Metal Micronutrients Research Articles

Effects of individual and combined metal foliar fertilisers on iron- and manganese-deficient Solanum lycopersicum plants

Using Fe- and Mn-deficient Solanum lycopersicum plants, we investigated the effects of Fe and Mn foliar fertilisers, either individually or combined, on plant biomass, leaf chlorophyll and metal micronutrient levels in leaves and roots. Plants were grown in hydroponics with different combinations of 0 or 45 μM Fe and 0 or 4.6 μM Mn. Foliar fertiliser formulations (9 mM FeSO4 and/or 3 mM MnSO4, supplemented with a surfactant) were applied in three consecutive doses. Fertilisation was applied to the first three leaf levels, while upper leaf levels were left untreated. Iron and Mn deficiency led to characteristic symptoms. Foliar treatments increased concentrations of Fe and Mn, biomass and chlorophyll in treated leaves, although re-greening was incomplete. Approximately 11–12 % of the Fe increase was in roots (likely mediated via phloem transport), but no Fe increase occurred in untreated leaves. Regarding Mn, a 2 % increase occurred in untreated leaves, but no increase occurred in roots. Iron fertilisation was effective not only in leaves treated with the fertiliser but also in roots, whereas Mn fertilisation had major effects on treated leaves and minor effects on untreated ones. The combined application of Fe + Mn was not detrimental to Fe- or Mn-deficient plants.

Distribution of Cu, Fe, Mn, and Zn in Two Mangroves of Southern Brazil

This study assessed the relation between Cu, Fe, Mn, and Zn in the soils of the mangroves of Antonina and Guaratuba, on the coastline of the State of Parana, and in the leaf tissues of A. shauerianaR. mangle, and L. racemosa through the analysis of correlation levels between these two compartments. Leaf samples were collected for ten individuals of each species in a 1000 m2 area delimited in each mangrove. Soil samples from 0-10 cm depth were taken from under the crown projection area of the selected trees to be submitted to chemical analysis. In the soils, metallic micronutrients presented the following order: Fe > Mn > Zn > Cu. In the leaves, concentrations were species dependent. InA. shaueriana and R. mangle, the profile was Mn > Fe > Zn > Cu, while in L. racemosa, the sequence was: Fe > Mn > Zn > Cu. Correlation analyses revealed only four significant correlations for Mn, Zn, and Cu in the soil and plant compartments. These results suggested that significant correlations depended on abiotic factors, inhibition between the elements, and immobilization and/or adsorptions of these metals by the soil.

Book Review: Principles of Plant-Microbe Interactions: Microbes for Sustainable Agriculture

Book Review: Principles of Plant-Microbe Interactions: Microbes for Sustainable Agriculture

Daily to decadal variability of size-fractionated iron and iron-binding ligands at the Hawaii Ocean Time-series Station ALOHA

Time-series studies of trace metals in the ocean are rare, but they are critical for evaluating both the residence times of the metals themselves and also the timescales over which the marine ecosystems that depend on micronutrient metals can change. In this paper we present two new time-series of the essential micronutrient iron (Fe) taken from the Hawaii Ocean Time-series (HOT) site, Station ALOHA (22.75°N, 158°W): a set of intermittent monthly surface samples taken from ∼50 dates between 1999 and 2011 by the HOT program, and a daily-resolved sample set from summer 2012 and 2013 containing ∼80 surface samples and 7 profiles to 1500m depth. The long-term monthly climatology of surface total dissolvable Fe (TDFe) concentrations covaried with the seasonal cycle of continental Asian dust deposition at Hawaii, indicating dust as the major source of TDFe to ALOHA surface waters and a short residence time for TDFe (order∼months). During the daily summer time-series, surface Fe was most variable in the larger size fractions (>0.4μm particulate and 0.02–0.4μm colloidal) and nearly constant in the smallest (<0.02μm) soluble size fractions, confirming that the larger size fractions have shorter residence times with respect to scavenging/settling. The most significant Fe event lasted three days in early August and “cascaded” through the Fe size fractions from largest to smallest; lacking evidence that dust triggered this event, we correlated it with the arrival of the edge of an anticyclonic eddy and an increase in diatom abundance at ALOHA. The surface Fe-binding ligand daily time-series showed that excess ligand concentrations lagged dFe by 1–2days, revealing a short residence time of ligands in the central North Pacific likely due to photochemical degradation. In the ferricline, the dissolved Fe (dFe) linear relationship with apparent oxygen utilization was used to establish a water column dFe:C ratio of 3.12±0.11μmol/mol and a pre-formed dFe concentration of 0.067±0.009nmol/kg that defines the central/mode waters of Station ALOHA. Finally, in deep waters near 1200m, where minimal temporal variation in dFe might be expected, dFe instead ranged over a factor of two in concentration (0.72–1.44nmol/kg), driven by the intermittent passing of the Loihi hydrothermal plume through Station ALOHA. This study not only provides the largest number of Fe measurements made at a single location anywhere in the global ocean to date but also reveals the strength of time-series measurements for exploring mechanisms and timescales of biogeochemical events.

Plant Nutrition 3: Micronutrients and metals

Summary In the third of three lessons spanning the topic of Plant Nutrition, we examine how micronutrients affect both plants and humans. Specifically, we examine the functions of the nine essential micronutrients Fe, Cu, Zn, Mn, Mo, Ni, B, Si and Cl with a particular focus on the unique chemistry of the metal micronutrients. Because the optimal concentration range of most micronutrients is quite narrow in the plant body, plants employ strategies at both the low end and high end of the optimal nutrient range to avoid deficiency and toxicity effects, although some plants hyperaccumulate micronutrients for defensive purposes. Efforts to improve human nutrition through biofortification, particularly of Fe, Zn and Se are discussed. We further examine how plants and people are affected by the toxic elements As, Cd and Al, and efforts to alleviate their harm through our understanding of plant micronutrition.

Flood zone biogeochemistry of the Ob River middle course

The flood zone of the Ob River, the largest (in watershed area) river of the Arctic Ocean basin, is tens of km wide and, after the Amazon's Varzea, is the world's second largest flooding territory. To better understand the biogeochemistry of the Ob River and adjacent surface waters, we studied, in May and July 2014, the dissolved and colloidal organic carbon and trace metals in small rivers, lakes, and flooded water bodies connected and disconnected with the mainstream as well as the Ob River itself. All major and trace elements were distributed among two major categories depending on their pattern of dependence on the dissolved organic carbon (DOC) concentration. Dissolved inorganic carbon (DIC), Na, Mg, Ca, sulfate, Sr, Mo, Sb and U exhibited a general decrease in concentration with the increase of the [DOC]. The lowest concentration of these elements was observed in DOC-rich humic, acidic (4.9 ≤ pH ≤ 6.1) upland lakes fed by surrounding bogs. These elements marked the influence of underground feeding in July during summer baseflow, which was most visible in flood lakes in the Ob riparian zone and the Ob River itself. In May, the flood lakes were statistically similar to the Ob River. The elevated concentration of DOC (up to 60 mg/L) in the upland lakes was not correlated with groundwater-related elements, suggesting a lack of significant groundwater feeding in these lakes. In contrast, insoluble, usually low mobile elements (Al, Fe, other trivalent hydrolysates, Ti, Zr, Hf) and some metals (Cr, Zn, Ni, Pb) demonstrated a steady increase in concentration with increasing DOC, with the lowest values observed in the Ob River and the highest values observed in small tributaries and organic-rich upland lakes in July. It follows that these elements are limited by their main carriers – organic and organo-ferric colloids, rather than by the availability of the source, peat and mineral soil or plant litter. While for the majority of non-colloidal, groundwater-fed elements with high mobility (DIC, Na, Mg, Ca, K, Sr…) the small tributaries can be used as representatives of the Ob main stream, this is not the case for low mobility “insoluble” elements, such as Fe, Al, trivalent and tetravalent hydrolysates, and metal micronutrients (Cu, Zn, and Mn). The low soluble elements and divalent metals exhibited a much lower concentration in the river mainstream compared to that in the flood lakes, upland lakes and small rivers. This difference is significantly more pronounced in the baseflow in July compared to the spring flood in May. Presumably, autochthonous processes, such as the photo-oxidation and bio-oxidation of organo-ferric colloids and phytoplankton uptake are capable decreasing the concentration of these elements in the river mainstream.

Effect of arsenic on concentrations and translocations of mineral elements in the xylem of rice

ABSTRACTBy using Particle-Induced X-ray Emission (PIXE) technique, the effect of arsenic (As) on the mineral contents and translocation in the xylem of rice (Oryza sativa L. cv. ‘Akihikari’) was studied. The results suggest that exogenous As increased the concentrations of phosphorus (P), calcium (Ca) magnesium (Mg), sulfur (S), and manganese (Mn) in xylem, while the concentrations of potassium (K) remained unchanged. The highest concentration of As to the rice roots did not have any clear effect on the translocation of P, Ca, S, and chlorine (Cl) in the xylem, indicating that the increasing concentrations of the minerals may be due to a condensation effect, resulting from the repression of water movement in xylem by As-toxicity. Among the metal micronutrients, As decreased the concentrations and translocations of iron (Fe), zinc (Zn), and copper (Cu).

Geo-environmental assessment of Al-Wala dam sediments, Jordan

Surface sediments of Al-Wala Reservoir central Jordan, were evaluated to characterize trace element distribution and sources related to various physicochemical variables. Metallic micronutrient distribution is determined by grain size analysis, parent material in the catchment, and anthropogenic activities. The suitability of reservoir sediment as a source of natural additives for replacing eroded topsoil was assessed by comparing the physiochemical characteristics of bottom sediments to normal worldwide soils. Textural analysis of bottom sediments is mainly composed of very fine-grained facies (clayey-silty facies), characterized by high content of different types of clay minerals and organic matters, medium-high cation exchange capacity, and optimal pH ranges for availability of most micronutrients. Among the metallic micronutrients measured: Fe, Zn, Cd, Cu and Mn, total abundance of Zn and Cd slightly exceeded the recommended safe levels for normal soils, but these concentrations my are decline when the sediments are exposed to air. Comparing our results with natural soils, it can be concluded that clayey-silty facies sediments can be considered as a good source of non-manufactured additives, whereas coarse-grained (sandy and granule facies) sediments as a good agricultural soil.

IRCHLB-IV-Abstracts of Presentations at the 4th International Research Conference on Huanglongbing

IRCHLB-IV-Abstracts of Presentations at the 4th International Research Conference on Huanglongbing

Metal micronutrients relationships in crop, soil, and common weeds of two maize (Zea mays L.) fields

Deficiencies of metal micronutrients are common in some calcareous soils. Samples of aerial parts of maize and five common weeds and also soil beneath these plants were collected and analyzed to investigate the status and relationships of metal micronutrients in soil, crop, and common weeds of maize field trials at two sites. Results showed that Fe concentration in five studied weeds was higher than that of maize; the highest Fe concentration was found in Convolvolus arvensis and Echinochloa crus-galli (first site) and in Convolvolus arvensis tissues (second site). At both sites, the highest Mn concentration was observed in aboveground parts of Echinochloa crus-galli. The concentration of Mn (both sites) and Fe and Cu (second site) were remarkably higher in Echinochloa crus-galli tissues in comparison with maize. Also the concentrations of Fe (both sites) and Cu (second site) were considerably higher in Convolvolus arvensis tissues in comparison with maize. Available Fe was the highest in the soil beneath Convolvolus arvensis and Portulaca oleracea (first site) and beneath Convolvolus arvensis and Cenopodium album (second site). The high value of available Fe in the soil beneath Convolvolus arvensis may explain why Fe concentration was the highest in aerial parts of this weed species.

Changes of Nutrient Contents in Tomato Fruits Under The Influence of Increasing Intensity of Manganese Nutrition

Abstract The aim of conducted in years 2008-2012 studies was to assess the efficiency of application of increasing manganese levels on the nutritive value of tomato fruits (Lycopersicon esculentum Mill. cvs. ‘Alboney F1’ and ‘Emotion F1’), expressed in the contents of macro- and micronutrients. Plants were grown in rockwool with application of nutrient solution characterized the following chemical composition (in [mg dm–3]): N-NH4 2.2, N-NO3 - 230, P - 50, K - 430, Ca - 145, Mg - 65, Cl - 35, S-SO4 - 120, Fe - 2.48, Zn - 0.50, Cu - 0.07, pH -5.50, EC - 3.00 mS cm–1. The following manganese plant nutrition levels were examined (in mg Mn · dm–3): 0.06 (control), 0.3, 0.6, 1.2 (Experiment I), 2.4, 4.8, 9.6 and 19.2 (Experiment II); (denoted as Mn-0, Mn-0.3, Mn-0.6, Mn-1.2, Mn-2.4, Mn-4.8, Mn-9.6; Mn-19.2). The source of manganese was manganese sulfate (MnSO4 · H2O, 32.3% Mn). The nutritive value of tomato fruits changed significantly under the influence of the application of wide range of manganese concentrations. It was found a significant reduction of the content of phosphorus (Exp. I, II), potassium (Exp. II), calcium (Exp. I, II) and magnesium (Exp. I, II). Manganese influence on the decreasing content of other metallic micronutrients (Fe, Zn, Cu) in fruits. Cultivar had a significantly influence on the content of: nitrogen (except Mn-2.4, Mn-4.8, Mn-9.6), potassium (in Exp. II, except Mn-4.8), calcium (except for Mn-0.6, Mn-2.4), magnesium (except Mn-0.3 and Mn-2.4), iron (except Mn-1.2), manganese and zinc (except control combination) and copper (except Mn-0.6 and Mn-1.2). The highest contents of N, Ca and Mg in fruits were recorded for the application of Mn-0, while for P and K - at 0.3 mg Mn dm–3, whereas it was lowest for all these nutrients (except N) in the case of Mn-19.2 (Exp. II). The reduction of nutrient contents amounted to (% changes: from the lowest content to the highest content): N (11.3), P (48.1), K (24.8), Ca (75.4), Mg (57.5), Fe (59.2), Zn (65.4) and Cu (43.7).

Differential remineralization of major and trace elements in sinking diatoms

Macronutrients in sinking phytoplankton are typically remineralized at different rates, but less is known about the fate of micronutrient metals associated with sinking cells. Scavenging, the presence of co‐occurring abiotic particles, and inadvertent contamination limit the utility of bulk analytical approaches to study remineralization of trace metals in sinking phytoplankton. We used synchrotron x‐ray fluorescence mapping to measure macronutrients (P, S, and Si) and trace metals (Fe, Ni, and Zn) in individual cells of the diatom Asterionellopsis glacialis during a spring bloom in subtropical waters off New Zealand. P, S, Zn, and Ni were released significantly faster than Fe and Si from sinking cells in the upper 200 m. Bulk particulate element fluxes to sediment traps indicated similar trends, but biogenic silica flux was attenuated much faster than Si was lost from intact sinking cells collected in the traps. The metals were spatially co‐located with P and S in upper ocean cells, but this association with P and S (based on a spatial resolution of 450 nm) was largely absent in sinking cells. In contrast, Fe retained a weak spatial association with Si, suggesting that remineralized Fe may be re‐scavenged onto cell surfaces. As a result, dissolved Fe : macronutrient stoichiometries in the water column likely underestimate stoichiometries in sinking cells. We propose linkages between the selective loss of diatom cellular components (e.g., ribosomes or phospholipid membranes, Zn‐finger proteins, and urease) and the observed recycling of specific elements (P, Zn, and Ni, respectively), which set the stoichiometry of macro‐ and micronutrient supply to surface waters.

Quantifying the Impact of Atmospheric Deposition on the Biogeochemistry of Fe and Al in the Upper Ocean: A Decade of Collaboration with the US CLIVAR-CO2 Repeat Hydrography Program

The aerosol deposition of continental material and its partial dissolution in the surface ocean exerts an important control on the distribution of iron and other potentially limiting trace metal (TM) micronutrients in the open ocean. This dust deposition has implications for the regulation of global climate through the coupling of biolimiting TM cycles, marine productivity, and the global carbon cycle. Thus, it is important to determine the locations of dust deposition in the open ocean and to quantify the magnitude and subsequent dissolution of the dust. At present, there are too few dust deposition estimates and solubility measurements in the open ocean to adequately constrain this key source term in global biogeochemical models. While early sampling efforts were invaluable in highlighting the importance of TMs in regulating nutrient cycling and phytoplankton productivity in vast ocean regions, they lacked the spatial resolution and global coverage required to constrain model simulations and identify features that illuminate the processes controlling TM distributions. Starting in 2003, the US Climate Variability and Predictability (CLIVAR)-CO2 Repeat Hydrography Program provided an hour of ship time for dedicated TM sampling at every degree of latitude or longitude along selected cruise tracks. The principal goals for CLIVAR TM sampling were to produce a high-resolution dissolved iron (Fe) and aluminum (Al) data set with global coverage to better understand upper-ocean Fe biogeochemistry, determine patterns of atmospheric dust deposition based on surface dissolved Al levels, and improve our estimates of the fractional solubility of aerosol TMs using a dedicated shipboard aerosol sampling program. This paper describes recent advances in our understanding of dust deposition and the solubility of aerosol material resulting from 10 years of collaborative work under the US CLIVAR-CO2 Repeat Hydrography Program.

Fate of colloids during estuarine mixing in the Arctic

Abstract. The estuarine behavior of organic carbon (OC) and trace elements (TE) was studied for the largest European sub-Arctic river, which is the Severnaya Dvina; this river has a deltaic estuary covered in ice during several hydrological seasons: summer (July 2010, 2012) and winter (March 2009) baseflow, and the November–December 2011 ice-free period. Colloidal forms of OC and TE were assessed for three pore size cutoffs (1, 10, and 50 kDa) using an in situ dialysis procedure. Conventionally dissolved (&lt; 0.22 μm) fractions demonstrated clear conservative behavior for Li, B, Na, Mg, K, Ca, Sr, Mo, Rb, Cs, and U during the mixing of freshwater with the White Sea; a significant (up to a factor of 10) concentration increase occurs with increases in salinity. Si and OC also displayed conservative behavior but with a pronounced decrease in concentration seawards. Rather conservative behavior, but with much smaller changes in concentration (variation within ±30%) over a full range of salinities, was observed for Ti, Ni, Cr, As, Co, Cu, Ga, Y, and heavy REE. Strong non-conservative behavior with coagulation/removal at low salinities (&lt; 5‰) was exhibited by Fe, Al, Zr, Hf, and light REE. Finally, certain divalent metals exhibited non-conservative behavior with a concentration gain at low (~ 2–5‰, Ba, Mn) or intermediate (~ 10–15‰, Ba, Zn, Pb, Cd) salinities, which is most likely linked to TE desorption from suspended matter or sediment outflux. The most important result of this study is the elucidation of the behavior of the "truly" dissolved low molecular weight LMW&lt; 1 kDa fraction containing Fe, OC, and a number of insoluble elements. The concentration of the LMW fraction either remains constant or increases its relative contribution to the overall dissolved (&lt; 0.22 μm) pool as the salinity increases. Similarly, the relative proportion of colloidal (1 kDa–0.22 μm) pool for the OC and insoluble TE bound to ferric colloids systematically decreased seaward, with the largest decrease occurring at low (&lt; 5‰) salinities. Overall, the observed decrease in the colloidal fraction may be related to the coagulation of organo-ferric colloids at the beginning of the mixing zone and therefore the replacement of the HMW1 kDa–0.22 μm portion by the LMW&lt; 1 kDa fraction. These patterns are highly reproducible across different sampling seasons, suggesting significant enrichment of the mixing zone by the most labile (and potentially bioavailable) fraction of the OC, Fe and insoluble TE. The size fractionation of the colloidal material during estuarine mixing reflects a number of inorganic and biological processes, the relative contribution of which to element speciation varies depending on the hydrological stage and time of year. In particular, LMW&lt; 1 kDa ligand production in the surface horizons of the mixing zone may be linked to heterotrophic mineralization of allochthonous DOM and/or photodestruction. Given the relatively low concentration of particulate versus dissolved load of most trace elements, desorption from the river suspended material was less pronounced than in other rivers in the world. As a result, the majority of dissolved components exhibited either conservative (OC and related elements such as divalent metals) or non-conservative, coagulation-controlled (Fe, Al, and insoluble TE associated with organo-ferric colloids) behavior. The climate warming at high latitudes is likely to intensify the production of LMW&lt; 1 kDa organic ligands and the associated TE; therefore, the delivery of potentially bioavailable trace metal micronutrients from the land to the ocean may increase.

In-Feed Use of Heavy Metal Micronutrients in U.S. Swine Production Systems and Its Role in Persistence of Multidrug-Resistant Salmonellae

The study aimed to characterize the role of heavy metal micronutrients in swine feed in emergence of heavy-metal-tolerant and multidrug-resistant Salmonella organisms. We conducted a longitudinal study in 36 swine barns over a 2-year period. The feed and fecal levels of Cu(2+) and Zn(2+) were measured. Salmonella was isolated at early and late finishing. MICs of copper sulfate and zinc chloride were measured using agar dilution. Antimicrobial susceptibility was tested using the Kirby-Bauer method, and 283 isolates were serotyped. We amplified pcoA and czcD genes that encode Cu(2+) and Zn(2+) tolerance, respectively. Of the 283 isolates, 113 (48%) showed Cu(2+) tolerance at 24 mM and 164 (58%) showed Zn(2+) tolerance at 8 mM. In multivariate analysis, serotype and source of isolates were significantly associated with Cu(2+) tolerance (P < 0.001). Fecal isolates were more likely to be Cu(2+) tolerant than those of feed origin (odds ratio [OR], 27.0; 95% confidence interval [CI], 2.8 to 250; P = 0.0042) or environmental origin (OR, 5.8), implying the significance of gastrointestinal selective pressure. Salmonella enterica serotypes Typhimurium and Heidelberg, highly significant for public health, had higher odds of having >20 mM MICs of Cu(2+) than did "other" serotypes. More than 60% of Salmonella isolates with resistance type (R-type) AmStTeKm (32 of 53) carried pcoA; only 5% with R-type AmClStSuTe carried this gene. czcD gene carriage was significantly associated with a higher Zn(2+) MIC (P < 0.05). The odds of having a high Zn(2+) MIC (≥8 mM) were 14.66 times higher in isolates with R-type AmClStSuTe than in those with R-type AmStTeKm (P < 0.05). The findings demonstrate strong association between heavy metal tolerance and antimicrobial resistance, particularly among Salmonella serotypes important in public health.

Impact of western Siberia heat wave 2012 on greenhouse gases and trace metal concentration in thaw lakes of discontinuous permafrost zone

Abstract. During the anomalously hot summer in 2012, surface air temperatures in Western Siberia were 5 to 15 °C higher than those observed during the previous period of &gt; 30 yr. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating of water in thermokarst ponds and lakes in discontinuous permafrost zones and compare these observations to previous field results obtained when the temperature was normal during the summer of 2010 in the same region. In 2012, thermokarst bodies of water shrank significantly, water levels dropped approximately 50 cm in large lakes and small (&lt; 10–100 m2) ponds, and shallow soil depressions disappeared. Based on samples from ~ 40 bodies of water collected previously and in 2012, first-order features of changes in chemical composition in response to increased water temperatures (from 14.1 ± 2.2 to 23.8 ± 2.3 °C in 2010 and 2012, respectively) were established. In these thermokarst bodies of water that covered a full range of surface areas, the average conductivity and pH were almost unchanged, whereas dissolved organic carbon (DOC), Cl- and SO42- concentrations were higher by a factor of ~ 2 during summer 2012 compared to periods with normal temperatures. Similarly, most divalent metals and insoluble trivalent and tetravalent elements were more concentrated by a factor of 1.7–2.4 in the summer of 2012 than normal periods. The average concentrations of dissolved CO2 and CH4 during the hot summer of 2012 increased by factors of 1.4 and 4.9, respectively. For most of the trace elements bound to colloids, the degree of colloidal binding decreased by a factor of 1.44 ± 0.33 (for an average of 40 elements) during the hot summer of 2012 compared to normal periods. Increases in CO2 and CH4 concentrations with the decreasing size of the body of water were well-pronounced during the hot summer of 2012. The concentrations of CO2 and CH4 rose by factors of 5 and 150, respectively, in small (≤ 102 m2) compared to large (≥ 104 m2) thermokarst (thaw) lakes. Taken together, these trends suggest that, for a conservative scenario of lake size distribution, lake water warming at high latitudes will produce (1) a significant increase in methane emission capacity from thaw lake surfaces; (2) decreased molecular sizes of trace element complexes and potential bioavailability of metal micronutrients in water columns; and (3) relatively conservative responses by CO2, DOC and trace element concentrations.

Review of the Application of Near-Infrared Spectroscopy Technology to Determine the Chemical Composition of Animal Manure

Animal manure contains a variety of chemical constituents that are highly valuable to agriculture, including nitrogen, phosphorus, potassium, and metal micronutrients. Although appropriately applied manure has numerous positive attributes, the excessive application of manure may lead to pollution of the atmosphere, water, or soil. To reconcile precision agriculture and the potential negative environmental influences of animal manure, it is necessary to develop rapid and robust methods to evaluate the chemical composition of animal manure. This paper summarizes recent advances in near-infrared reflectance spectroscopy (NIRS) in predicting moisture, dry matter, organic matter, nitrogen, phosphorus, carbon, and metal content in animal manure. The results indicate the high potential of NIRS as an efficient tool for monitoring the chemical composition of animal manure. Future prospects and needs related to increasing the feasibility of the industrial application of NIRS and improving NIRS prediction precision in determining the chemical composition of animal manure are discussed.

Dissolution of copper and iron from automotive brake pad wear debris enhances growth and accumulation by the invasive macrophyte Salvinia molesta Mitchell

Automotive vehicles release particulate matter into the environment when their brakes are applied. The environmental effects of this automotive brake pad wear debris (BPWD) on the environment is a matter of growing debate yet the effects on plants have been largely untested. In this study, the effect of BPWD on the growth of the aquatic invasive Salvinia molesta Mitchell was examined. Salvinia molesta, plants were grown hydroponically in distilled water or in a distilled water extract containing BPWD. Growth of floating leaves, submerged leaves, and leaf nodes were measured over 20d at 4-d intervals. At the conclusion of the study the amount of BPWD present in solutions and plant tissues was quantified using atomic absorption spectrometry (AAS). Cultivation of S. molesta in the water containing BPWD resulted in greater dissolution of Cu and Fe than occurred in the absence of plants. The tissue Cu and Fe concentrations of plants cultivated in the BPWD were significantly higher than plants grown in the absence of BPWD. Growth of S. molesta significantly increased when cultivated in the BPWD solutions in comparison to the distilled water. The results suggest that S. molesta and similar aquatic plants may be capable of increasing the dissolution of metal micronutrients from BPWD and utilizing those micronutrients to increase growth. Such growth responses could indicate that BPWD may interact with invasive floating macrophytes to more rapidly degrade the quality and stability of aquatic communities.

The influence of inorganic nitrogen fertilizer forms on micronutrient retranslocation and accumulation in grains of winter wheat.

The fortification of cereal grains with metal micronutrients is a major target to combat human malnutrition of Fe and Zn. Based on recent studies showing that N fertilization can promote Fe and Zn accumulation in cereal grains, we investigated here the influence of nitrate- or ammonium-based N fertilization on the accumulation of Fe, Zn, and Cu as well as metal chelator pools in flag leaves and grains of winter wheat. Fertilization with either N form increased the concentrations of N and of the metal chelator nicotianamine (NA) in green leaves, while 2'-deoxymugineic acid (DMA) remained unaffected. Despite the differential response to N fertilization of NA and DMA levels in flag leaves, N fertilization remained without any significant effect on the net export of these metals during flag leaf senescence, which accounted for approximately one third of the total Fe, Zn, or Cu content in leaves. The significant increase in the accumulation of Fe, Zn, and Cu found in the grains of primarily ammonium-fertilized plants was unrelated to the extent of metal retranslocation from flag leaves. These results indicate that an increased N nutritional status of flag leaves promotes the accumulation of Fe, Zn, and Cu in flag leaves, which is accompanied by an increased pool of NA but not of DMA. With regard to the far higher concentrations of DMA relative to NA in leaves and leaf exudates, DMA may be more relevant for the mobilization and retranslocation of these metals in high-yielding wheat production.

Dissolved and particulate trace metal micronutrients under the McMurdo Sound seasonal sea ice: basal sea ice communities as a capacitor for iron.

Dissolved and particulate metal concentrations are reported from three sites beneath and at the base of the McMurdo Sound seasonal sea ice in the Ross Sea of Antarctica. This dataset provided insight into Co and Mn biogeochemistry, supporting a previous hypothesis for water column mixing occurring faster than scavenging. Three observations support this: first, Mn-containing particles with Mn/Al ratios in excess of the sediment were present in the water column, implying the presence of bacterial Mn-oxidation processes. Second, dissolved and labile Co were uniform with depth beneath the sea ice after the winter season. Third, dissolved Co:PO3−4 ratios were consistent with previously observed Ross Sea stoichiometry, implying that over-winter scavenging was slow relative to mixing. Abundant dissolved Fe and Mn were consistent with a winter reserve concept, and particulate Al, Fe, Mn, and Co covaried, implying that these metals behaved similarly. Elevated particulate metals were observed in proximity to the nearby Islands, with particulate Fe/Al ratios similar to that of nearby sediment, consistent with a sediment resuspension source. Dissolved and particulate metals were elevated at the shallowest depths (particularly Fe) with elevated particulate P/Al and Fe/Al ratios in excess of sediments, demonstrating a sea ice biomass source. The sea ice biomass was extremely dense (chl a >9500 μg/L) and contained high abundances of particulate metals with elevated metal/Al ratios. A hypothesis for seasonal accumulation of bioactive metals at the base of the McMurdo Sound sea ice by the basal algal community is presented, analogous to a capacitor that accumulates iron during the spring and early summer. The release and transport of particulate metals accumulated at the base of the sea ice by sloughing is discussed as a potentially important mechanism in providing iron nutrition during polynya phytoplankton bloom formation and could be examined in future oceanographic expeditions.