A few thoughts, some far fetched, some closer to home.

1. Protected and soilless culture pre-supposes a relatively high level of technology, it can best be sustainably developed by wealthier nations, so the original statement assumes that the future holds technological advances for underdeveloped countries, or that developed nations would oversee the creation of these facilities.

2. Underdeveloped nations often have a scarcity of natural resources necessary for agriculture, and soilless culture would make efficient use of the available resources. (see reply above)

3. Your argument might have to consider the possibility that global agribusiness might control the entire food production of a poorer nation, or to explain why that would not matter.

4. Soilless culture means that there can be containment of any GM crops which might(?) contaminate the natural environment.

5. There is serious talk of a manned moon base, the further development of protected agriculture would facilitate the spread of mankind through space. The ultimate sustainability.

Yes, due to unavailability of land or good soil, harsh environmental conditions e.g. hail, high temperature. Growing vegetables under protection using soilless system will results in avaialbility of food

Soilless culture requires extensive knowledge of the nutrient requirements of each species grown, the level of nutrients existing within the medium, and the ability to deliver essential nutrients in very specific amounts as the crop demands it. If by protection, you mean some form of covering the crop, such as with a greenhouse structure, one has to factor in the cost of such a structure, the need to control the environment in such a structure and the need to provide the crop with all of its water and nutrient needs throughout its growing period. From an economical perspective, this greatly drives up the cost of food produced in such facilities compared to conventional production (such as in the soil under natural conditions). Production of crops will always be a risky venture, regardless of how "controlled" it is.

Here some results from papers that provide insights into the sustainability of the greenhouse production:

A comparative analysis of greenhouse versus open-field tomato production in Kenya showed that although the introduction of the greenhouse technologies was low due to the cost of greenhouse installation and maintenance, this is a short term problem because the long term use of the technology is economically viable. In fact, the mean income for greenhouse tomato growers was almost twice higher than that of open-field tomato growers. In addition, net profit m-2 and gross margin m-2 for greenhouse tomato farmers were found to be 10 times higher than that of their open-field counterparts, implying that greenhouse tomato production system is more profitable than the open-field system.

For more information see Wachira, John Mwangi 2012. Comparative analysis of greenhouse versus open-field small-scale tomato production in Nakuru-North District, Kenya. Thesis. Egerton University.

A work of Muñoz et al. (2008) revealed that environmental burden per kg of tomato grown in open-field production was greater than that for tomatoes produced in greenhouses with respect to factors such as the use of water, fertilizers and pesticides.

Muñoz, P., Antón, A., Nuñez, M., Paranjpe, A., Ariño, J., Castells, X., Montero, J.I. and Rieradevall, J. 2008. Comparing the environmental impacts of greenhouse versus open-field tomato production in the mediterranean region. Acta Hort. (ISHS) 801:1591-1596.

Generally, the comparison between hydroponic greenhouse and open-field cultivation show that soilless greenhouse cultivation reduces the environmental impact due to lower levels of fertilizers and pesticides in the environment, lower consumption of water and higher production per area.

Compared to open-field, hydroponic greenhouse productions reduce the following environmental impacts: terrestrial toxicity (-40%), aquatic toxicity (-65%), human toxicity (-25%), reduction of atmospheric ozone (-20%), eutrophication (-45%), acidification (-20%), but in the case in which fossil energy is used to heat the greenhouse, the soilless productions increase global warming (+10%) and exhaustion of the natural resources (+22%). Nevertheless, the use of renewable energy (wood) mitigates these negative impacts.

Boulard T. 2008. Scénarios d’évolution des productions légumières sous serre. INRA-URIH, Montpellier France. Oral presentation.

I will agree that the mean income of the producer is greater under greenhouse production, but that is not the same as the cost of production. Greenhouse tomatoes, which can be produced at times of the year when field grown tomatoes (and other veggies) cannot, command a much higher market price than field grown crops, which of course increases the price paid by the consumer. And while greenhouse tomatoes are "prettier" than most filed tomatoes, in my humble opinion they lack the flavor and texture of a field grown tomato. I have no references to support the commonly held opinion that they are also less nutritious as well. Field grown vegetables are so dependent on the proper weather conditions that we are restricted to specific times of the year growing them, causing the market to be flooded with produce at peak production, thus affecting the supply and demand relationship. Unfortunately, those farmers do not get paid as well for their produce as the greenhouse producer, but the consumer benefits from the lower prices and can take steps to preserve those products by canning or freezing (not very sustainable either). I doubt you'll ever see a cannery purchasing produce from a greenhouse operation. With the ability to recycle the water used in a controlled environment, along with no soil tillage and reduced pesticides, I certainly agree there are some environmental benefits to greenhouse production, other than the fact that greenhouse production usually generates lots of plastic, which hopefully can be recycled.

I would like to add a few thoughts in this debate.

Protected and soiless culture is not something new and despite the fact that it is the most intensive farming technique over the years it tends towards a more environmental friendly way of cultivating vegetables due to the increasing cost of agrochemicals.

I think that there are pros and cons as always. The pros, to name a few, of using such a technique are: 1) high yield (e.g. greenhouses in Northern Europe can achieve 10 times higher yield than tomato field crops), 2) the ability to fully control the environment and apply the best conditions for each crop, 3) adjustment of harvesting time 4) the potential to use water of low quality or the ability to cultivate in regions where soils are degraded etc.

The cons are: 1) high investment costs, 2) highly expertised personnel, 3) high running costs (energy, agrochemicals) etc.

Regarding the quality of greenhouse products I think that they are familiar with field crop products, providing that final product is harvested at the right time. The example of greenhouse tomatoes that are of lower quality comparing to field grown tomatoes is very simple put, because you have to consider that these tomatoes are usually come from far away markets and fruits have been harvested very early, therefore their taste is inferior to field grown tomatoes which coming from local markets and fruits are harvested when fully mature. So it is not the technique itself but marketing needs that affect quality.

In my opinion, in order to apply sustainable agriculture practices in greenhouses you have to have the expertise and low cost energy (geothermy, solar energy, biofuel). If one can apply the best environment for the plants then the yield ismaximized and the need for agrochemicals and inputs is minimal comparing to the net profit.

All good and valid points. I've been a tomato grower for over 49 years (field grown) and I am likely biased due to my love for the flavor of a tomato that receives the full spectrum of sunlight and soil minerals.

Hydroponics, Aeroponics and other soiless method of growing horticultural crops are good particularly when they are targeted at seed production. Aeroponics is presently been used to produce healthy seed tuber in yam at IITA-Ibadan, Nigeria.

The production of healthy food and seed tuber in yams and vegetatively propagated crops is almost impossible because of soil born pathogens, and particularly nematode, beetles and other pest which cause disease to crops in the soils.

Research should go beyond providing foliar-sprayed agrochemical to incorporating pesticides into fertilizer and look into other possibilities of reducing soil-born pathogen beyond critical level. Until then, soiless medium remains the answer to healthy plant growth.

It is very interesting to read the deliberations and insights shared in this fourm.It is more than two years since the above shared information on the topic ,it may be  useful to look at what additional scientific knowledge has been around.Two parrallel scientific activities like understanding soil-plant system and efficacy to improve this system through nanotechnology and fully understanding the implications of soilless culture driven cultivation may be actively promoted by active investors are worth watching where the fundamental agricultural and horticultural economy is shifting.As the sun driving the every life systems in the world and so many living organisms beneath the soil are thriving due to photosynthesis of plant life, we are curious to understand the change and implications of nanotechnology driven cultivation or soilless cultivation being attempted to project sustaniabilty of life systems of agriculture,public health,environment.50-60 years of fertilizar based agriculture and pesticide induced control of plant protection and growth had resulted in concern allround.Aquaphonics is an another derivative of soilless farming and as far research is concerned it is very exciting to know how precisely micronutrients, protection against pathogens are understood cropwise requirements.