What technologies/strategies exist to help us meet the water and nutritional demands of the future?
When weighing the most basic survival needs for human life, you can isolate three that are necessary building blocks: air, water, and nutrients (food). Assuming that there is adequate air to breathe, humanity would focus on the latter two items. Therefore, they must accept that food must be determined in terms of water. Without water, nutrients could not be produced. Even if there is a water source, consideration must be made to determine the reservation of as much potable water as is necessary for drinking as potential dehydration is far more expedient for immediate survival than starvation needs. Depending on the nature of the ecosystem, the capabilities for survival choices may vary. They will all, however, require freshwater, which is currently in short supply, estimated to be far less than 1% of global water, even less of which is potable for uses like drinking, cooking, and ingestion (Marris, 2008). This thinking exercise of deciding the path of the most basic human needs is not a difficult one. It is preclusive to another more involved line of questioning; how can nutrients be most effectively maximized in terms of the water available especially when translated to the current and future needs of a growing population in the developed world?
Modern agronomy has transformed farming into a commercial enterprise enabling the multiplication of humanity across the globe. Due to the development of Western economies, there is no longer the single farmer working with his family and his livestock to till the fields and bring his crops to market. Instead there is the commercial farm that dwarfs the original with advances in machinery, land use, fertilizer, and irrigation technologies. The accesses to copious amounts of food have also allowed population to exponentially multiply, also contributing to dwindling water resources.
Increased uses of fossil fuels globally including a heavy use in agriculture and livestock production have given way to global warming. This in turn has increased the difficulties found in traditional agriculture. Rain can no longer be relied upon to irrigate an overheated planet where soil is becoming increasingly dry and erosive (Collins, 2007). Also, due to pollution of other non-saline sources, irrigation sources can become more scarce leading to vital ecosystems being lost. All of these inputs are placing a heavy tax on the land and what may be seen, as increasing land salinity will overshadow a freshwater supply to agriculture. In 2005, it is estimated that “20% of all irrigated farmland in the world, 23% in the United States alone, is affected by salinization” (6, Zhu, 2005). Diamond writes of the problem as it plagues conventional agronomists who utilize drip-irrigation, common in the United States and Australia,
"Irrigation salinization has the potential for arising in dry areas where rainfall is too low or too unreliable for agriculture, and where irrigation is necessary instead, as in parts of southeastern Australia. If a farmer "drip-irrigates," i.e., installs a small irrigation water fixture at the base of each fruit tree or crop row and allows just enough water to drip out as the base of the tree's or crop's roots can absorb, then little water is wasted, and there is no problem. But if the farmer instead follows the commoner practice of "broadcast irrigation," i.e., flooding the land or else using a sprinkler to distribute the water over a large area, then the ground gets saturated with more water than the roots can absorb. The unabsorbed excess water percolates down to the deeper level of salty soil, thereby establishing a continuous column of wetted soil through which the deep-lying salt can percolate either up to the shallow root zone and the surface, where it will inhibit or prevent growth of plants other than salt-tolerant species, or else down to the groundwater table and from there into a river" (401).These thresholds do not come without a significant price, leading a search for increased alternative agronomic technologies that use less of the aforementioned inputs (land, water, etc.) to gain the same benefits. There is a movement from molecular biology aiming to find a mechanism for increasing the halotolerance of seeds and crops (the adaptation of living organisms to conditions of high salinity) (Zhu, 2005) as well as modification to crops to allow for genetic modification allowing crops to be more productive while using the same amount of water (Marris, 2008). However, methods of agriculture that don’t utilize soil mediums should be expanded simultaneously. Focusing specifically on the developed world in commercial or potential commercial use, two of these alternatives are currently available in the form of hydroponics and aeroponics. These are promising technologies fighting to take hold in a marketplace devoted to economies of scale and maximized yield often at the cost of natural systems.
Hydroponics is a technology of growing plants or crops growing without soil, in either a nutrient-dense mineral solution by itself or in an inert medium providing mechanical support for the root structures in addition to the solution (Jensen, 1997). In conventional farming, soil acts as a conduit to root structures receiving water and minerals. When studied, it was found that with the receipt of these inputs, the soil element was no longer necessary for growth. They may be open or closed systems, however, they typically are cut off from the immediate external environment (indoor facilities) often in the form of greenhouses. This allows the control of water evaporation, regulation of temperature issues that allow for year round growth, and other elemental controls such as pests and weather-related issues such as storms and droughts (Jensen, 1995). These systems allow for minimal water, land, and energy use in comparison to conventional agricultural systems while maintaining a comparable if not superior product.
Beginning and the use of hydroponics can be capital-intensive, however, the payoff in controls and spatial necessities is clear. For the argument of this exercise it is clear that this is a form of agriculture that uses minimal water inputs for maximum nutrient outputs when directly compared to traditional commercial or home agriculture. In addition to the consumption of less water in the initial farming technique, water can also be captured and reused from evaporative sources and from the plant growth infrastructures themselves. Reusing water throughout the system enables for growth that otherwise could not occur with conventional agriculture. The water conservation possibilities via use of treated effluent, collected groundwater, and other gray water (wastewater) sources leave larger quantities of drinkable water available for use outside of agriculture. In some studies, most notably in Tunisian urban farms, using treated wastewater for irrigation purposes has not only been found to be safe, but has also shown higher production yields that those crops irrigated using traditional groundwater sources (United Nations, 1996), which is also the case when using gray water for hydroponic agriculture.
Aeroponics is a method of agriculture utilizing misted nutrient solution in a soilless system, without a growing medium (Barak, 1996). While this system does require the inputs of apparatus growing technologies including a mist system and plants “beds”, it is far less water intensive per square meter that traditional farming and even hydroponic systems. Plants require a mist that is then taken up by their root systems and then metabolized throughout the plant. It has been shown that with the proper inputs, plants can grow to the same size as seen in standard agriculture with comparable if not increased nutrition potential due to the superior method of nutrient transfer via mist solution. It is comparable to hydroponic technologies, however, aeroponics use even less water and do not require a growing medium, allowing for more plants to be grown in a spatial system. This system is currently gaining popularity in urban farming design due to it’s dedication to limited spaces, no use of growth material, and extremely low use of water. It differs very little from hydroponic farming techniques outside of better water utilization and the lack of a growing medium, however, remains less popular commercially.
Both hydroponics and aeroponics stretch the natural constraints of conventional agriculture to meet human needs. Both enable year round production or nutrients as they take away the natural constraints of growing seasons. They both also control for vectors such as pathogens and pests which plague conventional agriculture. This in turn controls and drastically decreases the use of pesticides and herbicides producing a higher quality product in an organic sense making products safer for human consumption. Without the use of pesticides and herbicides, a disconnect in the pollution cycle is created which has plagued modern and conventional agriculture, making the land fallow and prone to salinization, as well as polluting other water sources.
Also, both systems allow for use in densely populated areas, such as urban centers where agriculture is not currently or historically been considered as a pertinent use of land. This will aid the movement of rural and hinterland agricultural forays into urban and suburban centers while not becoming an overwhelming draw on their water systems that could be easily retrofitted to use gray water (wastewater). In essence, the benefits of hydroponic and aeroponic farming are a quality, nutrient-dense product with the use of far less land, energy, and water, all things for which current and future societies will have to develop conservation techniques in an unpredictable ecological environment.
Bibliography
Barak, P., Smith, J.D., Krueger, A.R., and Peterson, L.A. (1996) Measurement of short-term nutrient uptake rates in cranberry by aeroponics. Plant, Cell, and Environ. 19:237-242.
Collins, W. et al. (2007) "The physical science behind climate change," Scientific American, p. 64-73, August.
Diamond, Jared. (2005) Collapse: How Societies Choose to Fail or Succeed, New York: Penguin Books.
Jensen, Merle H. (1997) “Hydroponics,” Hortscience, 32:6, October. http://ag.arizona.edu/PLS/faculty/MERLE.html [Accessed 23-Oct-2008]
Marris, Emma. (2008) “More Crop Pet Drop,” Nature, 452:20, March 2008
Urban Agriculture, (1996) The United Nations Development Programme, New York City, Chapters 7, 9.
Zhu JK, Bressan RA, Hasegawa PM, Pardo JM, Bohnert HJ. 2005. Salt and crops: salinity tolerance. In Success Stories in Agriculture. Council for Agricultural Science and Technology, Autumn/Winter 2005. http://www.faculty.ucr.edu/~jkzhu/articles/2005/bohnert.pdf [Accessed 23-Oct-2008]
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