This is the third and the last part of the special issue on Mineral Biofortification and Metal/Metalloid Accumulation in Food Crops. A brief description of the research articles included in this part of the special issue is provided.

Zinc deficiency in plant and human are common. In this context, our study was hypothesised that the combine soil and foliar nano Zn (new technology) application may be a better strategy to improve zinc use efficiency, grain yield and biofortification of wheat. This manuscript indicates that soil Zn application along with 3 kg/ha of foliar nano Zn increased plant and grain zinc concentration and accumulation, dry matter, grain yield, Zn partitioning index and Zn intake in wheat.

Elemental selenium is generally water insoluble and not bioavailable for plant uptake. However, elemental selenium in nanoscale of 70–75 nm can be taken up by Canadian oat (Avena sativa L. cv. Saddle), and concentrations of selenium in oat tissues increased with an increasing treatment level of nanoscale elemental selenium in the soil. Compared with the control, the soil treatments with nanoscale elemental selenium at 1–10 mg/kg significantly enhanced the oat grain yield.

Agronomic biofortification is a promising approach to alleviate zinc and iron malnutrition in human beings. The combined soil/foliar application of zinc and nitrogen, iron and nitrogen, and zinc, iron and nitrogen leads to enhanced nutrient concentrations in edible parts of crop plants. This approach not only improves the micronutrient (zinc and iron) concentration but also the economic yield, and thus, is a win–win situation for growers as well as consumers.

Nitrogen can affect the uptake of some microelements and their joint application can preserve forage yield and replenish the necessary minerals in the animal diet. This study has confirmed that the fertilisation of silage maize (Zea mays L.) with N and Se plus Zn could be an important tool in achieving such requirements. Crop biofortification is important due to the increase of essential mineral content in the animal diet, and indirectly human diet through the enrichment of the food chain.

The effectiveness of agronomic biofortification with selenium may depend on methods and rates of application; and these factors may also influence residual effects on succeeding crops. We studied different methods for applying Se for biofortification of common bean and assessed residual effects of soil Se additions on Mombaça grass. The biofortification efficacy varied among the assessed Se addition methods. Se-enriched fertilisers showed residual effects, since they were efficient for increasing Se contents in Mombaça grass grown in the second experiment without Se application.

Green manuring and elemental sulfur (S) fertilisation is an innovative approach for biofortification of cereal grain cropping system. Sunhemp green manuring increased Zn and Mn by 11%, Fe by 18% and Cu by 17% in basmati rice grain compared with fallow (no green manuring). Sulfur applied at 40 kg ha⁻¹ to basmati rice and durum wheat increased grain Zn, Fe, Cu and Mn as well as grain yields in both crops compared with a no-S (control).

Strategies are needed to improve zinc (Zn) nutritional quality of wheat, to increase dietary intake within the human population. Therefore, we hypothesised that inoculations of different diazotrophic bacteria might have synergetic relationships with soil Zn application, in relation to plant and grain concentrations, growth, yield, ZnUE and daily intake of biofortified wheat grains. We verified that agronomic biofortification of staple food with 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.

A deficient intake of zinc and selenium, essential micronutrients with antioxidant, anti-cancer and anti-viral properties, is common in humans and livestock worldwide. This deficiency can be alleviated by agronomic biofortification, a practice that increases their concentrations in edible parts of crops through mineral application. The present study has demonstrated the suitability of field peas to be biofortified under Mediterranean conditions, since the Zn and Se combined application produced an enriched grain in these nutrients and a higher grain yield.

Zinc (Zn) deficiency in basmati rice grown under submerged conditions leads to decreased crop yields and nutritional quality. Application of Zn increased grain and straw yield in basmati rice and improved Zn content and uptake in plants grown in Zn-deficient soil. Zn application at 10 kg ha⁻¹ was the best treatment to attain high yield and maximum profit in a Zn-deficient soil.

Selenium is an essential element for humans and animals. This study reports on the enrichment of selenium in rocket plants and the results showed that when selenium is added as selenate, the plants accumulate high amounts of selenium. Although further research is needed to optimise the selenate application rate so as to avoid leaching and subsurface water contamination, it seems feasible to produce a vegetable of high nutritional value for human consumption without negatively affecting the environment.

Iron (Fe)-deficiency in cereal crops is causing worldwide malnutrition and many metabolic disorders such as anaemia in human. Along the low accumulation of Fe in cereals, heavy metals i.e. (Cd, Pb, Hg etc) contamination in agricultural soils are transferring to humans, causing more adverse impacts on human health sustainability. We review recent advances in biofortification approaches; i.e. agronomic, transgenic and genetic approaches, while simultaneously addressing Fe biofortification and heavy metals mitigation in food chain for sustainable living.

Continuous use of inorganic phosphate fertilisers (iPFs) adversely affects soil fertility, reduces plant phosphorus-use efficiency, increases soil heavy metal concentrations, and poses severe human health risks. This article summarises the potential of organic amendments (OAs) over iPFs to stimulate plant growth and yield, increase phosphorus availability in soil, and reduce plant heavy metal uptake by immobilising them in soil. This summary will contribute towards organic farming and sustainable agricultural practices.

Lead is a toxic element that inhibits the growth and development of plants and causes mutations in DNA. In this study, the effects of Halopteris filicina extract on tolerance to lead stress in tomato plants were determined by measuring changes in chlorophyll content, root and stem length and DNA stability. Depending on the lead concentration, H. filicina extracts were found to reduce lead uptake and oxidative stress.

The recent increasing trend of industrialisation has imposed heavy metal pollution that has affected crop productivity worldwide. Understanding the physiological and molecular mechanism through omic approaches is a prerequisite to improve the target mechanism in crops, which is still lacking. The present manuscript emphasises the current understanding of physiological and molecular mechanisms and proposes an integrated omic study to improve the sustainability of crop production.

Durum wheat (Triticum durum Desf.) has great genetic diversity and is widely used in human diets but has the potential to accumulate Cd, which has significant adverse effects on human health. We assessed 130 durum wheat accessions phenotypically and using three different molecular markers. Results showed that utilisation of appropriate molecular markers will reduce the time and cost for grain Cd evaluation, and will allow durum breeders to accelerate progress to select genotypes with desired alleles.

Iron (Fe) is an essential nutrient for all organisms, but it can be toxic as a heavy metal when in excess. This work was conducted to evaluate morpho-physiological responses of fenugreek to high doses of Fe. Antioxidant enzymes were enhanced to detoxify reactive oxygen species activity produced under Fe stress. High-performance liquid chromatography phenol analysis showed a production of special compounds under Fe stress. We conclude that fenugreek is an accumulator plant that uses multiple mechanisms to adapt to Fe stress.

Heavy metals can cause several damages in physiology and nutrition of legumes plants. Our work showed that cadmium and lead induced a diminution of growth and a perturbation of physiological and biochemical process. Moreover, lead was shown less harmful to fenugreek. On the other hand, legumes could be used in the phytostabilisation process in polluted soils. Lead is more accumulated in the roots than cadmium, and then it is more suitable to be used for remediation of Pb-polluted soil.