Availability Of Other Nutrients Research Articles

Increased leaf area index and efficiency drive enhanced production under elevated atmospheric [CO2 ] in a pine-dominated stand showing no progressive nitrogen limitation.

Enhancement of net primary production (NPP) in forests as atmospheric [CO2 ] increases is likely limited by the availability of other growth resources. The Duke Free Air CO2 Enrichment (FACE) experiment was located on a moderate-fertility site in the southeastern US, in a loblolly pine (Pinus taeda L.) plantation with broadleaved species growing mostly in mid-canopy and understory. Duke FACE ran from 1994 to 2010 and combined elevated [CO2 ] (eCO2 ) with nitrogen (N) additions. We assessed the spatial and temporal variation of NPP response using a dataset that includes previously unpublished data from 6 years of the replicated CO2 × N experiment and extends to 2 years beyond the termination of enrichment. Averaged over time (1997-2010), NPP of pine and broadleaved species were 38% and 52% higher under eCO2 compared to ambient conditions. Furthermore, there was no evidence of a decline in enhancement over time in any plot regardless of its native site quality. The relation between spatial variation in the response and native site quality was suggested but inconclusive. Nitrogen amendments under eCO2 , in turn, resulted in an additional 11% increase in pine NPP. For pine, the eCO2 -induced increase in NPP was similar above- and belowground and was driven by both increased leaf area index (L) and production efficiency (PE = NPP/L). For broadleaved species, coarse-root biomass production was more than200% higher under eCO2 and accounted for the entire production response, driven by increased PE. Notably, the fraction of annual NPP retained in total living biomass was higher under eCO2 , reflecting a slight shift in allocation fraction to woody mass and a lower mortality rate. Our findings also imply that tree growth may not have been only N-limited, but perhaps constrained by the availability of other nutrients. The observed sustained NPP enhancement, even without N-additions, demonstrates no progressive N limitation.

Improved Organic Fertilisers Made from Combinations of Compost, Biochar, and Anaerobic Digestate: Evaluation of Maize Growth and Soil Metrics

Treated bio-residues can be used as biostimulants in crops within the circular economy approach to reduce the use of traditional fertilisers. In this work, we optimised the combination rates for three types of treated bio-residues (compost, biochar, and anaerobic digestate (AD)) in two microcosm trials, one with a combination of compost and biochar and other with biochar and AD. The crop used was maize, and the variables analysed were plant growth, and soil chemical and biological properties. The combination of bio-residues improved plant growth and soil biological activity to a greater extent than one product alone; that is, compost and biochar performed better than compost alone and biochar, and AD performed better than biochar alone. However, while the concentration in the plant biomass of several essential nutrients for crops increased in the treatments with compost and biochar, and with biochar and AD, compared to the untreated controls, the nitrogen concentration was reduced. This was due to the competition for nitrogen between the plant and the soil microbiome, whose activity was activated. Due to the importance of nitrogen in plant growth, the increase in biomass production could be explained not only by the higher availability of other nutrients but also by the plant-growth-promoting activity exerted by the more active soil microbiome. Further research should focus on validating this hypothesis and unravelling the mechanisms involved. From the environmental site, the presence of biochar in the mixtures of organic residues reduced the soil nitrogen at risk of lixiviation and sequestered carbon, which partially compensated for the increased CO2 emissions because labile forms of carbon were present in the remaining organic residues.

Rhizobium as Biotechnological Tools for Green Solutions: An Environment-Friendly Approach for Sustainable Crop Production in the Modern Era of Climate Change.

Modern and industrialized agriculture enhanced farm output during the last few decades, but it became possible at the cost of agricultural sustainability. Industrialized agriculture focussed only on the increase in crop productivity and the technologies involved were supply-driven, where enough synthetic chemicals were applied and natural resources were overexploited with the erosion of genetic diversity and biodiversity. Nitrogen is an essential nutrient required for plant growth and development. Even though nitrogen is available in large quantities in the atmosphere, it cannot be utilized by plants directly with the only exception of legumes which have the unique ability to fix atmospheric nitrogen and the process is known as biological nitrogen fixation (BNF). Rhizobium, a group of gram-negative soil bacteria, helps in the formation of root nodules in legumes and takes part in the BNF. The BNF has great significance in agriculture as it acts as a fertility restorer in soil. Continuous cereal-cereal cropping system, which is predominant in a major part of the world, often results in a decline in soil fertility, while legumes add nitrogen and improve the availability of other nutrients too. In the present context of the declining trend of the yield of some important crops and cropping systems, it is the need of the hour for enriching soil health to achieve agricultural sustainability, where Rhizobium can play a magnificent role. Though the role of Rhizobium in biological nitrogen fixation is well documented, their behaviour and performance in different agricultural environments need to be studied further for a better understanding. In the article, an attempt has been made to give an insight into the behaviour, performance and mode of action of different Rhizobium species and strains under versatile conditions.

Studies on the synergistic Interplay of Vitamin D and K for Improving Bone and Cardiovascular Health

Nutrients perform their roles either directly or through interaction with other nutrients inside our body. The nature of interactions between nutrients can be synergistic, which brings about maximum benefit to the host, or antagonistic, i.e., one nutrient affects the uptake and availability of other nutrients in the body. These interactions need to be critically analysed and acknowledged to harness their positive health benefits. Combining nutrients having a synergistic effect may help in lowering the threat of cardiovascular ailment, osteoporosis, and other health issues. This study aims to qualitatively review the information that is currently available upon the synergistic effects of co-supplementing Vitamin D and K on bone and cardiovascular health among various age groups. The methodology followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A structured search of two databases-PubMed and Google Scholar—was carried out, and articles were identified that focused upon the dual supplementation of Vitamin D and K, which has been shown to improve bone and cardiovascular health among users. The search was restricted to the English language, conducted, and published between 2006 and 2021. Overall, 12 studies involving 8216 participants were included in the qualitative analysis. Among these, 5 were randomized controlled trials, 6 were observational studies, and 1 was interventional studies. The results were interpreted based on improved bone health by assessing the progress in Bone Mineral Content (BMC), lower extremity function, Bone Mineral Density (BMD), and bone turnover. In contrast, improvement in cardiovascular health was recorded based on the Carotid Intima-media Thickness (CIMT), arterial stiffness, high systolic and diastolic blood pressure, and the structure of the heart. Out of a total 12 studies, 11 studies showed that Vitamin D work in synergy with Vitamin K and also has a significant role in improving bone fractures, low BMD, and cardiovascular disorders. Further research and clinical trials on these Vitamins in different age groups and disease conditions are warranted.

A tale of two players: the role of phosphate in iron and zinc homeostatic interactions.

This minireview details the impact of iron-phosphate and zinc-phosphate interactions in plants and provides perspectives for further areas of research regarding nutrient homeostasis. Iron (Fe) and zinc (Zn) are among the most important micronutrients for plant growth and have numerous implications for human health and agriculture. While plants have developed efficient uptake and transport mechanisms for Fe and Zn, emerging research has shown that the availability of other nutrients in the environment influences the homeostasis of Fe and Zn within plants. In this minireview, we present the current knowledge regarding homeostatic interactions of Fe and Zn with the macronutrient phosphorous (P) and the resulting physiological responses to combined deficiencies of these nutrients. Fe and P interactions have been shown to influence root development, photosynthesis, and biological processes aiding Fe uptake. Zn and P interactions also influence root growth, and coordination of Zn-dependent transcriptional regulation contributes to phosphate (Pi) transport in the plant. Understanding homeostatic interactions among these different nutrients is of critical importance to obtain a more complete understanding of plant nutrition in complex soil environments.

ZN AS A VITAL MICRONUTRIENT IN PLANTS

Macro and micronutrients are vital for the growth and productivity of the plants. Zinc (Zn) is considered to be one of the essential micronutrients for the growth and development of cereals as well as fodder crops. It is also a regulatory cofactor for all those enzymes which are required for the synthesis of chlorophyll, proteins and carbohydrates. The functioning of these enzymes is affected significantly due to Zn deficiency and there will be a retarded growth and productivity of plants. Deficiency of Zn is a universal problem among cereal crops. The concentration of Zn varies from 6-1.2 mg/kg in various soils, whereas its concentration reaches 20-300 ppm in plants. Zn deficiency leads to chlorosis in the leaves of plants. Various reasons affect the availability of Zn in the plants, which include soil type, pH of the soil and availability of other nutrients that work antagonistically for the absorption of Zn. Zn applied as the fertilizer gets converted into unavailable form by making insoluble complexes and thus not available for plants. Hence the best alternative to this issue is the use of Zn solubilising bacteria (ZSB). These ZSB will accumulate in the rhizosphere zone of the plants and will reduce the requirement of the applied Zn fertilizer. It will prevent Zn toxicity in the soil and will enhance the uptake of other macronutrients like phosphorus to the plants.

Quality Assessment of Chicken Breast Fillets Treated with Custard Apple (Annona squamosa) Leaves Extract

Background: Meat and meat products are perishable due to high content of moisture and easy availability of other nutrients. Oxidative rancidity and microbial growth are the major causes of their spoilage. Synthetic antioxidants viz. BHA, BHT, TBHQ etc. are used in the chicken processing industry for maintaining quality of chicken products. However, due to evidence of their toxic effects on human health there is interest in the scientists and manufacturers to use natural preservatives with antioxidants and antimicrobials properties. Hence, the study was undertaken to assess the effect of custard apple (Annona squamosa) leaves extract (CLE), on the quality of chicken breast fillets. Methods: Chicken breast fillets were treated separately by dipping in 0.1, 0.3 and 0.5% aqueous solutions of CLE, distilled water and 100 ppm solution of BHT. Samples were stored under refrigeration (4±1oC) conditions and analyzed on 0th, 3rd, 6th and 9th day of storage. Result: Total phenolic content, ascorbic acid content, DPPH radical scavenging assay and ferric reducing antioxidant power of CLE were 57.13±0.22 µgGAE/mg, 163.23±0.40 µgAA/mg, 32.20±0.42% and 132.43±0.50 µMFe (II) equi/g respectively. The fillets treated with 0.5% solution of CLE were acceptable till sixth day with significantly (p less than 0.01) higher sensory scores than the controls. The pH, WHC, ERV, tyrosine value, TBARS value, total plate count and psychrophilic count of the sixth day samples treated with 0.5% CLE were 5.72±0.01, 65.32±0.31%, 19.40±0.59ml, 9.50±0.37 mg/100g, 0.316±0.002 mgMDA/Kg, 4.90±0.01 log10CFU/g and 3.68±0.02 log10CFU/g respectively. It can be concluded that 0.5% aqueous solution of CLE can be used for extension of shelf life of chicken breast fillets up to 6 days at refrigeration (4±1oC).

Negative effects of nitrogen override positive effects of phosphorus on grassland legumes worldwide

Anthropogenic nutrient enrichment is driving global biodiversity decline and modifying ecosystem functions. Theory suggests that plant functional types that fix atmospheric nitrogen have a competitive advantage in nitrogen-poor soils, but lose this advantage with increasing nitrogen supply. By contrast, the addition of phosphorus, potassium, and other nutrients may benefit such species in low-nutrient environments by enhancing their nitrogen-fixing capacity. We present a global-scale experiment confirming these predictions for nitrogen-fixing legumes (Fabaceae) across 45 grasslands on six continents. Nitrogen addition reduced legume cover, richness, and biomass, particularly in nitrogen-poor soils, while cover of non-nitrogen-fixing plants increased. The addition of phosphorous, potassium, and other nutrients enhanced legume abundance, but did not mitigate the negative effects of nitrogen addition. Increasing nitrogen supply thus has the potential to decrease the diversity and abundance of grassland legumes worldwide regardless of the availability of other nutrients, with consequences for biodiversity, food webs, ecosystem resilience, and genetic improvement of protein-rich agricultural plant species.

Soil tillage affects soybean growth and promotes heavy metal accumulation in seeds

When soybean is grown in soils with high heavy metal concentrations, it may introduce those contaminants into the human food chain, posing risks to human health. This study evaluated the effect of tilling the soil with high Cu, Zn, and Mn levels on soybean physiology and metal accumulation in seeds. Disturbed and undisturbed soil samples were collected in two different sites: a vineyard with high heavy metal concentration and a grassland area, containing natural vegetation. Two soybean cultivars were sown and grown in the greenhouse. Photosynthetic parameters and biochemical analysis of oxidative stress were performed. Cu, Zn, and Mn in leaves and seeds, dry mass, and weight of seeds were evaluated. Soil structure had a high influence on plant growth and physiology, while soil site had a high impact on heavy metal accumulation in leaves and seeds. Soybean plants that grown in vineyard soils with high heavy metal concentrations, accumulated 50% more Zn in leaves and seeds, 70% more Cu in leaves, and 90% more Cu in seeds, than those plants grown in grassland soils. Besides, Zn concentration in seeds was higher than the permissible limit. Moreover, the disturbance of both vineyard soil and grassland soil was not good for plant growth and physiology, which have increased TBARS and H2O2 concentration in plants, transpiration rate, metal concentration in leaves and seeds. Soil disturbance may have caused organic matter oxidation and changes in the composition and quantity of soil microorganisms and it affects the availability of other nutrients in the soil.

AZOLLA: POTENTIAL BIOFERTILIZER FOR INCREASING RICE PRODUCTIVITY, AND GOVERNMENT POLICY FOR IMPLEMENTATION

Rice is the staple food for the significant population of Asia. Due to projected population growth in this region, the demand for this food is also predicted to be increased exponentially soon. Nitrogen (N) plays a dominant role in increasing rice yield as it is the most critical yield-limiting nutrient of rice. Chemical N fertilizers which are a major source in supplying N nutrients to rice, have adverse effects on overall soil and environmental health in the long term. The application of free-floating aquatic fern Azolla as a biofertilizer can be an alternative to improve rice yield without degrading the environment. It provides a natural source of many nutrients, especially N, improves the availability of other nutrients, plays a critical role in weed suppression, enhances soil organic matter, and improves efficiency of the inorganic fertilizers while maintaining the suitable soil pH condition for rice growth, which overall contribute to rice yield increment. Therefore, Azolla application has tremendous potential to improve soil health and boost yield sustainability.

Environmental Control of Phosphorus Acquisition: A Piece of the Molecular Framework Underlying Nutritional Homeostasis.

Homeostasis of phosphorus (P), an essential macronutrient, is vital for plant growth under diverse environmental conditions. Although plants acquire P from the soil as inorganic phosphate (Pi), its availability is generally limited. Therefore, plants employ mechanisms involving various Pi transporters that facilitate efficient Pi uptake against a steep concentration gradient across the plant-soil interface. Among the different types of Pi transporters in plants, some members of the PHOSPHATE TRANSPORTER 1 (PHT1) family, present in the plasma membrane of root epidermal cells and root hairs, are chiefly responsible for Pi uptake from the rhizosphere. Therefore, accurate regulation of PHT1 expression is crucial for the maintenance of P homeostasis. Previous investigations positioned the Pi-dependent posttranslational regulation of PHOSPHATE STARVATION RESPONSE 1 (PHR1) transcription factor activity at the center of the regulatory mechanism controlling PHT1 expression and P homeostasis; however, recent studies indicate that several other factors also regulate the expression of PHT1 to modulate P acquisition and sustain P homeostasis against environmental fluctuations. Together with PHR1, several transcription factors that mediate the availability of other nutrients (such as nitrogen and zinc), light, and stress signals form an intricate transcriptional network to maintain P homeostasis under highly diverse environments. In this review, we summarize this intricate transcriptional network for the maintenance of P homeostasis under different environmental conditions, with a main focus on the mechanisms identified in Arabidopsis.

Nitrogen Source Governs Community Carbon Metabolism in a Model Hypersaline Benthic Phototrophic Biofilm.

Increasing anthropogenic inputs of fixed nitrogen are leading to greater eutrophication of aquatic environments, but it is unclear how this impacts the flux and fate of carbon in lacustrine and riverine systems. Here, we present evidence that the form of nitrogen governs the partitioning of carbon among members in a genome-sequenced, model phototrophic biofilm of 20 members. Consumption of NO3 - as the sole nitrogen source unexpectedly resulted in more rapid transfer of carbon to heterotrophs than when NH4 + was also provided, suggesting alterations in the form of carbon exchanged. The form of nitrogen dramatically impacted net community nitrogen, but not carbon, uptake rates. Furthermore, this alteration in nitrogen form caused very large but focused alterations to community structure, strongly impacting the abundance of only two species within the biofilm and modestly impacting a third member species. Our data suggest that nitrogen metabolism may coordinate coupled carbon-nitrogen biogeochemical cycling in benthic biofilms and, potentially, in phototroph-heterotroph consortia more broadly. It further indicates that the form of nitrogen inputs may significantly impact the contribution of these communities to carbon partitioning across the terrestrial-aquatic interface.IMPORTANCE Anthropogenic inputs of nitrogen into aquatic ecosystems, and especially those of agricultural origin, involve a mix of chemical species. Although it is well-known in general that nitrogen eutrophication markedly influences the metabolism of aquatic phototrophic communities, relatively little is known regarding whether the specific chemical form of nitrogen inputs matter. Our data suggest that the nitrogen form alters the rate of nitrogen uptake significantly, whereas corresponding alterations in carbon uptake were minor. However, differences imposed by uptake of divergent nitrogen forms may result in alterations among phototroph-heterotroph interactions that rewire community metabolism. Furthermore, our data hint that availability of other nutrients (i.e., iron) might mediate the linkage between carbon and nitrogen cycling in these communities. Taken together, our data suggest that different nitrogen forms should be examined for divergent impacts on phototrophic communities in fluvial systems and that these anthropogenic nitrogen inputs may significantly differ in their ultimate biogeochemical impacts.

Effects of Liming on Dithionate and Oxalate Extractable Aluminium in Acid Soils

Liming and phosphorus (P) applications are recommended practices for improving crop production in acid soils of the tropics. Although considerable work has been done to establish liming rates for acid soils in many parts of the world, information on the effects of lime on the forms of aluminium which actively sorb P in such soils is minimal. A greenhouse pot experiment was conducted at Waruhiu Farmers Training Centre, Githunguri to evaluate the effect of liming on oxalate and dithionate extractable aluminium in acid soils. Extremely (pH 4.48) and strongly (pH 4.59) acidic soils were evaluated. Four liming (CaO) rates namely 0, 2.2, 5.2 and 7.4 tonnes ha-1 for extremely acidic and 0, 1.4, 3.2, and 4.5 tonnes ha-1 for strongly acidic soils were evaluated. The experiment was laid out in a Randomized Complete Block Design (RCBD) and replicated three times. Data collected included: initial soil chemical properties, oxalate (Alo) and dithionate (Ald) aluminium levels. The tested soils had high exchangeable Al (> 2 cmol Al kg-1), Al saturation of (> 20% Al) and low extractable P values (< 15 mg P kg-1 soil). Liming significantly (p=.05) reduced Alo by 70% and 68% in extremely and strongly acidic soils respectively and Ald by 78% in both extremely and strongly acidic soils compared to control. Use of 7.4 tonnes ha-1 of lime in extremely acidic soils and 4.5 tonnes ha-1 of lime in strongly acidic soils significantly (p=.05) reduced both Alo and Ald by > 68% compared to no lime. It was, therefore, concluded that liming contributes to the reduction of soluble Alo and Ald in acid soils of the Kenya highlands leading to increased soluble P availability. Studies are required to provide short and long term optimal liming rates that reduce Alo and Ald without distabilizing availability of other nutrients in field conditions under wide range of acid soils.

Understanding Soil Phosphorus

Phosphorus is the second most important crop nutrient after Nitrogen. It is an essential macronutrient that plays important role in all crop biochemical processes such as photosynthesis, respiration, energy storage, transfer, cell division, cell enlargement and nitrogen fixation. It is also important in seed germination, seedling establishment, root, shoot, flower and seed development. Despite its importance in crop nutrition, availability of the nutrient in soils for plant uptake is limited by several soil factors. The factors include: soil pH levels, clay mineralogy, organic matter, free iron and aluminium, calcium carbonate, soil temperatures and availability of other nutrients among other factors. Availability of phosphorus for plant uptake can be managed by adoption of practices such as liming acidic soils, application of organic amendments in both alkaline and acidic soils, tillage practices and regulation of time and method of P fertilizer application.

Nutrient regulation of late spring phytoplankton blooms in the midlatitude North Atlantic

AbstractThe duration and magnitude of the North Atlantic spring bloom impacts both higher trophic levels and oceanic carbon sequestration. Nutrient exhaustion offers a general explanation for bloom termination, but detail on which nutrients and their relative influence on phytoplankton productivity, community structure, and physiology is lacking. Here, we address this using nutrient addition bioassay experiments conducted across the midlatitude North Atlantic in June 2017 (late spring). In four out of six experiments, phytoplankton accumulated over 48–72 h following individual additions of either iron (Fe) or nitrogen (N). In the remaining two experiments, Fe and N were serially limiting, that is, their combined addition sequentially enhanced phytoplankton accumulation. Silicic acid (Si) added in combination with N + Fe led to further chlorophyll a (Chl a) enhancement at two sites. Conversely, addition of zinc, manganese, cobalt, vitamin B12, or phosphate in combination with N + Fe did not. At two sites, the simultaneous supply of all six nutrients, in combination with N + Fe, also led to no further Chl a enhancement, but did result in an additional 30–60% particulate carbon accumulation. This particulate carbon accumulation was not matched by a Redfield equivalent of particulate N, characteristic of high C:N organic exudates that enhance cell aggregation and sinking. Our results suggest that growth rates of larger phytoplankton were primarily limited by Fe and/or N, making the availability of these nutrients the main bottom‐up factors contributing to spring bloom termination. In addition, the simultaneous availability of other nutrients could modify bloom characteristics and carbon export efficiency.

Long Term Fertilizer Management Effect on Nutrient Dynamics in Rainfed Rice-lentil System in Transect 4 of IndoGangetic Plain

The present study analyzed the effect of different organic and inorganic fertilizers on soil nutrient dynamics in a long-term field experiment under rainfed rice-lentil system. The experiment was operative at Agricultural Research Farm, Institute of Agricultural Sciences, B.H.U Varanasi, Uttar Pradesh, India. Carbon dynamics was investigated on surface soil on the basis of distribution of Walkley & Black Carbon, in active pool (AP) or labile carbon (oxidisable at low concentration of H2SO4) in relation to passive pool (PP) or non labile carbon (oxidisable at high concentration of H2SO4) and its indices carbon management index (CMI). The effect of eight different treatments including unfertilized, 100% N from farm yard manure, 100% recommended dose of fertilizer, 50% RDF + 50% N Foliar), 50% RDF, 50% RDF + 50% N FYM), 50% N FYM and Farmers practices i.e. application of 20kg N ha-1 The availability & uptake of major nutrients were studied. The results revealed: That mixed application of inorganic fertilizers and FYM substantially increase the soil organic carbon pool, sustainability index over remaining treatments. Higher fertilizer application rates resulted in higher and sustained crop yields which had been reflected in sustainability yield index. A significant Pearson correlation was found between SOC, AP, PP, exchangeable K2O content, soil microbial biomass carbon and SYI. (The result indicated to adopt conjunctive use of nutrient management which promote the SOC more labile and, induce availability of other nutrients coupled with SMBC that translate into higher crop yields.

Double‐Annual Forage Crop Rotation Controls Nutrient Surpluses in Nitrogen‐Based Organic Fertilization

Core Ideas In intensive forage systems, 170 kg N ha−1 just from manures limits C sequestration. Biennial rotations of four crops maximize nutrient recirculation in calf‐rearing farms. Double‐annual forage crop rotation reduces P surpluses in crop–livestock systems. The use of organic fertilizers from stock‐raising activity is usually based on the nitrogen (N) criterion. The objective of our research is to evaluate whether this N criterion led to positive or environmentally risky changes, mainly in organic carbon (OC) storage and the availability of the main nutrients. Three biennial rotations of four crops were set up in a 6‐yr time‐frame. The treatments included a control (no N added); two mineral treatments, where 250 kg N ha−1 yr−1 was provided at two different times during the rotation; three cattle manure treatments, which provided 170, 250, and 500 kg N ha−1 yr−1; and four treatments in which the two lowest manure rates were complemented with mineral N (80 and 160 kg N ha−1 yr−1). Over the 6‐yr period, the measured soil OC increases were equivalent to approximately 25, 43, and 35% of the manure OC applied, respectively, following the manure rate increases. Furthermore, equivalences were of −5, 23, and 25% when compared with full mineral fertilization. The positive slope of phosphorus availability was 1.2 mg Olsen‐P kg−1 to 10 kg P ha−1 applied from manures (N/P = 4) when starting from a threshold of 15.9 mg Olsen‐P kg−1. The availability of other nutrients (Mg, Zn, and Na) also increased with increasing manure rates. In a medium‐term experiment, the manure rate of 250 kg N ha−1 yr−1 optimized the nutrient recirculation. In the long term, rotations should be redesigned to control P surpluses, or the amount of N applied from manures should be reduced.

Role of Magnesium in Vitamin D Activation and Function.

Nutrients usually act in a coordinated manner in the body. Intestinal absorption and subsequent metabolism of a particular nutrient, to a certain extent, is dependent on the availability of other nutrients. Magnesium and vitamin D are 2 essential nutrients that are necessary for the physiologic functions of various organs. Magnesium assists in the activation of vitamin D, which helps regulate calcium and phosphate homeostasis to influence the growth and maintenance of bones. All of the enzymes that metabolize vitamin D seem to require magnesium, which acts as a cofactor in the enzymatic reactions in the liver and kidneys. Deficiency in either of these nutrients is reported to be associated with various disorders, such as skeletal deformities, cardiovascular diseases, and metabolic syndrome. It is therefore essential to ensure that the recommended amount of magnesium is consumed to obtain the optimal benefits of vitamin D.

Contribution of increased mutagenesis to the evolution of pollutants-degrading indigenous bacteria.

Bacteria can rapidly evolve mechanisms allowing them to use toxic environmental pollutants as a carbon source. In the current study we examined whether the survival and evolution of indigenous bacteria with the capacity to degrade organic pollutants could be connected with increased mutation frequency. The presence of constitutive and transient mutators was monitored among 53 pollutants-degrading indigenous bacterial strains. Only two strains expressed a moderate mutator phenotype and six were hypomutators, which implies that constitutively increased mutability has not been prevalent in the evolution of pollutants degrading bacteria. At the same time, a large proportion of the studied indigenous strains exhibited UV-irradiation-induced mutagenesis, indicating that these strains possess error-prone DNA polymerases which could elevate mutation frequency transiently under the conditions of DNA damage. A closer inspection of two Pseudomonas fluorescens strains PC20 and PC24 revealed that they harbour genes for ImuC (DnaE2) and more than one copy of genes for Pol V. Our results also revealed that availability of other nutrients in addition to aromatic pollutants in the growth environment of bacteria affects mutagenic effects of aromatic compounds. These results also implied that mutagenicity might be affected by a factor of how long bacteria have evolved to use a particular pollutant as a carbon source.

Assessing the effects of iron enrichment across holobiont compartments reveals reduced microbial nitrogen fixation in the Red Sea coral Pocillopora verrucosa.

The productivity of coral reefs in oligotrophic tropical waters is sustained by an efficient uptake and recycling of nutrients. In reef‐building corals, the engineers of these ecosystems, this nutrient recycling is facilitated by a constant exchange of nutrients between the animal host and endosymbiotic photosynthetic dinoflagellates (zooxanthellae), bacteria, and other microbes. Due to the complex interactions in this so‐called coral holobiont, it has proven difficult to understand the environmental limitations of productivity in corals. Among others, the micronutrient iron has been proposed to limit primary productivity due to its essential role in photosynthesis and bacterial processes. Here, we tested the effect of iron enrichment on the physiology of the coral Pocillopora verrucosa from the central Red Sea during a 12‐day experiment. Contrary to previous reports, we did not see an increase in zooxanthellae population density or gross photosynthesis. Conversely, respiration rates were significantly increased, and microbial nitrogen fixation was significantly decreased. Taken together, our data suggest that iron is not a limiting factor of primary productivity in Red Sea corals. Rather, increased metabolic demands in response to iron enrichment, as evidenced by increased respiration rates, may reduce carbon (i.e., energy) availability in the coral holobiont, resulting in reduced microbial nitrogen fixation. This decrease in nitrogen supply in turn may exacerbate the limitation of other nutrients, creating a negative feedback loop. Thereby, our results highlight that the effects of iron enrichment appear to be strongly dependent on local environmental conditions and ultimately may depend on the availability of other nutrients.