Agronomic Biofortification Research Articles

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.

Agronomic Biofortification to Fight Zinc Malnutrition

Agronomic Biofortification to Fight Zinc Malnutrition

Agronomic Biofortification of Zinc in Pakistan: Status, Benefits, and Constraints

Micronutrient malnutrition (e.g., zinc) is one of the major causes of human disease burden in the developing world. Zinc (Zn) deficiency is highly prevalent in the Pakistani population (22.1%), particularly in women and children (under 5 years) due to low dietary Zn intake. In Pakistan, wheat is the primary staple food and is poor in bioavailable Zn. However, the number of malnourished populations has decreased over the last decade due to multiplied public awareness, accelerated use of Zn fertilizers (particularly in wheat and rice), initiation of several national/international research initiatives focusing on Zn biofortification in staple crops and availability of supplements and Zn fortified meals merchandise, nonetheless a large number of people are facing Zn or other micronutrient deficiencies in the country. There are few reports highlighting the significant increase in daily dietary Zn uptake in population consuming biofortified wheat (Zincol-2016) flour; indicating the positive prospect of biofortification interventions up scaling in lowering the risk of dietary Zn deficiency in rural and marginalized communities. Zinc fertilizer strategy has not only helped in enhancing the grain Zn concentration, but it also helped in improving crop yield with high economic return. In addition, Zn biofortified seeds have exhibited strong inherent ability to withstand abiotic stresses and produce higher grain yield under diverse climatic conditions. However, there are many constraints (soil, environment, genetic diversity, antinutrients concentration, socioeconomic factors etc.) that hinder the success of biofortification interventions. This review highlights the status of Zn deficiency in Pakistan, the success of agronomic and genetic biofortification interventions. It also discusses the economics of agronomic biofortification and cost effectiveness of Zn fertilization in field conditions in Pakistan and the potential of Zn biofortified seeds against abiotic stresses. Furthermore, it also highlights the constraints which limit the sustainability of biofortification interventions.

Improving Grain Micronutrient Content of Durum Wheat (Triticum turgidum var. durum) through Agronomic Biofortification to Alleviate the Hidden Hunger

Improvement of durum wheat grain quality through agronomic biofortification becomes a priority research area and an effective route to combat malnutrition. An experiment was conducted to evaluate the effect of micronutrient application to different varieties of durum wheat and seeding rate on final harvest grain quality under different growing locations. The treatments were arranged in split-split plot design where the varieties were assigned in the main plot, micronutrients into the subplots, and seeding rate into the sub-subplots. Each variety was sown at four levels of seeding rates and treated with ZnSO₄ and FeSO4 applied foliarly, both at a rate of 25 Kg ha−1 during flowering. Micronutrients were applied in the form of ZnSO₄ 7H2O and FeSO₄ 7H2O. The study confirmed that application of 25 Kg ha−1 ZnSO₄-containing fertilizer has increased mineral content from 33.04 mg Kg−1 to 56.73 mg kg−1. The tested durum wheat varieties significantly differ in their capacity to accumulate grain Zn and Fe concentrations. Higher amount of Zn (20 mg kg−1) and Fe (10 mg kg−1) were accumulated by the landrace 208304 than by Asassa, an improved commercial variety. Increasing seeding rate from 100–175 Kg ha−1 has reduced grain Zn and Fe concentrations. Grain mineral concentration was significantly lower at the Mekelle location than at the Melfa location. It can be concluded that foliar application of ZnSO₄ and FeSO4 to the landrace, acc.208304, combined with 125 Kg seeds ha−1 can produce better Zn and Fe denser durum wheat grain. This will help to combat the hidden hunger, especially in resource poor countries, where fortified foods are limited in access and unaffordable by small-scale farmers.

Selenium biofortification enhances ROS scavenge system increasing yield of coffee plants

There are conclusive evidences of selenium (Se) deficiency in Brazilian soils and foods. Brazil is the largest producer and consumer of coffee worldwide, which favors agronomic biofortification of its coffee. This study aimed to evaluate effects of foliar application of three formulations and six rates of Se on antioxidant metabolism, agronomic biofortification and yield of coffee beans. Seven Se concentrations (0, 10, 20, 40, 80, 100 and 160 mg L−1) were applied from three formulations of Se (sodium selenate, nano-Se 1500, and nano-Se 5000). Selenium application up to 40 mg L−1 increased the concentration of photosynthetic pigments such as chlorophylls, pheophytins and carotenoids in coffee leaves. Foliar application of Se ranging from 20 to 80 mg L−1 decreased lipid peroxidation and concentration of hydrogen peroxide, but increased superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase activities in coffee leaves. These results indicated that foliar Se application stimulates antioxidative metabolism to mitigate reactive oxygen species. Foliar application of 20 mg Se L−1 of sodium selenate increased coffee yield by 38%, and 160 mg Se L−1 of nano-Se 5000 increased dramatically coffee yield by 42%. Selenium concentration in grains ranged from 0.116 to 4.47 mg kg−1 (sodium selenate), 4.84 mg kg−1 (nano-Se 1500) and 5.82 mg kg−1 (nano-Se 5000). The results suggest the beneficial effect of Se on the increment of photosynthetic pigments, antioxidative metabolism, increased coffee yield and nutritional quality of grains. The recommended foliar Se application in this study can mitigate abiotic stressors such as high temperatures resulting in higher yield of coffee plants.

Agronomic biofortification of zinc in different rice genotypes

Zinc deficiency in soils and plants is a global micronutrient deficiency problem reported in many countries. Zinc deficiency can be corrected by enriching the food grains through fertilizer application to the plant in both soil and foliar method. A field experiment on agronomic biofortification with zinc in rice was carried out during thaladi season of 2013-14 and 2014-15 at Tamil Nadu Agricultural University, Coimbatore. The experiment was laid out in split plot design with three replications consisted of two zinc levels (-Zn and +Zn, 100 kg ZnSO4. 7 H2O ha-1 plus foliar spray @0.5%) in main plot and 18 rice genotypes in subplot. Soil and foliar application of zinc significantly increased the grain and straw yield and also the zinc concentration in processed rice grains. Based on the zinc concentration in processed rice the genotype Co43, Improved white ponni, ADT 38 and TRY 1 showed higher response for zinc application.

Micronutrient Biofortification in Rice through New Breeding Techniques (NBTs): Bangladesh Perspective

Background: Micronutrient deficiencies are serious health issues in developing countries of Asia and Africa, where millions of people are suffering from inadequate micronutrient intake. In Bangladesh, micronutrient deficiencies are found severe due to low income, food habits, and rice-based staple food consumption, (rice has an insufficiency of different types of vitamins and minerals). To lessen micronutrient malnutrition, supplementation has been employed but has not yet reached the goal. Agronomic and genetic biofortification has the potential to address micronutrient deficiencies. Biofortification in Rice grain is a convenient and affordable way to supply the desired micronutrients. The development of micronutrient-rich popular rice cultivars through conventional breeding is currently being harnessed for the limitation of natural resources of the related donor rice cultivars containing the required amount of micronutrients. To overcome these hurdles of conventional breeding, genetic engineering and genome editing have emerged as promising tools of micronutrient biofortification in rice. Methods: Identify the needs and explore the potential strategies by the search for relevant literature known to the authors was carried out to complete this review. Results: Highlighted here the sources, functions, and requirements of iron, zinc, vitamin A, vitamin B1, vitamin B9, and betanin in rice and their biofortification through conventional breeding, genetic engineering, and genome editing including their promises and hindrances. Conclusion: New breeding techniques are timely alternatives for developing nutrient-rich rice cultivars to eliminate hidden hunger and poverty in Bangladesh.

Quantification and Tissue Localization of Selenium in Rice (Oryza sativa L., Poaceae) Grains: A Perspective of Agronomic Biofortification.

In worldwide production, rice is the second-most-grown crop. It is considered a staple food for many populations and, if naturally enriched in Se, has a huge potential to reduce nutrient deficiencies in foodstuff for human consumption. This study aimed to develop an agronomic itinerary for Se biofortification of Oryza sativa L. (Poaceae) and assess potential physicochemical deviations. Trials were implemented in rice paddy field with known soil and water characteristics and two genotypes resulting from genetic breeding (OP1505 and OP1509) were selected for evaluation. Plants were sprayed at booting, anthesis and milky grain phases with two different foliar fertilizers (sodium selenate and sodium selenite) at different concentrations (25, 50, 75 and 100 g Se·ha−1). After grain harvesting, the application of selenate showed 4.9–7.1 fold increases, whereas selenite increased 5.9–8.4-fold in OP1509 and OP1505, respectively. In brown grain, it was found that in the highest treatment selenate or selenite triggered much higher Se accumulation in OP1505 relatively to OP1509, and that no relevant variation was found with selenate or selenite spraying in each genotype. Total protein increased exponentially in OP1505 genotype when selenite was applied, and higher dosage of Se also increased grain weight and total protein content. It was concluded that, through agronomic biofortification, rice grain can be enriched with Se without impairing its quality, thus highlighting its value in general for the industry and consumers with special needs.

Simultaneous Biofortification of Rice With Zinc, Iodine, Iron and Selenium Through Foliar Treatment of a Micronutrient Cocktail in Five Countries.

Widespread malnutrition of zinc (Zn), iodine (I), iron (Fe) and selenium (Se), known as hidden hunger, represents a predominant cause of several health complications in human populations where rice (Oryza sativa L.) is the major staple food. Therefore, increasing concentrations of these micronutrients in rice grain represents a sustainable solution to hidden hunger. This study aimed at enhancing concentration of Zn, I, Fe and Se in rice grains by agronomic biofortification. We evaluated effects of foliar application of Zn, I, Fe and Se on grain yield and grain concentration of these micronutrients in rice grown at 21 field sites during 2015 to 2017 in Brazil, China, India, Pakistan and Thailand. Experimental treatments were: (i) local control (LC); (ii) foliar Zn; (iii) foliar I; and (iv) foliar micronutrient cocktail (i.e., Zn + I + Fe + Se). Foliar-applied Zn, I, Fe or Se did not affect rice grain yield. However, brown rice Zn increased with foliar Zn and micronutrient cocktail treatments at all except three field sites. On average, brown rice Zn increased from 21.4 mg kg–1 to 28.1 mg kg–1 with the application of Zn alone and to 26.8 mg kg–1 with the micronutrient cocktail solution. Brown rice I showed particular enhancements and increased from 11 μg kg–1 to 204 μg kg–1 with the application of I alone and to 181 μg kg–1 with the cocktail. Grain Se also responded very positively to foliar spray of micronutrients and increased from 95 to 380 μg kg–1. By contrast, grain Fe was increased by the same cocktail spray at only two sites. There was no relationship between soil extractable concentrations of these micronutrients with their grain concentrations. The results demonstrate that irrespective of the rice cultivars used and the diverse soil conditions existing in five major rice-producing countries, the foliar application of the micronutrient cocktail solution was highly effective in increasing grain Zn, I and Se. Adoption of this agronomic practice in the target countries would contribute significantly to the daily micronutrient intake and alleviation of micronutrient malnutrition in human populations.

Agronomic biofortification of maize (Zea mays L.) with zinc by using of graded levels of zinc in combination with zinc solubilizing bacteria and Arbuscular mycorrhizal fungi

Field experiment was conducted in black and red soils in order to study agronomic biofortification of Maize with Zinc using Arbuscular Mycorrhizal (AM) fungi and Zinc Solubilizing Bacteria (ZSB) in combination with graded levels of ZnSO4. Treatment consisted of two factors viz., microbial inoculation (M1: control, M2: AM fungi, M3: ZSB and M4: M2+M3) and graded levels of ZnSO4 (S1: 0, S2: 12.5, S3: 25, S4: 37.5, S5: 50 Kg ha −1 and S6: 0.5% foliar spray @ 45 and 65 DAS) replicated three times in Randamized Block Design. Application of AM fungi and ZSB in combination with 50 Kg ha−1 of ZnSO4 had recorded enhanced Zn content of maize grain to a tune of 25.9 and 26.6 ppm respectively under black and red soil which contributed to an increase of 22.0 and 21.4% over the absolute control. AM fungi and ZSB in combination with 37.5 Kg ha−1 of ZnSO4 had highest Zn content of maize grain and an increase of 10.4 and 10.6% respectively were recorded for black and red soil over the control. The highest grain Zn content was observed in S5 (ZnSO4 @ 50 kg ha−1) and the increase was 15.6 and 15.2% respectively for black and red soil followed by 37.5 (S4), 25 (S3), 12.5 Kg ha −1 of ZnSO4 (S2) and 0.5% foliar spray @ 45 and 65 DAS (S6) over control but the increase was not appreciable beyond 37.5 kg ha−1 (S4) in black soil.

Calcium biofortification of Rocha pears, tissues accumulation and physicochemical implications in fresh and heat-treated fruits

Low dietary intake of Ca in humans has been epidemiologically linked to various diseases, which can have serious health consequences over time. Accordingly, the development of an agronomic itinerary for Ca biofortification of Rocha pears and the assessment of physicochemical deviations prompted this study. Two orchards with contrasting soil and water characteristics were selected, characterized through orthophotomaping and, during fruits development, leaves were sprayed twice with Ca(NO3)2 (0.1, 0.3 and 0.6 kg ha−1) or CaCl2 (0.4, 0.8 and 1.6 kg ha−1), followed by pulverization only with CaCl2 (first once with 4 kg ha−1 and then four times with 8 kg ha−1). During fruits development net photosynthesis, stomatal conductance, transpiration rates, instantaneous and water use efficiency, only showed minor deviations, which indicated that the threshold of toxicity was not surpassed. Calcium contents varied during fruits development and at harvesting the average biofortification index varied between 47 %–63 % and 24 %–59 % in each of the orchards. Besides, the equatorial region of the fruits showed for all treatments (substantially in Ca treated samples) higher Ca contents in the epidermal and in the central regions. Fresh and heat-treated fruits (in a thermomix at 90 °C, during 10 min) biofortified with Ca only revealed minor differences and the sensory acceptability did not vary markedly. It is concluded that, although prevailing a heterogeneous distribution of Ca in fruit tissues, high indexes of biofortification in Rocha pears can be prompt in the orchards, without substantial physicochemical changes. Accordingly, agronomic biofortification with Ca can be used as a strategy for benefiting consumer’s health.

Strategies for applying selenium for biofortification of rice in tropical soils and their effect on element accumulation and distribution in grains

This study aimed to investigate the effects of the selenium (Se) application via soil (SeVI) and leaf (SeIV and SeVI) on agronomic attributes of rice and the spatial distribution of Se and other elements in biofortified rice grains. For this, a field trial was conducted using six Se rates (0, 5, 10, 20, 40, and 80 g ha−1). Physiological evaluations in rice leaves, rice grain yield, and Se and other elements content were assessed. Spatial distributions of Se and other elements were visualized mapping the biofortified rice grains with μXRF. The results showed that the strategies and rates of Se applied to the plants were effective for producing Se-rich rice grains. Although Se application did not change the rice yield, it affected some enzyme activities, improving the antioxidant system of the plant. The spatial distribution of the different elements found in the biofortified rice grains varied substantially, with Se accumulations mainly in the endosperm, whereas P, K, Fe, and Zn accumulate in the embryo. Agronomic biofortification of rice with Se, via soil or leaf, is a promising strategy to be adopted in tropical soils in order to produce rice grains with adequate Se contents for human consumption.

Agronomic biofortification with zinc in curly lettuce cultivars

In underdeveloped countries, zinc deficiency is a public health problem. The main foods consumed in these countries have low levels of the nutrient, making their consumption insufficient to meet the minimum daily requirements. Therefore, the aim of this study was to evaluate agronomic biofortification with zinc in curly lettuce cultivars. The experiment was carried out at the Universidade Federal de Uberlândia - Monte Carmelo Campus, using a complete randomized block design in a 4 × 5 factorial scheme with four replications. The factors consisted of four curly lettuce cultivars (Brida, Isabela, Thais, and Vanda) and five doses of leaf zinc (0, 400, 800, 1200 and 1600 g ha-1 of Zn). The following traits were evaluated: zinc leaf content, plant height, SPAD index, total fresh mass, stem diameter, head diameter, number of leaves per plant, and estimated average yield. Data were subjected to analysis of variance by the F test (? = 0.05) and means were compared by Tukey test at 5% probability and regression analyzes. According to the results obtained, the cultivar Thais can be considered the lettuce with highest leaf zinc content and the most biofortified. It is advisable to use 700 g ha-1 of leaf zinc to obtain biofortified lettuce with increased yield.

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.

Agronomic Bio-fortification of Rice and Maize with Iron and Zinc: A Review

Earlier, the agriculture system was oriented more towards achieving higher agronomic yields than the nutritional quality of food. Green revolution significantly enhanced the crop production primarily rice, wheat and maize production was boosted to meet the energy needs of growing population. As a consequence of the predominance of cereal-based staples that are fundamentally low in micronutrients, specifically Zn and Fe, more than 2 billion people worldwide suffer from an insidious type of deficiency known as micronutrient malnutrition. Just moderate amounts of micronutrient malnutrition can affect cognitive development, reduce disease resistance and increase the risk of women dying during childbirth. The approach to micronutrient fertilization has been shown to improve the yield and nutritional content of the staples. Agronomic biofortification provides an immediate and effective method to enhance accumulation of micronutrients especially Zn and Fe in cereals. An adequate amount of plant available micronutrients is a prime requisite to ensure adequate nutrient uptake. Most of the cereals are grown in soils deficit in Zn and under reduced conditions of rice ecosystem, its availability is decreased due to formation of less soluble Zn complexes with sulphate and carbonate. The form of fertilizer used, timing and method of application is critical for the enhancement of the grain quality of Zn and Fe. The effectiveness of agronomic biofortification can be enhanced by application of synthetic chelated micronutrient fertilizers and/or organic fertilizers fortified with micronutrients in combination with NPK ensuring proper nourishment of crops with adequate nutrient supply by slow release of nutrients in soil solution. Further, the response of foliar application has shown better results than soil application. Previous studies suggest that Zn fertilization not only enhances Zn concentration in grain but also improves the overall performance of maize crop. Agronomic biofortification of crops is advantageous in terms of accessibility, rapid result, ease in application and high sustainability.

Increasing zinc concentration in maize grown under contrasting soil types in Malawi through agronomic biofortification: Trial protocol for a field experiment to detect small effect sizes.

The prevalence of micronutrient deficiencies including zinc (Zn) is widespread in Malawi, especially among poor and marginalized rural populations. This is due to low concentrations of Zn in most staple cereal crops and limited consumption of animal source foods. The Zn concentration of cereal grain can be increased through application of Zn‐enriched fertilizers; a process termed agronomic biofortification or agro‐fortification. This trial protocol describes a field experiment which aims to assess the potential of agronomic biofortification to improve the grain Zn concentration of maize, the predominant staple crop of Malawi. The hypotheses of the study are that application of Zn‐enriched fertilizers will create a relatively small increase in the concentration of Zn in maize grains that will be sufficient to benefit dietary supplies of Zn, and that the effectiveness of agronomic biofortification will differ between soil types. The study will be conducted at three sites, Chitedze, Chitala, and Ngabu Agricultural Research Stations, in Lilongwe, Salima, and Chikwawa Districts respectively. These three sites represent locations in the Central and Southern Regions of Malawi. At each site, two different sub‐sites will be used, each corresponding to one of two agriculturally important soil types of Malawi, Lixisols, and Vertisols. Within each sub‐site, three Zn fertilizer rates (1, 30, and 90 kg/ha) will be applied to experimental plots using standard soil application methods, in a randomized complete block design. The number of replicates at plot level has been informed by a power analysis from pilot study data, assuming that a minimum 10% increase in Zn concentration of grain at 90 kg/ha relative to the concentration at 1 kg/ha is of interest. Grain mass (yield), stover mass, and both stover and grain Zn concentrations will be measured at harvest. A second year of cropping will be used to establish whether there are any residual benefits to grain Zn concentration. The potential for Zn agronomic biofortification will be communicated to relevant academic and government stakeholders through a peer review journal article and a briefing paper.

Agronomic Biofortification of Stevia rebaudiana with Zinc Oxide (ZnO) Phytonanoparticles and Antioxidant Compounds

Agronomic biofortification is a process used to increase the concentration of essential elements in plants through fertilization and thus improve their nutritional quality. Increasing the content of Zn+2 in Stevia rebaudiana plants would imply adding value to the crop. The use of ZnO phytonanoparticles, in addition to increasing the content of Zn+2, can also generate an inductor effect that promotes the synthesis of metabolites of commercial interest. This study reports the effect of fertilization with ZnO phytonanoparticles on morphometric parameters of S. rebaudiana plants and the content of Zn+2, stevioside, rebaudioside A, total phenols, flavonoids and the antiradical activity of leaf extracts. Biofortification was carried out in a hydroponic culture using peat moss/agrolite as a support under a completely random experimental design. The green ZnO nanoparticles were added via root at different concentrations. The physiological and morphometric parameters of the plant were not affected with respect to the control by the use of phytonanoparticles. The biofortification of S. rebaudiana with ZnO phytonanoparticles at a concentration of 75 mg/L enhanced zinc content up to 406.8% with respect to the control. The total phenols (60.5%) and flavonoids (87.8%) were also increased without having a negative effect on plant growth. The biosynthetic pathway of steviol glycosides was not affected.

Impact of Agronomic Biofortification with Zinc on the Nutrient Content, Bioactive Compounds, and Antioxidant Capacity of Cowpea Bean (Vigna unguiculata L. Walpers)

Zinc intake deficiency is a public health problem and increasing the nutrient’s content in the edible parts of plants can help mitigate it. The objective of this work was to determine the effect of the edaphic and foliar application of zinc sulphate on the nutrient content, bioactive compounds, and antioxidant capacity of cowpea beans (Vigna unguiculata L. Walpers). A sample of 100 grains was taken, and the length, width, thickness, weight, ash content, fat, humidity, fibers, carbohydrates, protein, energy, macro- and micro- nutrients, total phenols, flavonoids, anthocyanins, and antioxidant capacity were determined. The 0.250 g edaphic-12.5 mM foliar dose produced grains of a greater weight and size. All of the edaphic and foliar doses increased the grain zinc content, and the highest value was found with the 0.125 g edaphic-50.0 mM foliar dose. The total phenols increased with 12.5 g of edaphic zinc, while phenols, flavonoids, and the antioxidant capacity increased with 50.0 mM foliar zinc. The edaphic and foliar application of zinc sulphate increased the grain weight and size, zinc content, total phenols, and antioxidant capacity. Therefore, edaphic and foliar zinc biofortification enriches this nutrient in cowpea grains, and could reduce micronutrient malnutrition in the urban and rural communities of Mexico.

Agronomic iodine biofortification of leafy vegetables grown in Vertisols, Oxisols and Alfisols

Iodine deficiency disorders (IDD) in sub-Saharan African countries are related to low dietary I intake and generally combatted through salt iodisation. Agronomic biofortification of food crops may be an alternative approach. This study assessed the effectiveness of I biofortification of green vegetables (Brassica napus L and Amaranthus retroflexus L.) grown in tropical soils with contrasting chemistry and fertility. Application rates of 0, 5 and 10 kg ha−1I applied to foliage or soil were assessed. Leaves were harvested fortnightly for ~ 2 months after I application before a second crop was grown to assess the availability of residual soil I. A separate experiment was used to investigate storage of I within the plants. Iodine concentration and uptake in sequential harvests showed a sharp drop within 28 days of I application in all soil types for all I application levels and methods. This rapid decline likely reflects I fixation in the soil. Iodine biofortification increased I uptake and concentration in the vegetables to a level useful for increasing dietary I intake and could be a feasible way to reduce IDD in tropical regions. However, biofortification of green vegetables which are subject to multiple harvests requires repeated I applications.

Effect of soil properties on time-dependent fixation (ageing) of selenate

Previous biofortification studies have established that the residual effect of added selenium (Se) fertilisers on second-season crops is minimal. To explore the fate of exogenous Se in soil, chemical and biological methods were employed to assess the change in Se bioavailability with time. Eight soils varying in physicochemical properties were spiked with sodium selenate (0.5 mg kg−1 Se) and incubated at 25 °C for different periods (1, 30, 60, 90 and 300 d). At the end of the incubation, soil Se was fractionated by a sequential extraction procedure into ‘soluble’, ‘adsorbed’ and ‘organically-bound’ Se fractions. Simultaneously, wheat was grown in the Se-aged soils, under controlled conditions for six weeks, and uptake was determined. A general decrease in Se solubility over time was observed, but the rate of decrease varied depending on soil type. A reversible first order model fitted the Se ageing kinetics well, except in an Oxisol. The most pronounced ageing was observed in calcareous soils. Concentrations of Se in the shoots of wheat grown in freshly spiked soils ranged from 71.8 ± 17.5 mg kg−1 in calcareous soils to 110 ± 31.6 mg kg−1 in non-calcareous, low-OM soils. With ageing, shoot Se concentrations decreased to <10 mg kg−1, with the lowest concentrations (0.31 ± 0.03 mg kg−1) measured in plants grown in calcareous soils. The Se concentrations in plants correlated well with the soluble Se fraction (extracted with 0.01 M CaCl2). The findings of this study can be used to make more informed decisions about the rate and frequency of Se fertiliser application in agronomic biofortification programs.