Anion Exchange Resin Membrane Research Articles

Bilayer Anion-Exchange Membrane with Low Borohydride Crossover and Improved Fuel Efficiency for Direct Borohdyride Fuel Cell.

The development of membranes with low fuel crossover and high fuel efficiency is a key issue in direct borohydride fuel cells (DBFCs). In previous work, we produced a poly(vinyl alcohol) (PVA)-anion-exchange resin (AER) membrane with a low fuel crossover and a low fuel efficiency by introducing Co ions. In this work, a bilayer membrane was designed to improve the fuel efficiency and cell performance. The bilayer membrane was prepared by casting a PVA-AER wet gel onto the partially desiccated Co-PVA-AER gel. The bilayer membrane showed a borohydride permeability of 1.34 × 10-6 cm2·s-1, which was even lower than that of the Co-PVA-AER membrane (1.98 ×10-6 cm2·s-1) and the PVA-AER membrane (2.80 × 10-6 cm2·s-1). The DBFC using the bilayer membrane exhibited a higher fuel efficiency (37.4%) and output power (1.73 Wh) than the DBFCs using the Co-PVA-AER membrane (33.3%, 1.27 Wh) and the PVA-AER membrane (34.3%, 1.2 Wh). Furthermore, the DBFC using the bilayer membrane achieved a peak power density of 327 mW·cm-2, which was 2.14 times of that of the DBFC using the PVA-AER membrane (153 mW·cm-2). The drastic improvement benefited from the bilayer design, which introduced an interphase to suppress fuel crossover and avoided unnecessary borohydride hydrolysis.

Characterizing phosphorus availability in waste products by chemical extractions and plant uptake

AbstractBackground: The fertilizer value of phosphorus (P) in waste products relies heavily on its availability to the subsequent crop.Aim: We studied the link between extractable P in waste products and apparent P recovery (APR, i.e., difference in plant P uptake between P amended and un‐amended soils divided by the amount of P added) using spring barley grown on three sandy soils.Methods: The products included sewage sludge, biomass ash, struvite, compost, meat and bone meal, biochar from sewage sludge, and industrial sludge. Soft rock phosphate and triple‐superphosphate (TSP) were included for comparison. Availability of P was characterized by extraction with water and solutions of sodium bicarbonate, citric acid, oxalic acid, hydrochloric acid, ammonium acetate, ammonium fluoride and anion exchange resin membranes. TSP was used to establish mineral‐fertilizer‐equivalents (MFE). Water and bicarbonate extractions were also applied to products incubated with soil before extraction.Results: The APR ranged 26 to 31% for TSP and 0 to 30% for waste products. APR correlated most strongly with bicarbonate extractable P. The correlation increased when products were incubated with soil before extraction.Conclusions: We conclude that bicarbonate extraction is a good indicator of potential P availability. However, interactions between waste products and soil properties modify P availability.

Potential of phosphorus fractions to trace sediment sources in a rural catchment of Southern Brazil: Comparison with the conventional approach based on elemental geochemistry

In areas with extensive soil erosion, there is a need to identify the sources supplying sediment to rivers in order to improve our understanding of erosion processes and to guide the implementation of effective soil management measures. Geochemical elements are often used as tracers in sediment fingerprinting studies. Among them, P has often been used as it may specifically trace sediment originating from cropland. Although P-fractions can provide more detailed information than the total P content, their potential to distinguish between different potential sources of sediments has rarely been tested. The objective of the current research was to evaluate the contribution of sediment sources in a rural catchment (Arvorezinha, 1.23 km2) of Southern Brazil, using different sets of tracers (i.e. P-fractions only, geochemical tracers only, and a combination of both tracers). Three potential sediment source types were identified in the catchment: (i) cropland, (ii) unpaved roads and (iii) stream channel banks. Thirty-one suspended sediment samples were collected in the river draining this catchment during 9 significant floods between 2009 and 2011. Estimates of P-fractions were obtained by Hedley fractionation using anion exchange resin membrane (Presin); 0.5 mol L−1 NaHCO3 (pH 8.5) (Pbic); 0.1 mol L−1 NaOH (PNaOH0.1); 1.0 mol L−1 HCl (PHCl); 0.5 mol L−1 NaOH (PNaOH0.5); and residual P (Presidual). Total organic (Porg) and inorganic P (Pinorg) were obtained by the ignition method. The concentrations of PHCl, PNaOH0.5 and Pinorg in suspended sediments were higher than those found in the sources. Accordingly, these fractions were considered not to be conservative and were excluded from further analysis. With the exception of Presidual, all P-fractions passed the Kruskal-Wallis H-test and were considered as potential tracers of sediment sources. When the P-fractions were combined with geochemical tracers, the discrimination power was much higher than when using geochemical tracers only. The Mahalanobis distance was 9% higher than that observed in the geochemical approach. The calculated contribution of sediment sources using the three approaches was very similar, and cropland was the dominant source of sediment, with calculated contributions of 56 ± 19, 46 ± 16 and 48 ± 16% for those approaches based on geochemical elements, P-fractions, and geochemical + P-fractions, respectively. These results demonstrate the effectiveness of some P-fractions to trace potential sediment sources in rural catchments, as they have a high discriminant power while remaining conservative during sediment transport in the catchment.

Fractionation and availability of phosphorus in acid soils of Hagereselam, Southern Ethiopia under different rates of lime

BackgroundPhosphorus (P) availability is commonly assumed to limit productivity in many tropical soils, yet there is relatively little information on the phosphorus chemical forms, distribution, and transformations that P undergoes in Ethiopian soils. We used a sequential fractionation scheme to assess phosphorus fractions of acid soils of Southern Ethiopia. The study area called Hagereselam is characterized by high soil acidity, and the availability of P in the study area is relatively low. As crop production in Ethiopia is dominated by low external input practices, native P remains the main contributor to plant P nutrition in many locations.ResultAlthough the total P concentration is 829.7 mg kg−1, the organic P content was relatively low (58 mg kg−1) and constituted on average less than 7% of the total P. The ratio of organic carbon to organic P was generally greater than 240, suggesting the potential for immobilization of P. The Al + Fe-associated P was the dominant inorganic P pool. The majority of the P occurred in recalcitrant form (568.3 mg kg−1). Readily available, exchangeable phosphate, as extracted by anion-exchange resin membranes, was present in very low concentrations (3.3 mg kg−1); moreover, labile P accounted for less than 2% (9.9 mg kg−1) of the total soil P.ConclusionLime was used as a reclamation material for acid soils, and the application of lime significantly affected the different P fractions and was involved in the transformation of P fraction. Organic P forms were significantly lower for higher levels of lime application, suggesting that lime amendment enhanced organic P decomposition. Moreover, application of lime increased Ca-P and decreased Al + Fe–P for acid soils.Graphical abstractEffect of lime of phosphorus pools

Occurrence of iron and aluminum sesquioxides and their implications for the P sorption in subtropical soils

The effect of the pedo-climatic variation in qualitative and quantitative soil sesquioxide contents and soil phosphorus (P) sorption capacities has been studied. In four soils (samples from A horizons) located along a southern Brazilian environmental gradient (EG) shown a decrease in crystallized iron oxides with the increase of altitude. Hematite and goethite were found at low EG altitudes in association with low soil organic carbon content, and goethite–ferrihydrite and gibbsite were found at high altitudes in association with high organic carbon content. The adsorbed soil P (measured by the remaining P) was predicted by the goethite content, and the desorbed P (measured by successive P extractions using anion exchange resin membranes) was predicted mainly by the goethite and clay content. In subtropical soils, even a smooth environmental gradient could determine the qualitative and quantitative iron and aluminum sesquioxide distributions that control soil P sorption capacities.

Phosphorus Sorption Dynamics of Anion Exchange Resin Membranes in Tropical Rain Forest Soils

Bioavailable P is recognized as a major constraint on productivity in many tropical rain forests. Nevertheless, insufficient knowledge about short‐term temporal patterns in soil labile P limits our understanding of the mechanisms controlling soil P supply in tropical forest soils. The use of field‐deployed anion exchange resin membranes (AEMs) to determine soil nutrient supply rates is increasingly common, however, the lack of information regarding their behavior over time in tropical wet forest soils interferes with interpretation of results. This study quantifies in situ labile P as measured by AEMs over various incubation periods (4, 8, 12, 14, 20, and 24 d) in the surface soil of two neighboring Costa Rican tropical rain forest Oxisols of differing P content (0.46 vs. 1.18 Mg ha−1, 0–10 cm). Using a nested design, we evaluated the importance of incubation length, environmental conditions (i.e., rainfall, temperature, and solar radiation), vegetation characteristics (i.e., basal area, stem density, and species composition), and total P status in driving spatial and temporal variability in AEM P. Spatially averaged AEM P in the site with higher P content ranged from 0.26 to 1.38 μg membrane−1 across all incubation periods; approximately two fold higher than AEM P in the more P‐deficient site (0.11–0.77 μg membrane−1). Temporal variability in AEM P was best explained by rainfall. Despite consistently high volumetric soil moisture (50–66%), increasing rainfall was associated with greater P availability in both sites. Mean P availability increased with plant basal area and basal area of legumes.

Phosphate rock dissolution and availability in some soils of semi-deciduous Rainforest Zone of Ghana

Alfisols and Ultisols of the semi-deciduous forest zone of Ghana are known to be moderately acid and very low in plant available phosphorus (P). These soils need to be fertilized to increase crop production but due to economic reasons local farmers are unable to afford water-soluble P fertilizers. Instead of expensive superphosphates, the use of less expensive phosphate rocks such as Togo rock phosphate (TRP), Gafsa rock phosphate (GRP) and 50% partially acidulated rock phosphate (PAPR) are possible alternative P sources for these soils. The rate of dissolution of TRP, GRP, PAPR and TSP in three benchmark soils of Ghana was assessed, and the effectiveness of these P sources determined in a greenhouse using maize (Zea mays var. Toxpino) as a test crop. The dissolution of the P sources in three soils Bekwai, Nzima (Ultisols) and Kokofu (Alfisol) along a toposequence was investigated in an incubation study and also in a greenhouse experiment. The rate of dissolution of the P fertilizers was determined in the laboratory by extracting with anion exchange resin membrane (AEM), 0.1M NaOH and 1M HCl at 21 days interval for 105 days. In the greenhouse study, each P source was added at the rate of 60 mg P kg-1 soil, and sown to maize (Zea mays. var.Toxpino) for 28 days. The results of the incubation study showed that the amount of P extracted by the AEM and HCl, following the addition of the P sources, decreased with incubation time in all three soils. However, there was an increase in NaOH-P in all the three soils as incubation progressed. The increase in the NaOH-P suggested that the dissolved P was adsorbed by Fe and Al oxides. The greenhouse results showed that dry matter yield was in the order TSP = PAPR > GRP > TRP. Relative to TRP, the PAPR and GRP were reactive enough to provide plant available P to satisfy the early P requirement for maize growth. Togo PR has little potential for direct application in the three soils.

Effect of the Extraction Period on the Routine Assessment of Soil P Status by Ion‐Exchange Resin Membranes

The cation–anion exchange resin membrane (CAERM) system is one of the most promising alternative methodologies for the assessment of soil phosphorus (P) availability. Nevertheless, the CAERM method has a recommended period of extraction (16 h) that limits its applicability. With the aim to improve the use of CAERM in routine laboratory work, seven extraction times were studied and compared for repeatability and biological accuracy, using 150 samples of soils and covering a wide range of properties. The results showed dissimilar quantities of extractable P, according to the nature of soils and the period of extraction time. On average of all soils, values of extractable P ranged from a 2.4 mg kg−1 and 26.7 mg kg−1 in 0.25‐h and 16‐h extraction times, respectively. Relative to the repeatability aspects, the results reveal a tendency of increasing results with the decrease of the period of extraction, showing coefficient variation (CV) values ranging from 5% (16 h) to 14% (0.25 h). All the extraction periods tested for the CAERM presented highly significant values of r (0.824–0.943) between extractable P and each of the three biological parameters: relative yield of ryegrass, P content, and P uptake. Considering the three biological parameters simultaneously, the best results were obtained for extraction periods of 8 h, 2 h, and 4 h. Based on the results, and considering both practical and accuracy aspects, it is conclude that 2 h of extraction is a valid alternative to the 16‐h standard extraction period for the CAERM methodology.

Relationships Between Agronomic and Environmental Soil Test Phosphorus in Three Typical Cultivated Soils in China

A study was conducted to determine the relationships between agronomic soil test P and environmental soil test P in three soils predominately distributing in three typical agricultural production areas of China. Soil P was analyzed using Bray-1 (BP), Olsen (OP), and Mehlich-3 (MP) methods as agronomic tests, and using Fe-oxide impregnated filter paper (FeP), anion-exchange resin membrane (RP), and water (WP) as environmental tests. There were linear relationships between soil P extractable with all the tests evaluated. The regression coefficients, R 2, ranged from 0.8164 to 0.9409 between each two of the agronomic soil test P, and ranged from 0.4702 to 0.8990 between each two of the environmental soil test P, when the three soils were considered separately. When soil test P was analyzed across all the three soils, the highest regression R 2 was found between OP and MP (0.7940) amongst agronomic soil test P, and between FeP and RP amongst environmental soil test P (0.8842). While all of the three agronomic soil test P was linearly related to each of the environmental soil test P across the three soils, strongest relationships were found between OP and environmental soil test P. Agronomic OP may be adopted as an analytical tool for environmental prediction of soil P.

Evaluation of Agronomic and Environmental Soil P Test Methods in a Network of Hungarian Long‐Term Field Trials

Winter wheat shoot weight and phosphorus (P) concentrations, corn leaf weight and P concentrations, and soil AL, Olsen, H2O, Bray 1, Pi (Fe-oxide impregnated paper strip) and AERM (anion exchange resin membrane) contents were determined in a network of uniform Hungarian national long‐term field trials. P application had a significant effect on soil P test values at different P levels and sites. The relationship between the different soil P test methods was studied separately for different soil groups (all, acid, and calcareous soils). Corn leaf weight was influenced by the sites much more than by soil P supply level, whereas corn leaf P percentage was influenced by both sites and P levels. For winter wheat, both sites and soil P levels had a positive effect on wheat shoot weight. Wheat shoot P percentage was influenced by the soil P supply much more than by the sites. Correlation between corn leaf P percentage and the Pi or AERM extractable P and between wheat shoot P percentage and the Pi and AERM P values was logarithmic.

Development of Chemical Sensors and Their Application to Flow Analysis Systems

Flow analysis has many advantages concerning sensitivity, accuracy, repeatability and analytical throughput etc, compared with a batchwise analysis. The flow-based method makes the involved analytical processes automatic and rapid. Therefore, the combination of a chemical sensor with the flow method enhances the performances of the chemical sensor. Especially, potentiometric detection using ion-selective electrodes has been widely used in flow analysis due to its features, simplicity in analytical operation and wide dynamic range in analysis. This paper reports on several chemical sensors applied to flow systems that we have engaged so far concerning: (1) Liquid membrane type ion-selective electrodes, such as nitrate, vitamin B1, tetrafluoroborate and surfactants sensitive electrodes based on an oleophilic anion exchange resin membrane and a hydrophobic ion exchanger. (2) Flow titration by using both a buffer solution and its corresponding electrode, such as a pH glass electrode with a pH buffer, a cupper(II) ion-selective electrode with a metal ion buffer solution and a redox electrode with a potential buffer solution. (3) Surface plasmon resonance sensors for succarides and some endocrine disrupting chemicals based on a boronic acid polymer membrane and antigen or antibody immobilized membrane. (4) Sequential injection analysis combined with beads injection technique for vitellogenin as biomarker for assessing the pollution of environment in hydrosphere.

Time-Dependent Phosphorus Extractability from Soils Treated with Different Fertilizer Phosphorus Sources

Effect of application of different fertilizer phosphorus (P) sources (diammonium phosphate—DAP, single super phosphate—SSP, phosphate rock—PR, partially acidulated phosphate rock—PAPR, basic slag phosphate—BSP, and humo phosphate—HP), and time (up to three years of soil-fertilizer P equilibration) on soil extractable P was studied on two representative Italian soils, principally differing in pH values and the capacity to retain P. Phosphorus extractability was measured by seven chemical and two nonconventional soil P test methods based on the use of anion exchange resin membranes and iron oxide coated paper strips. The increases in the amount of extracted P following soil P fertilization were practically in the same order for both Ravenna and Paliano soils: DAP > SSP > HP > BSP > PAPR > PR; that order reflecting the corresponding scale of P water solubility. More P tended, however, to be dissolved from PR treatment in more acidic soil. On an average, the effectiveness of the different soil P test procedures in extracting P from two soils was in the order: Egner-P > Bray2-P > Olsen-P > Mehlich3-P > resin-P > iron oxide-strip-P > Bray1-P > water-P > CaCl2-P. The Egner soil P test method appeared to overestimate P bioavailability of all P treatments in the calcareous soil, while both the Egner and Bray2 soil tests overestimated the amount of extractable P of the PR treatment in the other soil. Data of P extracted by the Olsen and Mehlich3 procedures resulted the most closely correlated with the corresponding data obtained with the nonconventional soil P test procedures, currently considered with potential for use in widely ranging soils fertilized with water soluble as well as water insoluble P fertilizers.

Experimental alteration of vivianite to lepidocrocite in a calcareous medium

AbstractVivianite [Fe3(PO4)2·8H2O] is easily oxidized in the presence of air. In this work, we studied the oxidation and incongruent dissolution of vivianite in a calcareous medium containing an anion-exchange resin (AER) that acted as a sink for phosphate. Freshly prepared vivianite suspensions with calcite sand and an AER membrane were oxidized and stirred by bubbling air or CO2-free O2. Experiments were finished when oxidation rate and P removal by the AER became slow, which was at 53 days (air system) or 28 days (CO2free O2 system). At these times, the respective values of the Fe(II)/total Fe ratio were 0.29 and 0.12, and the respective values of the atomic P/Fe ratio were 0.15 and 0.11. The final product of the oxidation was poorly crystalline lepidocrocite in the form of thin (1 ­ 5 nm), irregular lamellae that were soluble in acid oxalate. The unit-cell edge lengths of this lepidocrocite were a= 0.3117, b= 1.2572, and c= 0.3870, vs. a= 0.3071, b= 1.2520 and c= 0.3873 nm for the reference lepidocrocite. The lepidocrocite lamellae contained occluded P (P/Fe atomic ratio = 0.03 ­ 0.04). The results of this and a previous study made us hypothesize that this occluded P is structural and occupies tetrahedral sites adjacent to the empty octahedral sites in the sheets extending on ﹛010﹜.

Phosphorus reserves and availability in soils receiving long-term manure applications

In agricultural areas where intensive farming practices are common, applications of phosphorus (P) in amounts larger than crop requirements have led to an increased incidence of soils with a high P concentration. Accumulation of P in soil generally results in a greater potential for P enrichment of surface runoff and P losses during drainage. Estimating the size of the available P pool and the P supplying capacity of such soils is useful for calculating P-use efficiencies as related to agronomic practices and can be useful for assessing soil P characteristics that may have a negative impact on the environment. In this work, the available P content of 29 soils from farms with intensive confined animal operations was determined using eight traditional and three P-sink methods. The results obtained are discussed in relation to the degree of P saturation (DPS) of the same soils. The residual P availability status was evaluated via successive anion exchange resin membrane extraction of the soils. The cumulative P removed after eleven extractions fitted well a first-order equation, the asymptote of which represents the potential amount of desorbable P (Ultimate Releasable P). Relationships between the soil P test values and both the Ultimate Releasable P and the DPS lead to the conclusion that about 50% of the soils examined have a high potential for releasing P to surface and ground waters.

Effect of time, fertilizer phosphorus sources, and fertilization systems on phosphorus extractability of two soils from hungary

The effects of two fertilizer phosphorus (P) sources, i.e., single superphosphate (SSP) and Algerian rock phosphate (ARP), and two fertilization systems, i.e., yearly application of 35 kg ha− 1 P for 5 years (NKP35) and initial build-up doses of 175 kg ha− 1 P (NKP175), on soil P extractability were evaluated at two sites of Hungary, i.e., Szentgyörgyvölgy (Szgyv site, soil pHKCl=4.7), and Kompolt (Kplt site, soil pHKCl=5.1). Soil P availability was assessed one year and five years after the P fertilizer application, respectively in 1994 and 1998, according to six different chemical soil P test methods [Mehlich3 (M3-P), Olsen (Ols-P), Bray-Kurtz1 (Br1-P), Bray-Kurtz2 (Br2-P), Egner–Riehm–Domingo (Egn-P), and van der Paauw (Pw)], and two P-sink procedures [iron oxide-impregnated filter paper (Pi-P) and anion exchange resin membrane (AEM-P)]. No significant increases (p>0.05) in soil extractable P were observed in 1994 for the different treatments at both sites, except for the trials treated with single superphosphate applied at the maximum rate (NKP175SSP). In 1998, at the Szgyv site the amounts of P extracted from all the fertilized P trials increased significantly, when compared with the corresponding data of 1994, with the highest increases being presented by the NKP175SSP and NKP175ARP variants. In contrast at the Kplt site, increases in soil available P level in 1998 were significant for both NKP35 treatments (SSP and ARP). Changes were not significant for the NKP175ARP treatment, while there was a significant decrease for the NKP175SSP treatment, relative to the data of 1994. For both soils, the Egner and Bray2 extractants overestimated soil P availability in the trials treated with rock phosphate.

Comparison of the agronomic effectiveness of a phosphate rock and triple superphosphate as phosphate fertilisers for tea (Camellia sinensis L.) on a strongly acidic Ultisol

Phosphorus deficiency is a major problem affecting tea production in the highly weathered acid soils of humid and sub-humid tropics which are known to have high P fixing capacities. As many of these soils are strongly acidic and receive high rainfall, low-cost phosphate rock (PR) may effectively supply the plant P needs and limited preliminary experiments suggest this is so. A long-term glasshouse trial was conducted on 8-month old tea seedlings to compare the agronomic effectiveness of a locally available PR (Eppawala phosphate rock, EPR) with triple superphosphate (TSP) applied to a strongly acidic (pH water 4.55) marginally P deficient Rhodustult from Sri Lanka at six rates ranging from 10 to 60 kg P ha−1. The results showed that TSP or EPR fertiliser at a rate as low as 10 or 20 kg P ha−1 was sufficient to obtain maximun tea yield. The agronomic effectiveness of EPR was equal to that of TSP at the 5- and 10-month samplings. The concentration of soil P extracted by a cation–anion exchange resin membrane (resin-P) was higher in the TSP treated soil at 5 months due to its greater solubility but at 10 months, the EPR produced higher resin-P due to its increased dissolution over time. In the presence of tea plants, 52% of P from the EPR applied at the rate of 10 kg ha−1, was dissolved at 5 months compared to 75% of dissolution at the 10-month sampling. In the absence of plants, the corresponding dissolution figures were 40% at 5 months and 55% at 10 months. The concentration of inorganic P extracted by 0.1 M NaOH (NaOH-Pi) (loosely characterising Fe + Al bound P) was significantly higher in the TSP treated soil and concentration of P extracted by 0.5 M H2SO4 (Ca bound P) was higher in the EPR treated soil. The results suggest that the low-cost, locally available EPR may be used profitably as a maintenace P fertiliser for tea plantations in moderately P deficient soils, which need to be confirmed by field studies.

Addition of phosphorus to soils with low to medium phosphorus retention capacities. II. effect on soil phosphorus extractability

Knowledge of the change in soil extractable phosphorus (P) as a consequence of soil P fertilization could be useful in discriminating soils with a potential for soil P release to runoff or movement of P along the soil profile. In this research, soils with low to medium P retention capacity were equilibrated for 90 days with soluble P (KH2PO4) at rate of 100 mg P kg‐1 soil. After this period, soil samples both with and without the P addition were analyzed using six conventional methods: 1) Olsen, 2) Bray 1,3) Mehlich3,4) Egner, 5) Houba, dilute CaCl2 solution, and 6) distilled water, and three “innovative”; P‐sink methodologies: 1) Fe oxide‐coated paper strip, 2) anion exchange resin membrane, and 3) cation‐anion exchange resin membrane. The soils without P addition had low levels of extracted P as determined by all nine procedures. Net increases in the amount of P extracted from the soils with added P ranged from 4.2 mg kg‐1 (CaCl2 extraction) to 57.6 mg kg‐1 (cation‐anion resin membrane extraction). Relationships between change in extracted P and i) physical and chemical characteristics, and ii) soil P sorption properties are also presented and discussed.

Litter dynamics and monthly fluctuations in soil phosphorus availability in an Amazonian agroforest

Commercial plantation agroforests offer a promising land-use alternative for small-scale farmers in tropical America because of their potential to produce high-value cash crops with less soil degradation than traditional annual cropping systems. In low- to no-input tree-based agroecosystems growing in tropical Ultisols and Oxisols, soil P availability depends heavily on factors that influence mineralization from decomposing litter. Using anion exchange resin membranes (AERMs), we monitored monthly fluctuations in soil solution P in an eight-year-old peach palm ( Bactris gasipaes)–cupuassu ( Theobroma grandiflorum) commercial plantation agroforest to determine if changes in P availability were related to environmental factors controlling organic matter decomposition (precipitation, soil moisture and temperature) and seasonal fluctuations in litterfall and fruit harvest. Decomposition and C, N, and P dynamics in leaf litter were also studied to determine if soil P availability might be related to species differences in litter quality (initial leaf C, N and P contents) and thus differing rates of P release or immobilization. Although AERMs acted as dynamic exchangers, they appeared adequately sensitive to detect fluctuations in monthly soil P availability, despite inherently low soil extractable P concentrations. Soil P availability was greatest early in the rainy season, when both litterfall and a cycle of soil-wetting and drying were initiated, decreasing during the mid-rainy season when fruit production peaked. AERM P was greatest in superficial palm root mats, where decomposing litter accumulates, and in mineral soil beneath palm litter. This corresponded with greater N and P release from more P-rich palm leaf litter. Phosphorus immobilization in initially P-poor cupuassu leaves appears to have contributed to lowered P availability in soil underlying this species’ litter. Phosphorus availability was lowest in bare mineral soil located agroforest alleys where litter accumulation was minimal. Greater overall P availability in peach palm litter-covered soil and root mats may contribute to observed higher productivity in this species.

Effect of swine manure and urea on soil phosphorus supply to canola

Limited information exists as to the effect of liquid swine manure on soil phosphorus (P) availability in Western Canadian soil. Swine manure is most often applied to meet additional requirements for nitrogen (N) and research to date has emphasized N effects. The effect of swine manure and urea on P supply to canola was investigated under controlled environment condition. Canola (Brassica napus) was grown in pots with manure or urea added to two Saskatchewan soils (sandy loam and clay loam) at 0 and 100 mg N kg‐1. Plants were grown to maturity, and yield and nutrient content were determined. Phosphorus supply rates in soils were measured in the pots using anion exchange resin membrane probes. Additions of swine manure and urea enhanced canola P accumulation and led to a higher proportion of P in seeds. This response was more evident in the manure treatment than with urea. Soil amended with manure significantly increased N and P supply rates in soils as the manure contains N and P. On the contrary, application of urea significantly increased N supply rate, but led to a slight decrease in the measured soil supply rate of available P. Despite the apparent decrease in soil supply of available P in urea treatment, canola maintained its N:P ratio by increasing P absorption, possibly due to a greater root mass.

Using an Ion Sink to Extract Microbial Phosphorus from Soil

Two ion sinks (FeO‐coated paper and anion exchange resin membrane) were tested to improve accuracy and precision in analysis of microbial P (Pm) in soil biomass. We used a noncarcinogenic biocide, hexanol. Ion‐sink extracted FeO‐Pm [Pm(FeO)] and resin‐Pm [Pm(Res)] were compared with bicarbonate extracted Pm [Pm(Bic)]. Fractional recovery of Pm (Kp) was determined with 50 μg Pm from five different organisms, first, from preparations without soil, giving Kp of 0.49 for Pm(Bic), 0.63 for Pm(FeO), and 0.66 for Pm(Res), and second, from soil‐organism mixes, giving Kp of 0.36 for Pm(Bic), 0.49 for Pm(FeO), and 0.52 for Pm(Res) This indicated ion sinks can improve accuracy of Pm recovery. We tested 18 Kansas soils with three different levels of C + N substrates to provide varying levels of microbial activity. For unamended soils, Pm values (mg kg−1) were 5.9 for Pm(Bic), 8.2 for Pm(FeO), and 6.3 for Pm(Res) Corresponding values in soils with low levels of C + N amendments were 6.0 for Pm(Bic), 18.2 for Pm(FeO), and 18.7 for Pm(Res) In soils with high levels of C + N amendments plus alfalfa (Medicago sativa L.), corresponding values were 12.7 for Pm(Bic), 30.9 for Pm(FeO), and 37.3 for Pm(Res) Above 10.0 mg kg−1, Pm(FeO) and Pm(Res) were at least twice as much as Pm(Bic) In addition, Pm(FeO) and Pm(Res) both had lower CVs than Pm(Bic), indicating greater precision by the ion‐sink methods.