Soil Zn Application Research Articles

Effects of zinc application on the growth and photosynthetic characteristics of pecan at the seedling stage.

Pecan (Carya illinoinensis) is sensitive to Zn, which is involved in basic physiological and biochemical processes. To explore the growth and physiology of pecan in response to Zn application, we used 1-year-old annual grafted seedlings (Pawnee) and applied four concentrations of Zn fertilizer (0.05, 0.10, 0.20 and 0.40g·plant-1 ); a control (CK; no Zn fertilization) was also included. The growth characteristics, anatomical structure of the leaves and photosynthesis were assessed. Compared with the CK, photosynthesis and chlorophyll (Chl) fluorescence parameters, leaf area and leaf structure significantly increased at Zn concentrations of 0.05 and 0.10g·plant-1 . In addition, growth of pecan at the seedling stage increased in response to moderate Zn application. In contrast, treatment with 0.20 and 0.40g·Zn·plant-1 dramatically decreased these physiological indices and inhibited pecan growth. The results show that moderate soil Zn application promotes pecan growth and development by increasing photosynthesis. However excess Zn concentrations were not conducive to seedling growth. The concentration of 0.1g·Zn·plant-1 was best when considering long-term soil Zn applications, providing a theoretical foundation for microelement management of pecan.

Combined Selenium and Zinc Biofortification of Bread-Making Wheat under Mediterranean Conditions.

Millions of people worldwide have an inadequate intake of selenium (Se) and zinc (Zn), and agronomic biofortification may minimise these problems. To evaluate the efficacy of combined foliar Se and Zn fertilisation in bread making wheat (Triticum aestivum L.), a two-year field experiment was established in southern Spain under semi-arid Mediterranean conditions, by following a split-split-plot design. The study year (2017/2018, 2018/2019) was considered as the main-plot factor, soil Zn application (50 kg Zn ha−1, nor Zn) as a subplot factor and foliar application (nor Se, 10 g Se ha−1, 8 kg Zn ha−1, 10 g Se ha−1 + 8 kg Zn ha−1) as a sub-subplot factor. The best treatment to increase both Zn and Se concentration in both straw, 12.3- and 2.7-fold respectively, and grain, 1.3- and 4.3-fold respectively, was the combined foliar application of Zn and Se. This combined Zn and Se application also increased on average the yield of grain, main product of this crop, by almost 7%. Therefore, bread-making wheat seems to be a very suitable crop to be used in biofortification programs with Zn and Se to alleviate their deficiency in both, people when using its grain and livestock when using its straw.

Source-Sink Manipulation Affects Accumulation of Zinc and Other Nutrient Elements in Wheat Grains.

To better understand the source–sink flow and its relationships with zinc (Zn) and other nutrients in wheat (Triticum aestivum L.) plants for biofortification and improving grain nutritional quality, the effects of reducing the photoassimilate source (through the flag leaf removal and spike shading) or sink (through the removal of all spikelets from one side of the spike, i.e., 50% spikelets removal) in the field of the accumulation of Zn and other nutrients in grains of two wheat cultivars (Jimai 22 and Jimai 44) were investigated at two soil Zn application levels. The kernel number per spike (KNPS), single panicle weight (SPW), thousand kernel weight (TKW), total grain weight (TGW) sampled, concentrations and yields of various nutrient elements including Zn, iron (Fe), manganese (Mn), copper (Cu), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg), phytate phosphorus (phytate-P), phytic acid (PA) and phytohormones (ABA: abscisic acid, and the ethylene precursor ACC: 1-aminocylopropane-1-carboxylic acid), and carbon/N ratios were determined. Soil Zn application significantly increased the concentrations of grain Zn, N and K. Cultivars showing higher grain yields had lower grain protein and micronutrient nutritional quality. SPW, KNPS, TKW (with the exception of TKW in the removal of half of the spikelets), TGW, and nutrient yields in wheat grains were most severely reduced by half spikelet removal, secondly by spike shading, and slightly by flag leaf removal. Grain concentrations of Zn, N and Mg consistently showed negative correlations with SPW, KNPS and TGW, but positive correlations with TKW. There were general positive correlations among grain concentrations of Zn, Fe, Mn, Cu, N and Mg, and the bioavailability of Zn and Fe (estimated by molar ratios of PA/Zn, PA/Fe, PA × Ca/Zn, or PA × Ca/Fe). Although Zn and Fe concentrations were increased and Ca was decreased in treatments of half spikelet removal and spike shading, the treatments simultaneously increased PA and limited the increase in bioavailability of Zn and Fe. In general, different nutrient elements interact with each other and are affected to different degrees by source–sink manipulation. Elevated endogenous ABA levels and ABA/ACC ratios were associated with increased TKW and grain-filling of Zn, Mn, Ca and Mg, and inhibited K in wheat grains. However, the effects of ACC were diametrically opposite. These results provide a basis for wheat grain biofortification to alleviate human malnutrition.

Common Bean Yield and Zinc Use Efficiency in Association with Diazotrophic Bacteria Co-Inoculations

Enrichment of staple food with zinc (Zn) along with solubilizing bacteria is a sustainable and practical approach to overcome Zn malnutrition in human beings by improving plant nutrition, nutrient use efficiency, and productivity. Common bean (Phaseolus vulgaris L.) is one of a staple food of global population and has a prospective role in agronomic Zn biofortification. In this context, we evaluated the effect of diazotrophic bacterial co-inoculations (No inoculation, Rhizobium tropici, R. tropici + Azospirillum brasilense, R. tropici + Bacillus subtilis, R. tropici + Pseudomonas fluorescens, R. tropici + A. brasilense + B. subtilis, and R. tropici + A. brasilense + P. fluorescens) in association with soil Zn application (without and with 8 kg Zn ha−1) on Zn nutrition, growth, yield, and Zn use efficiencies in common bean in the 2019 and 2020 crop seasons. Soil Zn application in combination with R. tropici + B. subtilis improved Zn accumulation in shoot and grains with greater shoot dry matter, grain yield, and estimated Zn intake. Zinc use efficiency, recovery, and utilization were also increased with co-inoculation of R. tropici + B. subtilis, whereas agro-physiological efficiency was increased with triple co-inoculation of R. tropici + A. brasilense + P. fluorescens. Therefore, co-inoculation of R. tropici + B. subtilis in association with Zn application is recommended for biofortification and higher Zn use efficiencies in common bean in the tropical savannah of Brazil.

Effect of zinc and boron on growth, yield and economics of linseed (Linum usitatissimum L.) under medium land of Jharkhand

An experiment was conducted during Rabi 2018-19 and 2019-20 at Research Farm of Birsa Agricultural University, Kanke, Ranchi, Jharkhand to study “The effect of Zinc and Boron on growth, yield and economics of Linseed (Linum usitatissimum L.) under medium land of Jharkhand”. The experiment was laid out in randomized block design with three replications. The treatments comprised soil application of Zn @ 5 kg/ha, foliar application of ZnSO4 @ 0.5% at 45 DAS, soil application of Zn @ 5 kg/ha + foliar application of ZnSO4 @ 0.5% at 45 DAS, soil application of B @ 1.5 kg/ha, foliar application of Borax @ 0.3% at 45 DAS, soil application of B @ 1.5 kg/ha + foliar application of Borax @ 0.3% at 45 DAS, foliar application of ZnSO4 @ 0.5% + foliar application of Borax @ 0.3% at 45 DAS, soil application of Zn @ 5 kg/ha + soil application of B @ 1.5 kg/ha compared with control treatment along with RDF (40:20:20 kg NPK/ha) common to all treatments. Foliar application of ZnSO4 @ 0.5% + foliar application of borax @ 0.3% at 45 DAS found superior in terms of maximum plant height (53.75 cm and 55.14 cm), plant stand (201 and 216), dry matter accumulation (3.66 g/plant and 3.70 g/plant) yield attributing characters viz., number of capsules per plant (29.02 and 38.67), number of seeds per capsule (6.00 and 8.57), 1000 seed weight (7.59 g and 7.64 g), seed yield (12.99 q/ha and 13.35 q/ha), net return (₹ 33230/ha and ₹38201/ha) and B:C ratio (1.82 and 2.19) in both years respectively.

Zinc application enhances yield and alters micronutrients concentration in pigeonpea (Cajanus cajan L. Millsp.)

Zinc (Zn) deficiency prevails in different soils and crops of the world. Soil Zn deficiency adversely affects growth, yield and micronutrients (Zn, copper (Cu), iron (Fe) and manganese (Mn)) concentration in different crops including pigeonpea (Cajanus cajan L. Millsp.), a protein rich legume crop grown consumed in different parts of the world. Therefore, we carried out a 2-years field experiment on a Zn-deficient Vertisol with 20 different pigeonpea genotypes and 3 levels of Zn treatments in a split-plot design with 3 replications, to study the effect of Zn application on yield, micronutrients concentration and uptake by pigeonpea genotypes. The 3 levels of Zn treatments were no Zn (no Zn fertilizer was applied), soil Zn (20 kg Zn ha−1) and soil + foliar Zn. Compared to no Zn application, soil and soil + foliar application of Zn enhanced mean grain yield by 15 and 24%, stover yield by 13 and 29% and total biomass yield of pigeonpea genotypes by 13 and 29%, respectively. Soil + foliar application of Zn significantly increased mean grain Zn concentration by 33% compared to no Zn application. Soil and soil + foliar Zn application led to reduction in mean grain Cu concentration by 9 and 10%, respectively, and did not significantly increase or decrease grain Fe and Mn concentration. Soil and soil + foliar application of Zn significantly increased mean grain Zn, Fe and Mn uptake by pigeonpea genotypes compared to no Zn application. Soil + foliar application of Zn had significantly higher mean grain Zn, Fe and Mn uptake compared to soil Zn application. The grain, stover and total biomass yield, micronutrients concentration in grain and stover and micronutrients uptake by the genotypes were different under various treatments. The genotypes ICPL 87119, BDN 2, JKM 7, Virsa Arhar 1, DT 23 and AAUT 2007–10 under soil application of Zn and ICPL 87119, BDN 2, JKM 7 and Virsa Arhar 1 under soil + foliar application of Zn were found promising for cultivation to obtain higher grain yield and micronutrients uptake.

Biofortification of Silage Maize with Zinc, Iron and Selenium as Affected by Nitrogen Fertilization.

Agronomic biofortification is one of the main strategies for alleviation of micronutrient deficiencies in human populations and promoting sustainable production of food and feed. The aim of this study was to investigate the effect of nitrogen (N)fertilization on biofortification of maize crop (Zea mays L.) with zinc (Zn), iron (Fe) and selenium (Se) grown on a micronutrient deficient soil under greenhouse conditions. Factorial design experiment was set under greenhouse conditions. The experiment consisted of two levels of each N, Zn, Fe and Se. The levels for N were 125 and 250 mg N kg−1 soil; Zn were 1 and 5 mg Zn kg−1 soil; levels of Fe were 0 and 10 mg Fe kg−1 soil; levels of Se were 0 and 0.02 mg Se kg−1 soil. An additional experiment was also conducted to study the effect of the Zn form applied as a ZnO or ZnSO4 on shoot growth, shoot Zn concentration and total shoot Zn uptake per plant. Shoot Zn concentrations increased by increasing soil Zn application both with ZnSO4 and ZnO treatments, but the shoot Zn concentration and total Zn uptake were much greater with ZnSO4 than the ZnO application. Under given experimental conditions, increasing soil N supply improved shoot N concentration; but had little effect on shoot dry matter production. The concentrations of Zn and Fe in shoots were significantly increased by increasing N application. In case of total uptake of Zn and Fe, the positive effect of N nutrition was more pronounced. Although Se soil treatment had significant effect, N application showed no effect on Se concentration and accumulation in maize shoots. The obtained results show that N fertilization is an effective tool in improving the Zn and Fe status of silage maize and contribute to the better-quality feed.

Effect of different sources of zinc on the activities of plant and soil enzymes

The present investigation was conducted to study the effect of zinc fertilization on major biomeric characteristics, yield and post-harvest soil nutrient status. The experiment was carried out at college of Agriculture, Vellayani during 2017 - 2019. The experiment was laid out in Randomized Block Design with eight treatments and three replications. The treatments were Absolute control (T1), N, P, K as per POP- 75:45:25 kg ha-1 (T2), N, P, K+ Soil application of Zn as ZnSO4- 10 kg ha-1 (T3), N, P, K+ Foliar application of Zn as 0.5 per cent ZnSO4 (T4), N, P, K+ Zn as Zn EDTA-18 kg ha-1 (T5), N, P, K+ Zn solubilizer -5 per cent (T6), N, P, K+ Zn Humate- 44 kg ha-1 (T7), N, P, K+ K solubilizer 5 per cent (T8). From the study, it was observed that the treatment T7 with the application of N, P, K+ Zn Humate (44 kg ha-1) recorded the highest for enzymes such as carbonic anhydrase, peroxidase and catalase viz., 910 EU g-1, 48.17 activity min-1 g-1 and 27.06x103 units ml-1, respectively. An incubation study was carried out to assess the trend os activity of the enzymes and the results revealed peroxidase and carbonic anhydrase showed an increasing trend in activitfy while peroxidase registered a decreasing trend. Treatment T4 with the application of Soil + Zn as 1.5 ppm ZnSO4 registered the highest value for peroxidase (11.98 activity min-1 g-1) and carbonic anhydrase activity (385 EU g-1) in the incubation study.

Biofortification of Zn and Fe in Chickpea through Agronomic Intervention in Medium Black Soils of Karnataka

Background: Bio-fortification, the process of integrating nutrients into food crops, provides a sustainable and economic way of increasing the density of micronutrients in important staple crops. Agronomic bio-fortification is the easiest, practicable and fastest way for bio-fortification of pulse grains with Fe, Zn, or other desirable micronutrients. Increasing micronutrient rich foods and improving dietary diversity will substantially reduce micronutrient disorders.Methods: A field experiment was conducted during the post rainy seasons of 2015, 2016 and 2017 at Zonal Agricultural Research Station, Kalaburagi, University of Agricultural Sciences, Raichur (Karnataka) to know the effect of soil and foliar fertilization of Zn and Fe on chickpea genotypes. Two genotypes (Annigeri 1 and JG 11) and six fertilization treatments (Control, 0.5% Zn, 0.1% Fe, Zn + Fe, seed treatment with 2 g Zn kg-1 seeds and soil application of Zn) were tested in medium black soils in split plot design with three replications.Result: The pooled data of three seasons indicated that the genotype JG 11, performed better than Annigeri 1 in terms of seed yield (1309 kgha-1), net returns (₹ 31634ha-1) and B: C ratio (2.52). On biofortification of Zn and Fe, foliar fertilization of Zn @ 0.5% + Fe @ 0.1% at flowering stage recorded significantly higher grain yield (1321 kgha-1), net returns (₹ 31179ha-1) and B: C ratio (2.44) over rest of the treatments. Further, foliar fertilization of Zn + Fe had significant influence on nutrient concentration (Zn and Fe) in chickpea grains. Thus, it could be concluded that combined biofortification of Zn + Fe to chickpea crop could be the viable agronomic intervention for getting higher productivity and nutritional security.

Biofortification of Forage Peas with Combined Application of Selenium and Zinc Under Mediterranean Conditions

Agronomic biofortification can be used to alleviate the deficient intake of selenium (Se) and zinc (Zn) by livestock. These two essential micronutrients for human and animals play an important role in many physiological functions and biological processes. The aim of the present study was to evaluate the suitability of forage peas, crop with an increasing importance as plant protein source, to be biofortified with a combined treatment of Zn (as ZnSO4-7H2O) and Se (as Na2SeO4). A 2-year field experiment was established in southern Spain under semiarid Mediterranean conditions, by following a split-split-plot design. The study year (2017/2018, 2018/2019) was considered the main-plot factor, soil Zn application (50 kg Zn ha−1, nil Zn) as a subplot factor, and foliar application (nil, 10 g Se ha−1, 8 kg Zn ha−1, 10 g Se ha−1 + 8 kg Zn ha−1) as a sub-subplot factor. The combined application of 50-kg soil Zn ha−1 and the foliar application of 10 g Se ha−1 + 8 kg Zn ha−1 was the most effective treatment to increase the concentration in forage of Zn and Se, 4-fold and 5-fold, respectively, as well as the Zn bioavailability, forage yield (close to 30%), and crude protein (~ 8%). Thus, forage peas could be considered a very suitable crop to be included in biofortification programs under Mediterranean conditions with Zn and Se as target minerals.

Zinc-Induced Effects on Productivity, Zinc Use Efficiency, and Grain Biofortification of Bread Wheat under Different Tillage Permutations

Zinc (Zn) deficiency is a global concern for human health and causes a decrease in crop production and nutritional characteristics. A two-year field study was planned to evaluate comparative effects of various Zn application approaches in bread wheat under plough tillage (PT) and zero tillage (ZT) system. Cultivation of wheat under ZT improved the soil organic carbon (17%), total soil porosity (11%), soil microbial biomass nitrogen (5%), and carbon (5%) in comparison to PT system averaged across the two years. Various efficiency indices were significantly influenced by Zn application methods during both years of experimentation. However, grain Zn contents were maximum with foliar-applied Zn in PT (31%) and soil-applied Zn under the ZT system (29.85%). Moreover, Zn use also enhanced the bioavailable Zn as lower phytate contents and phytate to Zn molar ratio were recorded. The highest bioavailable Zn was calculated for foliar (30%) and soil application (28%). Under both tillage systems, the maximum net benefits were obtained through Zn seed priming; nevertheless, ZT resulted in higher net benefits than PT due to low associated costs. In conclusion, Zn nutrition through different methods enhanced the productivity, profitability, and grain biofortification of wheat under PT and ZT systems.

Zinc from foliar-applied nanoparticle fertiliser is translocated to wheat grain: A 65Zn radiolabelled translocation study comparing conventional and novel foliar fertilisers

Foliar zinc (Zn) fertilisers can be used to supplement or replace soil applications of Zn in situations where soil properties may decrease the plant bioavailability of Zn. However, conventional foliar Zn formulations such as zinc sulfate can cause leaf damage due to the rapid release of high amounts of Zn2+ into leaf tissue which can be locally phytotoxic. Zinc oxide nanoparticles (ZnO-NPs) offer an alternative approach by providing a more sustained release of Zn into leaf tissue, and potentially avoiding the need for multiple applications. We compared the efficacy of ZnO-NPs and microparticles (ZnO-MPs) to that of conventional formulations (ZnCl2 and ZnEDTA) in wheat. This is the first study to use 65Zn radiolabelled formulations and gamma spectrometry to determine the translocation of Zn to the grains and subsequent efficiency of foliar-applied ZnO-NP fertilisers. We found that ZnEDTA was the most efficient fertiliser in terms of the proportion of applied Zn translocated to wheat grain. We also investigated the effect of Zn application rate on fertiliser efficiency. For all forms of Zn, when plants were treated with Zn at 750 mg/L or 75 mg/L, there were no significant differences in the concentration of applied Zn translocated to the grain. This suggests that current Zn application rates could be decreased while still maintaining the nutritional quality of grain. Finally, using photo-stimulated luminescence (PSL) autoradiography and synchrotron-based X-ray fluorescence microscopy (XFM) we showed that the grain distribution of foliar-applied Zn mirrors that of Zn derived from root uptake.

Effects of zinc application on cadmium (Cd) accumulation and plant growth through modulation of the antioxidant system and translocation of Cd in low- and high-Cd wheat cultivars

Cadmium (Cd) contamination is a big challenge for managing food supply and safety around the world. Reduction of the bioaccumulation of cadmium (Cd) in wheat is an important way to minimize Cd hazards to human health. This study compared and highlighted the effects of soil and foliar applications of Zn on Cd accumulation and toxicity in cultivars with high Cd accumulation (high-Cd wheat) and low Cd accumulation (low-Cd wheat). Both foliar and soil Zn applications provided effective strategies for reducing wheat grain Cd concentrations in the high-Cd wheat by 26–49% and 25–52%, respectively, and these also significantly reduced the concentrations in wheat stems and leaves. Foliar and soil Zn applications significantly reduced Cd in leaves and stems of the low-Cd wheat but had no effects on grain Cd. Both soil and foliar Zn applications significantly alleviated Cd toxicity by regulation of Cd transport genes, as reflected by the increased grain yield and antioxidant enzyme activity in the wheat tissues. Gene expression in response to zinc application differed in the two wheat cultivars. Down-regulation of the influx transporter (TaNramp5) and upregulation of the efflux transporters (TaTM20 and TaHMA3) in the high-Cd wheat may have contributed to the Zn-dependent Cd alleviation and enhanced its tolerance to Cd toxicity. Additionally, foliar Zn applications down-regulated the leaf TaHMA2 expression that reduced root Cd translocation to shoots, while soil Zn applications down-regulated the root TaLCT1 expression, which contributed to the reduction of root Cd concentrations. Soil (99 kg ZnSO4·7H2O ha−1) and foliar (0.36 kg ZnSO4·7H2O ha−1) Zn applications can effectively decrease the Cd in grains and guarantee food safety and yield, simultaneously. The presented results provide a new insight into the mechanisms of, and strategies for, using Zn for the Cd reduction in wheat.

Zinc (Zn) application methods influences Zn and iron (Fe) bioavailability in brown rice

In this study, we evaluated the possibility of increasing Zn and Fe bioavailability in twenty-six popularly grown rice cultivars by external application of Zn through soil and/or foliar means. A field experiment was conducted in an Inceptisol applying Zn through soil and/or foliar means and the harvested whole grains were processed to brown rice and subsequently analysed for Zn, Fe, phytic acid and crude protein contents. Native Zn concentration in the brown rice of those tested cultivars varied from 22.9 to 79.7 with a mean of 40.3 mg kg−1. Zn concentration in brown rice increased to the tune of 17 and 95% upon Zn application through soil and soil + foliar, respectively, over the control across the tested cultivars. Zn application further caused a decrease in the phytic acid/Zn molar ratio to the magnitude of 64.0 and 23.0% upon soil + foliar and sole soil application, respectively. The decrease in phytate/Zn molar ratio was higher in high yielding varieties followed by local varieties, aromatics and hybrids and thus increased the bioavailability of Zn in brown rice. An antagonistic effect was also observed on the iron content in brown rice upon application of Zn. The decrease in iron concentration in brown rice was higher with soil + foliar application than with only soil application of Zn. Zn application through soil + foliar over basal application could be a useful strategy to produce Zn dense grains and to reduce the phytate/Zn and phytate/Fe molar ratios and thus enhancing their bioavailability. Application of Zn fertilizers can also enhance crude protein content in brown rice.

Soil and foliar zinc application to biofortify broccoli (Brassica oleracea var. italica L.): effects on the zinc concentration and bioavailability

Agronomic zinc (Zn) biofortification of crops could help to alleviate dietary Zn deficiency, which is likely to affect more than one billion people worldwide. To evaluate the efficiency of agronomic Zn biofortification of broccoli, four application treatments were tested: no Zn application (control); soil application of 5 mg/kg ZnSO<sub>4</sub>·7 H<sub>2</sub>O (soil); two sprays (15 mL/pot each) of 0.25% (w/v) ZnSO<sub>4</sub>·7 H<sub>2</sub>O (foliar); and soil + foliar combination. Soil Zn application increased Zn-DTPA (diethylenetriamine pentaacetic acid) concentration by 3.7-times but did not affect plant growth or plant Zn concentration. Foliar Zn application increased stem + leaves and floret Zn concentration by 78 and 23 mg Zn/kg, respectively, with good bioavailability based on phytic acid concentration. Boiling decreased mineral concentration by 19%, but increased bioavailability by decreasing the phytic acid concentration. The entire broccoli could constitute a good nutritional source for animals and humans. An intake of 100 g boiled florets treated with the foliar treatment will cover about 36% of recommended dietary intake (RDI) of Zn, together with 30% of Ca, 94% of K, 32% of Mg, 6% of Na, 55% of P, 60% of S, 10% of Cu, 22% of Fe, 43% of Mn, and 35% of Se RDIs.

Zinc-biofortified wheat required only a medium rate of soil zinc application to attain the targets of zinc biofortification

ABSTRACT Zinc (Zn) deficiency is prevalent in human populations in developing countries. The present study compared two wheat (Triticum aestivum L.) cultivars [Jauhar-2016 (standard wheat) and Zincol-2016 (Zn-biofortified wheat)] for Zn biofortification with optimum soil Zn application. For this, Zn (at 0, 3, 6, 12 and 24 mg Zn kg−1) was applied to pots having an alkaline calcareous soil. Grain yield, grain Zn concentration and grain Zn bioavailability in both cultivars were significantly increased by Zn fertilization. However, Zn application decreased iron (Fe) and phytate concentration in grains of both cultivars. As compared to Jauhar-2016, Zincol-2016 had significantly higher grain Zn concentration and grain Zn bioavailability at all the respective soil Zn rates excepting only at control. At 6 mg Zn kg−1, Zincol-2016 attained in grains a desired concentration of Zn (53 mg Zn kg−1) and a desired level of human Zn bioavailability (2.8 mg d−1 for women and was 3.0 mg d−1 for men). Jauhar-2016 also attained such comparative levels but only at a plant toxic rate of Zn (24 mg Zn kg−1). Conclusively, soil Zn application (agronomic biofortification) to Zn-biofortified wheat (Zincol-2016) may be a promising approach to decrease human Zn deficiency in population groups dependent on wheat-based diets.

Residual effects of soil Zn fertilization on soil characteristics, yield and quality of Platycodon grandiflorum

ABSTRACT Zinc (Zn) deficiency is common worldwide and is a major limiting factor in the cultivation of Platycodon grandiflorum because most P. grandiflorum is cultivated on soils with slight or severe levels of Zn deficiency in China. To investigate the effects of soil Zn fertilization on P. grandiflorum and its residual effects on soil characteristics, a randomized complete block design was conducted at the experimental station of Shandong Agricultural University China in 2016–2018. In 2016, ZnSO4 · 7H2O was used as Zn fertilizer. The fertilizer levels of Zn fertilizer were designed as 0, 4, 6, 8 and 10 kg ha−1 and were denoted as CK, Zn4, Zn6, Zn8 and Zn10. No Zn fertilizer was used in 2017 and 2018. The results showed that soil Zn fertilization increased the quantity of soil bacteria, and actinobacteria, Zn8 and Zn10 treatments increased the soil fungal quantity in 2017, whereas the effect was observed only in the Z10 treatment in 2018. Soil Zn fertilization enhanced the activity of polyphenol oxidase, decreased that of phosphatase, and did not influence the invertase activity in both 2017 and 2018. Both the yield and the quality of P. grandiflorum in the succeeding three years increased due to the soil Zn fertilization in 2016. Overall, soil Zn application is a suitable approach to the cultivation of P. grandiflorum, and the residual effects of a one-time soil Zn fertilization could last at least two years.

Nutrition, yield and nutrient export in common bean under zinc fertilization in no-till system

ABSTRACT Zinc (Zn) is one of the most deficient plant micronutrients in agricultural crops. The objective of this study was to evaluate plant nutrition, grain yield and nutrient export rate in response to soil and foliar Zn fertilization in common bean (Phaseolus vulgaris L.). Two field experiments in no-till system were carried out using two common bean cultivars, BRS Esteio (black bean) and IPR Campos Gerais (Carioca bean). Treatments were composed of soil Zn application during sowing and foliar Zn spray at flowering stage. Soil Zn application had effect on leaf Zn concentration in IPR Campos Gerais and did not affect grain yield of both cultivars. Foliar Zn spray increased leaf Zn concentration by approximately two times in both cultivars, but negatively affected the grain yield in BRS Esteio. Leaf concentration of N, Ca and S were affected by soil Zn application and leaf concentration of Mn was affected by foliar Zn spray, while leaf concentration of P, K, Mg, Cu and Fe were not influenced by the soil and foliar Zn treatments. In treatments without Zn, the descending order of nutrient export rate from the experimental site was as follows: N > K > P > Ca ≈ S > Mg for macronutrients and Fe > Mn > Cu > Zn for micronutrients. Foliar Zn spray increased the export rate of Zn, P, Ca, Mg, S, Mn, Cu and Fe in IPR Campos Gerais, while soil Zn application resulted in higher export rate of P, K and Mn in BRS Esteio.

Soil and foliar zinc biofortification of broccolini: effects on plant growth and mineral accumulation

Millions of people have Zn-deficient diets, so Zn-biofortified crops could prevent such deficiency. The aim of this study was to evaluate the use of agronomic Zn biofortification of broccolini – a new hybrid crop variety derived from a cross between kalian cabbage and broccoli. Plants were grown in pots using a Zn deficient soil. Four fertiliser treatments were tested: (1) control; (2) soil application of 5 mg ZnSO4•7H2O kg–1 soil; (3) foliar application at the early flowering stage of 0.5% (w/v) ZnSO4•7H2O; (4) combined soil and foliar treatments. Florets were harvested in four sequential harvests. There was a decrease in both growth and leaf composition of Zn, Ca, Fe and Mg. Soil Zn application increased floret production. There were increases in the Zn concentration stem+leaves and florets of 12- and 2.5-fold in foliar and soil+foliar treatments respectively. PA:Zn molar ratios decreased under both foliar and soil+foliar treatments. Boiling reduced Zn concentration by 40%, along with a decrease of other mineral nutrients. A soil+foliar treatment can increase both plant growth and Zn concentration in broccolini, and boiled 100 g portion of biofortified florets fertilised at rates in this study would deliver ~49 mg Zn, a 46% increase than in the non-biofortified broccolini.

Health risk assessment of heavy metals (Zn, Cu, Cd, Pb, As and Cr) in wheat grain receiving repeated Zn fertilizers

Soil application of Zn fertilizer is an effective approach to improve yield and Zn accumulation in wheat grain. However, it remains unclear whether repeated Zn application can result in high accumulation of heavy metals (HMs) in soils and grains and thus represents a potential risk for human consumption. This study aimed to evaluate the health risk assessment of HMs in a wheat production system which had continuously received 8 years of Zn application at varying rates (0, 2.3, 5.7, 11.4, 22.7, 34.1 kg Zn ha−1). The results showed that Zn application significantly increased the soil total Zn concentration without affecting concentrations of As, Pb, Cd, Cu and Cr. Across Zn rates, Zn application increased grain concentrations of Zn, Pb and Cd by 75%, 51% and 14%, respectively, and reduced grain As concentration by 14%. The human health risk assessment revealed that the threshold hazard quotients for the individual HM were below 1, independent of Zn rates. The hazard index (HI) values at Zn rates of 11.4, 22.7 and 34.1 kg Zn ha−1 were significantly greater than that at null Zn treatment. Furthermore, exposures to As, Cu and Zn accounted for 97% of HI at all Zn rates. Analysis of the threshold cancer risk with Pb and As showed that ingestion of wheat grain even from highest Zn application rate wouldn’t bring the lifetime carcinogenic risk. In contrast, long-term Zn application significantly reduced the carcinogenic risk of As by 9.7–26.5%. In conclusion, repeated soil applications of Zn at optimal rate (5.7 kg Zn ha−1) didn’t cause health risk for Zn, Cu, Cd, Pb, Cr, and As, while improving productivity and grain Zn concentration of wheat to meet human recruitment. Our study highlights the importance of appropriate Zn fertilizer management in improving grain quality while reducing HMs risks from human consumption.