Fertilizer: Organic or Inorganic?

Which type of fertilizer wins out when it comes to meeting our food demands and protecting the planet?

Those who tend to plants – whether they be solitary gardeners maintaining backyard plots or farmers in command of agricultural mega-crops – have a choice when it comes to the type of fertilizer they feed them.  Fertilizer is any additive that provides essential nutrients like nitrogen and potassium to growing plants and can be organic – derived from plants or animals – or inorganic – derived from minerals or synthesized by humans.  Each has both advantages and disadvantages and is ultimately integral to maintaining the grand-scale generation of plants necessary to sustain the demands of our booming society.

Elephants have been kindly fertilizing plants for centuries. Photo courtesy of wackystuff/Flickr Creative Commons

Fertilization by organics is a natural process that occurs whether or not humans are involved, but it cannot support the enormity of our current food system.  In fact, it’s thought that the use of synthetic nitrogen fertilizers is responsible for feeding nearly half of Earth’s population.  Organic fertilizer is not as effective as inorganic fertilizer in that it generally has lower nutrient content, solubility, and nutrient release rates.  Furthermore, it is more difficult to tailor organic fertilizer to meet specific nutrient needs, as it is derived from such diverse sources and its nutrient amounts cannot be known without testing.  Despite these drawbacks, organic fertilization is invaluable.  In fact, Enzo Favoino and Dominic Hogg, authors of “Waste Management & Research: The potential role of composting in reducing greenhouse gases,” say that applying organic matter to soil may heighten its ability to sequester carbon dioxide, and “increasing organic matter in soils may cause other greenhouse gas-saving effects, such as improved workability of soils, better water retention, less production and use of mineral fertilizers and pesticides, and reduced release of nitrous oxide.”

Nitrogen fertilizer being spread on corn fields in Hardin County, Iowa. Photo courtesy of eutrophication&hypoxia/Flickr Creative Commons

Although world hunger would swell without the assistance of inorganic fertilizers, they are not perfect either.  They deliver more nutrients better, but they require non-renewable resources like phosphorous and potassium, which are mined.  Nitrogen – as it makes up the majority of our atmosphere – is essentially infinite, but in order to be used by plants it must first be “fixed,” or converted into ammonia.  This process, when performed by humans, requires fossil fuels, the burning of which is responsible for global climate change.  According to Aleksander Abram and D. Lynn Forster’s “Primer on Ammonia, Nitrogen Fertilizers, and Natural Gas Markets,” in 2004 “317 billion cubic feet [of natural gas were] used to manufacture ammonia” in the U.S.  In addition, inorganic fertilizers do not consist entirely of nutrients but also include compounds like salt, which can build up in soil and change its chemistry, making it less suitable for planting.  Inorganic fertilizers are also more susceptible to leaching and wash away more easily, exacerbating problems like eutrophication, the depletion of oxygen in bodies of water due to overactive plant growth, which can lead to mass die-offs of aquatic fauna.  Around half of all U.S. lakes are currently eutrophic, and many coastal waters are now considered “dead zones.”

While neither type of fertilizer is flawless, both have their merits, inorganic more efficient and reliable and organic healthier for the soil and the planet.  At this point in the global food situation, the composting of organic mass to yield fertilizer can only act to supplement the use of inorganic fertilizers, but as long as humanity continues to eat and leave food scraps behind, composting will remain a viable option for sustaining both worldwide food production and the Earth.