Agriculture Sans Soil

The United Nations projects that the world will hold 9.6 billion people by 2050 with more than 75% living in urban areas. Continuous population growth leads to increased competition for food and resources. Combined with the negative effects of climate change and widespread overfishing, our ability to produce enough food via conventional agriculture may be in jeopardy. With a clear need for sustainable solutions, could hydroponic and aquaponic systems be the key to close the food gap? EN explores why these centuries-old practices are relevant today.

The Basics. The word “hydroponic” is Latin for “working water.” Simply put, it’s a soil-less method for cultivating plants, where plant roots are submerged in a highly-oxygenated, nutrient-rich water. Aquaponics are similar but go one step further to replace chemical nutrient solutions used in hydroponics with nutrients supplied from fish in a water tank (aquaculture). The result is an integrated system where fish waste provides plants a food source and, in turn, plants filter water for the fish. Under normal circumstances, fish waste is removed from aquatic environments. This is not necessary with an aquaponic system because plant roots and bacteria convert ammonia from waste into nitrates (a form of nitrogen) used by plants to support growth.

The Benefits. A primary benefit of these systems is improved sustainability and reduced environmental impact. The World Resources Institute estimates that conventional agriculture contributes ¼ of global greenhouse gas emissions, occupies 37% of landmass, and uses 70% of water from lakes, rivers, and aquifers. Hydroponics can efficiently recirculate water in closed-loop systems and use an estimated 70-90% less water than soil-based gardening. Aquaponic systems also result in increased efficiency and crop yield since roots more-readily obtain necessary nutrients in liquid cultures. A 2015 study in International Journal of Environmental Research and Public Health reported more than 10 times higher yield for hydroponic-grown lettuce versus conventional methods. Aquaponics can be used to simultaneously raise fish and fresh produce at various scales, with faster growth cycles, and in settings where conventional agricultural production is limited (climate, urban settings, limited space, contamination).

The Bottom Line. No single solution can ensure sustainable food production and global food security. While hydroponic and aquaponic systems are not without their unique set of challenges (high energy needs, system stability, technical difficulty, high expenses), alternatives to soil-based agricultural may be an important part of meeting the world’s growing food demand.

—Bridget Cassady, PhD, RDN

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