Soil Zinc Research Articles

Effects of zinc and boron application in soil on growth and yield of Papaya cv. red lady

Effects of zinc and boron application in soil on growth and yield of Papaya cv. red lady

Predictive Mapping of Soil Micronutrients Using Geographic Information System for Site Specific Management Interventions in a Semiarid Farm, India

Deficiency of soil micronutrients has an adverse impact on crop productivity in intensive agriculture. Plant availability, spatial pattern and distribution of soil micronutrients such as iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) content in surface soils were evaluated for an agricultural farm in semiarid region of India. Other soil properties viz. soil pH, electrical conductivity (EC), soil organic carbon (SOC) content and equivalent calcium carbonate (CaCO3) content at the farm were also analysed to depict the soil chemical environment, controlling micronutrient availability. Plant available micronutrient contents within farm soils had very high data variability (coefficient of variation >30%). Soil available micronutrients content were negatively correlated with soil pH and positively correlated with SOC content. As per semivariogram analysis, plant available Fe, Mn, Zn and Cu content within farm soils had moderate spatial dependency as indicated by nugget to sill ratio between 0.30 and 0.50 and had spatial parameter ranges of 404, 801, 954 and 1529 m, respectively. Prediction map of plant available Fe content by inverse distance weightage (IDW) method showed a few patches of iron deficiency (< 4.50 mg kg-1) and a marginal level (4.50 - 9.00 mg kg-1). Spatial distribution map of plant available Zn content through lognormal ordinary kriging method indicated a patch of marginal Zn level (0.60 - 1.20 mg kg-1) within the farm soils. Farm scale spatial variability maps of plant available Mn and Cu content, generated by ordinary kriging method with good accuracy and effectiveness, indicated its adequate level with respect to crop nutrition. The spatial distribution maps of soil available micronutrients content for the farm could be served as reference for its precise and site specific management for intensive crop cultivation, higher productivity and profitability.

THE IMPACT OF SOIL HEAVY METAL ACCUMULATION ON THE GROWTH OF SUNN HEMP (Crotalaria juncea L.)

Sunn Hemp plants, specifically Crotalaria juncea, are effective in absorbing and reducing the accumulation of heavy metals like cadmium, zinc, lead, and copper in soil. This plant species belongs to the Fabaceae family and is not only important for its phytoremediation capabilities but also for its agricultural value as a fiber and manure crop. Overall, Sunn hemp plants are crucial in mitigating the harmful effects of heavy metal contamination. The experiment was conducted in a greenhouse using a Completed Randomized Design (CRD) with 5 treatments and 6 replications to assess the impact of varying concentrations of heavy metals on Sunn hemp growth. The heavy metals were created by combining Cadmium (Cd), Copper (Cu), Lead (Pb), and Nickel (Ni). Each treatment of heavy metal contamination using 200ml of solution: T0 is the negative control. T1 containing 0.9 (Cd) + 4.0 (Cu) + 0.18 (Pb) + 0.7 (Ni). T2 containing 11.90 (Cd) + 19.80 (Cu) + 36.00 (Pb) + 28.90 (Ni). T3 containing 23.80 (Cd) + 39.60 (Cu) + 72.00 (Pb) + 57.80 (Ni). T4 containing 35.70 (Cd) + 59.40 (Cu) + 108.0 (Pb) + 115.60 (Ni). The study analyzed the impact of heavy metal concentrations on the growth of sunn hemp. Data included soil pH, plant height, flower count, pod count, root and shoot length, fresh and dry weight. Results showed that T4 showed excellent growth performance in terms of height, number of flowers, and dry weight. Sunn hemp has the ability to store heavy metals to a greater extent in its roots and has a remarkable capacity for long-term survival.

Total and Extractable Micronutrients in Tropical Acid Soils of Lampung, Indonesia

ABSTRACT The study aimed to determine the total and available amounts of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in the humid tropical acid soils of Lampung, Indonesia, and to identify the key factors affecting them. Topsoil samples were taken from 10 agricultural fields and 6 natural fields in 16 sub-districts of Lampung, Indonesia. The average total contents of Fe (26.36 g kg−1), Cu (8.97 mg kg−1), and Zn (53.24 mg kg−1) are generally below the world-soil average contents and those in other acid soils, which may be due to eluviation of Fe, Cu, and Zn into subsoil induced by high rainfall and the low natural contents of especially Cu and Zn in the parent rocks (acid volcanic rocks and sandstone). In contrast, the average total Mn content (1.20 g kg−1) is 2 to 8 times higher than that commonly found in acid soils and the world-soil average content, indicating that the parent materials may contain high Mn-bearing minerals. The total Fe, Mn, and Zn are positively correlated to the clay content, exchangeable-Ca and -Mg, and exchangeable-Mg, respectively, whereas the total Cu has no correlation to any soil properties. The amounts of available Fe, Mn, Cu, and Zn account for on average 0.38%, 6.20%, 21.50%, and 4.40% of the total contents, respectively. Around 6%, 12.5%, and 56% of the soil samples exhibit Mn, Cu, and Zn deficiency, respectively, and 25% face Fe toxicity. Total Fe and Mn are the main factors determining available Fe and Mn, respectively, whereas exchangeable-Mg and organic-C content mainly control available Cu and Zn, respectively.

Bioaugmentation of Phanerochaete concrescens KS7 for enhanced growth and zinc nutrition in rice (Oryza sativa L.)

Bioaugmentation of microbial strains could act as sustainable intervention in soil for enhancing the availability of nutrients. Zinc deficiency is widely reported across the world and application of zinc based fertilizers mostly resulted in formation of unavailable zinc in soil. A fungus with zinc solubilisation was isolated from rice and identified as Phanerochaete concrescens KS7. Inoculation of fungus in culture medium resulted in decrease of pH to 4.4 and analysis of medium revealed higher content of citric and gluconic acid in comparison with uninoculated broth. Indole acetic acid production by the strain was found to be enhanced in presence of tryptophan under broth conditions. Zinc solubilisation potential of strain was quantified in medium amended with insoluble zinc source. There was enhanced root growth and significantly higher zinc concentration in rice seedling on inoculation with KS7. There was increase in plant height, leaf area, number of grains per panicle and grain yield per plant on inoculation with P. concrescens in two selected varieties of rice grown in zinc deficient soil. Partition analysis was done for zinc in root, stem and grains and there was significant increase of zinc content in rice grain on inoculation with KS7. Total and available zinc was quantified from soil after harvest of rice and found that zinc contents were higher in soil of KS7 inoculated plants. Phanerochaete concrescens KS7 could act as potential solubilizer of zinc in soil and improve the zinc content of crop produce especially in zinc deficient soils.

Effects of Returning Green Manure-Chinese Milk Vetch on the Availability and Transformation of Zinc in Purple Tidal Mud Soil under Rice Cultivation

This study aimed to investigate the impact of different levels of Chinese milk vetch (Astragalus sinicus L.) incorporation on the availability and transformation of zinc in purple tidal mud soil under rice cultivation. A two-year pot experiment was conducted, comprising seven treatments: a control group without fertilizer, a control group with Chinese milk vetch application, a control group with chemical fertilizer application, and four treatment groups with varying levels of Chinese milk vetch application following chemical fertilizer application. Results showed that Chinese milk vetch application increased the content of available zinc (DTPA-Zn) in purple tidal mud soil. Sole application of Chinese milk vetch ultimately enhanced the transfer factor of zinc in purple tidal mud soil and reduced the distribution index. However, applying Chinese milk vetch after chemical fertilizer application ultimately decreased the transfer factor of zinc and increased the distribution index. Furthermore, sole application of Chinese milk vetch facilitated the conversion of zinc in purple tidal mud soil into available forms, while applying it after chemical fertilizer application promoted the transformation of zinc into ineffective forms, with a greater conversion observed at higher levels of Chinese milk vetch application.

Changes in Soil Zinc Fractions Upon Inoculation of Zinc Solubilizing Bacteria (ZnSB) Under Rice Rhizospheric Soil

ABSTRACT Zinc (Zn) is an essential micronutrient that is found in almost all classes of enzymes. Its deficiency is a well-documented problem among cereal crops that causes decreased crop yields and nutritional quality. Therefore, an experiment was implemented in a randomized block design which included the treatments of bacterial inoculation consisting of T1 (Control), T2 (100% RDF;100:40:20), T3(100% RDF + 25 kg ZnSO4.7 H2O), T4(100%RDF+ ZnSB1– Bacillus sp. strain BAU_A2 @750 ml ha−1), T5 (100%RDF+ ZnSB2– Priestia megaterium strain BAU_A3 @750 ml ha−1), T6 (100%RDF+ ZnSB3-Bacillus subtilis strain BAU_A5@750 ml ha−1). The mineral NPK was applied as per treatments. The results indicated the maximum values of water soluble exchangeable Zn and organically bounded Zn in treatments consisting ZnSB1, ZnSB2 and ZnSB3, respectively. The WS+EXCH-Zn was significantly increased by 68.57%, 28.26%, 18%, 98.14%, 41.30%, 30.00% and 128.12%, 55.55%, 37.25%, 43%, 62.22% and 43.13% in first year (2018–19) and second year (2019–2020) under the soil treated with ZnSB1-Peribacillus simplex strain BAU_A1, ZnSB2-Bacillus sp. strain BAU__A2 and ZnSB3-Bacillus subtilis strain BAU_A5 along with 100%RDF over control, application of recommended dose of fertilizer with and without application of 25 kg ZnSO4 ha−1, respectively. However, the maximum decrement in Mn-oxide-bounded zinc (1.12 mg kg−1 soil) was observed with T6 which was significantly higher by 158%, 194.4%, 185.71% over control, 100% RDF with and without application of 25 kg ZnSO4 ha−1, which showed the solubilization of zinc with the activity of ZnSB in soil. The study may be beneficial to mitigate the zinc deficiency in soil and malnutrition in children.

Critical Ranges of Zinc in Soils and Leaves in Relation to Visual Symptoms in Apple Orchards of Temperate Jammu and Kashmir, India

A comparative study of leaf and soil Zn in healthy and unhealthy apple orchards was undertaken to diagnose Zn deficiency in major apple growing blocks of district Doda, Jammu and Kashmir, India during July–August, 2014. Available Zn content in healthy orchards ranged from 1.0–3.6 mg kg-1 in surface soils and from 0.67–2.90 mg kg-1 in sub surface soils of entire district with respective mean values of 1.54 and 1.21 mg kg-1. The corresponding ranges for unhealthy orchards were found to be 0.50–0.99 mg kg-l and 0.40–0.83 mg kg-1 with respective mean values of 0.70 and 0.59 mg kg-1. The overall Zn content in leaves of normal healthy orchards ranged from 24.6–37.5 mg kg-1 whereas in unhealthy orchards, the range was 12.7–28.4 mg kg-1 with respective mean values of 30.36 and 19.25 mg kg-1. Higher Zn status of healthy orchards was ascribed to relatively better management practices being followed in these orchards when compared to others where absentee farming was prevalent. Available Zn showed significant positive correlations with leaf Zn and OC content, both in surface and sub surface soils, whereas its relationship with soil pH was negative. The proposed critical levels of Zn, both in soil and leaf could effectively differentiate the healthy and unhealthy orchards. However, in some cases symptom development could only be attributed to hidden hunger/interactions with other nutrient elements/environment or some external factors.

Plant-Microbe Interaction in Improving Zinc Nutrition in Rice: A Review

Zinc is an essential micro-nutrient that affects metabolic activities, including growth and cell proliferation in all living organisms. Zinc deficiency in agricultural soil has been increasing at an accelerated rate all over the world, leading to its deficiency in plants as well as humans. Zinc solubilising bacteria (ZSB) solubilise complex zinc in soil into plant absorbable compounds through several mechanisms such as the production of acid, chelating compounds, protons etc. further improving its bioavailability in plants and humans. Improving zinc nutrition through microbes is an effective measure to overcome its deficiency. ZSB with Plant Growth Promoting (PGP) traits can be an additional advantage as along with increasing zinc amount in plant it would also promote overall growth of plants through PGP traits and can act as a biocontrol agent against several crop pathogens. In this review we attempt to study the significance of zinc; status and deficiency of zinc in Indian soil and to understand how zinc solubilizing bacteria can prove to be an effective measure to increase zinc content in plants and overcome its deficiency.

Role of Woody Biomass Ash Material in Immobilization of Cadmium, Lead and Zinc in Soil.

Nowadays, we have observed the dynamic development of bio-heating plants that use wood biomass for heating or energy purposes. The result of this process is a reduction in carbon dioxide emissions as well as in the production of biomass ash (BA). Despite the waste nature of BA, it should be carefully analyzed and assessed for various applications, including environmental ones. Due to the features attributed to BA, including its alkaline reaction, the high capacity of its sorption complex, relatively low salinity, and significant content of macro- and microelements, a hypothesis was put forward in this work undertaken about the positive role of BA as an immobilizing factor for Cd-, Pb-, and Zn-contaminated soils. This research was based on a pot experiment in which four series were considered: (1) BA; (2) BA + Cd; (3) BA + Pb; and (4) BA + Zn. BA was used at doses of 30, 60, and 90 mg pot-1, and metals at doses of 2 mg Cd, 100 mg Pb, and 300 mg Zn kg-1 of soil. The test plant was corn grown for green mass. The study took into account the influence of BA on the content of the total forms of heavy metals (Metot) and their available forms (Meav). In the soil without the addition of metals, a significant increase in the content of Cdtot and Cdav, and a decrease in the content of Zntot were observed due to the application of BA. The addition of metals against the background of the BA used resulted in a significant increase in Cdtot, Pbtot, and Zntot, as well as an increase in the available forms of Pbav but a decrease in Znav. However, there was no significant increase in the Cdav content. The obtained results may indicate the potentially immobilizing role of BA only in the case of zinc. They may constitute the basis for further, more detailed research aimed at determining the role of BA in the immobilization of various metals in soil.

Biofortification of wheat in salt-affected soil through seed priming and soil application of zinc

ContextGiven the global significance of wheat production and consumption, it is imperative to achieve high yields of nutritious wheat grains. However, the inadequate availability of zinc (Zn) in salt-affected soils can aggravate salt stress, decrease wheat grain yield, and grain Zn concentration. This study compared the effectiveness of soil Zn application and seed Zn priming in increasing Zn biofortification and grain yield of Zn-biofortified wheat grown in alkaline-calcareous soil affected by salts. MethodsEighteen pots were filled with alkaline-calcareous soil containing elevated levels of soluble salts and exchangeable sodium (Na). The pots were subjected to soil Zn application (0 or 8 mg kg−1) and seed priming (control/non-, hydro-, or Zn-primed seeds) treatments, applied to a Zn-biofortified wheat (cv. Zincol-2016). Plant samples were collected at the heading and maturity stages to measure parameters related to plant growth and grain quality. FindingsSoil Zn application increased grain and straw yields across seed priming treatments by a maximum of 23 %, and seed Zn priming increased grain and straw yields across soil Zn rates by a maximum of 21 %. This yield response was accompanied by significant increases in grain potassium and Zn concentrations at maturity, as well as non-significant to significant increases in photosynthetic parameters (stomatal conductance, photosynthetic rate and transpiration rate) in flag leaves during heading. Additionally, compared to control, the combined treatment of soil Zn application and seed Zn priming decreased grain Na concentration by 14 %. Compared to control, both soil Zn application and seed Zn priming significantly increased grain Zn concentration. With the combined application treatment, the grain Zn concentration reached 27 mg kg−1, but it remained significantly below the desired level of >37 mg kg−1. Seed Zn priming decreased the phytate-to-Zn molar ratio in grains, while the treatments that received soil Zn application exhibited the lowest values of this ratio, potentially increasing Zn bioavailability to humans. ConclusionsThe findings suggest that soil Zn application is more effective in enhancing grain yield and Zn concentration, while seed Zn priming remains crucial in low-Zn and high-salt soils. Future research should optimize Zn application strategies for Zn-biofortified wheat cultivated in salt-affected fields.

The coupling of sulfide and Fe-Mn mineral promotes the migration of lead and zinc in the redox cycle of high pH floodplain soils

In this study, we investigated the impact of fluctuating water levels on the distribution of lead (Pb) and zinc (Zn) in soil and sediments at a historical Pb-Zn smelting site along the Xiangjiang River. Despite the high pH levels (7 to 11) in the study area, which generally inhibits heavy metal solubility, we found that regular changes in water levels still affect Pb-Zn movement. Soil analysis revealed distinct redox zones within the unconfined aquifer, as shown by the variable Fe/Mn and Ce/Ce* ratios. Advanced techniques such as Mn K-edge XAFS, Mössbauer spectroscopy, and TOF-SIMS indicated persistent Fe-Mn redox cycling and highlighted the presence of Pb and Zn-rich manganese oxides near sulfur-bearing minerals. These findings suggest that acidic microzones produced by the oxidation of sulfur-bearing minerals become "refuges" for microbial and heavy metal activity. Considering that sulfur-containing minerals are widespread waste types in nonferrous metal smelting sites, these findings are instructive for a better understanding of the transformation mechanisms of heavy metal ions in nonferrous metal smelting-polluted environments and for guiding pollution remediation strategies.

Numerical simulation of heavy metal migration in stabilized soils under multi-field coupling

Heavy metal contamination of soils has become a global issue. In pursuit of a reference for the management of heavy metal pollution, numerical simulations were used here to investigate the migration pattern of heavy metals in soil under multi-field coupling of rainfall, temperature, and hydraulic conductivity. Models were built using TOUGHREACT, and measured and simulated values were compared with those of existing studies to verify the accuracy of the software in simulating coupled water vapor-thermal transport and rainfall infiltration. Taking Nanjing rainfall data as an example, the transport pattern of zinc in soil under multi-field coupling was explored. Although evaporation and rainwater infiltration were found to increase with the temperature, the effects of evaporation and temperature counteracted each other, resulting in a weak influence of temperature on heavy metal transport. The hydraulic conductivity of stabilized soil was the main factor controlling zinc migration, with the saturation and heavy metal concentration clouds of soil columns tending to stabilize when the hydraulic conductivity of solidified soil was under 1 × 10-11 m/s.

Lead and zinc chemical fraction alterations in multi-metal contaminated soil with pomelo peel biochar and biochar/apatite incubation

The issue of heavy metal soil contamination is widespread, and the negative effects of heavy metals on the ecosystem depend on their chemical speciation in contaminated soil. Pomelo peel-derived biochar produced at 300 °C (PPB300) and 500 °C (PPB500) and its combination with apatite ore (AP) was applied to immobilize lead (Pb) and zinc (Zn) in agricultural multi-metal polluted soil. Soil amendments including biochar (PPB300 and PPB500) at concentrations of 3%, 5%, and 10%, as well as a mixture of biochar and apatite (AP) at 3:3% and 5:5% weight ratios, were introduced into the soil matrix. The chemical forms of Pb and Zn in incubated soil samples and control soil (CS) were studied utilizing the Tessier’s sequential extraction procedure. The chemical partitioning of heavy metals was carried out using Tessier’s extraction protocol, yielding fractions representing exchangeable (F1), carbonate (F2), Fe/Mn oxide (F3), organic matter (F4), and residual (F5) forms. Quantification of Pb and Zn concentrations was accomplished via inductively coupled plasma mass spectrometry (ICP-MS). Observations revealed notable elevations in pH, organic carbon (OC), and electrical conductivity (EC) levels within the treated soil relative to the control soil (p < 0.05). After incubating PPB300, PPB500, and AP for 30 days, there was a reduction in the exchangeable fraction of Pb and Zn by approximately 64% and 58% respectively. This reduction was achieved by transforming heavy metals from mobile fractions to immobile fractions using five primary mechanisms: chemical and physical adsorption, electrostatic attraction, the formation of complexes via interactions with active groups, cation exchange processes, and precipitation events mediated by phosphate, carbonate ions, or hydroxyl ions within an alkaline environment. Therefore, pomelo peel-derived biochar and the blend of biochar/apatite show promise as materials for mitigating heavy metal pollution in soil.

Soil zinc application decreases arsenic and increases zinc accumulation in grains of zinc-biofortified wheat cultivars

Context Arsenic (As) is a noxious metalloid for plants, animals and humans. Elevated levels of As in soils may cause it to accumulate to above-permissible levels in wheat grains, posing a threat to human health. Moreover, vulnerable population groups in developing countries have inadequate dietary zinc (Zn) linked to cereal-based diets. Aims The present study evaluated the effect of soil Zn application on accumulation of As and Zn in grains of two Zn-biofortified wheat (Triticum aestivum L.) cultivars (Akbar-2019 and Zincol-2016). Methods Wheat plants were grown on an alkaline calcareous soil spiked with three levels of As (0, 5 and 25 mg kg−1). Before sowing, two rates of Zn (0 and 8 mg kg−1) were also applied to the soil. Key results Arsenic spiking in soil decreased plant dry matter yield, chlorophyll pigments, and phosphorus (P) and Zn accumulation, and increased As accumulation in wheat. By contrast, soil Zn application enhanced crop yield and increased P and Zn accumulation, with a simultaneous decrease in As accumulation in both cultivars. Compared with the Zn control, soil Zn application decreased grain As concentration by 26%, 30% and 32% for plants grown in soil spiked with 0, 5 and 25 mg As kg−1, respectively. Conclusions Applying Zn to As-spiked soil mitigates the harmful effects of As by increasing Zn and decreasing As concentrations in wheat, resulting in improved grain quality for human consumption. Implications Zinc application to crop plants should be recommended for addressing the health implications associated with As-contaminated crops and human Zn deficiency.

67Zn and 111Cd labelled green manure to determine the fate and dynamics of zinc and cadmium in soil–fertilizer–crop systems

ABSTRACT Isotope source tracing enables to accurately determine the fate of nutrients that are applied with fertilizers to soils. While this approach is well established for major nutrients such as nitrogen, it is not yet established for trace metals. Here, we aimed to determine the fate of the micronutrient zinc (Zn) and the contaminant cadmium (Cd) that were applied with an organic fertilizer to a soil–wheat system. A pot study was conducted in which wheat was grown on an alkaline soil. The soils received green manure and/or soluble Zn fertilizer and were compared with non-fertilized control treatments (n = 4 experimental replicates). The green manure was labelled with the stable isotopes 67Zn and 111Cd. For an efficient sample throughput, a method was provided and validated to determine enriched stable isotope ratios (67Zn:66Zn and 111Cd:110Cd) and the Zn and Cd concentrations in one analytical run. To this end, single collector ICP-MS analyses and stable isotope mass balances calculations were combined. Applying this method revealed that the addition of green manure increased neither Zn nor Cd concentrations in wheat grains due to biomass dilution effects. Isotope source tracing showed that the largest fraction of these metals in the wheat shoots derived from the soil in all treatments (Zn 87–99 %, Cd 94–98 %). Moreover, the addition of green manure increased the transfer of Zn and Cd from soil to wheat by a factor 1.9 for both elements. This increased transfer was likely related to a nitrogen fertilization effect that increased root and shoot biomass and thereby the soil exploration of the wheat. This study demonstrated how the fate and dynamics of multiple trace metals can be efficiently determined in soil–fertilizer–crop systems using isotope source tracing.

A biocompatible NPK+Fe+Zn slow release fertilizer: synthesis and its evaluation in tomato plant growth improvement

Slow-release fertilizers (SRFs) play an essential and necessary role in sustainable agriculture. Using slow-release and environment friendly fertilizers can increase the growth of plants and reduce the loss of nutrients. Considering the deficiency of iron (Fe) and zinc (Zn) in calcareous soils, a slow-release fertilizer was prepared based on the polymeric nanocomposite, which contains NPK, Fe, and Zn. Its potential was evaluated on tomato plant growth by conducting an experiment in a factorial completely randomized design with three replications. Two levels of salinity (2 and 5 ds m−1, two types of soil texture) clay loam and sandy loam) and five levels of fertilizers were examined in the experiment. To this, the graphene oxide-chitosan coated-humic acid@Fe3O4 nanoparticles (Fe3O4@HA@GO-Cs), and the graphene oxide-chitosan coated-ammonium zinc phosphate (AZP@GO-Cs) were used as Fe and Zn sources, respectively. Then, the optimal Fe and Zn fertilizers in the presence of urea, phosphorus, and potassium slow- release fertilizers (SRF) were investigated under greenhouse conditions. The results indicated that the best improvement in growth and nutrient uptake in plants was achieved by using the SRF. Notably, in the shoots of tomato plants, the nitrogen, phosphorus, potassium, Fe, and Zn concentration increased by 44, 66, 46, 75, and 74% compared to the control. The use of nanofertilizer can be an effective, biocompatible, and economical option to provide Fe and Zn demand in plants.

Interaction of Zinc Mineral Nutrition and Plant Growth-Promoting Bacteria in Tropical Agricultural Systems: A Review.

The relationship between zinc mineral nutrition and plant growth-promoting bacteria (PGPB) is pivotal in enhancing agricultural productivity, especially in tropical regions characterized by diverse climatic conditions and soil variability. This review synthesizes and critically evaluates current knowledge regarding the synergistic interaction between zinc mineral nutrition and PGPB in tropical agricultural systems. Zinc is an essential and fundamental micronutrient for various physiological and biochemical processes in plants. Its deficiency affects plant growth and development, decreasing yields and nutritional quality. In tropical regions, where soil zinc availability is often limited or imbalanced, the PGPB, through different mechanisms such as Zn solubilization; siderophore production; and phytohormone synthesis, supports Zn uptake and assimilation, thereby facilitating the adverse effects of zinc deficiency in plants. This review outlines the impacts of Zn-PGPB interactions on plant growth, root architecture, and productivity in tropical agricultural systems. The positive relationship between PGPB and plants facilitates Zn uptake and improves nutrient use efficiency, overall crop performance, and agronomic biofortification. In addition, this review highlights the importance of considering indigenous PGPB strains for specific tropical agroecosystems, acknowledging their adaptability to local conditions and their potential in sustainable agricultural practices. It is concluded that Zn fertilizer and PGPBs have synergistic interactions and can offer promising avenues for sustainable agriculture, addressing nutritional deficiencies, improving crop resilience, and ensuring food security.

Changes in chemical fractionation of copper and zinc in soil as a function of incubation moisture content and organic matter amendments

Copper and zinc are essential micronutrients that are potentially toxic when present in excess in soils. Their bioavailability depends on their speciation in soil, but this may vary with environmental conditions. Aeration and hence redox conditions, and organic matter amendments are among the factors likely to cause variation on metal fractionation. We have monitored the chemical fractionation of both native and added copper and zinc in a clay loam top soil during a 5-month laboratory incubation. The effects of aeration (moist soil or flooded) and addition of two organic matter amendments, alfalfa straw or leaf compost, were studied. Metal spike was more labile than legacy metal, and was slowly redistributed over the incubation period. Organic matter caused short-lived flushes of metals, attributed to metal chelation with soluble organic matter. This effect was greater for straw than for more stable compost. There was no evidence that added organic matter increased the capacity of soil organic matter to immobilise metal. Flooding solubilized soil metal (hydr)oxides, releasing legacy Cu and Zn, but with less effect on the capacity to immobilise metal spike. Effects of flooding and organic matter addition were not additive. Both metals appear to be precipitated as sulphides under reducing conditions, and accounted for in the acid soluble phase. Monitoring the dynamics of metal distribution gives a more comprehensive understanding of underlying processes than would a single measurement, and is closer to in campo conditions than slurry microcosms.

Zinc in Different Soils and Foliar Content in Commercial Corn Planted on Calcareous Soils of Quintana Roo, Mexico

Zinc in Different Soils and Foliar Content in Commercial Corn Planted on Calcareous Soils of Quintana Roo, Mexico