CA) is “a concept for resource-saving agricultural crop production that strives to achieve acceptable profits together with high and sustained production levels while concurrently International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 7 Number 01 (2018) Journal homepage: http://www.ijcmas.com

A field experiment was conducted at the experimental site of Faculty of Agriculture of Suez Canal University, Ismailia, Egypt, to evaluate the effect of hydrogel addition on tomato (Solanum lycopersicum L.) growth and some soil chemical properties. The experiment was laid out in a randomized complete block design having six treatments with three replicates as follow: control, two hydrogel levels (HG1, 2 g plant -1 and HG2, 4 g plant ), recommended fertilizers for tomato (F) and combination of hydrogel and half amounts of recommended fertilizers (HG1+0.5 F and HG2+0.5 F). The obtained results showed that hydrogel application to plants with 4 g hydrogel + half the recommended amount of fertilizer (HG2+0.5 F) enhanced nitrogen (N), phosphorus (P) and potassium (K) content of fruits. The highest value of root dry weight was obtained with the treatment (HG1+0.5 F). Also, the highest dry weight of the shoots was in the case of treatments (HG1+0.5 F) and (HG2+0.5 F). The highest weight of ...

A series of freeze-thawed, polyvinyl alcohol nanocomposite hydrogels were prepared using various loading levels (0-15 wt%) of hydrophilic natural Na-montmorillonite nanoclay. The morphology of nanocomposite hydrogels, their dehydration kinetics at different temperatures and the effect of Na-montmorillonite on the gelation process were investigated. The results showed a partially exfoliated morphology for the prepared nanocomposite hydrogels. Also by increasing the amount of nanoclay incorporated into the specimens, the gel fraction values of nanocomposite hydrogels were increased. According to the dehydration tests, the dehydration rates of nanocomposite hydrogels exhibited an inverse dependency on the nanoclay loading level and a direct dependency on the dehydration temperature. Finally, it was concluded that the dehydration mechanism of all specimens prepared is non-Fickian at 20°C, while it is Fickian at 37°C and 55°C.

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The use of some novel and efficient crop nutrient-based superabsorbent hydrogel nanocomposites (SHNCs), is currently becoming increasingly important to improve the crop yield and productivity, due to their water retention properties. In the present study a poly(Acrylamide-co-acrylic acid)/AlZnFe 2 O 4 superabsorbent hydrogel nanocomposite was synthesized and its physical properties characterized using Energy Dispersive X-ray (EDX), FE-SEM and FTIR spectroscopic techniques. The effects of different levels of SHNC were studied to evaluate the moisture retention properties of sandy loam soil (sand 59%, silt 21%, clay 19%, pH 7.4, EC 1.92 dS/m). The soil amendment with 0.1, 0.2, 0.3 and 0.4 w/w% of SHNC enhanced the moisture retention significantly at field capacity compared to the untreated soil. Besides, in a separate experiment, seed germination and seedling growth of wheat was found to be notably improved with the application of SHNC. A delay in wilting of seedlings by 5-8 days was observed for SHNC-amended soil, thereby improving wheat plant growth and establishment.

The world population is increasing day by day, demanding more food to be produced from the limited resources available. The increasing demand for food is being fulflled through intensive farming, which
otherwise requires more fertilizers and pesticides to be applied. This extensive and unavoidable use of these amendments is causing environmental pollution in the form of greater utilization of fossil fuels
and eutrophication through extensive use of fertilizers, thereby producing more pollution and causing environmental threats. There is a dire need to produce alternatives to the conventional amendments in
the form of fertilizers and pesticides which do little harm to the environment and have more capacity to produce optimum crop yields, ensuring soil health and quality. In this regard, nanotechnology in the
form of nano-fertilizers and nano-pesticides could be a great step towards the achievement of sustainable development goals (Ditta 2012; Ditta et al. 2015; Ditta and Arshad 2016).

Loss control of nutrients and water has been considered as a global challenge of agriculture because it faced with concurrent management of these two necessities of crop production. Herein, a bio-based slow-release fertilizer (SRF) has been developed using reinforcement of starch-g-poly(acrylic acid-co-acrylamide) superabsorbent polymer with natural char nanoparticles (NCNPs). Incorporation of urea in the matrix of nano-biocomposite resulted in the efficient SRF formulation with remarkable water absorbency (215.1 g/g). Variables including starch, monomers, cross-linker, and nano-filler dosages were optimized using screening the urea release behavior of samples in various pHs (3-10) and salt solutions (NaCl, CaCl 2 , and FeCl 3). NCNPs acted as physical cross-linker as well as nano-filler and formed H-bondings between the oxygenated groups of the polymer and nano-particles. Urea release measurements in water indicated a well slow-release property of SRF formulations, 70 % of nitrogen released during 21 days. The release time was prolonged with increasing the amount of NCNPs because the favorable interfacial polymer-filler interactions resulted in slower nitrogen diffusion and consequently , slower release rate at neutral and basic pHs. The water-retention of soils containing two different SRFs (with and without nano-filler) showed that NCNPs could double the water-retention compared with the neat polymer. While nitrate leaching rate in the soil for pure urea was measured to be 591.8 mg/L, the starch-g-poly (acrylic acid-co-acrylamide)/NCNPs/Urea decreased the leaching loss of N up to 49.5 mg/L. The soil burial degradation test indicated that the presence of NCNPs in the network of polymer could facilitate the degradation process of the SRF samples.

Nanotechnology is defined as "the understanding and control of matter at dimensions of roughly 1-100 nm, where unique properties make novel application Nano-fertilizers are nutrient carriers that are being developed using substrates with Nano dimensions of 1 -100 nm. Nano particles have extensive surface area and capable of holding abundance of nutrients and release it slowly and steadily such that it facilitates uptake of nutrients matching the crop requirement without any associated ill effects of customized fertilizer inputs.

Biotic P is the main factor regulating the acid phosphatase activity when the soil total P is low, being the organic P the main fraction of this total P. Fertilization had not effect on this enzyme activity. Fertilization of P increase the immobilized microbial P fraction.

Andisols are very important land resources supporting high human population density. Maize (Zea mays L.) production on Andisols located in the Purhepecha Region of central Mexico is representative of the highlands conditions of Mexico and Latin America. Farmers struggle with low crop yield and low soil nutrient availability. A 2-year field study was conducted to evaluate the effects of green manures either tilled into the soil (CT) or cut and left on the surface as a mulch (ZT), on maize yield and soil quality. Green manure treatments were: vetch (Vicia sativa L.), oat (Avena sativa L.) and none. No extra N was added to maize. Green manure and tillage had a significant effect on maize grain yield, N uptake and P uptake with CT vetch performing better than ZT oat. Soil organic C and total N were significantly higher under ZT than under CT management. Soils with vetch had higher P concentration. Soil under ZT oat had the highest infiltration rate and penetration resistance compared with other treatments. There appears to be a trade off between soil productivity and intrinsic soil physical properties among soil treatments. #

Water and nutrients are two important inputs to agriculture that need to be used judiciously with higher efficiency to save these limited resources. For these purposes, a series of nanoclay-polymer composite (NCPC) superabsorbent nutrient carriers were prepared. These NCPCs were based on the reactions of different types of nanoclays (10 wt %) with partially neutralized acrylic acid and acryl amide by a free-radical aqueous solution copolymerization reaction with N,N 0 -methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator. The nanoclays isolated from three different types of soils were dominant in kaolinite (clay I), mica (clay II), and montmorillonite (clay III), and a portion of each was freed from amorphous aluminosilicate. Thus, there were six different types of nanoclays used, namely, those dominated by kaolinite, mica, and smectite with and without amorphous aluminosilicate. Fourier transform infrared spectroscopy and X-ray diffraction (XRD) investigations showed evidence of interaction between the clays and polymer. XRD investigation also showed that the reaction between the polymer and clays I and II occurred on the surface of various clay particles without intercalating into the stacked silicate galleries, whereas in the case of clay III (the smectite-dominated clay), evidence indicated the intercalation of polymer into the stacked silicate galleries of the clay and the exfoliation of the clay. The water absorbency decreased in the NCPCs compared to that of the pure polymeric hydrogel. In case of the pure polymer, the entire amount of nutrient loading released within 15 h of incubation; this was higher than that of the NCPCs. In the initial stage (up to 15 h), no significant differences in nutrient release were observed among the different polymer/clay composites, but there were differences in later stages. Among the different NCPCs, the percentage release of nutrients at 48 h ranged from around 70% in the polymer/clay III composite to 90% in the polymer/clay I composite. The presence of amorphous aluminosilicates in clay did not make any difference in the nutrient-release rate.

A leaching study was conducted to evaluate effectiveness of fertilizer loaded nanoclay/superabsorbent polymer composites (NCPCs) as a slow release carrier of nutrients. Three types of NCPCs (I, II and III) synthesized from Kaolinite, Illite and Smectite dominated nanoclays, respectively were loaded separately with di-ammonium phosphate (DAP) and urea solution. Release of P and total mineral N from NCPCs loaded with DAP and urea, respectively, were compared with corresponding conventional fertilizer (CF). Release of P and N were studied independently with a factorial CRD experiment under four types of fertilizer (NCPC-I, NCPC-II, NCPC-III and CF) in combination with three types of soils (Alfisol, Inceptisol and Vertisol). Cumulative P and total mineral N recovery significantly increased under NCPC-I (?57.3 and ?16.2 %, respectively), NCPC-II (?55.2 and ?15.4 %, respectively) and NCPC-III (?88.3 and ?27.3 %, respectively) over CF. Reduced nutrient losses (P fixation and N volatilization) under NCPC treated soils owing to their slow release property resulted in higher recovery. Moreover, NCPC doped with smectite type of clay (NCPC-III) endowed with better slow release property than NCPC-I and NCPC-II.

A leaching study was conducted to evaluate effectiveness of fertilizer loaded nanoclay/superabsorbent polymer composites (NCPCs) as a slow release carrier of nutrients. Three types of NCPCs (I, II and III) synthesized from Kaolinite, Illite and Smectite dominated nanoclays, respectively were loaded separately with di-ammonium phosphate (DAP) and urea solution. Release of P and total mineral N from NCPCs loaded with DAP and urea, respectively, were compared with corresponding conventional fertilizer (CF). Release of P and N were studied independently with a factorial CRD experiment under four types of fertilizer (NCPC-I, NCPC-II, NCPC-III and CF) in combination with three types of soils (Alfisol, Inceptisol and Vertisol). Cumulative P and total mineral N recovery significantly increased under NCPC-I (?57.3 and ?16.2 %, respectively), NCPC-II (?55.2 and ?15.4 %, respectively) and NCPC-III (?88.3 and ?27.3 %, respectively) over CF. Reduced nutrient losses (P fixation and N volatilization) under NCPC treated soils owing to their slow release property resulted in higher recovery. Moreover, NCPC doped with smectite type of clay (NCPC-III) endowed with better slow release property than NCPC-I and NCPC-II.

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Clay minerals are natural materials well known for
their role in retention and persistence of organic and
inorganic compounds in soil. Clay minerals are being
modified through different processes to alter their
charge and surface properties tailored for specific
purposes. Modified clays in general include pillared
layered clays, organoclays, nanocomposites, acid and
salt-induced and thermally and mechanically induced
modified clays. Pillared organoclays and nanocomposites
constitute a novel class of materials, mainly one
kind of modification of expanding 2 : 1 clay minerals.
Acid and salt treatments lead to modification of the
catalytic properties of clays. Clay mineral–polymer
nanocomposites are the hybrids which exhibit a
change in composition and structure on a scale of
nanometres. Modified clay imparts slow-release property
to fertilizers and enhances the water-holding
capacity of soil. Therefore, understanding the methods
of clay modification and properties of modified clays
may facilitate development of agricultural management
systems that ensure long-term sustainability of soil
resources

Biodegradable polymer-coated controlledrelease fertilizers (PC-CRFs) are essential means to reduce cost, improve marketability, conserve land fertility, achieve high crop yields and combat climate challenges. It is known that about 15-30% of any fertilizer packed in a PC-CRF does not get released due to the concentration gradient difference across the polymer coatings. To release the trapped fertilizer(s), it is desired that polymerbased coatings should biodegrade after the fertilizer is completely released into the soil. This review has aimed to provide a comprehensive account for various biodegradable polymers/blends derived either from natural or synthetic sources which are cited in the literature for PC-CRFs. In addition, this review covers the discussion on their classification criteria, trends in the processes of fertilizer coatings, methodological issues for their biodegradation assessment, coating attributes that affect the biodegradability and an outlook into their biodegradation kinetic models that involve enzymes and microbial processes. It also concludes that experimental as well as modeling data are insufficient to assess the biodegradation contribution of the overall nutrient release in PC-CRFs.

The nanocomposites of general layered clays and metal sulfides could be produced from reactions of the layered clay aqueous suspensions and water-soluble metal-thiourea complexes. The clay could be saponite, montmorillonite, hectorite and laponite, while the metal sulfide could be cobalt sulfide, nickel sulfide, zinc sulfide, cadmium sulfide, and lead sulfide. In the nanocomposites, the clay could be incorporated with the metal sulfide pillars and metal sulfide nanoparticles.

The nanocomposites of general layered clays and metal sulfides could be produced from reactions of the layered clay aqueous suspensions and water-soluble metal-thiourea complexes. The clay could be saponite, montmorillonite, hectorite and laponite, while the metal sulfide could be cobalt sulfide, nickel sulfide, zinc sulfide, cadmium sulfide, and lead sulfide. In the nanocomposites, the clay could be incorporated with the metal sulfide pillars and metal sulfide nanoparticles.