Plant Available Zinc Is Influenced by Landscape Position in the Amhara Region, Ethiopia

Impact of zinc and iron agronomic biofortification on grain mineral concentration of finger millet varieties as affected by location and slope

Background

Food crop micronutrient concentrations can be enhanced through agronomic biofortification, with the potential to reduce micronutrient deficiencies among rural population if they have access to fertilizers. Here we reported the impact of agronomic biofortification on finger millet grain zinc (Zn) and iron (Fe) concentration.

Methods

A field experiment was conducted in farmers' fields in Ethiopia in two locations; over two seasons in one district (2019 and 2020), and over a single season (2019) in a second district. The experimental design had 15 treatment combinations comprising 3 finger millet varieties and 5 soil-applied fertilizer treatments: (T1) 20 kg ha^-1 FeSO₄ + 25 kg ha^-1 ZnSO₄ + NPKS; (T2) 25 kg ha^-1 ZnSO₄ + NPKS; (T3) NPKS; (T4) 30% NPKS; (T5) 20 kg ha^-1 FeSO₄ + NPKS. The treatments were studied at two slope positions (foot and hill), replicated four times in a randomized complete block design.

Results

Grain Zn concentration increased by 20% in response to Fe and Zn and by 18.9% due to Zn addition. Similarly, grain Fe concentration increased by 21.4% in T1 and 17.8% in T5 (Fe). Zinc fertilizer application (p < 0.001), finger millet variety (p < 0.001), and an interaction of Fe and Zn had significant effect on grain Zn concentration. Iron fertilizer (p < 0.001) and interactive effect of Fe fertilizer and finger millet variety (p < 0.01) had significant effects on grain Fe concentration. Location but not slope position was a source of variation for both grain Zn and Fe concentrations.

Conclusion

Soil application of Zn and Fe could be a viable strategy to enhance grain Zn and Fe concentration to finger millet grain. If increased grain Zn and Fe is bioavailable, it could help to combat micronutrient deficiencies.

Serum concentration of zinc, copper, iron, and its associated factors among pregnant women of small-scale farming in western Ethiopia

Micro-nutrients are required in small amounts to maintain growth and cell functioning to complete the life cycle through reproductions. However, pregnant women in developing countries like Ethiopia are vulnerable to multiple micro-nutrient deficiencies. Therefore, this study aimed at assessing the serum level of metals and associated factors like dietary diversity, and health-related problems in pregnant women among small-scale farming in Kellem Wellega, western Ethiopia. A cross-sectional laboratory-based study was conducted from June to August 2021 on 417 pregnant women attending antenatal care at rural healthcare facilities. Data was collected by using per-tested structured questionnaires via face-to-face interviews. The data analysis was conducted using SPSS version 24.0, and multivariate logistic regression analysis was performed to determine the association between predictor and outcome variables. A statistically significant was considered at p value < 0.05 for all the analyses. Our study findings showed that 62.1, 80.9, and 71.9% of the participants were deficient in iron, zinc, and copper micro-nutrient levels, respectively. Pregnant women who could not have formal education were 3.24 (AOR = 3.24, 95% CI 1.33-7.91) and 3.98 (AOR = 3.98, 95% CI 1.2-13.15) times more likely to show zinc and copper deficiency than those who attended secondary school and above, respectively. Furthermore, pregnant women involved only in farming activities were 0.57 (AOR = 0.57, 95% CI 0.36-0.91) and 4.33 (AOR = 5.72, 95% CI 2.34-13.97) times more likely to be exposed to iron and zinc deficiency than those who were engaged in other activities. This study revealed that pregnant women with low income were 6.36 times more likely to be exposed to zinc micro-nutrient deficiencies than those with high-income participants (AOR = 6.36, 95% CI 1.47-27.61). Additionally, those participants who ate a varied diet between 1 and 4 items per day were 2.26 (AOR = 2.26, 95% CI 1.43-3.59) and 2.77 (AOR = 2.77, 95% CI 1.6-4.61) times more likely to suffer zinc and copper micro-nutrient insufficiency than those who consumed 5-10 items per day. Finally, pregnant women who developed diarrhea in the past three months were 1.82 (AOR = 2.77, 95% CI 1.14-2.92) and 2.52 (AOR = 2.52, 95% CI 1.3-4.91) times more likely to be exposed to iron and copper deficiency than those who never show the symptoms, respectively. This study identified low concentrations of zinc, iron, and copper in the blood serum of pregnant women of small-scale farmers.

Potential mobilization of cadmium and zinc in soils spiked with smithsonite and sphalerite under different water management regimes

Particulate cadmium (Cd) and zinc (Zn) are ubiquitous in agricultural soils of Pb-Zn mining regions. Water management serves as an important agronomic measure altering the bioavailability of Zn and Cd in soils, but how this affects particulate Cd and Zn and the underlying mechanisms remain largely unknown. Microcosm soil incubation combined with spectroscopic and microscopic characterization was conducted. During a two-year-long incubation period we observed that the concentrations of soil CaCl₂-extractable Zn and Cd increased 3-10 times in sphalerite-spiked soils and 1-2 times in smithsonite-spiked soils under periodic flooding conditions due to the long-term dissolution of sphalerite (SP) and smithsonite (SM). However, the increase in the concentration of CaCl₂-extractable metals (Zn: from 0.607 mg kg^-1 to 1.051 mg kg^-1 and Cd: from 0.047 mg kg^-1 to 0.119 mg kg^-1) was found only in SP-treatment under continuous flooding conditions, indicating the mobilization of metals. Ultrafiltration analysis shows that the nanoparticulate fraction of Zn and Cd in soil pore water increased 5 and 7 times in SP-treatments under continuous flooding conditions, suggesting the increment of metal pools in soil pore water. HRTEM-EDX-SAED further reveals that these nanoparticles were mainly crystalline ZnS and Zn-bearing sulfate nanoparticles in the SP-treatment and amorphous ZnCO₃ and ZnS nanoparticles in the SM-treatment. Therefore, the formation of the stable crystalline Zn-bearing nanoparticles in the SP-treatment may explain the elevation of the concentration of soil CaCl₂-extractable Zn and Cd under continuous flooding. The potential mobility of particulate metals should therefore be expected in scenarios of continuous flooding such as paddy soils and wetland systems.

Potential environmental risk of natural particulate cadmium and zinc in sphalerite- and smithsonite-spiked soils

Cadmium (Cd)-bearing sphalerite and smithsonite ore particles are ubiquitous in soils near metal-mining areas. Previous studies indicate that smithsonite is more readily dissolved in acidic waters and soils than sphalerite but the mobility of Cd and zinc (Zn) derived from these ores in soils is unknown. Using microcosm incubation experiments and microscopic and spectroscopic analysis, we found that the mobility of Cd and Zn derived from smithsonite is higher than from sphalerite. The mobilization rates of Cd (16.6%) and Zn (13.7%) released from smithsonite in soils after 30-day incubation experiments were higher than those from sphalerite (Cd, ~ 1.42%; Zn, ~ 0.75%). Moreover, the percentages of Cd²⁺ and Zn²⁺ in soil pore water showed a dynamic increase in smithsonite-spiked treatments but a decrease in sphalerite-spiked treatments. HRTEM-EDX-SAED analysis further indicates the occurrence of dynamic transformation of amorphous Cd and Zn species in soil pore water to crystalline ZnS and iron oxides in sphalerite-spiked soil but crystalline ZnCO₃ nanoparticles were dynamically transformed to amorphous metal-bearing species in smithsonite-spiked soil. The opposite transformation trends in pore water of Zn ore-spiked soils provide new insights into the Cd environmental risks in soils affected by Zn mining.

Unraveling the Mechanisms of Zinc Efficiency in Crop Plants: From Lab to Field Applications

Global food security and sustainability in the time of pandemics (COVID-19) and a growing world population are important challenges that will require optimized crop productivity under the anticipated effects of climate change [...].

Transcriptional Regulation of Genes Involved in Zinc Uptake, Sequestration and Redistribution Following Foliar Zinc Application to Medicago sativa

Zinc (Zn) is an essential micronutrient for plants and animals, and Zn deficiency is a widespread problem for agricultural production. Although many studies have been performed on biofortification of staple crops with Zn, few studies have focused on forages. Here, the molecular mechanisms of Zn transport in alfalfa (Medicago sativa L.) were investigated following foliar Zn applications. Zinc uptake and redistribution between shoot and root were determined following application of six Zn doses to leaves. Twelve putative genes encoding proteins involved in Zn transport (MsZIP1-7, MsZIF1, MsMTP1, MsYSL1, MsHMA4, and MsNAS1) were identified and changes in their expression following Zn application were quantified using newly designed RT-qPCR assays. These assays are the first designed specifically for alfalfa and resulted in being more efficient than the ones already available for Medicago truncatula (i.e., MtZIP1-7 and MtMTP1). Shoot and root Zn concentration was increased following foliar Zn applications ≥ 0.1 mg plant-1. Increased expression of MsZIP2, MsHMA4, and MsNAS1 in shoots, and of MsZIP2 and MsHMA4 in roots was observed with the largest Zn dose (10 mg Zn plant-1). By contrast, MsZIP3 was downregulated in shoots at Zn doses ≥ 0.1 mg plant-1. Three functional gene modules, involved in Zn uptake by cells, vacuolar Zn sequestration, and Zn redistribution within the plant, were identified. These results will inform genetic engineering strategies aimed at increasing the efficiency of crop Zn biofortification.