Enrichment of fertilizers with zinc: An excellent investment for humanity and crop production in India

Soil micronutrients linked to human health in India

Trace soil minerals are a critical determinant of both crop productivity and the mineral concentration of crops, therefore potentially impacting the nutritional status of human populations relying on those crops. We link health data from nearly 0.3 million children and one million adult women across India with over 27 million soil tests drawn from a nationwide soil health program. We find that soil zinc availability is positively associated with children's linear height growth, and soil iron availability is positively associated with hemoglobin levels. The link between soil zinc and childhood stunting is particularly robust-a one standard deviation increase in satisfactory soil zinc tests is associated with approximately 11 fewer children stunted per 1000. We also find that this zinc-stunting relationship is strongest in wealthier households. Our results suggest that soil mineral availability impacts human nutritional status and health in at least some areas of India, and that agronomic fortification may be a beneficial intervention.

Formulation of Zinc oxide/Gum acacia nanocomposite as a novel slow-release fertilizer for enhancing Zn uptake and growth performance of Spinacia oleracea L

Zinc (Zn) deficiency has caused nutritional disorders in 17% of the world's population; thus, producing Zn-enriched plants as a dietary source is necessary. Recently, nanofertilizers have gained much attention as a substitute for conventional fertilizers; however, soil application of polymer-coated Zn-based nanofertilizer has not been explored much. The present study depicts the green synthesis of ZnO nanoparticles using Melia azedarach L. leaf extract, whose phytoconstituents have reducing abilities. The synthesized nanoparticles were combined with gum acacia (GA) to form a ZnOGA nanocomposite. The structural and morphological properties of ZnOGA were studied using XRD, FTIR, FESEM, and EDX. A pot experiment study was carried out with Spinacia oleracea L. at various doses (3, 5, and 10 mg/kg) of the synthesized ZnOGA to evaluate its effectiveness as a slow-release fertilizer and was compared with a commercial Zn fertilizer. The plant growth studies revealed a significant increase in the phyto-morphological traits of the plants fertilized with ZnOGA compared to commercial fertilizer. The plants also displayed significantly higher contents of protein (17-47%), phenols (25-60%), proline (82-94%), total soluble sugar (20-31%), DPPH activity (70-72%), and Zn uptake (91-106%). The doses of ZnOGA played an imperative role in determining the growth and productivity of the plant. Soil column studies showed that ZnOGA reduces Zn leaching by 52% compared to commercial Zn fertilizer. This study signifies the potential of ZnOGA to be applied as an eco-friendly and sustainable substitute for conventional Zn fertilizer minimizing Zn losses and Zn deficiency-related health problems in human populations.

Conservation Tillage and Waste Crop Residue Based Zinc Fortification in Rice and Wheat under Reclaimed Sodic Soils: Progress toward Nutrient Circularity and Sustainability

Nearly 50% of the population across the globe is at risk of malnutrition with respect to zinc (Zn) in areas where a cereal based dietary system dominates. The present study estimated daily Zn intake in humans through field experiments in reclaimed sodic soil, utilizing waste crop residue (CR) in conservation tillage where CR played a vital role in enhancing Zn uptake in rice and wheat grains. Zn dynamics, its bioavailability, interaction with soil properties, and plausible contribution in dietary intake were studied extensively to supplement the research. A higher mobility factor (2.70%) and plant available Zn resulted in its higher uptake in rice (58.2 mg kg^-1) and wheat (67.2 mg kg^-1) under zero tillage in rice followed by zero tillage in wheat where CR was retained on the surface (ZT_R-ZT_W+CR). Daily Zn intake was found to be maximum (0.651 mg kg^-1 day^-1) under ZT_R-ZT_W+CR, demonstrating zinc sufficiency. Thus, this study may help in formulating actionable policies for combating both nutritional security and environmental hazards due to CR burning.

Biofortification: A long-term solution to improve global health- a review

Biofortification is a revolutionary technique for improving plant nutrition and alleviating human micronutrient deficiency. Fertilizers can help increase crop yield and growth, but applying too much fertilizer can be a problem because it leads to the release of greenhouse gases and eutrophication. One of the major global hazards that affects more than two million people globally is the decreased availability of micronutrients in food crops, which results in micronutrient deficiencies or "hidden hunger" in people. Micronutrients, like macronutrients, perform a variety of roles in plant and human nutrition. This review has highlighted the importance of micronutrients as well as their advantages. The uneven distribution of micronutrients in geological areas is not the only factor responsible for micronutrient deficiencies, other parameters including soil moisture, temperature, texture of the soil, and soil pH significantly affects the micronutrient concentration and their availability in the soil. To overcome this, different biofortification approaches are assessed in the review in which microbes mediated, Agronomic approaches, Plant breeding, and transgenic approaches are discussed. Hidden hunger can result in risky health conditions and diseases such as cancer, cardiovascular disease, osteoporosis, neurological disorders, and many more. Microbes-mediated biofortification is a novel and promising solution for the bioavailability of nutrients to plants in order to address these problems. Biofortification is cost effective, feasible, and environmentally sustainable. Bio-fortified crops boost our immunity, which helps us to combat these deadly viruses. The studies we discussed in this review have demonstrated that they can aid in the alleviation of hidden hunger.

Soil zinc deficiency and child stunting: Evidence from Nepal

We examine the negative child health impacts of soil zinc (Zn) deficiency in Nepal. Soil Zn deficiency limits both crop yields and the Zn concentration in food crops, leading many to speculate that it underlies human Zn deficiency and child stunting, globally and particularly in South Asia. We find strong evidence that soil Zn deficiency does have a causal impact on child stunting in Nepal's Tarai region, the breadbasket of the country. Using causal bounds, we find that a 1 part per million increase in plant-available soil Zn - achievable with application of Zn-enriched fertilizer - decreases child stunting by between 1 and 7.5 percentage points. Multiple statistical sensitivity tests indicate that this relationship is unlikely to be manufactured by omitted, relevant variables.

Agronomic biofortification of food crops: An emerging opportunity for global food and nutritional security

Fortification of food with mineral micronutrients and micronutrient supplementation occupied the center stage during the two-year-long Corona Pandemic, highlighting the urgent need to focus on micronutrition. Focus has also been intensified on the biofortification (natural assimilation) of mineral micronutrients into food crops using various techniques like agronomic, genetic, or transgenic. Agronomic biofortification is a time-tested method and has been found useful in the fortification of several nutrients in several crops, yet the nutrient use and uptake efficiency of crops has been noted to vary due to different growing conditions like soil type, crop management, fertilizer type, etc. Agronomic biofortification can be an important tool in achieving nutritional security and its importance has recently increased because of climate change related issues, and pandemics such as COVID-19. The introduction of high specialty fertilizers like nano-fertilizers, chelated fertilizers, and water-soluble fertilizers that have high nutrient uptake efficiency and better nutrient translocation to the consumable parts of a crop plant has further improved the effectiveness of agronomic biofortification. Several new agronomic biofortification techniques like nutripriming, foliar application, soilless activation, and mechanized application techniques have further increased the relevance of agronomic biofortification. These new technological advances, along with an increased realization of mineral micronutrient nutrition have reinforced the relevance of agronomic biofortification for global food and nutritional security. The review highlights the advances made in the field of agronomic biofortification via the improved new fertilizer forms, and the emerging techniques that achieve better micronutrient use efficiency of crop plants.

Agronomic Biofortification of Zinc in Rice for Diminishing Malnutrition in South Asia

Zinc (Zn) is increasingly recognized as an essential trace element in the human diet that mediates a plethora of health conditions, including immune responses to infectious diseases. Interestingly, the geographical distribution of human dietary Zn deficiency overlaps with soil Zn deficiency. In South Asia, Zn malnutrition is high due to excessive consumption of rice with low Zn content. Interventions such as dietary diversification, food fortification, supplementation, and biofortification are followed to address Zn malnutrition. Among these, Zn biofortification of rice is the most encouraging, cost-effective, and sustainable for South Asia. Biofortification through conventional breeding and transgenic approaches has been achieved in cereals; however, if the soil is deficient in Zn, then these approaches are not advantageous. Therefore, in this article, we review strategies for enhancing the Zn concentration of rice through agronomic biofortification such as timing, dose, and method of Zn fertilizer application, and how nitrogen and phosphorus application as well as crop establishment methods influence Zn concentration in rice. We also propose data-driven Zn recommendations to anticipate crop responses to Zn fertilization and targeted policies that support agronomic biofortification in regions where crop responses to Zn fertilizer are high.

Application of a novel nanocomposite containing micro-nutrient solubilizing bacterial strains and CeO2 nanocomposite as bio-fertilizer

Chemical fertilizers are used in modern agricultural practice to increase plant output. They possess anthropogenic compounds which are hazardous, result in poor soil quality, poor crop nutrition and pollutes the water table. Currently, food crops that lack in micro-nutrients (Zn, silicates and Se) can be enriched with micronutrients by use of fertilizers. Eco-friendly bio-fertilizers have been proved to provide a known population of microorganisms that create a mutual benefit to the plants & the rhizosphere soil. Nanomaterials are often used in plant fertilizer formulation, allowing for controlled release and targeted delivery of beneficial nanoscale components, as well as to boost plant production and reduce environmental pollutants. In the present study we identified a multipotent micronutrient solubilizing bacterium (MSB) - Pseudomonas gessardi and Pseudomonas azotoformans as a bio-fertiliser. Comparative study of the formulated MSB, with nanocomposite prepared with the soya chunks as natural carrier material and chemically synthesized cerium oxide was performed on the growth of fenugreek for its effectiveness. The SEM images of nanocomposite showed the non-uniform distribution of CeO₂ in bio-inoculant with an average size of 25.24 nm. The current study deals with increase in the shoot and root length of the fenugreek plant with only 75 ppm of CeO₂ in nanocomposite, thereby preventing bioaccumulation of Ce in soil. This work gives a potential use of CeO2 nanocomposite with MSB bio-inoculants which could be applied to soil deficient with the micronutrients that can enhance the crop yield.

Assessment of Biofortification Approaches Used to Improve Micronutrient-Dense Plants That Are a Sustainable Solution to Combat Hidden Hunger

Malnutrition causes diseases, immune system disorders, deterioration in physical growth, mental development, and learning capacity worldwide. Micronutrient deficiency, known as hidden hunger, is a serious global problem. Biofortification is a cost-effective and sustainable agricultural strategy for increasing the concentrations or bioavailability of essential elements in the edible parts of plants, minimizing the risks of toxic metals, and thus reducing malnutrition. It has the advantage of delivering micronutrient-dense food crops to a large part of the global population, especially poor populations. Agronomic biofortification and biofertilization, traditional plant breeding, and optimized fertilizer applications are more globally accepted methods today; however, genetic biofortification based on genetic engineering such as increasing or manipulating (such as CRISPR-Cas9) the expression of genes that affect the regulation of metal homeostasis and carrier proteins that serve to increase the micronutrient content for higher nutrient concentration and greater productivity or that affect bioavailability is also seen as a promising high-potential strategy in solving this micronutrient deficiency problem. Data that micronutrients can help strengthen the immune system against the COVID-19 pandemic and other diseases has highlighted the importance of tackling micronutrient deficiencies. In this study, biofortification approaches such as plant breeding, agronomic techniques, microbial fertilization, and some genetic and nanotechnological methods used in the fight against micronutrient deficiency worldwide were compiled.

Identification and Analysis of Zinc Efficiency-Associated Loci in Maize

Zinc (Zn) deficiency, a globally predominant micronutrient disorder in crops and humans, reduces crop yields and adversely impacts human health. Despite numerous studies on the physiological mechanisms underlying Zn deficiency tolerance, its genetic basis of molecular mechanism is still poorly understood. Thus, the Zn efficiency of 20 maize inbred lines was evaluated, and a quantitative trait locus (QTL) analysis was performed in the recombination inbred line population derived from the most Zn-efficient (Ye478) and Zn-inefficient inbred line (Wu312) to identify the candidate genes associated with Zn deficiency tolerance. On this basis, we analyzed the expression of ZmZIP1-ZmZIP8. Thirteen QTLs for the traits associated with Zn deficiency tolerance were detected, explaining 7.6-63.5% of the phenotypic variation. The genes responsible for Zn uptake and transport across membranes (ZmZIP3, ZmHMA3, ZmHMA4) were identified, which probably form a sophisticated network to regulate the uptake, translocation, and redistribution of Zn. Additionally, we identified the genes involved in the indole-3-acetic acid (IAA) biosynthesis (ZmIGPS) and auxin-dependent gene regulation (ZmIAA). Notably, a high upregulation of ZmZIP3 was found in the Zn-deficient root of Ye478, but not in that of Wu312. Additionally, ZmZIP4, ZmZIP5, and ZmZIP7 were up-regulated in the Zn-deficient roots of Ye478 and Wu312. Our findings provide a new insight into the genetic basis of Zn deficiency tolerance.

Wheat Leaf Antioxidative Status—Variety-Specific Mechanisms of Zinc Tolerance during Biofortification

In this study, we evaluated the leaf antioxidative responses of three wheat varieties (Srpanjka, Divana, and Simonida) treated with two different forms of zinc (Zn), Zn-sulfate and Zn-EDTA, in concentrations commonly used in agronomic biofortification. Zn concentration was significantly higher in the flag leaves of all three wheat varieties treated with Zn-EDTA compared to control and leaves treated with Zn-sulfate. Both forms of Zn increased malondialdehyde level and total phenolics content in varieties Srpanjka and Divana. Total glutathione content was not affected after the Zn treatment. Zn-sulfate increased the activities of glutathione reductase (GR) and guaiacol peroxidase (GPOD) in both Srpanjka and Divana, while glutathione S-transferase (GST) was only induced in var. Srpanjka. Chelate form of Zn increased the activities of GST and GPOD in both Simonida and Divana. Catalase activity was shown to be less sensitive to Zn treatment and was only induced in var. Srpanjka treated with Zn-EDTA where GPOD activity was not induced. Concentrations of Zn used for agronomic biofortification can induce oxidative stress in wheat leaves. The antioxidative status of wheat leaves could be a good indicator of Zn tolerance, whereas wheat genotype and chemical form of Zn are the most critical factors influencing Zn toxicity.

Genetic determinants of micronutrient traits in graminaceous crops to combat hidden hunger

KEY MESSAGE

Improving the nutritional content of graminaceous crops is imperative to ensure nutritional security, wherein omics approaches play pivotal roles in dissecting this complex trait and contributing to trait improvement. Micronutrients regulate the metabolic processes to ensure the normal functioning of the biological system in all living organisms. Micronutrient deficiency, thereby, can be detrimental that can result in serious health issues. Grains of graminaceous crops serve as an important source of micronutrients to the human population; however, the rise in hidden hunger and malnutrition indicates an insufficiency in meeting the nutritional requirements. Improving the elemental composition and nutritional value of the graminaceous crops using conventional and biotechnological approaches is imperative to address this issue. Identifying the genetic determinants underlying the micronutrient biosynthesis and accumulation is the first step toward achieving this goal. Genetic and genomic dissection of this complex trait has been accomplished in major cereals, and several genes, alleles, and QTLs underlying grain micronutrient content were identified and characterized. However, no comprehensive study has been reported on minor cereals such as small millets, which are rich in micronutrients and other bioactive compounds. A comparative narrative on the reports available in major and minor Graminaceae species will illustrate the knowledge gained from studying the micronutrient traits in major cereals and provides a roadmap for dissecting this trait in other minor species, including millets. In this context, this review explains the progress made in studying micronutrient traits in major cereals and millets using omics approaches. Moreover, it provides insights into deploying integrated omics approaches and strategies for genetic improvement in micronutrient traits in graminaceous crops.

Combined application of zinc-lysine chelate and zinc-solubilizing bacteria improves yield and grain biofortification of maize (Zea mays L.)

Malnutrition a health disorders arising due to over or low use of minerals, vitamins and nutritional substances required for proper functioning of body tissues and organs. Zinc (Zn) is the most important mineral required for the normal metabolism of plants and humans. Zinc-deficiency is one of the major cause of malnutrition globally. Maize is highly susceptible to Zn-deficiency and inflicts Zn-deficiency to humans and other animals being nourished on it. This study evaluated the effect of zinc-lysine chelate alone (0.1, 0.5, 1.0 and 1.5%) as seed priming and in combination with Zn-solubilizing bacteria (PMEL-1, PMEL-48, PMEL-57and PMEL-71)) on grain biofortification of autumn maize. The Zn accumulation in different parts (roots, stem, leaves, grains and cob pith) was quantified. Results indicated that Zn contents were 18.5% higher in the seeds primed with 1.5% solution of Zn-lysine chelate and inoculation of ZSB strains compared to control treatments. Seed priming with 1.5% Zn-lysine chelate in combination with ZSB inoculation significantly improved cob diameter and cob length by 16.75% and 42% during 2016 and by 11.36% and 34.35% during 2017. The increase in 100 grains weight over control was 18.4% and 15.27% for 2016 and 2017, respectively. The Zn contents were increased by 15.3%, 15.6%, 49.1%, and 33.0% in grain, cob-pith, stemand roots, respectively compared from control. Thus, the combined application of 1.5% Zn-lysine chelates along with ZSB inoculation could be used for combating malnutrition.

Zinc in cereal grains: Concentration, distribution, speciation, bioavailability, and barriers to transport from roots to grains in wheat

Zinc (Zn) is an essential micro-nutrient for humans, and Zn deficiency is of global concern. In addition to inherited and pathological Zn deficiencies, insufficient dietary intake is leading cause, especially in those consuming cereal grains as a stable food, in which Zn concentration and bioavailability are relatively low. To improve Zn levels in the human body, it is important to understand the accumulation and bioavailability of Zn in cereal grains. In recent years, knowledge on the molecular mechanisms underlying Zn uptake, transport, homeostasis, and deposition within cereal crops has been accumulating, paving the way for a more targeted approach to improving the nutrient status of crop plants. In this paper, we briefly review existing studies on the distribution and transport pathways of Zn in major small-grained cereals, using wheat as a case study. The findings confirm that Zn transport in plants is a complex physiological process mainly governed by Zn transporters and metal chelators. This work reviews studies on Zn uptake, transport, and deposition in wheat plants, summarizes the possible barriers impairing Zn deposition in wheat grains, and describes strategies for increasing Zn concentration in wheat grains.

Green Synthesis of Zinc Oxide Nanoparticles: Fortification for Rice Grain Yield and Nutrients Uptake Enhancement

Applications of metal oxide nanoparticles in the agriculture sector are being extensively included as the materials are considered superior. In the present work, zinc oxide nanoparticle (ZnO NPs), with a developing fertilizer, is applied in the fortification of rice grain yield and nutrient uptake enhancement. To evaluate the role of ZnO NP, two field experiments were conducted during the 2018 and 2019 seasons. ZnO NPs were small, nearly spherical, and their sizes equal to 31.4 nm, as proved via the dynamic light scattering technique. ZnO NPs were applied as a fertilizer in different concentrations, varying between 20 and 60 mg/L as a foliar spray. The mixture of ZnSO₄ and ZnO NP₄₀ ameliorated yield component and nutrients (N, K, and Zn) uptake was enhanced compared to traditional ZnSO₄ treatment. Nevertheless, the uptake of the phosphorous element (P) was adversely affected by the treatment of ZnO NPs. Thus, treatment via utilizing ZnO NPs as a foliar with a very small amount (40 ppm) with of basal ZnSO₄ led to a good improvement in agronomic and physiological features; eventually, higher yield and nutrient-enriched rice grain were obtained.

Designing better input support programs: Lessons from zinc subsidies in Andhra Pradesh, India

India has one of the largest agricultural input support programs in the world, delivered in the form of subsidies to farmers, raising concerns about its sustainability. This paper evaluates the performance of one such support, the micronutrient subsidy program in the state of Andhra Pradesh (AP) and presents a case for providing this support in the form of direct cash transfers. Under the program, key soil micronutrients- zinc, boron, and gypsum were distributed free of cost to farmers living in micronutrient-deficient areas, with identification and targeting managed entirely by the state. We survey 1621 farmers, 61 agriculture extension officers, and 78 agriculture input dealers to assess the efficacy of the program and to identify bottlenecks preventing effective targeting, with a focus on zinc. We find that use of non-subsidized zinc is high in AP, and awareness of benefits of zinc and physical access to input dealer shops are significant predictors of zinc use. We argue that the free provision of micronutrients may have created demand among farmers, but there is little justification to continue subsidizing such a program at such high rates or resorting to public distribution. We find that micronutrient procurement and distribution has become a burden on extension staff and crowds out the private sector. Our analysis shows that the subsidy can benefit more farmers if it is channeled through the network of private fertilizer dealers. We use administrative data on budgetary outlays and digital soil maps to suggest fiscal redistribution in the form of direct cash transfers that may ensure more effective targeting at a lower cost to the state.

Zinc Hyperaccumulation in Plants: A Review

Zinc is an essential microelement involved in many aspects of plant growth and development. Abnormal zinc amounts, mostly due to human activities, can be toxic to flora, fauna, and humans. In plants, excess zinc causes morphological, biochemical, and physiological disorders. Some plants have the ability to resist and even accumulate zinc in their tissues. To date, 28 plant species have been described as zinc hyperaccumulators. These plants display several morphological, physiological, and biochemical adaptations resulting from the activation of molecular Zn hyperaccumulation mechanisms. These adaptations can be varied between species and within populations. In this review, we describe the physiological and biochemical as well as molecular mechanisms involved in zinc hyperaccumulation in plants.

Production and Implication of Bio-Activated Organic Fertilizer Enriched with Zinc-Solubilizing Bacteria to Boost up Maize (Zea mays L.) Production and Biofortification under Two Cropping Seasons

Bio-activated organic fertilizers (BOZ) were produced by enriching the zinc oxide (ZnO)-orange peel waste composite with Zn solubilizing bacteria (ZSB: Bacillus sp. AZ6) in various formulations (BOZ1 (9:1), BOZ2 (8:2), BOZ3 (7:3) and BOZ4 (6:4)). The produced BOZs, along with ZnO, ZnSO4, ZSB were applied to maize crop (Zea mays L.) under field conditions in two different cropping season and the growth, yield, physiology, plant Zn contents and quality of maize were investigated. Results revealed significant variation in the aforementioned parameters with the applied amendments. The BOZ4 performed outclass by exhibiting the highest plant growth, yield, physiology, Zn contents, and quality. On average, an increase of 53%, 49%, 19%, 22%, 10%, 4%, and 30% in plant height was noticed with BOZ4 application over control, ZnO, ZnSO4, BOZ1, BOZ2, BOZ3, and ZSB, respectively. BOZ4 enhanced the dry shoot-biomass 46% than control. Likewise, the photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll contents, carotenoids, and carbonic anhydrase activity were increased by 47%, 42%, 45%, 57%, 17%, and 44%, respectively, under BOZ4 over control in both cropping seasons. However, BOZ4 reduced the electrolyte leakage by 38% as compared to control in both cropping seasons. BOZ4 increased the Zn contents of grain and shoot by 46% and 52%, respectively, while reduced the phytate contents by 73% as compared to control. Application of BOZ4 revealed highest average fat (4.79%), crude protein (12.86%), dry matter (92.03%), fiber (2.87%), gluten (11.925%) and mineral (1.53%) contents, as compared to control. In general, the impact of cropping seasons on maize growth, yield, physiology, Zn contents, and quality were non-significant (with few exceptions). Thus, bio-activation of ZnO with ZSB could serve as an efficient and economical strategy for boosting up the growth, yield, physiological, and quality parameters of maize under field conditions.

A metalloproteomic analysis of interactions between plasma proteins and zinc: elevated fatty acid levels affect zinc distribution

Serum albumin is a highly abundant plasma protein associated with the transport of metal ions, pharmaceuticals, fatty acids and a variety of small molecules in the blood. Once thought of as a molecular 'sponge', mounting evidence suggests that the albumin-facilitated transport of chemically diverse entities is not independent. One such example is the transport of Zn²⁺ ions and non-esterified 'free' fatty acids (FFAs) by albumin, both of which bind at high affinity sites located in close proximity. Our previous research suggests that their transport in blood plasma is linked via an allosteric mechanism on serum albumin. In direct competition, albumin-bound FFAs significantly decrease the binding capacity of albumin for Zn²⁺, with one of the predicted consequences being a change in plasma/serum zinc speciation. Using liquid chromatography (LC), ICP-MS and fluorescence assays, our work provides a quantitative assessment of this phenomenon, and finds that in the presence of high FFA concentrations encountered in various physiological conditions, a significant proportion of albumin-bound Zn²⁺ is re-distributed amongst plasma/serum proteins. Using peptide mass fingerprinting and immunodetection, we identify candidate acceptor proteins for Zn²⁺ liberated from albumin. These include histidine-rich glycoprotein (HRG), a multifunctional protein associated with the regulation of blood coagulation, and members of the complement system involved in the innate immune response. Our findings highlight how FFA-mediated changes in extracellular metal speciation might contribute to the progression of certain pathological conditions.

Zinc biofortification of cereals-role of phosphorus and other impediments in alkaline calcareous soils

Alkaline calcareous soils are deficient in plant nutrients; in particular, phosphorus (P) and zinc (Zn) are least available; their inorganic fertilizers are generally applied to meet the demand of crops. The applied nutrients react with soil constituents as well as with each other, resulting in lower plant uptake. Phosphorus availability is usually deterred due to lime content, while Zn availability is largely linked with alkalinity of the soil. The present manuscript critically discusses the factors associated with physicochemical properties of soil and other interactions in soil-plant system which contribute to the nutrients supply from soil, and affect productivity and quality attributes of cereals. Appropriate measures may possibly lessen the severity of nutritional disorder in cereal and optimize P and Zn concentrations in grain. Foliar Zn spray is found to escape most of the soil reactions; thus, Zn bioavailability is higher either through increase in grain Zn or through decrease in phytate content. The reactivity of nutrients prior to its uptake is deemed as major impediments in Zn biofortification of cereals. The article addresses physiological limitation of plants to accumulate grain Zn and the ways to achieve biofortification in cereals, while molecular mechanism explains how it affects nutritional quality of cereals. Moreover, it highlights the desirable measures for enhancing Zn bioavailability, e.g., manipulation of genetic makeup for efficient nutrient uptake/translocation, and also elucidates agronomic measures that help facilitate Zn supply in soil for plant accumulation.

ABA Alleviates Uptake and Accumulation of Zinc in Grapevine (Vitis vinifera L.) by Inducing Expression of ZIP and Detoxification-Related Genes

Abscisic acid (ABA) is a plant hormone that can mitigate heavy metal toxicity. Exogenous ABA and ABA mimic 1 (AM1) were applied to study the influence on Zn uptake and accumulation in Vitis vinifera L. cv. Merlot seedlings exposed to excess Zn. The seedlings were treated with either normal or excess levels of Zn in combination with applications of ABA and AM1. Excess Zn exposure resulted in decreased lateral root length, decreased photosynthesis, elevated uptake, and accumulation of Zn in roots, trunks, and stems, decreased jasmonic acid content in roots and leaves, and induced the expression of Zn transportation- and detoxification-related genes. Remarkably, in the presence of toxic amounts of Zn, the exogenous application of ABA, but not of AM1, reduced the uptake and accumulation of Zn in roots and induced higher expression of both ZIP genes and detoxification-related genes in root and leaf. These results indicate that exogenous ABA enhances the tolerance of grape seedlings to excess Zn and that AM1 is not a suitable ABA mimic compound for Zn stress alleviation in grapes.

Cruz PC, Borromeo TH, Lalusin A, Hernandez JE, Acuin C, Reinke R, Swamy BPM. Zinc and Iron Nutrition Status in the Philippines Population and Local Soils

The Philippines is one of the major rice-producing and rice-consuming countries of Asia. A large portion of its population depends on rice for their daily caloric intake and nutritional needs. The lack of dietary diversity among poor communities has led to nutritional consequences, particularly micronutrient deficiencies. Iron-deficiency anemia (IDA) and zinc deficiency (ZnD) are two serious nutritional problems that affect the health and economic sector of the country. Since rice dominates the Filipino diet by default, biofortification of rice will help improve the micronutrient status. The Philippine government has proactively initiated various programs and policies to address micronutrient deficiencies, particularly through fortification of basic food commodities. Biofortification, the fortification of rice with micronutrients through breeding, is considered the most sustainable and cost-effective strategy that can benefit large vulnerable populations. However, developing promising genotypes with micronutrient-enriched grains should be coupled with improving micronutrient bioavailability in the soil in order to optimize biofortification. This review documents the prevailing soil Zn-deficiency problems in the major rice production areas in the Philippines that may influence the Zn nutritional status of the population. The article also reports on the biofortification efforts that have resulted in the development of two biofortified varieties approved for commercial release in the Philippines. As nutritional security is increasingly recognized as a priority area, greater efforts are required to develop biofortified rice varieties that suit both farmers' and consumers' preferences, and that can address these critical needs for human health in a sustainable and cost-effective manner.

Zinc Absorption From Agronomically Biofortified Wheat Is Similar to Post-Harvest Fortified Wheat and Is a Substantial Source of Bioavailable Zinc in Humans

BACKGROUND

Limited data exist on human zinc absorption from wheat biofortified via foliar (FBW) or root (hydroponically fortified wheat, HBW) zinc application. Stable isotope labels added at point of consumption (extrinsic labeling) might not reflect absorption from native zinc obtained by intrinsic labeling.

OBJECTIVES

We measured fractional and total zinc absorption (FAZ, TAZ) in FBW and HBW wheat, compared with control wheat (CW) and fortified wheat (FW). The effect of labeling method was assessed in HBW (study 1), and the effect of milling extraction rate (EXR, 80% and 100%) in FBW (studies 2 and 3).

METHODS

Generally healthy adults (n = 71, age: 18-45 y, body mass index: 18.5-25 kg/m2) were allocated to 1 of the studies, in which they served as their own controls. In study 1, men and women consumed wheat porridges colabeled intrinsically and extrinsically with 67Zn and 70Zn. In studies 2 and 3, women consumed wheat flatbreads (chapatis) labeled extrinsically. Zinc absorption was measured with the oral to intravenous tracer ratio method with a 4-wk wash-out period between meals. Data were analyzed with linear mixed models.

RESULTS

In study 1 there were no differences in zinc absorption from extrinsic versus intrinsic labels in either FW or HBW. Similarly, FAZ and TAZ from FW and HBW did not differ. TAZ was 70-76% higher in FW and HBW compared with CW (P < 0.01). In studies 2 and 3, TAZ from FW and FBW did not differ but was 20-48% higher compared with CW (P < 0.001). Extraction rate had no effect on TAZ.

CONCLUSIONS

Colabeling demonstrates that extrinsic zinc isotopic labels can be used to accurately quantify zinc absorption from wheat in humans. Biofortification through foliar zinc application, root zinc application, or fortification provides higher TAZ compared with unfortified wheat. In biofortified wheat, extraction rate (100-80%) has a limited impact on total zinc absorption. These studies were registered on clinicaltrials.gov (NCT01775319).

Fortification and bioavailability of zinc in potato

BACKGROUND

Most agricultural soils have low zinc (Zn) content available to crops, which results in a significant decrease in productivity and in public health problems. However, the priming of potato tubers in solutions with Zn can be an effective strategy for their fortification. In order to evaluate the effect of Zn concentrations and tuber priming time on the fortification and bioavailability of Zn, potato tubers were primed in solutions containing 0, 10, 20 and 30 mg mL^-1 Zn during 12, 16, 20, and 24 h, respectively. The dry matter and the content of Zn and phytic acid (PA) in tubers were assessed in order to obtain the PA:Zn molar ratio.

RESULTS

Longer priming time increased the Zn content in the cortex of the tubers. High Zn concentration in the solution increased the content of Zn linearly in both the cortex and the central region of the tuber, whereas in the periderm the content levels adjusted to the non-linear logistical model, showing saturation at a minimum of 10 mg mL^-1 Zn in the solution. An increase in the bioavailability of Zn was verified when there was higher Zn concentration in the solution.

CONCLUSION

A substantial increase in Zn bioavailability was obtained by priming the tubers for 12 h in 10 mg mL^-1 Zn. © 2019 Society of Chemical Industry.

Interventions to Improve Micronutrient Status of Women of Reproductive Age in Southeast Asia: A Narrative Review on What Works, What Might Work, and What Doesn't Work

Objectives To provide an overview of nutrition-specific and nutrition-sensitive interventions that could improve micronutrient status of women of reproductive age. Methods This narrative review has a special focus on Southeast Asia, as the work was undertaken within the framework of the SMILING (Sustainable Micronutrient Interventions to controL deficiencies and Improve Nutrition status and General health in Southeast Asia) project. Results In order for new interventions to become accepted, comprehension and interpretation of potential impact of different strategies by policymakers and non-nutritionists is needed. By presenting a wide overview of strategies, and discussing the context and current consensus on these strategies, the review aims to help with the formulation of new recommendations for national programs in Southeast Asia. Conclusions Current policies in Southeast Asia to improve micronutrient status of women of reproductive age are focused too much on single micronutrient supplementation for pregnant women (iron and folic acid supplements). A more holistic approach, including both nutrition-specific and nutrition-sensitive interventions, is needed.

The Role of Nanotechnology in the Fortification of Plant Nutrients and Improvement of Crop Production

Nutrient deficiency in food crops is seriously affecting human health, especially those in the rural areas, and nanotechnology may become the most sustainable approach to alleviating this challenge. There are several ways of fortifying the nutrients in food such as dietary diversification, use of drugs and industrial fortification. However, the affordability and sustainability of these methods have not been completely achieved. Plants absorb nutrients from fertilizers, but most conventional fertilizers have low nutrient use and uptake efficiency. Nanofertilizers are, therefore, engineered to be target oriented and not easily lost. This review surveys the effects of the addition of macro- and nanonutrients to soil, the interaction, and the absorption capability of the plants, the environmental effect and food content of the nutrients. Most reports were obtained from recent works, and they show that plants nutrients could be enriched by applying nanoparticulate nutrients, which are easily absorbed by the plant. Although there are some toxicity issues associated with the use of nanoparticles in crop, biologically synthesized nanoparticles may be preferred for agricultural purposes. This would circumvent the concerns associated with toxicity, in addition to being pollution free. This report, therefore, offers more understanding on the application of nanotechnology in biofortification of plant nutrients and the future possibilities offered by this practice. It also highlights some of the ills associated with the introduction of nanomaterials into the soil for crop’s improvement.

Zinc in soils, water and food crops

A basic knowledge of the dynamics of zinc (Zn) in soils, water and plants are important steps in achieving sustainable solutions to the problem of Zn deficiency in crops and humans. This paper aims at reviewing and discussing the relevant aspects of the role of Zn in the soil-water-plant agro biological system: from the origins of Zn in soils and water to soil Zn deficiency distribution and the factors affecting soil Zn availability to plants, therefore to elucidate the strategies potentially help combating Zn deficiency problems in soil-plant-human continuum. This necessitates identifying the main areas of Zn-deficient soils and food crops and treating them with Zn amendments, mainly fertilizers in order to increase Zn uptake and Zn use efficiency to crops. In surface and groundwater, Zn enters the environment from various sources but predominately from the erosion of soil particles containing Zn. In plants is involved in several key physiological functions (membrane structure, photosynthesis, protein synthesis, and drought and disease tolerance) and is required in small but nevertheless critical contents. Several high revenue food crops such as beans, citrus, corn, rice etc are highly susceptible to Zn deficiency and biofortification is considered as a promising method to accumulate high content of Zn especially in grains. With the world population continuing to rise and the problems of producing extra food rich in Zn to provide an adequate standard of nutrition to increase, it is very important that any losses in production easily corrected so as Zn deficiencies are prevented.

How Could Agronomic Biofortification of Rice Be an Alternative Strategy with Higher Cost-Effectiveness for Human Iron and Zinc Deficiency in China?

Background:

Iron and zinc deficiencies affect human health globally, especially in developing countries. Agronomic biofortification, as a strategy for alleviating these issues, has been focused on small-scale field studies, and not widely applied while lacking of cost-effectiveness analysis (CEA).

Objective:

We conducted the CEA of agronomic biofortification, expressed as USD per disability-adjusted life years (DALYs) saved, to recommend a cost-effectiveness strategy that can be widely applied.

Methods:

The DALYs were applied to quantify the health burden due to Fe and/or Zn deficiency and health cost of agronomic biofortification via a single, dual, or triple foliar spray of Fe, Zn, and/or pesticide in 4 (northeast, central China, southeast, and southwest) major Chinese rice-based regions.

Results:

The current health burden by Fe or Zn malnutrition was 0.45 to 1.45 or 0.14 to 0.84 million DALYs for these 4 regions. Compared to traditional rice diets, the daily Fe and/or Zn intake from Fe and/or Zn-biofortified rice increased, and the health burden of Fe and/or Zn deficiency decreased by 28% and 48%, respectively. The cost of saving 1 DALYs ranged from US$376 to US$4989, US$194 to US$2730, and US$37.6 to US$530.1 for the single, dual, and triple foliar Fe, Zn, and/or pesticide application, respectively, due to a substantial decrease in labor costs by the latter 2 applications.

Conclusions:

Agronomic biofortification of rice with the triple foliar spray of Fe, Zn, and pesticide is a rapidly effective and cost-effectiveness pathway to alleviate Fe and Zn deficiency for rice-based dietary populations.

Layered Double Hydroxides: Potential Release-on-Demand Fertilizers for Plant Zinc Nutrition

A novel zinc (Zn) fertilizer concept based on Zn-doped layered double hydroxides (Zn-doped Mg-Fe-LDHs) has been investigated. Zn-doped Mg-Fe-LDHs were synthesized, their chemical composition was analyzed, and their nutrient release was studied in buffered solutions with different pH values. Uptake of Zn by barley (Hordeum vulgare cv. Antonia) was evaluated in short- (8 weeks), medium- (11 weeks), and long-term (28 weeks) experiments in quartz sand and in a calcareous soil enriched with Zn-doped Mg-Fe-LDHs. The Zn release rate of the Zn-doped Mg-Fe-LDHs was described by a first-order kinetics equation showing maximum release at pH 5.2, reaching approximately 45% of the total Zn content. The Zn concentrations in the plants receiving the LDHs were between 2- and 9.5-fold higher than those in plants without Zn addition. A positive effect of the LDHs was also found in soil. This work documents the long-term Zn release capacity of LDHs complying with a release-on-demand behavior and serves as proof-of-concept that Zn-doped Mg-Fe-LDHs can be used as Zn fertilizers.

Apple pomace improves the quality of pig manure aerobic compost by reducing emissions of NH3 and N2O

In this study, the effects of apple pomace (AP) addition (0%, 5%, 10%, and 20% on a dry weight basis, named as control, AP1, AP2, and AP3) and citric acid (CA) addition on nitrogen conservation were investigated during aerobic composting of pig manure. Gaseous emissions of NH₃ and N₂O were inhibited by AP and CA addition, with AP's effect greater. The inhibition improved with increasing AP addition. The AP3 treatment was the most effective on NH₃ adsorption and transformation to [Formula: see text]-N, improved with subsequent transformation to [Formula: see text]-N, and inhibition of N₂O and [Formula: see text] production. Compared with control, AP3 showed the highest inhibition of accumulated NH₃ and N₂O emission, by 57% and 24%, respectively, and with a 19% increase of total Kjeldahl nitrogen in the compost. The further pot experiment proved the application of the AP amendment compost could improve the yield and trace element nutrient accumulation in Chinese cabbage when planted in a typical Zn-deficient soil. This study illustrates that AP application benefits both compost nitrogen conservation and fertilizer quality.

Valuing increased zinc (Zn) fertiliser-use in Pakistan

BACKGROUND AND AIMS

Use of zinc (Zn) fertilisers may be cost-effective in increasing crop yields and in alleviating dietary Zn deficiency. However, Zn fertilisers are underutilised in many countries despite the widespread occurrence of Zn-deficient soils. Here, increased Zn fertiliser-use scenarios were simulated for wheat production in Punjab and Sindh Provinces, Pakistan. Inputs and outputs were valued in terms of both potential yield gains as well as health gains in the population.

METHODS

The current dietary Zn deficiency risk of 23.9 % in Pakistan was based on food supply and wheat grain surveys. "Disability-adjusted life years (DALYs) lost" are a common metric of disease burden; an estimated 245,000 DALYs y^-1 are lost in Punjab and Sindh due to Zn deficiency. Baseline Zn fertiliser-use of 7.3 kt y^-1 ZnSO₄.H2O was obtained from published and industry sources. The wheat area currently receiving Zn fertilisers, and grain yield responses of 8 and 14 % in Punjab and Sindh, respectively, were based on a recent survey of >2500 farmers. Increased grain Zn concentrations under Zn fertilisation were estimated from literature data and converted to improved Zn intake in humans and ultimately a reduction in DALYs lost.

RESULTS

Application of Zn fertilisers to the area currently under wheat production in Punjab and Sindh, at current soil: foliar usage ratios, could increase dietary Zn supply from ~12.6 to 14.6 mg capita ^-1 d^-1, and almost halve the prevalence of Zn deficiency, assuming no other changes to food consumption. Gross wheat yield could increase by 2.0 and 0.6 Mt. grain y^-1 in Punjab and Sindh, respectively, representing an additional return of US$ >800 M and an annual increased grain supply of 19 kg capita ^-1.

CONCLUSIONS

There are potential market- and subsidy-based incentives to increase Zn fertiliser-use in Pakistan. Benefit-Cost Ratios (BCRs) for yield alone are 13.3 and 17.5 for Punjab and Sindh, respectively. If each DALY is monetised at one to three fold Gross National Income per capita on purchasing power parity (GNI_PPP), full adoption of Zn fertiliser for wheat provides an additional annual return of 405-1216 M International Dollars (I$) in Punjab alone, at a cost per DALY saved of I$ 461-619.

Novel Effects of Nanoparticulate Delivery of Zinc on Growth, Productivity, and Zinc Biofortification in Maize (Zea mays L.)

In the present investigation, nanoscale zinc oxide particulates (ZnO-nanoparticulates) were prepared using a modified oxalate decomposition method. Prepared ZnO-nanoparticulates (mean size = 25 nm) were characterized using techniques such as transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and zeta potential analyzer. Different concentrations (50, 100, 200, 400, 600, 800, 1000, 1500, and 2000 ppm) of ZnO-nanoparticulates were examined to reveal their effects on maize crop on overall growth and translocation of zinc along with bulk ZnSO4 and control. Highest germination percentage (80%) and seedling vigor index (1923.20) were observed at 1500 ppm of ZnO-nanoparticulates. The yield was 42% more compared to control and 15% higher compared to 2000 ppm of ZnSO4. Higher accumulation of zinc (35.96 ppm) in grains was recorded with application of 100 ppm followed by 400 ppm (31.05 ppm) of ZnO-nanoparticulates. These results indicate that ZnO-nanoparticulates have significant effects on growth, yield, and zinc content of maize grains, which is an important feature in terms of human health.

The assessment of soil availability and wheat grain status of zinc and iron in Serbia: Implications for human nutrition

The deficiency of zinc (Zn) and iron (Fe) is a global issue causing not only considerable yield losses of food crops but also serious health problems. We have analysed Zn and Fe concentrations in the grains of two bread wheat cultivars along native gradient of micronutrient availability throughout Serbia. Although only 13% of the soil samples were Zn deficient and none was Fe deficient, the levels of these micronutrients in grain were rather low (median values of 21 mg kg(-1) for Zn and 36 mg kg(-1) for Fe), and even less adequate in white flour. Moreover, excessive P fertilization of calcareous soils in the major wheat growing areas strongly correlated with lower grain concentration of Zn. Our results imply that a latent Zn deficiency in wheat grain poses a high risk for grain quality relevant to human health in Serbia, where wheat bread is a staple food.

Application of ZnSO4 or Zn-EDTA fertilizer to a calcareous soil: Zn diffusion in soil and its uptake by wheat plants

BACKGROUND

The objective of this study was to compare the efficiency of two Zn sources and two application methods on (i) Zn diffusion from fertilized soil to unfertilized soil, (ii) grain Zn concentration and (iii) grain Zn bio-accessibility to humans. In the laboratory experiment, 20 mg ZnSO4 or 4 mg Zn-EDTA were applied to a 5 mm and 1 mm-wide space in the soil in the half-cell technique. In the greenhouse experiment, Zn-ZnSO4 or Zn-ethylenediaminetetraacetic acid (Zn-EDTA) was mixed or banded with the soil at a rate of 20 or 4 mg Zn kg(-1) , respectively.

RESULTS

The results from the diffusion experiment showed that both the extractability and the diffusion coefficient of Zn were higher when Zn fertilizer was applied to a 1 mm-wide space than when it was applied to a 5 mm-wide space. Zn-EDTA had a greater diffusion distance than ZnSO4 . The greenhouse experiment showed that the mixed ZnSO4 application and the Zn-EDTA application (both mixed and banded) treatments significantly increased grain Zn concentration and bio-accessibility. The positive effect of Zn-EDTA on grain Zn concentrations and bio-accessibility was greater than that of ZnSO4 . The banded application reduced the effectiveness of ZnSO4 but not of Zn-EDTA.

CONCLUSION

It was concluded that Zn-EDTA was a better Zn source than ZnSO4 for increasing grain Zn content in a potentially Zn-deficient calcareous soil.

Analysis of Triticum aestivum seedling response to the excess of zinc

The effects of 50 and 300 mg L(-1) Zn(2+) (50 Zn and 300 Zn) were investigated in Triticum aestivum (cv. Żura) grown hydroponically for 7 days. Although wheat treated with 50 Zn took up relatively high amount of the metal (8,943 and 1,503 mg kg(-1) DW in roots and shoots, respectively), none of the morphological and cytological parameters were changed. After 300 Zn, the metal concentration increased to 32,205 and 5,553 mg kg(-1) DW in roots and shoots, respectively. It was connected with the depletion of shoot and root growth, their fresh and dry weight, water content and mitotic index of root meristematic cells. Microelement contents (Cu, Mn and Fe) after 50 Zn were changed only in roots, while 300 Zn disturbed ion balance in whole plants. The most evident ultrastructural alterations of root meristematic cells caused by both tested Zn(2+) doses included increased vacuolization, accumulation of granular deposits inside vacuoles and cell wall thickening. The effect of 300 Zn on root cell ultrastructure was greater that of 50 Zn. The majority of mitochondria had condensed matrix and swollen cristae, plastids contained plastoglobuli, nucleoli were ring-shaped, thinned down cytoplasm with lipid droplets and swollen endoplasmic reticulum cisternae appeared. In mesophyll cells, 50 Zn caused slight reorganization of chloroplast thylakoids and formation of condensed mitochondria. Three hundred Zn triggered more extensive, but not degenerative, changes: plasmolysis of some cells; chloroplasts with protrusions, changed thylakoid organisation and often large starch grains; irregular, condensed mitochondria. The results indicate that T. aestivum cv. Żura is relatively tolerant to Zn stress.

Nutritionally enhanced food crops; progress and perspectives

Great progress has been made over the past decade with respect to the application of biotechnology to generate nutritionally improved food crops. Biofortified staple crops such as rice, maize and wheat harboring essential micronutrients to benefit the world's poor are under development as well as new varieties of crops which have the ability to combat chronic disease. This review discusses the improvement of the nutritional status of crops to make a positive impact on global human health. Several examples of nutritionally enhanced crops which have been developed using biotechnological approaches will be discussed. These range from biofortified crops to crops with novel abilities to fight disease. The review concludes with a discussion of hurdles faced with respect to public perception, as well as directions of future research and development for nutritionally enhanced food crops.

Enriching rice with Zn and Fe while minimizing Cd risk

Enriching iron (Fe) and zinc (Zn) content in rice grains, while minimizing cadmium (Cd) levels, is important for human health and nutrition. Natural genetic variation in rice grain Zn enables Zn-biofortification through conventional breeding, but limited natural Fe variation has led to a need for genetic modification approaches, including over-expressing genes responsible for Fe storage, chelators, and transporters. Generally, Cd uptake and allocation is associated with divalent metal cations (including Fe and Zn) transporters, but the details of this process are still unknown in rice. In addition to genetic variation, metal uptake is sometimes limited by its bioavailability in the soil. The availability of Fe, Zn, and Cd for plant uptake varies widely depending on soil redox potential. The typical practice of flooding rice increases Fe while decreasing Zn and Cd availability. On the other hand, moderate soil drying improves Zn uptake but also increases Cd and decreases Fe uptake. Use of Zn- or Fe-containing fertilizers complements breeding efforts by providing sufficient metals for plant uptake. In addition, the timing of nitrogen fertilization has also been shown to affect metal accumulation in grains. The purpose of this mini-review is to identify knowledge gaps and prioritize strategies for improving the nutritional value and safety of rice.

Advances in the molecular understanding of biological zinc transport

Recognition of the importance of zinc homeostasis for health has driven a surge in structural data on major zinc-transporting proteins.

Global perspectives on trace element requirements

Trace elements are inorganic constituents of the human body present in concentrations less than 50mg/kg body weight. An exception is iron that is found in slightly higher amounts, 60 mg/kg body weight, but it is classified within this category due to its physiological roles. Requirements of trace elements can vary according to age, gender, growth, body composition, genetics, pregnancy, lactation, wound healing and burns, alcohol abuse, infections, and diseases (anemia, coronary artery, Keshan, Kashin-Beck). Additionally, interactions may occur with dietary factors, such as other minerals (iron versus copper), phytates (zinc), oxalates (iron), fiber (manganese), and polyphenolic compounds (molybdenum). On a global basis, requirements can vary according to soil and geographical location, food preparation and processing, food accessibility, cultural practices (geophagia) and pollution. Furthermore, global differences exist in body composition, ethnicity, and age of menarche.

Comparison of soil and foliar zinc application for enhancing grain zinc content of wheat when grown on potentially zinc-deficient calcareous soils

BACKGROUND

The concentration of Zn and phytic acid in wheat grain has important implications for human health. We conducted field and greenhouse experiments to compare the efficacy of soil and foliar Zn fertilisation in improving grain Zn concentration and bioavailability in wheat (Triticum aestivum L.) grain grown on potentially Zn-deficient calcareous soil.

RESULTS

Results from the 2-year field experiment indicated that soil Zn application increased soil DTPA-Zn by an average of 174%, but had no significant effect on grain Zn concentration. In contrast, foliar Zn application increased grain Zn concentration by an average of 61%, and Zn bioavailability by an average of 36%. Soil DTPA-Zn concentrations varied depending on wheat cultivars. There were also significant differences in grain phytic acid concentration among the cultivars. A laboratory experiment indicated that Zn (from ZnSO4 ) had a low diffusion coefficient in this calcareous soil.

CONCLUSION

Compared to soil Zn application, foliar Zn application is more effective in improving grain Zn content of wheat grown in potentially Zn-deficient calcareous soils.

Dietary mineral supplies in Africa

Dietary micronutrient deficiencies (MNDs) are widespread, yet their prevalence can be difficult to assess. Here, we estimate MND risks due to inadequate intakes for seven minerals in Africa using food supply and composition data, and consider the potential of food-based and agricultural interventions. Food Balance Sheets (FBSs) for 46 countries were integrated with food composition data to estimate per capita supply of calcium (Ca), copper (Cu), iron (Fe), iodine (I), magnesium (Mg), selenium (Se) and zinc (Zn), and also phytate. Deficiency risks were quantified using an estimated average requirement (EAR) 'cut-point' approach. Deficiency risks are highest for Ca (54% of the population), followed by Zn (40%), Se (28%) and I (19%, after accounting for iodized salt consumption). The risk of Cu (1%) and Mg (<1%) deficiency are low. Deficiency risks are generally lower in the north and west of Africa. Multiple MND risks are high in many countries. The population-weighted mean phytate supply is 2770 mg capita(-1) day(-1). Deficiency risks for Fe are lower than expected (5%). However, 'cut-point' approaches for Fe are sensitive to assumptions regarding requirements; e.g. estimates of Fe deficiency risks are 43% under very low bioavailability scenarios consistent with high-phytate, low-animal protein diets. Fertilization and breeding strategies could greatly reduce certain MNDs. For example, meeting HarvestPlus breeding targets for Zn would reduce dietary Zn deficiency risk by 90% based on supply data. Dietary diversification or direct fortification is likely to be needed to address Ca deficiency risks.

Zinc interaction with struvite during and after mineral formation

Sorption of Zn with struvite was assessed both during and after mineral formation at pH 9.0 for 1-100 μM (0.065-6.54 mg L(-1)) aqueous Zn. The Zn loadings of recovered solids were lower when Zn was present during struvite precipitation compared to when Zn was added to struvite-bearing solutions. X-ray absorption fine structure spectroscopy confirmed that Zn added to struvite-bearing solutions at concentrations≤5 μM sorbed as both octahedral and tetrahedral complexes (Zn-O 1.98-2.03 Å), with evidence for bidentate configuration (Zn-P 3.18 Å). Bidentate complexes were incorporated into the near-surface structure, contributing to distortion of the struvite ν3 PO4(3-) band in the Fourier transform infrared spectra. At Zn concentrations>5 μM, tetrahedral monodentate adsorbates (Zn-O 1.98 Å) dominated, transitioning to a Zn-phosphate precipitate at 100 μM. When Zn is present during struvite precipitation, octahedral monodentate sorbates detected at 1 μM (Zn-O 2.08-2.10 Å; Zn-P 3.60-3.64 Å) polymerized at 5-50 μM, ultimately forming a Zn-hydroxide precipitate at 100 μM. The lowest initial Zn concentrations (0.065 mg L(-1)) and resultant solid loadings from precipitation experiments (13 mg kg(-1)) are consistent with those reported for struvite recovered from wastewater, suggesting that similar Zn sorption processes may occur in more complex systems.