ArticleLiterature Review

Soil factors associated with zinc deficiency in crops and humans

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Abstract

Zinc deficiency is the most ubiquitous micronutrient deficiency problem in world crops. Zinc is essential for both plants and animals because it is a structural constituent and regulatory co-factor in enzymes and proteins involved in many biochemical pathways. Millions of hectares of cropland are affected by Zn deficiency and approximately one-third of the human population suffers from an inadequate intake of Zn. The main soil factors affecting the availability of Zn to plants are low total Zn contents, high pH, high calcite and organic matter contents and high concentrations of Na, Ca, Mg, bicarbonate and phosphate in the soil solution or in labile forms. Maize is the most susceptible cereal crop, but wheat grown on calcareous soils and lowland rice on flooded soils are also highly prone to Zn deficiency. Zinc fertilizers are used in the prevention of Zn deficiency and in the biofortification of cereal grains.

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... Although micronutrients are required in small amounts for crop growth, a balanced supply is necessary to achieve to the maximum yield potential as over fertilization can results in plant toxicity [1]. The availability and supply to the plant roots needs to be maintained throughout the crop growth period due to low mobility within the soil-plant system [1,2]. It is generally agreed that the total concentration of micronutrient in soil is not a reliable index of assessing bioavailability and predicting crop responses. ...
... Whether one application method or the other predominates largely depends on crop types, fertilizer products available, soil characteristics that affect degree of anticipated fixation, and initial nutrient levels and anticipated severity of the deficiency. For example, different crops cultivated in rotation vary considerably in susceptibility to micronutrient deficiencies [1,2]. Some crop species are known to release phyto-siderophores (graminaceous plants) and organic acids during deficiency, regulating micronutrient mobility and bioavailability by lowering pH and producing chelation in rhizosphere soils [16]. ...
... Micronutrient ions such as Cu 2+ and Zn 2+ tend to be adsorbed strongly through interaction with negatively charge sites on organic matter and clay minerals, and thus can show restricted mobility and availability in soils high in these soil constituents [2,65]. Further, the ion supply rate is adversely affected by dry soil conditions due to increased path length for diffusion as related to increased tortuosity [28,71]. ...
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An appropriate fertilization strategy is essential for improving micronutrient supply, crop nutrition, yield and quality. Comparative effects of different application strategies of micronutrient fertilizer were evaluated in two contrasting sites/soils (upper slope Chernozem and lower slope Solonetz) within a farm field located in the Brown soil zone of Saskatchewan, Canada. The study objective was to examine the impact of Cu, Zn, and B fertilizer application strategies on their mobility, bioavailability and fate in the soil as well as crop yield responses. The application strategies were broadcast, broadcast and incorporation, seed row banding, and foliar application of Cu, Zn, and B on wheat, pea, and canola, respectively. The study was laid out in a randomized complete block design (RCBD) with four treatment replicates for a specific crop and site. Crop biomass yields were not significantly influenced by micronutrient placement strategies at both sites. Pea tissue Zn concentration (35.2 mg Zn kg−1 grain and 5.15 mg Zn kg−1 straw) was increased by broadcast and incorporation of Zn sulfate on the Solonetz soil. Residual levels of soil extractable available Cu were increased significantly to 3.18 mg Cu kg−1 soil at Chernozem and 2.53 mg Cu kg−1 soil Solonetz site with the seed row banding of Cu sulfate. The PRS™-probe supply of Cu (1.84 µm Cu/cm2) and Zn (1.18 µm Zn/cm2) were significantly higher with broadcast application of corresponding micronutrient fertilizer in the Chernozem soil. Both the chemical and spectroscopic speciation revealed that carbonate associated Cu and Zn were dominant species that are likely to control the bioavailability of these micronutrients under field conditions.
... This is reflected as an effect on crop yield and zinc deficiency in human which affect population health [5,6]. Such deficiency can be reversed by the application of Zinc-based fertilizers [7]. Zinc-based fertilizers are widely and safely used in agricultural purposes to overcome zinc deficiency in many soils. ...
... In addition to its unique chemical properties and balance as expressed by a wide bandgap (3.37 eV), a high binding energy (60 MeV) and photostability [9]. Specially ZnO nano-discs are gaining attention due to their large diagonal to thickness ratio and large available surface area [7]. ...
... In this study the growth pattern of the ZnO lattice was reversed to lateral growth via the incorporation of chitosan with abundant lone pairs. The lone pair of the amine would interact with and occupy the Zn 2+ C-terminated 0001 polar surface of ZnO hindering the preferential growth of ZnO along the 0001-facet and allowing for the lateral growth of ZnO in < 01ı0 > into a flat nanodisc [7,20,21] (Fig. 3b). This evident from the morphology of the inorganic organic composite was investigated using the SEM. ...
Article
Nano-chemistry based fertilizers are gaining interest as eco-friendly alternative. Hybrid structures composed of organic and inorganic components are especially important. In this study, synthesis of ZnO-chitosan composite (ZnC) is reported, its interaction with ectodomain of cell surface pattern recognition receptor (PDBID: 4EBZ) and effect on strawberry transplants production were assessed. Various synthesis procedures were compared. FTIR and dispersive ultraviolet scanning were used for testing the complexation between ZnO and the polymeric amino poly-saccharide. The elemental composition of ZnC was quantitatively assessed by EDX. Scanning electron microscope (SEM) was used for morphological assessment. Variable concentrations of ZnC were used for spraying strawberry nurseries. The horticultural outcomes were monitored. The effects were compared in terms of essential elements, chlorophyll and carotene content by flame-photometry, atomic absorption and UV–Vis spectroscopy, respectively. Synthesized ZnC was composed of carbon (41%), nitrogen (10%), oxygen (35%) and zinc (14%). The SEM revealed that ZnO was in the form of a hexagonal nano-disc chelated into the amino poly-saccharide bed as confirmed by FTIR and UV spectroscopy. The synthesized structure was able to interact with the cell surface chitin elicitor receptor kinase due to its structural similarity with chitin. Bi-weekly spraying of strawberry nursery resulted in a significant increase in the number of runners and subcrowns. In conclusion, the developed ZnC can be used for increasing the production of strawberry nurseries. The developed composite is a promising fertilizer. It may support increasing the fruit production to meet the world increasing food demand and meet the sustainable development goals.
... This is of concern because alkaline calcareous soils make up a third of global agricultural land (Nazir et al., 2016;Moreno-Lora and Delgado, 2020). More than three billion people suffer from Zn deficiency worldwide (Cakmak, 2008;Alloway, 2009;White and Broadley, 2011;Clemens, 2014). This is attributed to diets reliant on crops produced in areas with low Zn phytoavailability or with low Zn concentrations, and can be compounded by insufficient fish or animal intake (Graham et al., 2007;White and Broadley, 2009;Gibson, 2012;McBeath and McLaughlin, 2014). ...
... Zinc adsorption is governed by pH, carbonates, organic matter, clay content and mineralogy, iron (Fe) and aluminum (Al) oxides, and interactions with other nutrients (particularly other metals and phosphates) (Donner et al., 2012;Liu et al., 2016;Wang et al., 2017;Komá rek et al., 2018;Peng et al., 2018). The decreased bioavailability of Zn in alkaline calcareous soils is attributed to the precipitation of Zn(OH) 2 or ZnCO 3 (Saeed and Fox, 1977;Shukla and Mittal, 1979;Uygu and Rimmer, 2000;Rehman et al., 2018), as well as specific and non-specific adsorption onto calcite (Saleh et al., 1998;Montilla et al., 2003;Alloway, 2009) and other soil components such as oxides (Buekers et al., 2007(Buekers et al., , 2008. ...
Article
Although complexation with soil organic matter may improve zinc (Zn) bioavailability to plants, the effect of Zn sorbent surfaces on the use of complexed Zn by plants remains unknown. The objective of this research was to elucidate how Zn complexation with humic substances (HS) and phytate affects the uptake of Zn by wheat plants depending on the main sorbent surface in growth media, i.e., carbonates and Fe oxides. To this end, two pot experiments were performed, one using Fe oxide-coated siliceous sand and the other using a mixture of calcareous and siliceous sand as the growth medium. Each experiment involved three Zn sources, Zn-HS complex, Zn phytate, and ZnSO4. All sources were applied with surface irrigation at two Zn rates (0.25 and 2 mg kg–1 growth medium). The Zn-HS complex significantly increased Zn uptake by plants in both media, relative to the other two Zn sources, but no significant difference was observed between Zn phytate and ZnSO4. In the calcareous medium, Zn-HS and Zn phytate resulted in significantly higher dry biomass yields of wheat than ZnSO4. In the siliceous medium, spike and shoot dry biomass yields with Zn-HS at the low rate and Zn phytate at both rates were not significantly different from those with ZnSO4 at the high rate. After harvest, approximately 50% of the Zn applied as Zn-HS remained extractable by diethylenetriaminepentaacetic acid (DTPA), while this proportion was less than 20% for the other Zn sources. Thus, Zn-HS and Zn phytate are sources of available Zn for plants, and they are more effective than ZnSO4 in increasing plant growth, particularly when carbonates are the main Zn sorbent surface.
... However, plants are not a good source of these micronutrients because staple crops have low concentrations of Zn and Fe in edible tissues [2]. In fact, plants often suffer from Zn and Fe deficiencies due to the scarcity of Zn or low availability of Fe in the soil [3,4]. Therefore, billions of people worldwide suffer from deficiencies of these two elements, leading to nutritional disorders [5]. ...
... More than half of AhZIPs have 3-5 TMDs, which is not consistent with the results of Guerinot [15], who proposed that ZIP proteins typically contained 8 TMDs. The variation in TMD number in ZIP proteins has been reported in several plant species such as maize (6-13 TMDs), potato (6-9 TMDs), trifoliate orange (6-9 TMDs) and P. trichocarpa (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) [27,28,30,31]. The ZIP family was generally predicted to have a 3 + 5 TMD architecture [15]. ...
Article
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Zinc/iron-regulated transporter-like protein (ZIP) family genes play crucial roles in metal uptake and transport in plants. However, little is known about their functions in peanut. Here, genome-wide analysis identified 30 peanut AhZIP genes that were divided into four classes. Most AhZIPs experienced whole-genome or segmental duplication. AhZIP proteins harbored 3–8 transmembrane domains and a typical ZIP domain, showing considerable homology with BbZIP from Bordetella bronchiseptica. Clustered AhZIPs generally share similar gene/protein structures; however, unique features were found in AhIRT1.2, AhZIP1.2, AhZIP3.5 and AhZIP7.8. RNA-seq data revealed that AhZIP2.1/2.2, AhZIP4.1/4.2 and AhZIP11.1/11.2 were highly and preferentially expressed in roots, nodule and reproductive tissues. RT-qPCR analysis indicated that transcriptional responses of AhZIPs to Fe/Zn deficiency are cultivar dependent. The expressions of AhIRT1.1, AhIRT1.2 and AhZIP6.1 were closely related to Fe uptake and translocation. AhIRT1.1 and AhZIP7.2 expression were significantly correlated with Zn accumulation. The expression of AhIRT1.1, AhIRT1.2, AhZIP3.6, AhZIP6.1 and AhZIP11.1 was associated with Mn uptake and translocation. The results confirmed that AhZIP genes play crucial roles in the uptake and transport of Fe, Zn and Mn in peanut, providing clues to further functionally characterize AhZIP genes in the future.
... Zinc fertilizers are used in the prevention of Zn deficiency and in the biofortification of cereal grains [11]. The main soil factors affecting the availability of Zn to plants are low Zn content; high pH; high calcite and organic matter contents; and high concentrations of Na, Ca, Mg, bicarbonate, and phosphate in the soil solution or in labile forms [11,12]. ...
... Zinc fertilizers are used in the prevention of Zn deficiency and in the biofortification of cereal grains [11]. The main soil factors affecting the availability of Zn to plants are low Zn content; high pH; high calcite and organic matter contents; and high concentrations of Na, Ca, Mg, bicarbonate, and phosphate in the soil solution or in labile forms [11,12]. It has been well-documented that foliar Zn spray is an effective strategy to biofortify cereals with Zn [13][14][15]. ...
Article
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Zinc (Zn) is an essential element involved in human metabolism, which can be supplied by an appropriate diet. Enhancing Zn enrichment in rice grains through agronomic biofortification is advocated as an immediate and effective approach to combat micronutrient malnutrition in hu-man. It has been well-documented that high grain Zn accumulation in rice can be achieved by Zn fertilizers management. This study evaluated the effects of foliar nitrogen (N) and Zn applied at the flowering and milky stages of brown rice plants with and without soil Zn application. A glasshouse pot experiment was conducted using a completely randomized design with four replicates. Soil Zn in the form of ZnSO4 was applied at 0 and 50 kg ha−1. Foliar fertilizer of 1% urea along with 0.5% ZnSO4 was applied and assigned as (1) nil foliar N and Zn (N0Zn0), (2) foliar N with nil Zn (N+Zn0), (3) nil foliar N with foliar Zn (N0Zn+), and (4) foliar N and Zn (N+Zn+) at flowering and milky stages. Foliar application of N and Zn increased grain yield and yield components in both soil Zn conditions. Grain Zn concentration in brown rice was the highest when foliar N and Zn were applied under nil soil Zn conditions; however, grain N concentration decreased by 13.1–28.5% with foliar application at flowering and 18.8–28.5% with application at the milky stage. The grain Zn content was increased by foliar application of N0Zn+ and N+Zn+ at flowering and milky stages. Applying foliar N and Zn at flowering or milky stages tended to increase the grain N content when Zn was applied to the soil, while nil soil Zn decreased the N content by 26.8% at flowering and milky stages under N0Zn+. The results suggest that the milky stage is the most suitable for foliar application of Zn for increasing (i) grain yield and (ii) N and Zn concentrations in brown rice without having a dilution effect.
... Zinc (Zn) deficiency in humans is a serious global health concern, especially in developing countries, which is gaining growing attention worldwide (Hambidge, 2000). It has been reported that more than two billion people suffering from Zn deficiency across the world (Alloway, 2009;White & Broadley, 2009). As the staple food for over 40 % of the world's population, wheat is considered as an important dietary source of calories, protein and micronutrients such as Zn (Velu et al., 2014). ...
... As the staple food for over 40 % of the world's population, wheat is considered as an important dietary source of calories, protein and micronutrients such as Zn (Velu et al., 2014). However, more than half of the world's wheat is grown on zinc-deficient soils (Alloway, 2009;Cakmak et al., 2010), resulting in low Zn bioavailability in wheat grain, which fails to provide the required Zn needed for human health and nutrition. In addition, under intensive agriculture model, the adoption of high-yielding wheat varieties would further reduce the Zn concentration in grain through the dilution effect (Fan et al., 2008;Liu et al., 2014). ...
Article
Sustainable strategies are essential for zinc (Zn) biofortification and cadmium (Cd) reduction in staple food crops. Herein, we evaluated the phytotoxicity of Glyzinc under foliar and root application (FA&RA) in a lab-scale experiment, and then investigated its Zn efficiency and Cd reduction through foliar application on wheat (Triticum aestivum L.) under field conditions. Compared to RA, FA of Glyzinc exhibited no adverse effect on wheat growth and oxidative stresses at all doses. In field conditions, FA of Glyzinc remarkably increased Zn (28.7%), S (10.4%), Cu (17.3%) and crude protein (9.1%) content in wheat grain at 100 mg/L without damaging wheat yield. Furthermore, FA of Glyzinc significantly reduced the grain phytic acid (PA) (23.7%) and Cd level (19.5%), as well as PA to Zn molar ratio (32.3%). Overall, our results indicate that Glyzinc has great potential as a high-efficiency foliar fertilizer for Zn biofortification and safe crop production in nano-enabled agriculture.
... In Canada, spring wheat contained greater concentrations of Cd and Se when grown in regions where the soil parent material was inherently richer in Cd or Se, but not all the minerals followed this pattern (Gawalko et al., 2002). While N fertilization has shown to increase grain Zn and Fe concentration (Gooding et al., 2012;Monasterio & Graham, 2000), the impact of N fertilization on grain Zn and Fe concentrations varies considerably due to plant available Zn and Fe, as well as other soil characteristics (i.e., soil type, pH, organic matter) (Alloway, 2009;Erenoglu et al., 2001;Kutman et al., 2010;Miner et al., 2018;Rehman et al., 2018). ...
... Hatfield and Walthall (2015) discuss the interactions among genetics, environment, and management (G × E × M) as a framework for studying agricultural systems. Nutrient content may vary considerably between different crop cultivars (Grusak & Dellapenna, 1999), and soil type plays a significant role in the bioavailability of some minerals for wheat (i.e., Fe and Zn availability in calcareous soil) (Alloway, 2009;. Zebarth et al. (1992) found greater variability in grain mineral concentration between different study locations than N fertilizer management treatments. ...
Article
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Abstract Correlations between plant available soil and grain mineral concentrations are often assumed, yet few studies examine these associations. Here, soil and wheat grain samples were analyzed from a semi‐arid dryland cropping study in the northern Great Plains conducted between 2006 and 2011. Continuous spring wheat (fertilized) (Triticum aestivum L; CSW) was compared with wheat following 5 yr of perennial forages of either alfalfa (Medicago sativa L.), intermediate wheatgrass (fertilized) (Thinopyrum intermedium (Host) Barkw. & D.R. Dewey sbsp. Intermedium; IWG), or an alfalfa/intermediate wheatgrass mixture (fertilized; MIX). Wheat performance (yield, 1,000 kernel weight [TKW], and crude protein [CP] concentration), and associations between 11 plant available soil mineral concentrations and 11 wheat grain mineral concentrations were assessed. Wheat following alfalfa had greater yield than all treatments, greater TKW than CSW, greater CP than IWG and CSW, but lower grain Zn concentration than IWG (p ≤ .05). Wheat grain following IWG had greater Fe and Mn concentration than MIX, greater Mg concentration than CSW, and lower S concentration than all treatments (p
... Some of the microbes mediated mineralization of minerals in the soil and others are promoting the growth of the plants through various processes and mechanisms considered as "plant growth-promoting microorganisms" or "plant growth-promoting rhizobacteria." It was observed from the study which indicated that soils of developing countries, namely, India, China, Pakistan, Iran, and Turkey were deficient in various minerals including micronutrients (Cakmak et al. 1999;Alloway 2009) and reported that most of the Indian soils are deficient in extractable Fe, Zn, Cu, and Mn by 11.2, 48.1, 7 and 5.1%, respectively (Gupta, 2005), further Zn deficiency in the soil expected to increase from 49% to 63% by 2025 (Singh, 2009). ...
Chapter
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Malnutrition is a major challenge for the world to develop a think-tank to alleviate and provide the right access to food globally and also secure them nutritionally. Among various factors, these micronutrients, namely, zinc (Zn), iron (Fe), iodine (I), and selenium (Se) played important role in human health which is most deficient in the diet in developing countries including African and Asian Continent. According to WHO (2020), Asia stands top in the case of undernourished people (381 million), followed by Africa (250 million) and last Latin America and the Caribbean (48 million). In case of child malnutrition, approximately 191 million children of less than 5-year age were stunted and wasted during 2019, whereas 38 million children under less than 5 years were overweight. Although, there is more option to improve dietary foods with essential micronutrient and this can only be possible through food fortification, supplementation, dietary diversification, and biofortification. Among, biofortification with essential micronutrients in the targeted crop can be achieved through breeding, agronomic, genetic engineering, and microorganism approaches. These approaches can be employed in the pulse crops to exploit essential micronutrients. Few pulse crops like pigeon pea, chickpea, and lentils showed great potential to overcome micronutrient deficiencies prevalent among the vulnerable group. This chapter is dedicated to the importance of pulse crops along with their nutritive values and bioavailability of micronutrients in human beings’ vis-a-vis enrichment of pulse grains through biofortification involving various approaches. Also enlighten the role of pulse biofortification in providing opportunities, challenges, and future strategies to alleviate malnutrition across the world.
... Also, phosphorus application at planting is a common practice in rice cultivation, and it affects Zn uptake by increasing its binding in the root cells [106,107]. Other factors that affect soil Zn availability are low soil organic matter, eroded soil, soil temperature, soil Zn content, and antagonistic effects of other nutrients such as calcium, iron, sodium, magnesium, and copper [86,102,108,109]. Thus, soil properties have an important effect on rice production and agronomic approaches play a pivotal role in addressing soil nutrient availability. ...
Article
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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 bio-fortification 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.
... Although most studies addressed macronutrient management, there are strong indications that micronutrient deficiencies significantly limit crop productivity (Kihara et al., 2017;Vanlauwe et al., 2015). Micronutrient deficiencies have been observed worldwide (Kihara et al., 2017), and zinc (Zn) deficiency is considered to be the most common (Alloway, 2009;Cakmak, 2008;Cakmak et al., 1994;Hacisalihoglu, 2020;Rodella et al., 2017;Sadeghzadeh and Rengel, 2011). Zn is required by all living organisms in small concentrations, playing an essential role in enzymatic reactions and metabolic activities, especially in nitrogen metabolism (Cakmak, 2008;Sadeghzadeh and Rengel, 2011). ...
Article
Agricultural output needs significant increases to feed the growing population. Fertilizers are essential for plant production systems, with nitrogen (N) being the most limiting nutrient for plant growth. It is commonly supplied to crops as urea. Still, due to volatilization, up to 50 % of the total N application is lost. Slow or controlled release fertilizers are being developed to reduce these losses. The co-application of zinc (Zn) as a micronutrient can increase N absorption. Thus, we hypothesize that the controlled delivery of both nutrients (N and Zn) in an integrated system can improve uptake efficiency. Here we demonstrate an optimized fertilizer nanocomposite based on urea:urea-formaldehyde matrix loaded with ZnSO4 or ZnO. This nanocomposite effectively stimulates maize development, with consequent adequate N uptake, in an extreme condition - a very nutrient-poor sand substrate. Our results indicate that the Zn co-application is beneficial for plant development. However, there were advantages for ZnO due to its high Zn content. We discuss that the dispersion favors the Zn delivery as the nanoparticulated oxide in the matrix. Concerning maize development, we found that root morphology is altered in the presence of the fertilizer nanocomposite. Increased root length and surface area may improve soil nutrient uptake, potentially accompanied by increased root exudation of essential compounds for N release from the composite structure.
... Zinc (Zn) acts as a catalyst, cofactor, or regulatory element in plant cells along with being an essential component of various enzymes like carbonic anhydrase, alcohol dehydrogenase and copper (Cu)/Zn superoxide dismutase (CSD), and lots of Zn-finger domain-containing proteins (Broadley et al. 2007). The low availability of Zn in soil is due to various contributing factors such as high pH, prolonged flooding, low redox potential, and high contents of bicarbonate and organic matter (Alloway 2009). This not only leads to lower seed vigor and survivability rates of the plants but also affects the human nutrition intake (Cakmak 2008). ...
Article
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During their lifespan, sessile plants have to cope with bioavailability of the suboptimal nutrient concentration and have to constantly sense/evolve the connecting web of signal cascades for efficient nutrient uptake, storage, and translocation for proper growth and metabolism. However, environmental fluctuations and escalating anthropogenic activities are making it a formidable challenge for plants. This is adding to (micro)nutrient-deficient crops and nutritional insecurity. Biofortification is emerging as a sustainable and efficacious approach which can be utilized to combat the micronutrient malnutrition. A biofortified crop has an enriched level of desired nutrients developed using conventional breeding, agronomic practices, or advanced biotechnological tools. Nutrient homeostasis gets hampered under nutrient stress, which involves disturbance in short-distance and long-distance cell–cell/cell-organ communications involving multiple cellular and molecular components. Advanced sequencing platforms coupled with bioinformatics pipelines and databases have suggested the potential roles of tiny signaling molecules and post-transcriptional regulators, the microRNAs (miRNAs) in key plant phenomena including nutrient homeostasis. miRNAs are seen as emerging targets for biotechnology-based biofortification programs. Thus, understanding the mechanistic insights and regulatory role of miRNAs could open new windows for exploring them in developing nutrient-efficient biofortified crops. This review discusses significance and roles of miRNAs in plant nutrition and nutrient homeostasis and how they play key roles in plant responses to nutrient imbalances/deficiencies/toxicities covering major nutrients—nitrogen (N), phosphorus (P), sulfur (S), magnesium (Mg), iron (Fe), and zinc (Zn). A perspective view has been given on developing miRNA-engineered biofortified crops with recent success stories. Current challenges and future strategies have also been discussed.
... Although they are required in trace amounts, micronutrients (also known as trace elements) are equally essential for plant growth and their inadequacy, or abundance, has a significant impact on the sugarcane yield (Alloway, 2009;Majeed et al., 2022). In most soils within the Zimbabwe Sugar Industry (ZSI), micronutrients are considered to be available in concentrations that are sufficient for optimum plant growth, and the nutrition recommendations are mostly for primary nutrients. ...
Article
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Micronutrients are required by sugarcane in minute quantities and are rarely supplemented, as there is often enough for the crop in the soil. However, prolonged farming and diverse agronomic activities may have led to the exhaustion, or unavailability, of some micronutrients. In order to investigate the effect of prolonged sugarcane farming without replenishing the soil's micronutrients, the concentrations of copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) were examined in cultivated soils, as well as in the nearby forested (uncultivated) soils. Soil samples were collected from cultivated sugarcane fields and their adjacent uncultivated fields across the Zimbabwe Sugar Industry (ZSI), which covered the Hippo Valley, Mkwasine, Triangle and the Zimbabwe Sugar Association Experimental Station (ZSAES). The soils were analysed for their micronutrient content and characterised by their texture, pH, Electrical Conductivity (EC) and Organic Matter (OM). Concentrations of Cu were found to be within the adequate range in all samples, while 39% of the cultivated fields had Zn concentrations below the lowest critical concentration of 1.5 ppm. Mkwasine had the highest zinc deficiency in 50% of the cultivated soils, followed by Triangle with 45%, and then the Hippo Valley and the ZSAES, with 33%. The soils had higher concentrations of Mn and Fe, with 98% and 4% of the samples exhibiting concentrations above their respective adequacy range. Generally, there were no significant differences in the concentration of micronutrients between the cultivated and uncultivated soils. There were weak correlations between micronutrient concentrations and the soil's pH, OM and clay content.
... Soils that contain less than 0.5 mg/kg DTPA-extractable Zn are Zn deficient soils (Liu et al. 2020a;Lindsay and Norvell 1978). Zinc fertilization to combat Zn deficiency in the plant could be done by foliar sprays of Zn salt, soil application, or seed treatment (Alloway 2009). Soil application is an easy and effective strategy in the actual practice of maize growth (Liu et al. , 2020b. ...
Article
Soil zinc (Zn) deficiency is one of the factors limiting maize crop productivity. As a fertilizer, Zn is an effective strategy for increasing yield and Zn concentration in maize grains. However, Zn as a heavy metal may accumulate in the soil thus, its environmental impact in agroecosystems requires analysis. During the 2019 and 2020 growing seasons, a plot experiment was conducted to assess the effects of the optimum Zn doses (0, 5.7, and 11.4 kg ha−1) on maize grain yield and soil eukaryotic alpha/beta diversity. The application of Zn increased significantly the chlorophyll soil plant analysis development (SPAD) values, 1000-grain weight, kernels per spike, and total grain yield. In the meantime, its effect on soil respiration rate and eukaryotic microorganism diversity was negligible except for a weak variable effect on the community structure of eukaryotic microorganisms due to Zn doses. The continuous maize plantation with the recommended NPK fertilizers for 2 years showed a decrease in the number of observed OTUs and a significant change in the beta diversity of the soil eukaryotic microorganisms in 2020 compared with 2019. Zn fertilizer is nontoxic to the diverse community of soil eukaryotic microorganisms while being beneficial in promoting maize crop productivity, and the maize growth will change the eukaryote of the newly cultivated land.
... In China, micronutrient content in soils is very low due to the dominance of calcareous and alkaline soils, and 40% of the land has a micronutrient deficiency. These micronutrient deficiencies, including zinc and selenium, affect crop yield and nutritional value in sweet corn production [13][14][15]. ...
Article
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Corn (Zea mays L.) is one of the major cereal crops cultivated worldwide. Zinc and selenium are important nutrients for humans and plants, and their deficiency is a cause for concern in most developing countries. Sweet corn fertilized with zinc and selenium can mitigate this problem. Therefore, the objective of this study was to investigate the effects of fertilization with Zn and Se on the yield and quality of sweet corn varieties under different planting densities. The experimental design used was a split-plot based on a randomized complete block design with three replications. Compared to the control, significant differences were recorded in grain yield, leaf area index, and plant height (i.e., Zn/Se + density + variety) treatments. Non-significant differences in the number of kernels per cob, sugar content and crude protein were recorded under different treatments. Significant differences in grain yield, water-soluble sugar, and zinc and selenium content in grain were recorded. Grain yield was higher in Selenium than in Zinc treatments, with a mean difference of 0.05 t ha−1. We conclude that grain yield and selenium content in grain were influenced by selenium foliar application, while water-soluble sugar and zinc content in grain were influenced by foliar zinc application.
... Most of the places around the world possess very low levels of plant available zinc. This shortage in the soil spreads zinc deficiency among the growing crops (Alloway 2009;Ahmed et al. 2021). In addition to the above, approximately 33% of the world population has taken zinc-deficient diets due to large intakes of cereals (Rehman et al. 2018;Aziz et al. 2019). ...
Article
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The rising population is increasing food demand, yet actual crop production is limited by the poor efficiency of classical fertilizers. In particular, only about 40–60% of fertilizer nitrogen, 15–20% of phosphorus and 50–60% of potassium are used by crop plants, the rest ending polluting the environment. Nanofertilizers are promising alternatives. Here, we review plant nutrients, synthesis of zinc oxide nanoparticles, encapsulation of nanoparticles in fertilizers, and effect on plants.
... Zn deficiency affects up to 30% of the world's population-nearly 2 billion people worldwide (Hotz and Brown, 2004;Gibson, 2012;Klassen-Wigger et al., 2018) and ranks fifth and eleventh in causing mortality and serious health issues, respectively, especially in the developing countries (WHO, 2002;Stevens et al., 2009). According to Alloway (2009), Zn deficiency in human beings is widespread in countries where individuals mostly consume cereal-based staple food produced on Zn deficient soils (Yaseen and Hussain, 2021), and about half of the cereal growing soils in the world are alleged to be deficient in plant-available Zn. Zn deficiency in soils is generally corrected with Zn application from external sources (Zn containing fertilizers). ...
Article
Globally, widespread micronutrient deficiencies have become a serious challenge for sustaining crop production systems and food security. Of all micronutrients, zinc (Zn) is the most deficient one. Hence, efficient Zn management is essential to achieve potential crop yields. A six-year field experiment was conducted on Typic Hapludalfs with maize-wheat cropping system to study the direct and residual Zn management effect on maize and succeeding wheat crop, respectively. The effect on soil available Zn was also evaluated. Three Zn application frequencies, viz. once (single year), alternate (every alternate year), and continuous (every year) at four Zn application rates, viz. 2.5, 5.0, 7.5, and 10.0 kg ha − 1 along with one control (no Zn) were investigated from 2013 to 2019. The Zn application significantly improved the crop yields, system sustainability, DTPA-Zn, and different Zn pools without causing any environmental risk. In general, the continuous application of Zn at 5.0 kg ha − 1 produced the best yield and system productivity. The economically optimal system productivity was obtained with 5.93 and 7.46 kg Zn ha − 1 for alternate and continuous frequency Zn application, respectively. The optimal DTPA-Zn to attain the highest system productivity of 7.64 t ha − 1 was 1.55 mg kg − 1. The crop yields were mainly influenced by the alternate and continuous application of Zn at lower rates (2.5, 5.0, and 7.5 kg ha − 1), whereas Zn fractions and DTPA-Zn were significantly influenced by Zn application at higher rate (10 kg ha − 1) irrespective of Zn application frequencies. Similar results were obtained with PCA analysis. The results of this study suggested the rationality of Zn application in attaining economically viable and environmentally sound maize-wheat system productivity.
... Zn deficiency affects up to 30% of the world's population-nearly 2 billion people worldwide (Hotz and Brown, 2004;Gibson, 2012;Klassen-Wigger et al., 2018) and ranks fifth and eleventh in causing mortality and serious health issues, respectively, especially in the developing countries (WHO, 2002;Stevens et al., 2009). According to Alloway (2009), Zn deficiency in human beings is widespread in countries where individuals mostly consume cereal-based staple food produced on Zn deficient soils (Yaseen and Hussain, 2021), and about half of the cereal growing soils in the world are alleged to be deficient in plant-available Zn. Zn deficiency in soils is generally corrected with Zn application from external sources (Zn containing fertilizers). ...
Article
Full-text available
Globally, widespread micronutrient deficiencies have become a serious challenge for sustaining crop production systems and food security. Of all micronutrients, zinc (Zn) is the most deficient one. Hence, efficient Zn management is essential to achieve potential crop yields. A six-year field experiment was conducted on Typic Hapludalfs with maize-wheat cropping system to study the direct and residual Zn management effect on maize and succeeding wheat crop, respectively. The effect on soil available Zn was also evaluated. Three Zn application frequencies, viz. once (single year), alternate (every alternate year), and continuous (every year) at four Zn application rates, viz. 2.5, 5.0, 7.5, and 10.0 kg ha⁻¹ along with one control (no Zn) were investigated from 2013 to 2019. The Zn application significantly improved the crop yields, system sustainability, DTPA-Zn, and different Zn pools without causing any environmental risk. In general, the continuous application of Zn at 5.0 kg ha⁻¹ produced the best yield and system productivity. The economically optimal system productivity was obtained with 5.93 and 7.46 kg Zn ha⁻¹ for alternate and continuous frequency Zn application, respectively. The optimal DTPA-Zn to attain the highest system productivity of 7.64 t ha⁻¹ was 1.55 mg kg⁻¹. The crop yields were mainly influenced by the alternate and continuous application of Zn at lower rates (2.5, 5.0, and 7.5 kg ha⁻¹), whereas Zn fractions and DTPA-Zn were significantly influenced by Zn application at higher rate (10 kg ha⁻¹) irrespective of Zn application frequencies. Similar results were obtained with PCA analysis. The results of this study suggested the rationality of Zn application in attaining economically viable and environmentally sound maize-wheat system productivity.
... The highest increases in grain Zn and Fe in response to N supply were observed in loamy soils (Fig. 7). The low contents of clay and organic matter of sandy soils in some cases combined with high pH and CaCO 3 content often lead to limited availability and uptake of Zn and Fe (Alloway, 2009). Meanwhile, compared with fine-textured (clay) soils, loamy soils support better root system growth. ...
Article
Human zinc (Zn) and iron (Fe) deficiencies can partly be alleviated by enhancing cereal concentrations of these micronutrients. Soil nitrogen (N) levels codetermine cereal grain yields and Zn and Fe nutrition of plants and grains. Grain Zn and Fe concentrations have been reported to be affected by both yield dilution and enhanced acquisition and grain allocation of Zn and Fe. A global meta-analysis of 100 publications concerning wheat, maize, and rice providing 785 records of Zn and 506 records of Fe allowed us to assess their relative importance and quantify the concentrations and bioavailability of Zn and Fe in major cereal grains over a wide range of N fertilization levels. Compared with the no N controls, N application significantly increased grain Zn and Fe concentrations in all crops except maize Zn. The increase in grain protein concentration correlated positively with the increases in Zn and Fe concentrations in all cereals except Zn in maize. In rice, the grain Zn and Fe concentration increase was independent of the rate of N applied. Grain concentrations of Zn and Fe in wheat and Fe in maize were positively correlated with N rate but were only higher than those in the controls above 40–60 kg N ha⁻¹. At lower N rates, the dilution effect was thus stronger than the enhancement effect. N supply had a larger effect on Zn and Fe concentrations in loamy textured soils or at lower soil available N and phosphorus (P), or higher soil organic matter and available Zn contents or with P and Zn fertilization, but the effect sizes differed among crops. Reductions in phytic acid concentration after N fertilization occurred in wheat, potentially improving micronutrient bioavailability. Thus, our findings indicate that N fertilization could be managed in ways that simultaneously support high grain yields and enhance nutritional quality for major cereals.
... The global decline in soil quality represents a challenge for improving grain Fe contents (Bouis and Welch 2010;Cakmak et al. 2010). Iron-deficient soils in cereal-growing zones cause inherently low grain Fe concentrations and are considered as a fundamental deficient source for Fe intake by dietary means (Alloway 2009). Rice and wheat cultivars, two main staple crops worldwide, which are widely used for human consumption have low amount of Fe as most is lost in processing due to removal of outer bran layers (Ludwig and Slamet-Loedin 2019). ...
Article
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Micronutrient deficiencies are a significant cause of malnutrition worldwide, particularly in developing countries, affecting nearly 1.8 billion people worldwide. Agriculture is the primary source of nutrients for humans, but the increasing population and reducing arable lands areas are putting the agricultural sector under pressure, particularly in developing and less developed countries, and calls for intensive farming to increase crop yield to overcome food and nutrients deficiency challenges. Iron is an essential microelement that plays a vital role in plant and human growth, and metabolism, but its deficiency is widely reported and affects nearly one-third of the world population. To combat micronutrient deficiency, crops must have improved nutritional qualities or be biofortified. Several biofortification programs with conventional breeding, biotechnological and agronomic approaches have been implemented with limited success in providing essential nutrients, especially in developing and under-developed countries. The use of nanofertilisers as agronomic biofortification method to increase yields and nutrients, micronutrient availability in soil and uptake in plant parts, and minimising the reliance on harmful chemical fertilisers is essential. Using nanoparticles as nanofertilisers is a promising approach for improving the sustainability of current agricultural practices and for the biofortification of food crop production with essential micronutrients, thus enhanced nutritional quality. This review evaluates the current use of iron nanofertilisers for biofortification in several food crops addressing critical knowledge gaps and challenges that must be addressed to optimise the sustainable application.
... An ample range of soil factors, typically total Zn level, elevated pH, and the maximum content of calcite, organic matter, Ca, Mg, Na, phosphate, and bicarbonate also influence the Zn availability in plants (Alloway, 2009). The inadequacy of Zn exhibits various symptoms that typically become apparent within 2 to 3 weeks after seedling transplantation of rice. ...
Article
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The experimental study was contrived to characterize two zinc-solubilizing bacteria (ZSB), namely BMRR126 and BMAR64, and their role in zinc (Zn) biofortification of rice. These bacteria solubilized Zn profoundly, determined qualitatively by halo-zone formation on a solid medium and quantitatively in a liquid broth by AAS and SEM-EDX. The lowering of pH and contact angle assessment of the liquid broth unveiled the establishment of the acidic conditions in a medium suitable for Zn solubilization. The characterization of both isolates on the basis of 16S rRNA gene analysis was identified as Burkholderia cepacia and Pantoea rodasii, respectively. These strains were also found to have some plant probiotic traits namely phosphate solubilization, production of siderophore, indole acetic acid (IAA), exopolysaccharide (EPS), and ammonia. The field experiments were performed at two diverse locations and under all treatments; the simultaneous use of BMRR126 and BMAR64 with zinc oxide (ZnO) resulted in the highest growth and productivity of the paddy crop. The utmost Zn achievement in the grain was estimated in a treatment (T9) (25.07 mg/kg) containing a consortium of BMRR126 and BMAR64 along with ZnO for the Terai region. The treatment containing single ZSB bioinoculant BMRR126 (T7) showed an elevated Zn amount in the rice grain (33.25 mg/kg) for the Katchar region. The soil parameters (pH, EC, organic carbon, NPK, available Zn, and dehydrogenase activity) were also positively influenced under all bacterial treatments compared to the uninoculated control. Our study clearly accentuates the need for Zn solubilizing bacteria (ZSB) to provide the benefits of Zn-biofortification in different regions.
... Zinc deficiency is commonly seen in the soils formed on the calcareous parent material in the arid and semi-arid climate zone and in the plants grown in these soils. This situation is generally associated with reduced zinc availability through the factors such as high pH, free calcium carbonate, low organic matter, insufficient and poor drainage, as well as the uneven application of basic fertilization (Alloway 2009;Rehman et al. 2012). Calcareous soils, which constitute more than one-third of the world's agricultural land, cause deficiencies in different nutrients, including Zn (S anchez-Rodr ıguez et al. 2021). ...
... Zinc sulfate (ZnSO 4 ) was proposed to counteract Zn deficiency, although in this form it quickly becomes unavailable, especially in calcareous or alkaline soils (Rico et al., 1996;Alloway, 2009). Thus, alternative forms of Zn were tested in order to minimize its loss and increase its use efficiency (Timsina and Conner, 2001). ...
Article
Lignin is a by-product of biorefineries and paper mills and is usually discarded or burnt. However, it may represent a source of novel fertilising products, able to support the sustainable intensification of agricultural productions. The aim of this review is to explore the literature regarding the effect of lignin application towards plant growth and nutrient use efficiency. First, we reviewed the biostimulant role of lignin, which was reported to positively perturbing plant hormonal balances or improving the efficiency of photosynthesis and respiration. Also, when added to soils, lignin was shown to enhance nitrogen uptake, as well as the development of beneficial soil microorganisms. Then, we summarised the research related to the chemical modifications of lignin structure devised to boost its bioactivity, an approach opening possibilities to tailor the effects of lignin addition on plant development. We further examined the literature about the use of lignin and its derivatives as starting substrates to produce sustainable materials (chelates, coatings, micro- and nano-materials) for the slow release of plant nutrients. Encouraging results emerged from the summarised articles, suggesting that lignin may replace the currently used synthetic polymers exploited to chelate or entrapping nutrients. We additionally hereby highlighted the role of lignin chemical nature in affecting its biological and release properties, hence pointing out the relevance of thoroughly studying its structure at a molecular level by the most advanced analytical tools. Finally, we suggested the need for researchers to combine their skills and expertise, in order to develop more efficient lignin-inspired fertilisers.
... Biofortification through agronomic approaches is simple and the least expensive but has some disadvantages like, regular application of mineral fertilizers, could impede the accessibility of other micronutrients and also cause environmental toxicity (Jha and Warkentin, 2020). In addition, soil factors such as higher pH, calcite, organic matter, and high concentration of other ions hinder the accessibility of micronutrients to the crop plants (Alloway, 2009). ...
Article
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Global food security, both in terms of quantity and quality remains as a challenge with the increasing population. In parallel, micronutrient deficiency in the human diet leads to malnutrition and several health-related problems collectively known as “hidden hunger” more prominent in developing countries around the globe. Biofortification is a potential tool to fortify grain legumes with micronutrients to mitigate the food and nutritional security of the ever-increasing population. Anti-nutritional factors like phytates, raffinose (RFO’s), oxalates, tannin, etc. have adverse effects on human health upon consumption. Reduction of the anti-nutritional factors or preventing their accumulation offers opportunity for enhancing the intake of legumes in diet besides increasing the bioavailability of micronutrients. Integrated breeding methods are routinely being used to exploit the available genetic variability for micronutrients through modern “omic” technologies such as genomics, transcriptomics, ionomics, and metabolomics for developing biofortified grain legumes. Molecular mechanism of Fe/Zn uptake, phytate, and raffinose family oligosaccharides (RFOs) biosynthesis pathways have been elucidated. Transgenic, microRNAs and genome editing tools hold great promise for designing nutrient-dense and anti-nutrient-free grain legumes. In this review, we present the recent efforts toward manipulation of genes/QTLs regulating biofortification and Anti-nutrient accumulation in legumes using genetics-, genomics-, microRNA-, and genome editing-based approaches. We also discuss the success stories in legumes enrichment and recent advances in development of low Anti-nutrient lines. We hope that these emerging tools and techniques will expedite the efforts to develop micronutrient dense legume crop varieties devoid of Anti-nutritional factors that will serve to address the challenges like malnutrition and hidden hunger.
... The causes of the Zn deficiency in soils include high Zn removal by crops due to high crop yields and intensive cropping systems, reductions in the application of organic manures, and the use of high analysis fertilizers, which provide only the main macronutrients. Millions of hectares of cropland are affected by Zn deficiency and approximately one third of the human population suffers from inadequate Zn intake (Alloway 2009). Different Zn fertilizers have been used to prevent Zn deficiency in soils. ...
Article
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The aim of this paper is to explore whether the long-term bioavailability of Zn in different soils can be predicted using operational extraction procedures. Green peas and beetroot were grown in two soils with contrasting physicochemical characteristics. Two Zn sources of different sizes (ZnO-nano or ZnO-bulk) were applied 1 year earlier, at different Zn application rates. The amounts of available Zn were assessed using the diffusive gradients in thin films (DGT) technique and different chemical extraction procedures: water-soluble (WS), CaCl 2 , rhizosphere-based low-molecular-weight organic acid (LMWOAs), DTPA-TEA, and NH 4 Ac. The different correlation and regression studies showed that the estimation of availability is dependent on the soil categorical variable, especially in the beetroot crop. Zn-DGT could be used to estimate the Zn concentration of the aerial part of the green pea using a general model for both soil and ZnO sizes. The estimation of long-term Zn bioavailability was successful using either medium-strength extractive solutions or the DGT technique. The extraction methods involving complexing agents or buffered salt solution overestimated the amount of bioavailable Zn in calcareous soil. Further studies will be necessary to know the amounts of Zn associated with the different soil fractions. Graphical abstract
... 13 Transgenic strategies for the biofortification of cereals with Zn are still in their infancy for enhanced root uptake, transport, and grain accretion capacity for Fe or Zn or both in recent work. 14,15 Providing crop plants with sufficient Zn through the soil and foliar fertilizer strategy under field conditions is essential for biofortification efforts. 16−18 As compared to traditional fertilizers, not only can cellulosic biopolymer based slow release nanocarriers currently improve the nutrient conversion ratio, but also their degradation by soil microorganisms occurs at a slower rate which creates a controlled release profile. ...
Article
Full-text available
Driven by the possibility of precise transformational change in nutrient-enrichment technology to meet global food demand, advanced nutrient delivery strategies have emerged to pave the path toward success for nutrient enrichment in edible parts of crops through bioderived nanocarriers with increased productivity. Slow and controlled release of nutrient carrier materials influences the nutrient delivery rate in soil and in the edible parts of crops with a sluggish nutrient delivery to enhance their availability in roots by minimizing nutrient loss. With a limited understanding of the nutrient delivery mechanism in soil and the edible parts of crops, it is envisaged to introduce nutrient-enrichment technology for nutrient delivery that minimizes environmental impact due to its biodegradable nature. This article attempts to analyze the possible role of the cellulose matrix for nutrient release and the role of cellulose nanocomposites and nanofibers. We have proposed a few cellulose derived biofortificant materials as nutrient carriers, such as (1) nanofibers, (2) polymer-nanocellulose-clay composites, (3) silk-fibroin derived nanocarriers, and (4) carboxymethyl cellulose. An effort is undertaken to describe the research need by linking a biopolymer derived nanocarrier for crop growth regulation and experimental nitrogen release analysis. We have finally provided a perspective on cellulose nanofibers (CNFs) for microcage based nutrient loading ability. This article aims to explain why biopolymer derived nutrient carriers are the alternative candidate for alleviating nutrient deficiency challenges which are involved in focusing the nutrient delivery profile of biopolymers and promising biofortification of crops.
... Microelement deficiencies are common in developed and developing countries, and have become a major global health concern. Experts have estimated that one-third of the world population is at risk of Fe deficiency (Alloway, 2009). Women of child-bearing age and children are more prone to microelement deficiencies because they have greater micronutrient needs (Grzeszczak, Kwiatkowski & Kosik-Bogacka, 2020). ...
Article
Full-text available
Iron (Fe) is an essential micronutrient of the body. Low concentrations of bioavailable Fe in staple food result in micronutrient malnutrition. Wheat ( Triticum aestivum L.) is the most important global food crop and thus has become an important source of iron for people. Breeding nutritious wheat with high grain-Fe content has become an effective means of alleviating malnutrition. Understanding the genetic basis of micronutrient concentration in wheat grains may provide useful information for breeding for high Fe varieties through marker-assisted selection (MAS). Hence, in the present study, genome-wide association studies (GWAS) were conducted for grain Fe. An association panel of 207 accessions was genotyped using a 660K SNP array and phenotyped for grain Fe content at three locations. The genotypic and phenotypic data obtained thus were used for GWAS. A total of 911 SNPs were significantly associated with grain Fe concentrations. These SNPs were distributed on all 21 wheat chromosomes, and each SNP explained 5.79–25.31% of the phenotypic variations. Notably, the two significant SNPs (AX-108912427 and AX-94729264) not only have a more significant effect on grain Fe concentration but also have the reliability under the different environments. Furthermore, candidate genes potentially associated with grain Fe concentration were predicted, and 10 candidate genes were identified. These candidate genes were related to transport, translocation, remobilization, and accumulationof ironin wheat plants. These findings will not only help in better understanding the molecular basis of Fe accumulation in grains, but also provide elite wheat germplasms to develop Fe-rich wheat varieties through breeding.
... Low Zn supplies from cereals could be due to low soil Zn content or low phytoavailability of Zn, resulting in a low Zn concentration in grains [43,44]. However, the high phytate content (phytate to Zn ratio > 15) further decreases Zn bioavailability and increases the risk of Zn deficiency in humans [6,45]. Traditional cerealprocessing methods such as fermentation, germination, soaking, and roasting reduce phytate content and increase mineral bioavailability [46]. ...
Article
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Recent surveys have revealed substantial spatial variation in the micronutrient composition of cereals in Ethiopia, where a single national micronutrient concentration values for cereal grains are of limited use for estimating typical micronutrient intakes. We estimated the district-level dietary mineral supply of staple cereals, combining district-level cereal production and crop mineral composition data, assuming cereal consumption of 300 g capita−1 day−1 proportional to district-level production quantity of each cereal. We considered Barley (Hordeum vulgare L.), maize (Zea mays L.), sorghum (Sorghum bicolor (L.) Moench), teff (Eragrostis tef (Zuccagni) Trotter), and wheat (Triticum aestivum L.) consumption representing 93.5% of the total cereal production in the three major agrarian regions. On average, grain cereals can supply 146, 23, and 7.1 mg capita−1 day−1 of Ca, Fe, and Zn, respectively. In addition, the Se supply was 25 µg capita−1 day−1. Even at district-level, cereals differ by their mineral composition, causing a wide range of variation in their contribution to the daily dietary requirements, i.e., for an adult woman: 1–48% of Ca, 34–724% of Fe, 17–191% of Se, and 48–95% of Zn. There was considerable variability in the dietary supply of Ca, Fe, Se, and Zn from staple cereals between districts in Ethiopia.
... Soil degradation and nutrient deficiency coupled with extreme weather events, and global climatic changes that drive the spread of pests and pathogens are a constant threat to plant productivity and food security. Especially zinc (Zn) deficiency, which affects about 30% of arable land (Alloway, 2009;Cakmak and Kutman, 2018), reduces crop growth and yield quality, and affects crop responses to biotic stress. Recent reports state that ≥20% of world yield loss of the five major crops (wheat, rice, potato, maize, and soybean) is associated with pathogens and pests (Savary et al., 2019). ...
Article
Metal hyperaccumulation is an exclusive evolutionary trait contributing to efficient plant defence against biotic stress. The defence can be based on direct metal toxicity or joint effect of accumulated metal and organic compounds, the latter being based on integrated signalling networks. While the role of metals in biotic stress defence of hyperaccumulators has been intensively studied, their role in the pathogen immunity of non-accumulator plants is far less understood. New findings show that in metal non-hyperaccumulating plants, localized hot spots of Zn, Mn and Fe increase plant immunity, while manipulation of nutrient availability may be used for priming against subsequent pathogen attack. The recent findings on the role of metals in plant-pathogen interactions are discussed considering the narrow line between deficiency and toxicity, host-pathogen nutrient competition and synergistic effects of simultaneous metal-biotic stress. The suitability of direct defence and joint effect hypotheses in the case of non-hyperaccumulating plants, and involvement of metals as active centres of immunity-related enzymes is discussed, as well as future challenges in revealing the mechanisms underlying the metal-mediated plant immunity.
... Lower content of zinc was may be due to higher pH values which resulted in formation of insoluble zinc containing compounds (Tandon, 1995) [15] . Another reason for lower zinc content in soils may be due to higher calcium and phosphorous content in soil solution (Alloway., 2009) [1] . Soil samples which were analysed for Iron content varied from 1.0 mg kg -1 to 29.0 mg kg -1 ( Table 2). ...
Article
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Livestock are an important asset and livelihood option for poor people in rain fed areas. Fodder crops are the plant species that are cultivated and harvested for feeding the animals in the form of forage, silage and hay. A survey was carried out in forage growing soils of Suryapet district of Telangana state. Seventy five representative surface soil samples (0-15 cm) were collected and analysed for their salient characteristics viz., pH, EC, OC, free CaCO3, available N, P2O5, K2O and micronutrients (Zn, Fe, Cu and Mn). Soil fertility maps were prepared for macronutrients. Results revealed that, soil pH ranged from 5.28 to 8.13. The soils were non-saline to slightly saline (0.05 to 1.04 dSm-1). The organic carbon ranged from 0.22 to 2.20 per cent. Free Calcium Carbonate content ranged from 1.04 to 18.82 per cent. With regard to available nutrients, the values varied from 132.9 to 277.0 kg N ha-1 for nitrogen, 9.6 to 97.5 kg P2O5 ha-1 for phosphorus, 78.0 to 384.6 kg K2O ha-1 for potassium. Among the micronutrients 17.33 and 9.33 percent soils were deficient in available zinc and iron respectively. Further, the soils were not deficient in Cu and Mn.
... The deficiency of zinc in the wheat-growing soils leads to an inherently low zinc concentration in grain and it is also known as a reason for low human zinc intake (Alloway, 2009) [5] . According to Bybrodi and Malakouti, 2003 [11] , when compared to other nutrient deficiencies like iron and copper, wheat is more sensitive to zinc deficiency. ...
Article
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Agronomic bio fortification is the way easier to improve the concentration of micronutrients in the grains of cereals than genetic bio fortification. It involves the soil and foliar application of nutrients. This paper explains the foliar application of the nutrients, which proved to be more effective than soil application in improving the yield components of the crops. This is the quickest method and also a very easier one to increase the micronutrients like iron and zinc in the cereals as the concentration of these nutrients is very less leading to deficiency, mainly in the areas where cereals are taken as the staple food. The main aim of this review is to focus on the agronomic bio fortification with zinc and iron in the cereals like rice and wheat.
Article
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Conservation agriculture is characterized by three principles which are linked to each other, namely; continuous minimum mechanical soil disturbance, continuous organic soil cover, diversified crop rotations in the case of annual crops or plant associations in case of perennial crops. Excessive tillage of agricultural soils may result in short term increases in fertility, but will degrade soils in the medium term. Soil erosion resulting from soil tillage has forced us to look for alternatives and to reverse the process of soil degradation. The logical approach to this has been to reduce tillage. The experiment on conservation tillage was undertaken at AICRP for Dryland Agriculture, Dr. PDKV, during 2018-19 and 2019-20. The results indicated higher soil moisture status at various crop growth stages and highest yield of soybean and chickpea was observed in reduced tillage as compared to other treatments. It was also observed that reduced tillage has given higher net returns and B:C ratio of soybean and chickpea than other treatments. Reduced tillage with BBF and crop residue mulch helped in slight build up in organic carbon and available nutrients in soil. The average energy use efficiency (6.62) and energy productivity (2.98) was found highest in reduced tillage with BBF.
Article
In the Krasnodar Territory, on the experimental field of the Krasnodar Research Centre for Animal Husbandry and Veterinary Medicine, an experiment was conducted to determine the effect of a new complex biofertilizer on the yield and biometric indicators of a vetch-triticale fodder grass mixture. The conducted experiment shows that with the use of a new complex bio-fertilizer, an increase in the density of planting is observed in triticale (by 16 pieces or by 24%) and in Glinkovskaya vetch by (15 pieces or by 30%). Empirically, it was found that it is best to cultivate vetch-triticale grass mixtures for livestock feed with varieties of Hungarian vetch, in particular with the Orlan variety, since this variety showed a greater increase in green mass both in the experimental and in the control variant. It was also found that the use of a new bio-fertilizer has a positive effect on the overall agrochemical characteristics of the soil, improving and enriching its composition.
Chapter
Zinc (Zn) occurs naturally in all types of soils. In addition, Zn and its diversified compounds concentrate on topsoil through atmospheric deposition, anthropogenic activities, and agricultural practices. This heavy metal plays an important role for plant physiology and metabolism, abiotic stress resistance, and productiveness. At high concentrations, it accumulates in various plant compartments like stems, roots, and leaves; through its all life cycle. Zinc is a heavy metal contaminating soils all over the world and negatively affects soil functionalities, plant growth, and soil microbiome at their higher concentrations. Conventional methods including physical, chemical, and biological techniques or their combinations seem to be effective in zinc bioremediation of polluted soils. Globally, this chapter tries to deal and discuss the current background level, occurrence, speciation, bioavailability, uptake detoxification mechanisms, and management of Zn-polluted soils to an acceptable and safe level.
Article
Since urease-based microbial induced calcium carbonate precipitation (MICCP) process produces high ammonia levels, alternative strategies are very useful in adopting the MICCP process for bioremediating heavy metals. This study aimed to investigate the potential application of two native L-asparaginase and urease-producing isolates and Sporosarcina pasteurii as an indicator strain in removing zinc (Zn) from a contaminated solution and immobilizing it in soil through MICCP method. Zn removal from contaminated solution was 70.36% and 71.46% in 4 mmol L⁻¹ Zn by S. pasteurii and urease-producing isolate, respectively. However, it was 97.32% when L-asparaginase-producing isolate was inoculated in solution with doubled Zn concentration (8 mmol L⁻¹ Zn). The overall mean reduction of Zn in soluble-exchangeable fraction of soil was the highest in L-asparaginase-producing isolate treatment (71.8%) in comparison to S. pasteurii (61.8%) and urease-producing isolate treatments (56.2%). In contaminated soil with 150, 300, 400, and 500 mg kg⁻¹ Zn, carbonate-bound Zn fraction increased to 79.2–85.35% and 83.86–85.12% in soil inoculated with S. pasteurii and urease-producing isolate, respectively. However, this fraction increased to 80.67, 84.95, 85.45, and 86.05%, respectively, in the case of L-asparaginase-producing isolate inoculation. Overall, the results confirmed the efficacy of both isolated strains in removing and immobilizing Zn in comparison to the indicator strain, which indicated the higher potential of the L-asparaginase strain. Therefore, due to the less ammonia production, L-asparaginase based MICCP process can be considered as a more environmentally friendly approach for bioremediating soil heavy metal.
Chapter
Trace elements (TEs) could have hazardous effects on soil and plants, therefore imposing maximum admissible restrictions on their concentrations in soil by governments or organizations. These limits are usually classified into many groups, depending on the soil usage, soil qualities, or both. The goal of this chapter was to investigate and assess the toxic effect of TEs in soil by identifying potential health issues in soils with maximum permissible values and managing their toxicity effects. The soil-to-human pathway was examined, and we identified three primary TE exposures: household, commercial, and farming. The limits of arsenic have been shown to provide a relative high-risk quotient (HQi) that tends to underestimate its risk. Other TE restrictions such as Cd, Cu, Pb, and Zn often lead to low HQi, which means that limitations are somewhat overprotective in those circumstances. This chapter also covers the management and remediation opportunities available to solve this crucial problem.
Article
Bu çalışmada, baraj ve deniz suyunda yetiştirilen gökkuşağı alabalığının yetiştirme ortamındaki (pH, sıcaklık, tuzluluk, oksijen içeriği ve doygunluk) farklılığın serumda bazı mineraller (kalsiyum, magnezyum, çinko, demir) ile biyokimyasal parametre düzeyine etkisinin araştırılması amaçlandı. Çalışma materyalini Samsun'da baraj suyu (Derbent Barajı) ve Karadeniz suyu (Yakakent) içinde yaklaşık 800-1000 gr ağırlığında 20 adet gökkuşağı alabalığı (Oncorhynchus mykiss) oluşturdu. Aralık ayında aynı günde her iki gruptan kan örnekleri alındı ve suyun pH, sıcaklık, oksijen içeriği ve doygunluk düzeyi YSK oksijen ölçer ile, tuzluluk ise refraktometri ile belirlendi. Toplam protein (TP), albümin (Alb), kolesterol (TK), glikoz (Glu), üre, kreatinin (Cre), ürik asit (UA), Aspartat transaminaz (AST), Alanin Aminotransferaz (ALT), trigliserit (TG) kalsiyum, magnezyum, demir ve çinko ile ALT, AST enzim aktivitelerinin otoanalizörde spektrofotometrik yöntemle belirlendi. Deniz suyunun tuzluluk, oksijen ve doygunluk düzeylerinin baraj suyundan daha yüksek olduğu ve pH ile sıcaklığın birbirine yakın olduğu gözlendi. Barajda yetiştirilen gökkuşağı alabalığında TP, Alb, Alb/Glo, TK, TG, UA ve Ca düzeylerinin denizde yetiştirilenlere göre önemli ölçüde yüksek olduğu belirlendi (P
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Zinc (Zn) is an essential micronutrient of plants and other organisms and is involved in many cellular processes. Zn deficiency is defined as the insufficient Zn available for optimal growth and can lead to a sharp decline in crop yield and quality. About 30% of the world's soils have Zn deficiency. Zn efficiency can be defined as the ratio of grain yield or above-ground dry matter yield to the total Zn uptake under both Zn-deficient and Zn-sufficient conditions. The present review focuses on the potential roles of Zn in the maintenance of plant physiological process, its uptake and translocation, plant response to Zn deficiency with emphasis on wheat, and biofortification strategies to enhance the bioavailability of Zn to wheat grains which might help in addressing significant human nutrition problems related to Zn deficiency.
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Graphene has triggered enormous interest in, and exploration of, its applications in diverse areas of science and technology due to its unique properties. While graphene has displayed great potential as a nano-delivery system for drugs and biomolecules in biomedicine, its application as a nanocarrier in agriculture has only begun to be explored. Conventional fertilizers and agricultural delivery systems have a number of disadvantages, such as: fast release of the active ingredient, low delivery efficiency, rapid degradation and low stability that often leads to their over-application and consequent environmental problems. Advanced nano fertilizers with high carrier efficiency and slow and controlled release are now considered the gold standard for promoting agricultural sustainability while protecting the environment. Graphene's attractive properties include large surface area, chemical stability, mechanical stability, tunable surface chemistry and low toxicity making it a promising material on which to base agricultural delivery systems. Recent research has demonstrated considerable success in the use of graphene for agricultural applications, including its utilization as a delivery vehicle for plant nutrients and crop protection agents, as well as in post-harvest management of crops. This review, therefore, presents a comprehensive overview of the current status of graphene-based nanocarriers in agriculture. Additionally, the review outlines the surface functionalization methods used for effective molecular delivery, various strategies for nano-vehicle design and the underlying features necessary for a graphene-based agro-delivery system. Finally, the review discusses directions for further research in optimization of graphene-based nanocarriers.
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Application of Zn fertilizers to agricultural field is a simple and effective way for farmers to manage Zn deficient stress in soils to avoid yield lose. Although a synergistic effect of Zn on N transformation in soil has been reported, the mechanism is not fully understood yet. In this study, we planted rice in soils with different combinations of Zn and N supply, and analyzed the plant growth and N uptake, the N transformation, microbial communities, enzyme activities and gene expression levels in rhizosphere soil to reveal the underlying mechanism. Results showed that Zn application promoted the rice growth and N uptake, increased the soil alkali-hydrolyzed N and NH4⁺, but decreased NO3⁻ and inhibited NH3 volatilization from the rhizosphere soil under optimal N condition. Zn supply significantly increased the relative abundances of Sphingomonas, Gaiella, subgroup_6, and Gemmatimonas, but decreased nitrosifying bacteria Ellin6067; while increased saprophytic fungi Schizothecium and Mortierella, but decreased pathogenic fungi Gaeumannomyces, Acremonium, Curvularia, and Fusarium in the rhizosphere soil under optimal N condition. Meanwhile, Zn application elevated the activities of protease, cellulase and dehydrogenase, and up-regulated the expression levels of napA, nirS, cnorB, and qnorB genes involved in the denitrification process in rice rhizosphere soil under optimal N condition. These results indicated Zn application could facilitate the soil N transformation and improved its availability by modifying both bacterial and fungal communities, and altering the soil enzyme activities and functional gene expression levels, ultimately promoted the N uptake and biomass of rice plant. However, this synergistic effect of Zn on rice growth, N uptake and soil N transformation strongly depended on the external N conditions, as no significant changes were observed under high N condition. Our results indicated that Zn co-fertilized with appropriate application of N is a useful strategy to improve the N bioavailability in rice rhizosphere soil and enhance the N uptake in rice plant.
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The rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system (RWCS) feeds more than 6 billion people in South Asia and across the world. In developing countries, almost 2 billion individuals are suffering from Zn and Fe micronutrient deficiency. This study aimed to adopt genetically enriched varieties of rice and wheat to manage the Zn and Fe deficiency with organic and inorganic fertilization in the food system. The experiment was designed for two years (2018-2019) under the split-plot design and was replicated three times. The results of the study indicate that the highest grain yield of wheat and rice was increased by 67.09 and 58.41 and 44.10 and 33.21% more NPKFeZn in the applied treatments compared to the control treatment during both years, respectively. The treatment carpet waste and Trichoderma viride was performed for higher yields (grain, straw, and biological) as compared to the rest of the treatment. In the main-plot, with application of NPKFeZn, higher Fe and Zn ranges of 54.27 and 52.91 and 35.71 and 34.29 parts per million (ppm), respectively, were recorded during both years. Similarly, the residual effects of NPKFeZn treatment in rice Fe and Zn concentration were recorded at 44.17 and 41.22 and 27.55 and 24.19 ppm during both years, respectively. It was found that there was 49.18 and 42.12 and 25.28 and 19.94% more Fe and Zn content, respectively, in grain as compared to the traditional varieties range of33 and 14 ppm for Fe and Zn, respectively. Ina sub-plot, for the wheat in carpet waste and Trichoderma viride treatment, the Fe and Zn contents were recorded as 55.21 and 54.62 and 37.05 and 35.53 ppm for the two years, respectively. In the traditional varieties of wheat, the range of Fe and Zn contents was 30 and 32 ppm, respectively. In the sub-plot of succeeding rice in carpet waste and Trichoderma viride treatment contents of Fe and Zn of 43.27 and 40.43 and 26.67 and 23.37 ppm were recorded during both years, respectively. On the basis of the interaction effect, the maximum total Fe and Zn uptake by wheat of 0.84 and 0.50 kg ha −1 , respectively, were recorded in the N3 × B1C3 treatments. Likewise, the maximum total Fe and Zn uptakes by rice of 0.62 and 0.39 kg ha −1 , respectively , were recorded with the interaction effect of N3 × B1C3 treatments. The hypothesis of the experiment was to manage malnutrition in society by diversifying genetically modified rice-wheat varieties in the RWCS. This research might assist in increasing nutritional security.
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A pot experiment was conducted during the 2019/2020 and 2020/2021 seasons to evaluate the effect of silver nanoparticles (SNPs), iron nanoparticles (FeNPs), zinc nanoparticles (ZnNPs), and nitrogen, phosphorus, and potassium nanoparticles (NPK NPs) and humic acid (HA) in improving the growth of Philodendron plants. Our findings indicated that the highest increase in plant height and leaf width was recorded with 60 mg/L SNPs. Additionally, the highest values in the number of leaves plant−1 were recorded with 60 mg/L SNPs compared to the control. FeNPs at 150 mg/L treatment gave the best result of total chlorophyll and carotenoid content, followed by SNPs at 60 mg/L and then NPK NPs at 2 mL/L in the two seasons. Furthermore, ZnNPs at 200 mg/L, SNPs at 20 mg/L, SNPs at 40 mg/L, and SNPs at 60 mg/L gave the best results of enzyme activity (catalase, peroxidase, and polyphenol oxidase). However, the treatments with 40 and 60 mg/L SNPs led to improve the anatomical characters of leaves and stem such as thickness of the blade, mesophyll tissue, xylem vessel diameter, vascular bundle dimension, stem diameter, and epidermis cell dimension compared with other treatments and the control.
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Management of organic matter and micronutrients is very important for the sustainable improvement of soil health. Poor soil organic matter usually results in lower availability of zinc (Zn) micronutrients in plants. Such deficiency in Zn causes a significant decrease in the growth and yield of crops. The need at the current time is to balance the application of organic amendments with Zn micronutrients to achieve optimum crop yields. Thus, the current study was conducted to investigate wheat, using compost as organic matter and Zn as a micronutrient. There were three levels of compost (i.e., control (0C), 5 t/ha (5C) and 10 t/ha (10C)) and four levels of Zn (control (0Zn), 2.5 kg Zn/ha (2.5Zn), 5.0 kg Zn/ha (5.0Zn) and 10.0 kg Zn/ha (10.0Zn)) applied with three replicates. The addition of 10C under 10.0Zn produced significantly better results for the maximum enhancement in plant height (8.08%), tillers/m2 (21.61%), spikes/m2 (22.33%) and spike length (40.50%) compared to 0C. Significant enhancements in 1000-grain weight, biological yield and grain yield also validated the effectiveness of 10C under 10.0Zn compared to 0C. In conclusion, application of 10C with 10.0Zn showed the potential to improve wheat growth and yield attributes. The addition of 10C with 10.0Zn also regulated soil mineral N, total soil N and extractable soil P. Further investigation is recommended with different soil textures to verify 10C with 10.0Zn as the best amendment for the enhancement of wheat yield in poor organic matter and Zn-deficient soils.
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Zinc (Zn) deficiency is a fairly widespread agronomic constraint in many of the world cereal production regions. Zinc is an imperative micronutrient required for optimum plant growth. Low Zn availability in about 50% of the global land resulted in Zn deficiency in cereal grains. A two-year field experiment was conducted at Agronomy Research Farm, The University of Agriculture, Peshawar during Rabi season 2018-19 and 2019-20 to study the impact of Zn levels (0, 5, 10 and 15 kg ha-1), compost types (control, composted sheep manure (SMC), composted poultry manure (PMC) and farmyard manure compost (FYMC), and Zn solubilizing bacteria (ZnSB) [with (+) and without (-)] on Zn biofortification in order to overcome Zn deficiency. The experiment was set up in a three-replication randomized complete block design. The wheat variety "Pirsabak-2013" was planted at a 30 cm row-to-row spacing. The plot size was kept at 9 cm2, with 10 rows plot 1, and the seed was sown at a rate of 100 kg ha-1. The results showed that ZnSB application increased ShZnC (shoot Zn Conc.) to maximum level of 29.3 mg kg-1, ShZnUp (shoot Zn Uptake) to 176.0 g ha1, SZnUp (straw Zn Uptake) to 116.67 g ha-1, and TZnUp (total Zn uptake) to 230.3 g ha-1. In the case of compost types PMC resulted in maximum grain Zn uptake (GZnUp) (28.9 mg kg-1), ShZnUp (192.9 g ha1), GZnC (33.4 mg kg-1), GZnUp (125.06 g ha-1), SZnUp (125.26 g ha-1), and TZnUp (250.3 g ha-1). In case of Zn application, higher ShZnC (31.5 mg kg-1), ShZnUp (191.3 g ha1), GZnC (34.4 mg kg-1), SZnC (23.5 mg kg-1), GZnUp (128.98 g ha-1), SZnUp (129.29 g ha-1), TZnUp (258.3 g ha-1) was calculated with the use of 15 kg Zn ha-1 which was either statistically similar or followed by 10 kg Zn ha-1. A strong positive correlation was found among uptake by different plant parts (ZnG, ZnS, ShZnUp, GZnUp, SZnUp, TZnUp). It was concluded that combined application of PMC and Zn at the rate of 10 kg Zn ha-1 along with ZnSB (+) improved Zn biofortification and uptake in wheat crop under Zn deficient soils.
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The weathering and development of laterites can influence trace element cycling in (sub-) tropics. Zinc (Zn) is a ubiquitous trace metal that involves in both abiotic and biotic processes in soils. To explore Zn behavior in laterites, Zn cycling in (sub-) tropics, and the environmental impacts, Zn isotope systematics were presented for two laterite profiles from Yunnan province, southwest China. The laterite samples exhibit the δ66Zn of 0.02‰ – 0.56‰, indicating a light shift of Zn isotope ratios (Δ66Znlaterite-parent rock = -0.47‰ – 0.07‰) relative to bulk parent granite. This observation is attributed to the preferential preservation of light Zn isotopes on the surface of secondary Fe oxides. As a result, laterites are likely to control the instantaneous riverine δ66Zn in (sub-) tropical regions heavier than unweathered rocks. The isotopic signature of different vegetation covered soils show that shrub-covered soils are stronger leached (average 𝜏Zn = -0.61) and have a smaller Δ66Znlaterite-parent rock (= -0.15‰), relative to forest-covered soils (=-14~0.20‰). Due to the strong loss of Zn (average 𝜏Zn = -0.61 ~ -0.12) and large amounts of low-bioavailable Zn preserved in oxides, the micronutrient supplies for plant growth are difficult to maintain and need more fertilization. This study is helpful for a better understanding of global Zn cycling and the management of micronutrients in (sub-) tropical soil-plant systems.
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Zinc deficiency in crops can be diagnosed or predicted successfully using field observations, soil tests and/or plant analysis. Plant species and genotypes differ in their requirements for Zn, so the timing and method of diagnosis is critical. Using whole shoots of plants to diagnose Zn deficiency has been unreliable but specific plant parts (especially young leaves) are good indicators of the Zn status of a plant. Enzyme activities have the potential to be developed into useful diagnostic tests of Zn deficiency. Many chemical extractants have been used to assess the Zn status of soils. These soil tests have often been improved by including measurements of other soil properties (e.g. pH, clay, organic carbon). However, there is a need to standardize the procedures which measure both the quantity and intensity of Zn.
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Genotypes of plants vary widely in their tolerance of Zn-deficient soils, both in Zn uptake and utilization. Tolerance, here termed Zn efficiency because it appears to involve in most cases more efficient extraction of soil Zn, is heritable and may therefore be exploited in the breeding of crop plants. This review considers the extent of variability in Zn eficiency in species of crop and natural plants, the physiological and biochemical nature of the mechanisms of efficiency, what is known of the genetics of inheritance, screening techniques for identifying Zn-efficient types in breeding programs, and the agronomic arguments for a breeding solution to the problem of Zn-deficient soils.
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Zinc is a metallic element with atomic number 30 and stable isotopes of mass 66, 67, 68, and 70, averaging 65.38 a.m.u. The terrestrial chemistry of Zn is that of Zn (II) rather than Zn(0). The Zn (II) ion has an electron configuration of 1s 2, 2s 2, 2p 6, 3d 10, and therefore lacks unfilled d subshells in the well-known oxidation state, the requisite criterion for true transition metals. Zinc(II) has an ionic radius comparable with Mg(II) but a Lewis acidity more like that of the smaller Cu(II) ion. Zinc is an essential element for terrestrial life since it is required as either a structural component or reaction site in numerous proteins, the zinc-binding portions of which are highly conserved among species. Zinc sites in proteins consist of Zn polyhedra with apical S, N, or O, associated with cysteine, histidine, glutamic acid, aspartic acid, and water. Coordination numbers for zinc range from four in the case of structural Zn associated with four thiol groups derived from cysteine to six in the case of a number of reactive sites containing O and N as apices. The total concentration of zinc in soils depends on the composition of the parent material and soil mineralogy, especially the concentration of quartz, which tends to dilute most elements. Only a small fraction of the total zinc is exchangeable or soluble. About one-half of the dissolved zinc exists as the free hydrated cation. The concentration of dissolved complexes of zinc with inorganic ligands can be estimated by computerimplemented models and total concentrations as input. Similar approaches with organic ligands await further research. Most analytical determinations of zinc are made by spectrometric techniques such as atomic absorption spectrophotometry, inductively coupled plasma atomic emission spectroscopy, and inductively coupled plasma mass spectroscopy.
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One of the widest ranging abiotic stresses in world agriculture arises from low zinc (Zn) availability in calcareous soils, particularly in cereals. Cereal species greatly differ in their zinc effici ency (ZE), defined in this article as the ability of a plant to grow and yield well under Zn deficiency. ZE has been attributed mainly to the efficiency of acquisition of Zn under conditions of low soil Zn availability rather than to its utilization or (re)-translocation within a plant. A higher Zn acquisition efficiency, further, may be due to either or all of the following: an efficient ionic Zn uptake system, better root architecture, i.e. long and fine roots with architecture favouring exploitation of Zn from larger soil volume, higher synthesis and release of Zn-mobilizing phytosiderophore by the roots and uptake of Zn-phytosiderophore complex. Seed Zn content has also been suggested to affect ZE. This article attempts to examine critically the scanty and scattered reports available on the status of Zn deficiency globally; morphological, biochemical and physiological basis of regulation of ZE in cereals and approaches to improve ZE in terms of grain productivity and grain Zn vis-à-vis its bioavailability under conditions of poor Zn availability. A causal relationship between important Zn-containing enzymes, viz. carbonic anhydrase (CA), Cu/Zn-superoxide dismutase (SOD) activities and ZE is reported in wheat and other cereal species. Enhanced production and release of Fe-mobilizing phyto-metallophores known as phytosiderophores (PS), is another mechanism relevant for cereal species in adaptation to zinc deficiency.
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Plant Zn uptake from low Zn soils can be increased by Zn-mobilizing chemical rhizosphere processes. We studied whether inoculation with arbuscular mycorrhizal fungi (AMF) can be an additional or an alternative strategy. We determined the effect of AMF inoculation on growth performance and Zn uptake by rice genotypes varying in Zn uptake when nonmycorrhizal. A pot experiment was conducted with six aerobic rice genotypes inoculated with Glomus mosseae or G. etunicatum or without AMF on a low Zn soil. Plant growth, Zn uptake and mycorrhizal responsiveness were determined. AMF-inoculated plants produced more biomass and took up more Zn than nonmycorrhizal controls. Mycorrhizal inoculation, however, significantly increased Zn uptake only in genotypes that had a low Zn uptake in the nonmycorrhizal condition. We conclude that genotypes that are less efficient in Zn uptake when nonmycorrhizal are more responsive to AMF inoculation. We provide examples from literature allowing generalization of this conclusion on a trade off between mycorrhizal responsiveness and nutrient uptake efficiency.
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The development of rice (Oryza sativa L.) cultivars with a higher Zn content in their grains has been suggested as a way to alleviate Zn malnutrition in human populations subsisting on rice in their daily diets. This study was conducted to evaluate the effects of native soil Zn status and fertilizer application on Zn concentrations in grains of five rice genotypes that had previously been identified as either high or low in grain Zn. Genotypes were grown in field trials at four sites ranging in native soil-Zn status from severely deficient to high in plant available Zn. At each site a −Zn plot was compared to a +Zn plot fertilized with 15kg Zn ha−1. Results showed that native soil Zn status was the dominant factor to determine grain Zn concentrations followed by genotype and fertilizer. Depending on soil-Zn status, grain Zn concentrations could range from 8mg kg−1 to 47mg kg−1 in a single genotype. This strong location effect will need to be considered in estimating potential benefits of Zn biofortification. Our data furthermore showed that it was not possible to simply compensate for low soil Zn availability by fertilizer applications. In all soils fertilizer Zn was taken up as seen by a 50–200% increase in total plant Zn content. However, in more Zn deficient soils this additional Zn supply improved straw and grain yield and increased straw Zn concentrations by 43–95% but grain Zn concentrations remained largely unchanged with a maximum increase of 6%. Even in soils with high Zn status fertilizer Zn was predominantly stored in vegetative tissue. Genotypic differences in grain Zn concentrations were significant in all but the severely Zn deficient soil, with genotypic means ranging from 11 to 24mg kg−1 in a Zn deficient soil and from 34 to 46mg kg−1 in a high Zn upland soil. Rankings of genotypes remained largely unchanged from Zn deficient to high Zn soils, which suggests that developing high Zn cultivars through conventional breeding is feasible for a range of environments. However, it may be a challenge to develop cultivars that respond to Zn fertilizer with higher grain yield and higher grain Zn concentrations when grown in soils with low native Zn status.
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In 1998, the International Union of Soil Sciences (IUSS) officially adopted the world reference base for soil resources (WRB) as the Union's system for soil correlation. The structure, concepts, and definitions of the WRB are strongly influenced by the FAO-UNESCO legend of the soil map of the world (1-2). At the time of itsinception, the WRB proposed 30 "Soil Reference Groups" accommodating more than 200 ("second level") soil units. WRB (3-5) was endorsed by the IUSS in 1998 and provides an opportunity to create and refine a common and global language for soil classification. WRB aims to serve as a framework through which ongoing soil classification throughout the world can be harmonized. The ultimate objective is to reach international agreement on the major soil groups to be recognized at a global scale as well as on the criteria and methodology to be applied for defining and separating them. Such an agreement is needed to facilitate the exchange of information and experience, to provide a common scientific language, to strengthen the applications of soil science, and to enhance the communication with other disciplines and make the major soil names into household names
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Phosphate (P) is taken up by plants through high-affinity P transporter proteins embedded in the plasma membrane of certain cell types in plant roots. Expression of the genes that encode these transporters responds to the P status of the plants, and their transcription is normally tightly controlled. However, this tight control of P uptake is lost under Zn deficiency, leading to very high accumulation of P in plants. We examined the effect of plant Zn status on the expression of the genes encoding the HVPT1 and HVPT2 high-affinity P transporters in barley (Hordeum vulgare L. cv Weeah) roots. The results show that the expression of these genes is intimately linked to the Zn status of the plants. Zn deficiency induced the expression of genes encoding these P transporters in plants grown in either P-sufficient or -deficient conditions. Moreover, the role of Zn in the regulation of these genes is specific in that it cannot be replaced by manganese (a divalent cation similar to Zn). It appears that Zn plays a specific role in the signal transduction pathway responsible for the regulation of genes encoding high-affinity P transporters in plant roots. The significance of Zn involvement in the regulation of genes involved in P uptake is discussed.
Book
A deficiency of one or more of the eight plant micronutrients (boron, chlorine, copper, iron, manganese, molybdenum, nickel and zinc) will adversely affect both the yield and quality of crops. Micronutrient deficiencies in crops occur in many parts of the world, at various scales (from one to millions of hectares), but differences in soil conditions, climate, crop genotypes and management, result in marked variations in their occurrence. The causes, effects and alleviation of micronutrient deficiencies in crops in: Australia, India, China, Turkey, the Near East, Africa, Europe, South America and the United States of America, are covered, and these are representative of most of the different conditions under which crops are grown anywhere in the world. Links between low contents of iodine, iron and zinc (human micronutrients) in staple grains and the incidence of human health problems are discussed, together with the ways in which the micronutrient content of food crops can be increased and their bioavailability to humans improved. Detailed treatment of topics, such as: soil types associated with deficiencies, soil testing and plant analysis, field experiments, innovative treatments, micronutrients in the subsoil, nutrient interactions, effects of changing cropping systems, micronutrient budgets and hidden deficiencies in various chapters provides depth to the broad coverage of the book. This book provides a valuable guide to the requirements of crops for plant micronutrients and the causes, occurrence and treatment of deficiencies. It is essential reading for many agronomy, plant nutrition and agricultural extension professionals.
Chapter
Foods derived form plants are poorer sources of Zn for humans and monogastric animals when compared to those from animals because they can contain substances which interfere with the absorption and/or utilization (i.e., bioavailability) of Zn. Examples of these substances include phytic acid and certain types of fibre, especially fibre from whole cereal grains. However, these substances are also known to play important roles in either the life cycle of higher plants or possibly, in the prevention of several human diseases including heart disease and certain forms of cancer. Therefore, it is not wise to reduce the content of these substances in food crops or in diets without a more thorough understanding of their role(s) in plant growth or human health. Indeed, current recommended dietary goals for people in the United States advise that citizens double their daily consumption of foods high in fibre by eating twice as much whole cereal grain and legume seed products. Low molecular weight, soluble, anionic, Zn complexes comprise the majority of the naturally occurring forms of Zn in edible portions of food crops. Animal products contain higher concentrations of some substances which promote Zn bioavailability than do plant food products. Thus, it may be more desirable to increase the concentration of promoters of Zn bioavailability in plant foods than to reduce the level of antinutritive substances which interfere with the bioavialability of Zn. The nutritional quality of food crops, with respect to the Zn concentration in edible portions, can be increased significantly by applying available forms of Zn fertilizer to soils at levels in excess of those required for optimum plant growth.
Article
The essential micronutrient zinc occurs in plants either as a free ion, or as a complex with a variety of low molecular weight compounds. Zinc may also be incorporated as a component of proteins and other macromolecules. As a component of proteins, zinc acts as a functional, structural, or regulatory cofactor of a large number of enzymes. Many of the physiological perturbations resulting from zinc deficiency are associated with the disruption of normal enzyme activity, thus zinc-deficiency induced inhibition of photosynthesis is coincident with a decrease in activity of key photosynthetic enzymes. Zinc deficiency also increases membrane leakiness by inhibiting the activity of enzymes involved in the detoxification of membrane damaging oxygen radicles. Recent evidence suggests that zinc plays a key role in stabilizing RNA and DNA structure, in maintaining the activity of DNA synthesizing enzymes and controlling the activity of RNA degrading enzymes. Thus, zinc may play a role in controlling gene expression. Though our understanding of the function of zinc has increased greatly in the last thirty years, there are still many aspects of zinc metabolism that remain controversial. In the following review we summarize the current knowledge of the physiology of zinc and illustrate areas in which our knowledge remains incomplete.
Chapter
The zinc (Zn) content of soils, according to rather extensive surveys, is generally in the range of 10-300 ppm. Certainly Zn, because of its concentration, can be considered as a trace element in soil. It occurs most frequently in the lithosphere as the mineral ZnS (sphalerite). Zn appears to be scattered throughout the mineral fraction of soils. It is probably held in crystal lattices, by isomorphous substitution and as occluded ions. Since it is a trace element, it is usually surrounded, by many other solid phases. Zn can also be held, by exchange sites, and adsorbed to solid surfaces. Crops differ in their sensitivity to zinc deficiency. Zn deficiencies are frequently found on soils, with restricted root zones. The movement of Zn to plant roots is dependent on the intensity factors (concentration) and on the capacity factors (ability to replenish). Increasing the pH decreases the solubility of zinc in soils, and thereby reduces the concentration, the concentration gradient, and, hence, the uptake and availability of Zn to plants. Zn plays an important role in auxin formation and in other enzyme systems. Presently, Zn is recognized as an essential component in several dehydrogenases, proteinases, and peptidases.
Chapter
Characterizing zinc availability by soil testing provides important information on the pool size of zinc potentially available for uptake. Concentrations of zinc in soil solution, particularly at high soil pH, however, are very low and mobility and transport to the root surface are usually rate limiting factors of soil supply. Utilization of potentially available zinc is thus mainly or exclusively confined to rhizosphere soil. Root-induced changes in the rhizosphere are of particular imporatance for zinc uptake from soils. In soils of high pH, rhizosphere acidification by supply of ammonium nitrogen, or for legumes by N2 fixation, are effective mechanisms in enhancing zinc mobilization. The same holds true for rhizosphere acidification or enhanced excretion of organic acids and chelators as root responses to deficiency of phosphorus or iron. Root colonization by VA mycorrhizae increases spatial availability of zinc similarly to that of phosphorus. Mycorrhizal plants usually have higher zinc contents in the shoot dry matter and are less sensitive to zinc deficiency than non-mycorrhizal plants. As a rule, all factors which impair root colonization by VA mycorrhizae, including high levels of soil or fertilizer phosphorus, tend to decrease zinc contents in plants and increase the risk of zinc deficiency in plants grown on soils low in extractable zinc. Marked genotypical differences in zinc efficiency are usually caused by differences in zinc acquisition from soils. In lowland rice zinc deficiency is widespread in neutral and alkaline soils. Elevated bicarbonate concentrations are the major factor responsible for low zinc contents in rice plants grown on high pH soils, high in organic matter. In such soils the high bicarbonate concentrations impair zinc uptake by direct inhibition of root growth and activtiy.
Article
Phosphate (P) is taken up by plants through high-affinity P transporter proteins embedded in the plasma membrane of certain cell types in plant roots. Expression of the genes that encode these transporters responds to the P status of the plants, and their transcription is normally tightly controlled. However, this tight control of P uptake is lost under Zn deficiency, leading to very high accumulation of P in plants. We examined the effect of plant Zn status on the expression of the genes encoding the HVPT1 and HVPT2 high-affinity P transporters in barley (Hordeum vulgareL. cv Weeah) roots. The results show that the expression of these genes is intimately linked to the Zn status of the plants. Zn deficiency induced the expression of genes encoding these P transporters in plants grown in either P-sufficient or -deficient conditions. Moreover, the role of Zn in the regulation of these genes is specific in that it cannot be replaced by manganese (a divalent cation similar to Zn). It appears that Zn plays a specific role in the signal transduction pathway responsible for the regulation of genes encoding high-affinity P transporters in plant roots. The significance of Zn involvement in the regulation of genes involved in P uptake is discussed.
Chapter
Zinc fertilizers are commonly applied to many crops around the world. The most common sources are ZnSO4 and ZnO, but other inorganic products and sources such as chelates and natural organic complexes also are used. Industrial by-products containing Zn also are being processed and sold as Zn fertilizers. The levels of water-soluble Zn and weak acid-soluble Zn in granular Zn products give a good measure of their effectiveness for crops. Insoluble ZnNH4PO4 compounds form in ammonium phosphate fertilizers; these reaction products are not very available for crops, especially on sandy, neutral to alkaline soils under dry conditions. Zinc fertilizers are applied to soil mainly with NPK fertilizers, either by incorporating at the factory or bulk blending in granular form with other granular fertilizers. Soluble Zn fertilizers also are applied as foliar sprays to fruit and vegetable crops. Choice of Zn fertilizer depends on the intended method of application, relative agronomic effectiveness, price per unit of Zn, compatibility, and convenience in applicatior either alone or with other fertilizers.
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This paper examines the interactions between Zn and other nutrients in soil reactions, behaviour in plants and plant growth. It stresses the need for identification of the factor responsible for any Zn response to the addition of another nutrient compound. Of the many interactions of Zn with other nutrients, the most widespread and important to crop production are those with N and P fertilizers on soils with limiting supplies of both Zn and N or P. Similar interactions of Zn with other essential nutrients will also be important on soils with low supplies of both nutrients; such an interaction of Zn with Cu was strongly enhanced by an effect of Zn in depressing Cu absorption and almost eliminating grain production in wheat when Cu was not applied. Other interactions with potential significance for crop production in specific situations include the enhancement of Zn deficiency through depression of Zn absorption by effects of high concentrations of Fe and Mn in flooded soils and of P in suppressing mycorrhizal infection of roots. The many interactions of Zn with P are reviewed. Recent evidence that, when supplied high P at low Zn, plants accumulate high P in their leaves, precipitating Zn and increasing the plant’s internal requirement for Zn, provides a new insight into the long puzzling phenomenon of “P enhanced Zn requirements”.
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Publisher Summary This chapter considers the biochemistry, physiology, and agronomy of trace elements in plants in so far as they may influence host–pathogen relationships. Each of the micronutrients can be identified with specific biochemical pathways, so their effects on disease offer avenues for elucidating mechanisms of resistance in higher plants. Certain general principles may be demonstrated, but the complex nature of many interacting factors influencing plant health limits the extent to which simple patterns emerge. The quest for general principles is stimulated by the increasing prevalence of micronutrient deficiencies in modern agricultural systems, in which the use of the appropriate micronutrients may be seen as a form of biological control. In contrast to the largely structural, conformational, and osmotic roles of the macronutrients, the micronutrients act as catalysts, cofactors, and inhibitors. In these roles, supraoptimal concentrations are physiologically important. A number of trace elements, which are not recognized as essential to plants, strongly influence the host–pathogen balance. Criteria of essentiality are usually established in artificial conditions of laboratory and glasshouse. The chapter summarizes the principles which emerge from a study of macronutrient effects on incidence of disease in higher plants and the principles that seem to emerge from a study of the micronutrient effects on susceptibility to disease.
Article
Field experiments were carried out to study grain yield, zinc (Zn) efficiency and concentrations of Zn in shoot and grain of 37 bread wheat (Triticum aestivum) and three durum wheat (Triticum durum) cultivars grown in a Zn-deficient calcareous soil with (23 kg Zn ha−1), and without, Zn fertilization in 1993–1994 and 1994–1995. The same Zn-deficient soil was used in greenhouse experiments to study shoot dry weight, Zn efficiency and shoot Zn concentrations of 21 bread and three durum wheat cultivars (same cultivars used in the field experiments). Zinc fertilization of cultivars in the field enhanced grain yield on average by 30% in both years. Increases in grain yield to Zn fertilization varied substantially between cultivars from 8% to 76%. Accordingly, there was large variability in Zn efficiency of cultivars, expressed as the ratio of grain yield or shoot dry-matter yield produced under Zn deficiency compared to that under Zn fertilization. On average, Zn efficiency values ranged from 57% to 92% for grain yield in field experiments and from 47% to 83% for shoot dry weight in greenhouse experiments. Most of the cultivars behaved similarly in their response to Zn deficiency in the field and greenhouse. The cultivars selected from local landraces had both, a high Zn efficiency and high yield under Zn-deficient conditions. The bread wheat cultivars, improved for irrigated conditions, had generally low Zn efficiency and low yield, both in the field and greenhouse. All durum wheat cultivars in this study also showed low levels of Zn efficiency, grain yield and shoot dry weight under Zn deficiency. Overall, there was no relation between Zn efficiency values and Zn concentrations in grain or shoot dry matter. The results presented here demonstrate the existence of substantial variation in Zn efficiency among wheat cultivars, particularly bread wheat cultivars, and suggest that wheat landrace populations are a valuable source of genes to improve high Zn efficiency of wheat for Zn-deficient soils.
Article
The essential micronutrients for field crops are Fe, Zn, B, Mo, Cu and Mn. The incidence of micronutrient deficiency has increased in recent years. Iron and Zn deficiency are paid more attention because they negatively affect both food production and human health in a major part of the world. In this paper, the Fe, Zn, B, Mo, Mn and Cu deficiency status in soils and crops in China are reviewed. Iron and Zn deficiencies cause some serious problems in crop production in China, and B, Mn and Mo deficiency are second in importance. The corrections of these micronutrient deficiencies by fertilization, agronomic strategies and genotypic exploitation are also discussed. In China, a scarcity of water has caused a shift from flooded to aerobic conditions for rice production. The consequence for micronutrient availability is a function of the changes in both soil and plant factors.
Article
Zinc (Zn) deficiency is a persistent problem in flooded rice (Oryza sativa L.). Severe Zn deficiency causes loss of grain yield, and rice grains with low Zn content contribute to human nutritional Zn deficiencies. The objectives of this study were to evaluate the diethylenetriaminepentaacetic acid (DTPA) extraction method for use with reduced soils and to assess differences in plant availability of native and fertilizer Zn from oxidized and reduced soils. The DTPA‐extractable Zn decreased by 60% through time after flooding when the extraction was done on field‐moist soil but remained at original levels when air‐dried prior to extraction. In a pot experiment with one calcareous and one noncalcareous soil, moist‐soil DTPA‐extractable Zn and plant Zn uptake both decreased after flooding compared with the oxidized soil treatment for both soils. In the flooded treatment of the calcareous soil, both plant and soil Zn concentrations were equal to or less than critical deficiency levels even after fertilization with 50 kg Zn ha. We concluded that Zn availability measurements for rice at low redox potentials should be made on reduced soil rather than air‐dry soil and that applied Zn fertilizer may become unavailable to plants after flooding.
Article
After scrutiny of the pertinent literature analytical and tracer experiments with 65Zn along a toposequence of rice paddies in Tiaong, Quezon Province, Philippines are described. The higher catena member is moderately Zn deficient, the lower member extremely Zn deficient. Soil analysis reveals Tiaong soil to be slightly alkaline, smectitic, strongly humic, of high CEC and base saturation, of low plant available Zn (Bray method). The higher catena member (H) leads in Si, Al, K, Na, Zn, Cu, Ni, Co, Cr, Ba, the lower member (L) in C, Ca, Mg, Mn, P. The very high deficiency in (L) corresponds with higher humus-, Ca, Mg, and P concentrations, all potential agents to Zn fixation. Clay minerals are higher in less deficient (H). This, and studies of VAN BREMEN et al. (1980) would point to strong Zn organic fixation. However, DTPA-, dithionite- and oxalate-extracts represent only 2.5–25% pedogenic zinc, the rest is lithogenic and insoluble. Previous combustion scarcely increases these rates. This points against Zn organic linkages as predominating Zn fixation mechanism. Partial correlation, applied to VAN BREMEN's data also annihilates the high correlation between zinc and organic matter, which is replaced by strong ZnMg and Znbicarbonate correlations. Field tests with 65ZnSO4 in plastic tubes of 35 and 25 cm diameter, inserted in the rice fields, showed, that mobility, i.e. lateral and vertical translocation of the zinc was much more pronounced at (H) than at (L). After air drying the removed soil cores replanting was accompanied by much less Zn deficiency than in loco in the rice field. Drainage and at least temporary oxidation seems to be the primary requirement for soil rehabilitation.
Article
A national survey of agricultural topsoils and pastures was undertaken in the early 1990s to establish benchmark heavy metal concentrations. In total, 398 sites were sampled covering the major soil groups throughout the North and South Islands of New Zealand. Both pastoral farmed (312) and non‐farmed (86) sites were sampled. Composite soil samples were taken from two depths, as well as pasture samples from the same area, and analysed for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) concentrations. There was significant (P < 0.05) enrichment of Cd at the 0–7.5 cm depth in five of the eight soil groups on farmed sites (0.44 mg kg), over background non‐farmed soils (0.20 mg kg). Total soil Cd was highly correlated (P < 0.001) to total soil phosphate (P) suggesting Cd enrichment in pastoral soils was related to fertiliser P applications. There was no enrichment of As, Cu, Pb, or Zn at the 0–7.5 cm depth on farmed soils compared with non‐farmed soils. Results showed that soil concentrations of these elements were either typical of worldwide averages, or at the lower end of these ranges. There was, however, a significant (P < 0.05) increase in Cu concentrations in the 0–2.5 cm depth on most farmed soils (14.3 mg kg), compared with non‐farmed soils (11.4 mg kg). The main difference in heavy metal concentrations between non‐farm and pastoral pasture species was in the weed component. In general, the Cu, Zn, Pb, and As concentrations were essentially pedogenic in origin.
Article
Both iron oxides and carbonate minerals, such as calcite, can sorb zinc (Zn), and therefore are important in controlling the solution concentration and availability of Zn to plants growing in calcareous soil. When present together, interactions between these components affect their sorption behaviour. We investigated changes in the reactions of Zn with calcite at alkaline pH, as the calcite surface was progressively coated by iron oxide. Coated calcite surfaces were prepared that had from 0.05 to 1.45% iron oxide. The initial concentration of Zn and the amount of iron oxide on the calcite were the most critical factors affecting adsorption, precipitation of solid phases, and the desorbability of sorbed Zn. For pure calcite at small initial Zn concentrations (< 2.5 × 10−5 m) adsorption was dominant; with increasing concentration, precipitation of hydrozincite (ZHC) became more important. With increasing amounts of iron oxide the amount of Zn adsorbed increased, the desorbability of the Zn decreased, and precipitation became progressively less evident, and at 1.45% iron oxide content there was no evidence of any precipitation of ZHC. The calculated maximum adsorption attributable to the iron oxide coating was inversely proportional to the thickness of the oxides on the calcite, and greatly exceeded that of iron oxide as a separate phase. The common occurrence of iron-coated carbonates in calcareous soils and their capacity to adsorb Zn contributes to the problems of Zn deficiency, for which these soils are noted.
Article
Summary 185I. INTRODUCTION 186II. EFFECT OF ZINC ON PRODUCTION OF REACTIVE OXYGEN SPECIES 1861. Superoxide-generating NADPH oxidase 1862. Zinc deficiency potentiates iron-mediated free radical production 189(a) Iron accumulation in zinc-deficient plants 189(b) Iron-induced production of free radicals 1893. Zinc deficiency-enhanced photooxidation 191(a) Decrease in photosynthesis 191(b) Light-induced leaf chlorosis 192(c) Decrease in indole-3-acetic acid 192III. MEMBRANE DAMAGE BY REACTIVE OXYGEN SPECIES 1931. Impairments in membrane structure 1932. Phospholipids and –SH groups 1953. Alterations in ion absorption 195(a) Membrane-bound ATPases 195(b) Nutrient uptake 197(c) Changes in activity of ion channels 197IV. DETOXIFICATION OF REACTIVE OXYGEN SPECIES 1981. Superoxide dismutases 1982. H2O2-scavenging enzymes 198V. INVOLVEMENT OF ZINC IN PLANT STRESS TOLERANCE 199VI. CONCLUSIONS 199Acknowledgements 200References 200Zinc deficiency is one of the most widespread micronutrient deficiencies in plants and causes severe reductions in crop production. There are a number of physiological impairments in Zn-deficient cells causing inhibition of the growth, differentiation and development of plants. Increasing evidence indicates that oxidative damage to critical cell compounds resulting from attack by reactive O2 species (ROS) is the basis of disturbances in plant growth caused by Zn deficiency. Zinc interferes with membrane-bound NADPH oxidase producing ROS. In Zn-deficient plants the iron concentration increases, which potentiates the production of free radicals. The Zn nutritional status of plants influences photooxidative damage to chloroplasts, catalysed by ROS. Zinc-deficient leaves are highly light-sensitive, rapidly becoming chlorotic and necrotic when exposed to high light intensity. Zinc plays critical roles in the defence system of cells against ROS, and thus represents an excellent protective agent against the oxidation of several vital cell components such as membrane lipids and proteins, chlorophyll, SH-containing enzymes and DNA. The cysteine, histidine and glutamate or aspartate residues represent the most critical Zn- binding sites in enzymes, DNA-binding proteins (Zn-finger proteins) and membrane proteins. In addition, animal studies have shown that Zn is involved in inhibition of apoptosis (programmed cell death) which is preceded by DNA and membrane damage through reactions with ROS.
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South America has largest land area at global level to produce food and fibre crops. In addition, climatic conditions (temperature and water availability) are favourable, which further enhances the role of this continent in providing world food security. The Brazilian Cerrado, or savanna, a total area of about 205 Mha of acid soils is a good case in point. Similarly, Colombia, Bolivia, Venezuela, Peru and Ecuador also have large land areas, which can be utilized for crop production. However, the major soils of this continent are acidic and infertile. Hence, liming and fertiliser application are essential. Micronutrient deficiencies are an emerging limiting factor for annual crop production. In annual crops such as rice, corn, wheat, soybean and common bean, deficiencies of Zn, Cu, B, Mn and Fe have been reported. Adopting sound soil and crop management practices will not only enhance crop productivity but also help in reducing deforestation of tropical rainforests in South America. This strategy will permit less CO2 release to the atmosphere, conservation of soil, water and global climatic change. In South America, micronutrient management issues require a great of deal of research for improvement.
Article
The total land area of tropical Asia is approximately 800 million ha. Of this area, around 28%–29% is arable land [39], and this percentage has remained more or less stable over the last decade. Agricultural production, on the other hand, has increased dramatically over the same period. For instance, cereal production in the 11 largest south and southeast Asian countries increased by 30%, reflecting the intensification of agricultural production in tropical Asia. Most of this progress is due to the introduction of high-yielding varieties, increased fertilizer use and irrigation, and other technological improvements. Mudahar [95] estimated the contribution of fertilizers to the growth in rice production alone to be 7% in Nepal and as much as 45% in India, with a regionwide average of 24% for south and southeast Asia.
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Australia’s ancient landscape has soils of exceptionally low fertility and deficiencies of all known nutrients have been recorded. Deficiencies of Mo and Zn are most widespread, being common on acid and alkaline soils respectively. Zinc deficiency is notable for being the most widely distributed micronutrient problem globally as well as in Australia, occurring on all soil classes, acid and alkaline, sandy and clayey, humid and arid, and in hot and cold growing seasons. Many Australian soils are affected by the presence of fine, free lime in the form of shellgrit blown up over the continent when sea levels were low during the last ice age; such soils, especially the more sandy types are low in micronutrient cations, Fe, Zn, Mn, Cu and/or Co. Multiple nutrient deficiencies are common, giving rise to a wealth of nutrient interaction effects. Interactions between two or more micronutrients and between micro- and macro-nutrients are agronomically and economically important. The classical micronutrient sensitivities reported elsewhere are also seen in Australia, but importantly, breeding has been carried out for tolerance to deficient soils in the major cereal crops, as well as tolerance to the common nutrient toxicities, the latter in common with activities in many parts of the world. The first deliberately bred cereal variety (barley) tolerant to Mn deficiency was released in South Australia in 2004. An important feature of the agronomy of micronutrients is the yield benefit in micronutrient-deficient soils of sowing seeds with a high micronutrient density. The use of plant analysis for diagnosis is almost always warranted as some crop varieties may lose much yield potential before symptoms of some micronutrient deficiencies appear. Recent research in South Australia has demonstrated that on calcareous soils, multi-nutrient fluid fertilisers have provided more efficient responses to both macronutrients and micronutrients than granular fertilizers.
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Zinc (Zn) deficiency in soils and crop plants occurs nearly in all countries, particularly in cereal-growing areas. Turkey is among the countries with the most severe Zn-deficient soils. Previously, wheat grown in Central Anatolia was low yielding over many years, but the reason was unclear. In 1991/1992 a field experiment was conducted to determine whether micronutrients were a possible cause of the problem. Only with Zn application there was an impressive increase in growth and yield of wheat (T. aestivum L.). Based on these initial observations, a multi-institutional, long-term project on Zn deficiency in crop production in Central Anatolia was prepared and supported by the NATO “Science for Stability” Program. There were spectacular increases in grain yield of wheat with Zn fertilisation. In certain areas with very low yields (0.25 t ha1), Zn application enhanced grain yield by a factor of 6–8. The total amount of soil Zn was fairly high, between 40 and 80 mg −1, but the level of plant available Zn was extremely low (DTPAZn: around 0.1 mg −1 soil). Field experiments at different locations revealed that in soils containing less than 0.4 mg −1 DTPA-extractable Zn, wheat, particularly durum wheat, responded significantly to Zn applications. Compared to irrigated conditions, wheat was more sensitive to Zn deficiency under rainfed conditions. Plants emerging from seeds with very high Zn concentrations (up to 55 mg −1 dry weight) had increased seedling vigour and pathogen resistance, as well as yield. In addition, enhancing Zn concentration in seeds reduced seeding rate, with consequent economic benefits. The impressive effects of Zn fertilisers on crop yield evoked considerable interest by fertiliser companies, which in 1995 started producing Zn-containing compound fertilisers. Today, 12 years after the Zn deficiency problem was diagnosed as a critical problem for wheat production in Turkey, the total amount of Zn-containing compound fertilisers applied in Turkey is at a record level of 300,000 t. Ministry of Agriculture estimates put annual economic benefits from Zn fertilisation at US$100 million. As Zn deficiency is an important micronutrient deficiency in humans in Turkey, increases in grain Zn concentration by Zn fertilisation have obvious implications for human health.
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This chapter describes the micronutrient status of soils in India, the occurrence of deficiencies, responses of different crops to them, the suitability of various sources of the elements, and techniques for their application. Crops grown in most soils in India suffer from deficiencies of one or more micronutrients, even though the soils often contain apparently adequate total amounts of the respective elements. The nature and extent of deficiencies varies with soil type, crop genotype, management and agro-ecological situations. With the intensive cropping of high yielding varieties of rice and wheat, deficiency of zinc (Zn) initially, and subsequently deficiencies of iron (Fe) in rice, and manganese (Mn) in wheat, emerged as threats to sustaining high levels of food crop production. Micronutrient deficiencies are now frequently observed in intensively grown cereals, oilseeds, pulses and vegetable crops. With widespread and regular application of Zn fertilizers, the occurrence of Zn deficiency has declined in recent years, but multi micronutrient deficiencies are now becoming an increasing problem. Analysis of soil and plant samples has indicated that 49% of soils in India are potentially deficient in Zn, 12% in Fe, 5% in Mn, 3% in copper (Cu), 33% in boron (B) and 11% in molybdenum (Mo). Basal application to soil and/or foliar sprays of Zn, B and Mo, and foliar sprays of Fe and Mn have been recommended as the most suitable methods for correcting such deficiencies in crops.