Rice–wheat cropping systems feed millions of people in South and East Asia. However, cereal-based foods are inherently deficient in micronutrients. A strategy involving green manuring and elemental sulfur (S) fertilisation is an innovative approach for biofortification by enhancing bioavailability of micronutrients. We conducted an experiment with a basmati rice (Oryza sativa L.)–durum wheat (Triticum durum Desf.) cropping system that comprised main plot treatments of two green manure crops, Sesbania aculeata Pers. (prickly sesban) and Crotalaria juncea L. (sunhemp), and a fallow. Sulfur as bentonite-S (90% S) was applied in subplot treatments of 20 or 40 kg S ha⁻¹ to rice, 20 or 40 kg S ha⁻¹ to wheat, and 20 or 40 kg S ha⁻¹ to both rice and wheat, with a control (no S fertilisation). There were three replications in a split-plot design. Results showed that micronutrient concentrations and their uptake were in the order iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu) in both grains and straw of basmati rice and durum wheat. Compared with fallow, sunhemp green manuring increased Zn and Mn by 11%, Fe by 18% and Cu by 17% in basmati rice grain, and Zn by 21%, Mn by 8%, Fe by 12% and Cu by 8% in durum wheat grain. Compared with the no-S control, fertilisation at 40 kg S ha⁻¹ to both rice and wheat increased Zn by 30%, Fe by 33%, Cu by 23% and Mn by 24% in basmati rice grain, as well as rice grain yield by 10%. The same treatment increased Zn by 42%, Fe by 27%, Cu by 9% and Mn by 18% in durum wheat grain, as well as wheat grain yield by 26%. Thus, green manuring and addition of 40 kg S ha⁻¹ to both rotation crops is an effective strategy to ensure biofortification.

Zinc (Zn) deficiency in basmati rice grown under submerged conditions leads to decrease in yield and nutritional quality. Fertilisation with Zn is a cost-effective and rapid way to increase crop productivity with Zn-enriched grain. A field experiment was conducted with five Zn levels (0, 5, 10, 20 and 40 kg ha⁻¹) for two consecutive years to assess the effects of Zn fertilisation on yield, Zn content and accumulation in basmati rice grown in a Zn-deficient soil. Maximum grain and straw yields were measured with Zn application of 40 kg ha⁻¹, although statistically similar to yields with applications of 10 and 20 kg Zn ha⁻¹. Increases in average yield compared with the control varied from 14.8% to 27.7% for grain and from 20% to 33.5% for straw with Zn application treatments. Accumulation of Zn in basmati rice grains was highest with Zn application of 40 kg ha⁻¹, although not significantly different from accumulation with 10 and 20 kg Zn ha⁻¹. Indexes of Zn use efficiency were as follows: agronomic efficiency 21–88 kg kg⁻¹, physiological efficiency 6.93–7.39 t kg⁻¹, grain physiological efficiency 14.95–15.21 t kg⁻¹, apparent recovery efficiency 0.97–4.19%, and utilisation efficiency 6.7–31.0 t kg⁻¹. All of these were higher at lower Zn levels and decreased at increasing levels of Zn. The highest benefit–cost ratio occurred with Zn application of 10 kg ha⁻¹. Therefore, we conclude that Zn application of 10 kg ha⁻¹ was the best treatment in terms of high grain yield, maximum benefit–cost ratio, and Zn accumulation in a Zn-deficient soil.

ContextIron (Fe) is considered as a major cause of rural Tunisian soil contamination. Developing strategies for the cultivation of accumulator plants with permissible iron (Fe) concentrations is an urgent challenge.

AimsIn this study, the effects of FeSO₄ concentration (0, 50, 500 and 1000 mg L⁻¹) on fenugreek morpho-biochemical parameters were investigated.

MethodsThe use of fenugreek as a phytoremediation strategy to control not only the uptake of Fe but also its safe consumption after treatments was evaluated.

Key resultsResults showed that elevated Fe concentrations did not affect the germination rate, but, rather, decreased the radicle length and amylase activity. The elemental analysis showed that Fe uptake was higher in shoots than in roots, but lower in harvested seeds. The translocation factor was higher than 1, suggesting a safe use of fenugreek as an accumulator. Moreover, the increase in Fe concentrations reduced the chlorophyll content and enhanced the production of lipid peroxidation, hydrogen peroxide and superoxide dismutase more frequently on fenugreek shoots than on their roots. In turn, the maximum concentrations of flavonoids and phenols were recorded under the Fe concentration of 50 mg L⁻¹. High-performance liquid chromatography analysis showed that the gallic and syringic acids were the major phenols produced under Fe stress in shoots and that 50 mg L⁻¹ of added Fe concentration induced their elevation. However, the quercetin was detected only in roots and was reduced under the increasing Fe concentrations.

ConclusionsThese results showed that fenugreek is an accumulator plant with admissible concentrations of Fe accumulation, which deploys multiple mechanisms to adapt to Fe stress.

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.

Lead is a toxic element that accumulates in agricultural soils through various anthropogenic sources. It inhibits the growth and development of plants and causes mutations in DNA. Macroalgae such as Halopteris filicina contain multifunctional components that may improve plant tolerance to lead stress. In this study, seeds of tomato (Solanum lycopersicum) were subjected to six treatments comprising two levels of lead exposure (60 or 120 μM PbCl₂) with or without H. filicina extract (0.5% in distilled water), a distilled water control, and a positive control (H. filicina extract) for 7 days. Physiological responses were investigated. Seedlings that had been treated with 60 and 120 μM PbCl₂ without H. filicina extract showed root growth reduction of 55% and 68.6%, respectively, relative to the control, whereas for 60 and 120 μM PbCl₂-treated seedlings with H. filicina extract applied, the reductions in root growth were lower, at 27.44% and 50.51%. The seedling viability index was decreased by 68.14% at 120 μM PbCl₂ application without H. filicina extract, whereas a 42.48% reduction was recorded for 120 μM PbCl₂-treated seedlings with H. filicina extract applied. Moreover, PbCl₂ accumulation resulted in a decrease in leaf pigment content. Leaf pigment content was high in plants receiving the H. filicina extract. The rate of lipid peroxidation caused by PbCl₂ was reduced with application of H. filicina extract. Genomic template stability was determined by using the inter simple sequence repeat-PCR technique, which revealed a decrease in DNA stabilisation with an increase in lead accumulation. However, this was alleviated by application of H. filicina extract. Our findings indicate that H. filicina extract both stimulates plant growth and protects from toxic effects by reducing accumulation of metals in the cell.

Agronomic biofortification of staple food with zinc (Zn) in combination with diazotrophic bacteria is one sustainable and feasible strategy to improve plant nutrition, nutrient use efficiency and production and combat Zn malnutrition in human beings. Wheat (Triticum aestivum L.) is a staple food of the global population and has a prospective role in agronomic Zn biofortification. In this context, the effect of diazotrophic bacterial inoculations in seeds (no inoculation – Control, Azospirillum brasilense, Bacillus subtilis and Pseudomonas fluorescens) in association with soil Zn application (without (0) and 8 kg/ha) was evaluated on Zn nutrition, growth, yield and Zn use efficiencies in wheat in the 2019 and 2020 cropping seasons. Soil Zn application in combination with P. fluorescens improved Zn concentration in the leaf (38.8 and 45.9%), shoot (25.0 and 31%) and grain (34.0 and 33.3%) with greater shoot dry matter (9.4 and 9.9%) and grain yield (20.3 and 20.6%) as compared to controls in 2019 and 2020 respectively. Also, inoculation of P. fluorescens with Zn application improved Zn shoot and grain accumulation, zinc use efficiency, recovery and utilisation efficiency. With daily wheat consumption, these improvements would be associated with a with higher estimated Zn intake for the human population globally and within Brazil. However, agro-physiological efficiency was increased with inoculation of Bacillus subtilis. Therefore, inoculation of P. fluorescens in association with soil Zn application is recommended for agronomic biofortification, and to increase productivity and Zn use efficiencies in wheat in the tropical savannah of Brazil.

ContextAgronomic biofortification of wheat (Triticum aestivum L.) with zinc (Zn) is an effective approach to increase grain Zn concentration and productivity and alleviate Zn malnutrition in humans. Foliar Zn application is an alternative strategy to endorse soil Zn deficiency with better grain Zn partitioning.

AimsThis study aimed to better understand dose management of soil and foliar Zn application in wheat for biofortification.

MethodsThe objectives was to evaluate the effect of foliar applied nano Zn doses (0, 0.75, 1.5, 3 and 6 kg/ha (zinc oxide, ZnO) 50% at tillering and 50% at grain filling in combination) with soil Zn application (0 and 8 kg/ha, as zinc sulfate) on growth, nutrition, Zn use efficiencies, intake and yield biofortification of wheat in 2019 and 2020 under Brazilian savanna.

Key resultsCombined foliar and soil Zn application increased shoot and grains Zn concentration and accumulation with greater dry matter (9.8 and 10.6%) and grain yield (9.8 and 11%) of wheat as compared to control in 2019 and 2020 respectively. Zinc use efficiency (ZnUE), Zn utilisation efficiency and applied Zn recovery improved with soil Zn application and 2.5 kg/ha foliar nano Zn, but decreased with further increase in foliar Zn application. Zn sulfate stood out for increasing crop productivity while foliar spray with nano Zn for better grains biofortification of wheat.

ConclusionsSoil Zn application along with 3 kg/ha of foliar nano Zn increased plant and grains Zn concentration and accumulation, dry matter, grain yield, Zn partitioning index and Zn intake in wheat in tropical conditions of Brazil.

ImplicationsThe combined application of soil and foliar Zn in harsh tropical savannah condition could better improve Zn nutrition, crop growth, and productivity with better Zn biofortification and intake of wheat.

Development of selenium (Se)-enriched agricultural products can increase human daily dietary Se intake in Se-deficient areas. Canadian oat (Avena sativa L. cv. Saddle) is one of the common cereal grains in the world. Previous studies have shown that Se accumulation in oat can be significantly affected by soil Se, but few have dealt with different chemical forms of Se, including emerging nanoscale elemental Se particles (SeNPs). Because SeNPs have unique chemical and physical properties in comparing with bulk elemental Se, this laboratory study determined the effects of soil SeNP treatments of 0, 1, 5, and 10 mg/kg on Se bioconcentration in oat grain, compared with bulk elemental Se or selenate (Na₂SeO₄). The results showed that the soil SeNP treatments significantly increased Se concentrations in oat grain with an increase in the treatment level from 1 to 10 mg/kg (P < 0.05). The distribution of Se accumulated in oat tissues followed a descending order of root and grain > husk > stem and leaf. While the grain yield was reduced with the higher soil selenate treatments of 5–10 mg/kg, the soil SeNP treatment of 1–10 mg/kg significantly enhanced the oat grain yield, compared with the control. Concentrations of Se in oat grains in the soil SeNP treatments were approximately 7–20-fold higher than were the concentrations of those in the soil bulk elemental Se treatments, but were about 7–26% of the concentrations in oat grains in the soil selenate treatments. This study demonstrated that nanoscale elemental Se particles could be used for development of soil Se-amended fertilisers for Se-biofortified oat.

Recent industrialisation has seen an alarming increase in heavy metal pollution, raising the question of how to sustain food production in the presence of heavy metals. Several reviews have addressed the direct and indirect effects of heavy metals on crop physiological and biochemical processes. However, understanding of the physiological and molecular mechanisms requires integrating omic approaches to explore the target mechanism in general in crops, and those insights are still lacking. To date, most of the information related to omic approaches about heavy metals has been sparse and sporadic. This review, by means of examples, attempts to integrate different available proteomic, transcriptomic and genomic approaches in a nutshell along with underlying physiological and molecular mechanisms occurring in crops. Major identified transcription factors (TFs) (MYBs, WRKYs), transgenes (MT2, Nramp6, GSTU3, CIPK, MYB1 and DRE), up-regulated (CAT, SODs, POD and APX), down-regulated (ATPase subunits, Rubisco subunits and photosystem I (PSI) reaction centre) proteins, and miRNA (miR397, miR398a, miR408, OsmiR601 and miR166) for major heavy metals have been summarised. It provides a mode of action of heavy metals and their fate inside the plant. It also elucidates how these omics approaches facilitate in mitigating heavy metal stress and could help in addressing crop tolerance based on these mechanisms. Identifying donors with the aid of novel omic approaches could be useful for the development of HM tolerant crops, promoting future sustainability in heavy-metal-polluted soil and water resources.

Cadmium (Cd) is a non-essential heavy metal having toxic effects on all living organisms. Durum wheat (Triticum durum Desf.) is widely used in human diets but has the potential to accumulate Cd. It also has a high level of genetic diversity, which may be exploited to develop cultivars with low Cd content. We aimed to perform marker-assisted selection and validate previously identified Cd markers in durum wheat germplasm for use in the investigation of accessions that accumulate low grain Cd content. We assessed 130 durum wheat accessions phenotypically and using three different molecular markers. Grain Cd contents of the studied germplasm varied 4.91-fold (26.2–128.7 μg/kg) with an average of 58.2 μg/kg. Landraces showed lower average values of grain Cd content than cultivars. Three molecular markers (usw47, Cad-5B and KASP marker Cad-5B) were used to differentiate high and low Cd accumulating lines. Results showed high correlation and successfully classified the accessions to the expected high or low Cd level; 87 accessions showed the low Cd alleles, and 43 accessions the high Cd alleles, except for five accessions with the usw47 marker that showed heterozygous status. A significant correlation coefficient (r = 0.944*) was observed among the three molecular markers. Based on molecular markers, 96.2% of the accessions were classified accurately. The KASP assay was highly effective in successfully separating low from high Cd content accessions and could be used as a molecular tool in durum wheat breeding programs, with less cost and time, targeting reduced grain Cd levels. The results of this study will allow durum wheat breeders to accelerate their progress to select suitable genotypes with the desired alleles.

Context. Maintaining food and nutritional security for the ever increasing population of the world is a great chllenge. Zinc and iron are important micronutrients for both human health and plant growth. Insufficient intake of these micronutrients leads to their deficiency in human body which causes morbidity and mortality in different age groups of poor populations in developing countries.

Aims. Therefore, agronomic biofortification is considered the most promising approach to alleviate zinc and iron malnutrition in developing countries.

Methods. The studies reviewed in this article clearly show that the combined application of zinc and nitrogen, iron and nitrogen, and zinc, iron and nitrogen to the soil or to the foliage during the reproductive phase leads to enhanced nutrient (zinc and iron) content in edible parts of crop plants. This happens as the remobilisation and translocation of zinc, iron and urea are governed by the same genetic pathways inside the plant.

Key results. The soil/foliar application of micronutrients (zinc and iron) along with nitrogen (mainly through urea) improves not only the micronutrient (zinc and iron) content in edible parts of the crop plants but also the crop productivity, and thus, is a win–win situation for growers as well as consumers.

Conclusions. Foliar application of urea at 1–2% along with zinc or iron or both during the reproductive phase has been found more effective for biofortification point of view.

Implications. This article reviews the effects of zinc and iron application in combination with nitrogen on agronomic biofortification in important field crops.

Context. Agronomic biofortification is recognised as being an important strategy to increase selenium (Se) contents in food crops. The effectiveness of agronomic biofortification may differ depending on the methods of how Se is applied in agricultural systems.

Aims. This study aimed to evaluate different Se application methods (involving Se addition in the soil via Se-enriched fertilisers and foliar Se application) and rates for biofortification of common bean and to assess residual effects of soil Se additions for biofortification of Mombaça grass grown after the common bean.

Methods. Both experiments were carried out in a greenhouse. In the first cultivation (common bean), Se (as sodium selenate) was added at 0.0, 0.2, 0.4, 0.6, and 0.8 mg/dm³ using six different methods, as follows: Se-enriched monoammonium phosphate, Se-enriched urea, Se-foliar application, Se-enriched monoammonium phosphate + Se-enriched urea, Se-enriched monoammonium phosphate + Se-foliar application, and Se-enriched urea + Se-foliar application. To evaluate the residual effects of soil Se additions, Mombaça grass plants were grown after the common bean (second cultivation) without additional Se supply.

Key results. Agronomic biofortification effectiveness varied among methods, with higher Se contents in common bean grains being found when Se-enriched urea, Se-foliar application, and the combination of both methods were applied.

Conclusions. Selenium addition methods via soil using fertilisers as carriers to add Se, including Se-enriched monoammonium phosphate, showed a potential of residual effects on succeeding crops since these methods were efficient for increasing Se contents in Mombaça grass shoots.

To investigate the potentiality of Eruca sativa (rocket) to be enriched in selenium (Se) and, thus, to promote human health through consumption, a pot experiment was designed. Two rates, 5 and 10 mg/kg soil, of either selenite or selenate sodium salts were applied to appropriate pots, each filled with 1 kg of calcareous soil. Rocket seedlings were transplanted and grown in these pots, and to half of the pots the biostimulant Actiwave was added. Twelve weeks later, the plants were harvested and Se concentrations determined in shoots and roots. Plant growth characteristics were measured and plants biometrics were assessed by soil plant analyses development (SPAD), normalised difference vegetation index (NDVI) and normalised difference red edge (NDRE). Sulfur (S) and phosphorus (P) concentrations in plant samples were also determined to discuss possible interactions among the three elements. The highest Se concentration of 1070.5 mg/kg dry weight (DW) was observed for the high selenate rate without biostimulant, placing rocket in the group of Se hyperaccumulator plants. Toxic effects were recorded for the plants that received the high selenate rate, whereas no toxicity symptoms were observed for either selenite rate. According to Se concentrations in controls, biostimulant application significantly suppressed Se uptake and significantly increased S and P uptake. The same negative biostimulant effect on Se concentration in plants was clear in selenate treatments. When the results were expressed as total uptake (mg/pot), positive correlations among Se, S and P were found for selenate treatments, whereas for selenite treatments, the opposite was observed. Impressively, 1.6 mg Se/pot on a DW basis was accumulated in rocket shoots in the low selenate-rate without biostimulant treatment, corresponding to approximately 30% of the added 5 mg of selenate.

Context. Heavy metal contamination of soils is a serious environmental problem worldwide. Cadmium (Cd) and lead (Pb) are considered among the most important types of pollutants.

Aim. To investigate the response of a local fenugreek cultivar against lead and cadmium.

MethodsPhysiological changes were studied under different concentrations (0, 100, 200, 300 and 400 μM) of PbCl₂ and CdCl₂.

Key results. Fenugreek growth decreased gradually with increasing Cd and Pb supply. This decrease was accompanied by a gradual decline in shoot and root length and photosynthetic parameters. However, Cd treatments showed pronounced effects in fenugreek seedlings as compared to Pb. The tolerance index was between 0.41 and 0.81, which suggests relative tolerance of this cultivar to Pb and Cd. This species was also able to maintain stable water status. Nevertheless, in presence of high Cd concentration (400 μM), this species showed substantial decrease in CO₂ assimilation (86%), transpiration rate (87%), stomatal conductance (57%), chlorophyll content (35%) and carotenoid content (53%). Shoot proline content was increased significantly under 200 and 300 μM Cd, and slightly under 100 and 200 μM Pb. Furthermore, Cd and Pb induced a decrease in shoot magnesium and phosphorus content. Conversely, shoot iron content was increased. Data showed that fenugreek accumulated Cd, and translocated to the harvestable parts (up to 20 mg/kg DW under 400 μM). However, Pb was mostly accumulated in roots.

Conclusions. Our results revealed that the relative tolerance of fenugreek to Pb excess was coupled to a remarkable accumulation of this element in root, which favourite the phytostabilisation process.

Implications. FM, FL, SJ and OTZ execute the manipulation and the culture of plants. FM, OTZ, IN and KZ analyse and examine obtained results. FM, OTZ and KZ write and preparethe manuscript. IN, HM and KZ prepare the conception and the realisation ofthis work.

Context. Cadmium (Cd) toxicity and zinc (Zn) deficiency are of major concerns for crop growth and quality. Moreover, their interactive effects exert some controversial reports.

Aims. The effects of zinc oxide nanoparticles (ZnO NPs) and Cd on growth, physiology, and metal distribution in mung beans (Vigna radiata L.) was investigated.

Methods. Seven-day-old seedlings were treated with Zn (0, 1, 2, 4, 8, 16 and 32 μM) and Cd (0, 0.5, 1 μM) for 14 days.

Key results. Photosynthetic pigments, antioxidant enzyme activities, dry matter yield and metal concentration in tissues were significantly influenced by ZnO NPs and Cd. Considered on its own as a main effect, Zn application (16 μM) enhanced its accumulation in roots, stem and leaf by about 33-fold (314 mg kg⁻¹), 10-fold (60.6 mg kg⁻¹) and 17-fold (110.8 mg kg⁻¹), respectively, compared to control. However, accumulation was slower for interactions with Cd. While leaf Zn increased approximately 27 times (180 mg kg⁻¹) at 32 μM Zn, its interactions with lower and higher Cd increased only 6-fold (41.2 mg kg⁻¹) and 3-fold (21.4 mg kg⁻¹), respectively. Added ZnO NPs up to 4 μM under Cd contamination elevated the leaf Cd, which was restricted by higher supply. However, Cd accumulation in stem and root consistently rose, indicating a synergistic effect. ZnO NPs induced an upregulation of antioxidant enzymes to avert oxidative stress and maintain growth performance.

Implications. These findings may be suitable for formulating nanomaterials of desired particle sizes and testing on other crop to remediate Cd.

The intake of zinc (Zn) and selenium (Se), two essential micronutrients, is deficient worldwide both in humans and in livestock. This deficiency could be alleviated through agronomic biofortification, a practice that increases their concentrations in edible parts through mineral application. The aim of the present study was to evaluate in a 2-year field experiment (2017/18, 2018/19) the suitability of field peas to increase Zn and Se grain concentration after soil Zn application (50 kg Zn ha⁻¹; no Zn) and foliar application (0; 10 g Se ha⁻¹; 8 kg Zn ha⁻¹; 10 g Se ha⁻¹ + 8 kg Zn ha⁻¹). Zinc bioavailability (estimated by the molar ratio phytate/mineral), grain yield, thousand grain weight, grain crude protein and mineral status (magnesium, calcium and iron) of the grain were also evaluated by following a split-split plot design. For biofortification purposes, the combined foliar application of Zn (8 kg Zn ha⁻¹) and Se (10 g Se ha⁻¹) increased Zn and Se concentrations in grain by around 30% and 73%, respectively, as well as Zn bioavailability, decreasing the molar ratio phytate/Zn by 30%. The additional soil application of 50 kg Zn ha⁻¹ increased grain yield by 16%. Other nutritional parameters, such as content of protein or other essential minerals, were also improved (or at least not negatively affected) by the combined application of Zn and Se. All of these aspects evidenced the suitability of field peas for use in biofortification programmes through the simultaneous application of Zn and Se, which might also cheapen application costs.

Repeated and excessive use of inorganic phosphorus fertilisers adversely affects soil fertility, reduces plant phosphorus (P)-use efficiency, increases soil heavy metal concentrations and poses human health risks via food chain interaction. Organic amendments (OAs) are considered as cost-effective and environment-friendly supplement to inorganic P fertilisers that are produced from scarce phosphate rocks. Numerous studies have reported the synergistic and antagonistic effects of OAs on crop production, P solubility and availability, and immobilisation of heavy metals. However, the results of these studies are found to be variable and demand a critical review. This article summarises the environmental and health implications of continuous inorganic P fertilisers application along with a detailed overview of commonly available OAs and their efficacy to stimulate plant growth and yield. Moreover, this review describes the potentiality of OAs to increase the bioavailability of P in soil, discusses how and to what extent these soil amendments can immobilise heavy metals and reduce plant uptake, and finally provides future research directions for organic farming and sustainable agricultural practices.

Context. Biofortification of forage crops has become even more important, due to the improvement in livestock nutrition, but it has also had an indirect positive impact on the human diet.

Aim. This study investigated the effect of nitrogen and microelement (Zn and Se) fertilisation on yield and on the microelement composition of maize (Zea mays L.) silage.

Methods. Two field experiments were conducted using a two-factorial split-plot design with nitrogen fertilisation in three doses: 0, 120, 180 and 240 kg N/ha. The first experiment included foliar Zn fertilisation as the second factor (0, 1.5 kg Zn/ha and 1.5 kg Zn/ha + urea solution). The second experiment studied the effect of Se (10 g Se/ha).

Key results. Nitrogen fertilisation increased biomass yield, Cu and Mn concentration in silage maize. Application of Se and Zn did not affect the biomass yield, but it had a positive effect on Se and Zn concentration in plants. Zn and urea application in combination proved to be more efficient in increasing Zn concentration in plants when compared to Zn applied alone.

Conclusions. Nitrogen and fertilisation with Zn and Se can be a good tool in fodder plant biofortification because their application led to a yield increase (Zn), but at the same time to an improvement in the mineral composition of maize biomass, with essential elements (Zn and Se).

Implications. Although biofortification with 1.5 kg Zn/ha has achieved the concentration in maize biomass that can meet the nutritional needs of dairy cows, further research is needed to examine the adjuvant doses and forms of Zn to obtain high yields and Zn concentration in forage crops.

Biofortification of micronutrients, particularly of the iron (Fe) in cereals, is a viable, attractive, and sustainable strategy to cope with malnutrition as cereals are the major staple diets, particularly in developing countries. Increased concentrations of heavy metal/(loid)s (HMs); i.e. cadmium (Cd), lead (Pb), arsenic (As) etc. in agricultural soils is an increasing and serious challenge, posing severe health problems through food chain contamination. Accumulation of HMs in plants is challenging and contrasts to the development of biofortification strategies to combat micronutrient deficiencies. Agricultural biofortification strategies aim to increase plant uptake of mineral nutrients from soil and the translocation/storage of micronutrients to edible portions of cereal grains. However, it also means that any strategy to increase the uptake of Fe in plants may result in increased uptake of other toxic HMs. Therefore, the issue of HM contamination in cereals needs further understanding. This review describes the advancements in Fe biofortification strategies and the conflicting issue of HM accumulation in the grain of cereals.