Organic farming: is it useful?
I found this article on Science Daily this afternoon. Fertilization furnishes nutrients to promote crop health, yield, and pest control, however there has been significant popular concern over the potential human health issues with overuse of chemical methods in agriculture. Organic farming techniques have been gaining market shares among consumers, with producers touting the positive benefits of presumably healthier fruits and vegetables. According to Wikipedia, organic farming…
… relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests.
Standards for organic farming are set by local and national regulatory agencies, and rather stringent guidelines are in place for food items that can be marketed as “organic.” In the past 20 years, organic food has gone from zero to a $55 billion industry, with approximately 1% of the world total farmland now indicated as organically managed.
Well, other than the obvious marketing benefits, and some arguable health benefits, are there other benefits? A long term study of side-by-side organic and conventional farm plots has examined the diversity of soil microorganisms. In particular, scientists were interested in the numbers of a class of bacteria called nitrogen-fixing bacteria. All plants (and indeed, all living cells) require nitrogen as one of the four key elements acquired as a nutrient. Acquired nitrogen is incorporated into two of the four main cellular macromolecules, proteins and nucleic acids, and without a source of input nitrogen, a cell cannot construct these essential components. Nitrogen-fixing bacteria also have the same nutritional requirement, but are able to satisfy their nitrogen needs by extracting nitrogen from the atmosphere in the form of N2, nitrogen gas. Ultimately, all life on Earth utilizes the nitrogen assimilated by these bacteria in an indirect manner. Plants are able to take advantage of this process, and some plants (legumes) have a symbiotic relationship with nitrogen-fixing bacteria, which provide the plant with a source of ready to use nitrogen.
One argument that has been levied against conventional farming techniques is that it had been assumed that conventional pesticides were toxic to some degree to the symbiotic bacteria, leading potentially to more rapid depletion of soil nitrogen with conventional farming techniques in comparison to organic farming techniques. This study, from the February 2011 issue of Applied and Environmental Microbiology, found instead that the diversity of nitrogen-fixing bacteria did not depend at all on the type of farming technique used in the field, but instead was very significantly on what crop had been farmed there previously. This actually led to problems in organic farmlands, as legumes are frequently rotated into organic fields to replenish nitrogen levels, and would logically end up depleting nitrogen from the soil more slowly than non-legumes. This results in accumulation of nitrates and ammonia, which in turn suppress the growth of free-living nitrogen fixing bacteria. Soil in which barley and other non-legumous plants were cultivated deplete nitrogen rapidly during a season, which in turn promotes the growth of the nitrogen fixers. Nitrogen-fixing bacteria were actually present in higher numbers the following year in these fields.
So, what’s the take home message here? Should we not buy green? As with most things, there are pros and cons with any approach. As residents downstream in one of the major American watersheds, we are critically aware of the impact that large-scale conventional farming has on our environment. The Chesapeake Bay has historically been one of the most important fisheries in North America, but recently has been significantly impacted by the tremendous farm runoff that the Susquehanna River dumps into the bay. On the other hand, most of the world’s population is dependent on the products of conventional farming, and it is unlikely that current approaches to organic farming will be able to achieve the capacity necessary to feed people in North America, or elsewhere. I think it’s much more important to work to achieve a middle ground, and continue to adapt farming techniques in an attempt to minimize further environmental impact.
BONUS: What do you think?