There has been a lot of work done with respect to biofortification of staple foods. It has led to development of crops like iron, beans, vitamin A maize, Vitamin A rich cassava, orange fleshed sweet potatoes rich in Vitamin A, high zinc millet etc. This has been done through traditional plant breeding techniques and HarvestPlus a programme of the Food Policy Research Institute has been quite instrumental in the area. The genetic changes brought about by the breeding processes allow the biofortified plants to accumulate larger amounts of the given nutrients than normal. However for this to happen eg for iron or zinc, there should be enough of the micronutrient available for absorption from the soil or through other means of fertilizing the plants such as foliar application.

Depending on the nutrient of interest it is therefore  possible for fertilizer application to make a difference but the plant must genetically/physiologically be able to accumulate or synthesize higher levels of the micronurients  than usual.

So agronomic biofortification should not be seen as "the answer" to micronutrient and trace element deficiencies, but a strategy to work alongside the traditional strategies to improve nutrition? Plants that are able to take up and accumulate micronutrients and trace elements (species and cultivars that have these beneficial traits) would not have to be modified  and the only constraint would  be to supply these plants with the nutrients lacking from human diets? So if one has a problem with specific deficiencies (or multiple deficiencies at the same time?) within a community, a good means to naturally fight off these deficiencies is to plant crops in the community gardens that are able to take up higher concentrations of these elements from the soil, but you would first need to analyze the soil to determine whether these elements aren't lacking from the soils itself and if these elements are lacking from the soil, consider the application of enriched fertilizers either to the soil or as foliar sprays?

Are modified fertilizers available on the market and if so, are they available to anyone to purchase? Also, are there lists of crops that have these beneficial traits?

My main question would not be is it technologically feasible? I am sure that it can be done someway.

THE BIG QUESTION IS: will the farmers and even more important consumers and citizens grow, accept, buy and eat these foods????

In my opinion that has been THE PROBLEM in all these technocratic approaches.

Imposed solutions seldom work for a variety of reasons quite a lot of them being illogical to the scientific community, but very real and logical to others relying on other sources of information.

In consideration to the problem of micronutrient malnutrition in staple food crops, biofortification strategy through microbial transformation of unavailable forms of soil zinc and iron to plant available form is an important approach contributing to plant zinc and iron nutrition and growth promotion; and to overcome zinc and iron malnutrition in human population could be a viable option. The group of beneficial bacteria that colonize plant roots and enhance plant growth by a wide variety of mechanisms is known as plant growth promoting rhizobacteria (PGPRs). Biofortification of crops through application of PGPR can be therefore considered as a possible supplementary measure, can lead to increased micronutrient concentration in wheat and soybean crop, besides improving yield and soil fertility.

I do not think providing additional plant nutrients through fertilizers or soil bacterial action should be called biofortification. I think biofortification as a term should rather refer to modification of the plant itself giving it the ability to accumulate given micronutrents beyond conventional levels. There should be spcifications with respect to how high the levels should be for a plant to be considerred biofortified.

You are right, but the crop itself bio-fortified due to presence of these PGPR. Because these soil bacteria doing nothing with the plant itself instead to increase the availability of available form of these nutrient from unavailable form, which will be easily accessible to the plant and plant get biofortified. However, it is a good point of discussion whether is it biofortification?

The discussion is interesting. What I meant is that the term biofortification should really refer to the genetically enhanced ability of the given plants to accumulate the micronutrients from the soil not to how the plant nutrients become available for absorption. A different term should be used for the action of the rhizobacteria. There are also biofortified crops like vitamin A cassava or orange fleshed sweet potatoes both enriched with Vitamin A but Vitamin A is synthethized by the plant and is not abosorbed from the soil.

This turned out to be an interesting discussion. I agree with Dr. Covic, the term biofortification is 'too loosely used'. Biofortification could be through genetic modification, transgenetics, selective breeding or agronomic practices such as enhanced fertilizers or through plant growth promoting rhizobacteria (PGPRs). The goal of each of these methods is however to increase  the nutritional quality of crops to improve human nutrition. I also agree with Dr. Kan, people seldom accept modified crops. This is clear when you consider the global outcry against genetic modification, but enhancing crops through fertilizers is a common practice. The current role of macronutrient fertilizers in increase crop yields and thus also providing food security in many parts of the world cannot be denied, and "most people" has accepted the use of these fertilizers as the 'norm'. It is for this reason that I personally believe that agronomic biofortification through micronutrient enriched fertilizers and/or PGPRs could have a significant impact on the global problem of micronutrient malnutrition. The use of macronutrient (NPK) fertilizers is a global practice which, I think, would make these fertilizers the perfect means to supply agricultural plants also with the mineral nutrients humans need, instead of merely using these to improve plant growth and increasing yields. This is however, my personal opinion, but it would be interesting to hear the opinions of other people, but also why they have these opinions. Thank you for all that have participated in the discussion at present.

See publications from Ismail Cakmak - he is an emincence in the field of so-called "agronomic bioforitification" = enhancing nutrient levels in crops via (soil or foliar) application of nutrient-enriched fertilizers: https://www.researchgate.net/profile/I_Cakmak

The question is also about economic feasibility and sustainability: in the long term, "genetic biofortification" (i.e. conventional/traditional breeding or genetic modification) is the way to go as it is a one-time-investment; in the short term, to address acute micronutrient deficiency in vulnerable populations it is a good alternative/option, also in combination with biofortified crops where the full nutrient target levels have not yet been reached. 

An excellent response from Namukolo. Biofortification has to come through  modifications within the plants , instead of using a fortified fertilizer to realise elevation in nutrient density of the crop...

We are more concerned with genetic fortification as rightly pinpointed by  Meike, well said..

Unless we experience genetic biofortification simple nutrient enrichment is not a permanent solution. 

Since genetic biofortification  is  a  permanent solution  .. and one time investment

Discussion was so interesting. I want to add one point to it. Even though we elevate the nutrient application to a growing plant, it won't add more bioavailable form of nutrient to its seed. It will store that much amount of nutrient which will help the seed to grow while germinating and plant will never bother about human diet and malnutrition. That's why genetic modification so far consider as a good practice for bio fortification.

But is equally time consuming and complex in nature..This is the reason this approach is so unpopular amongst researchers .

Biofortification is no doubt a stable intervention, but the compromise on yield is significant. Hence, a parameter is need which balances both quality and quantity...

Check out this article:

Article Micronutrient Productivity: A comprehensive Parameter for Bi...

Recently we published a review on Genetic Basis and Breeding Perspectives of Grain Iron and Zinc Enrichment in Cereals and also tried to touch agronomic biofortification. You can find here: https://www.frontiersin.org/articles/10.3389/fpls.2018.00937/full

This is a very interesting discussion and I think that both agronomic and genetic biofortification have to be taken into consideration when fighting hidden hunger.

We recently pusblished a study about grain nutrients in barley and the potential of wild barley to improve nutrient concentrations. We see clear tendencies of wild barley accessions being able to improve grain quality, however we discuss the results with regard to total nutrient yield rather than pure nutrient concentration.

https://authors.elsevier.com/a/1YjKzcQUVkLRm