|Organic Farming Improves Soil Health, Delivers Nutrient-Rich Foods|
February 27, 2009
Based on a growing body of research, a panel of scientists has offered several
positive conclusions regarding the impacts of organic farming on soil quality
and the nutritional content of food.
The panel presented its findings at the annual meeting of the American
Association for the Advancement of Science (AAAS). The symposium was entitled
“Living Soil, Food Quality, and the Future of Food” and organized and sponsored
by Washington State University and The Organic Center, Boulder, CO.
The panel of scientists included Dr. Preston Andrews, Washington State
University, Dr. Jerry Glover, The Land Institute, and Dr. Alyson Mitchell,
University of California-Davis.
Over the last decade abundant research has compared the impacts of organic and
conventional farming systems on soil and food quality. Based on this body of
research, some of it carried out in field experiments and laboratories, the
panel offered six conclusions:
1. Studies of apple production demonstrate that organically farmed soils
display improved soil health as measured by increased biological diversity,
greater soil organic matter, and improved chemical and physical properties.
Enhancement of soil quality in organic apple production systems can lead to
measurable improvements in fruit nutritional quality, taste, and storability.
2. Organically farmed tomatoes have significantly higher levels of soluble
solids and natural plant molecules called secondary plant metabolites, including
flavonoids, lycopene, and vitamin C.
3. Organic farming can, under some circumstances, delay the onset of the
“dilution effect.” In hundreds of studies, scientists have shown that
incrementally higher levels of fertilizer negatively impact the density of
certain nutrients in harvested foodstuffs, hence the name, the “dilution [of
nutrients] effect.” Specifically, tomatoes grown with organic fertilizers
maintain constant concentrations of beneficial phenolic secondary plant
metabolites and antioxidants, even as fruit grow larger, whereas concentrations
of these same beneficial compounds decline with increasing fruit size when the
same tomato cultivar is grown using conventional methods and fertilizer.
4. Studies of 27 cultivars of organically grown spinach demonstrate
significantly higher levels of flavonoids and vitamin C, and lower levels of
nitrates. Nitrates in food are considered detrimental to human health as they
can form carcinogenic compounds (nitrosamines) in the GI tract and can convert
hemoglobin to a form that can no longer carry oxygen in the blood.
5. The levels of secondary plant metabolites in food appear to be driven by the
forms of nitrogen added to a farming system, as well as the ways in which the
biological communities of organisms in the soil process nitrogen. Compared to
typical conventional farms, the nitrogen cycle on organic farms is rooted in
substantially more complex biological processes and soil-plant interactions, and
for this reason, organic farming offers great promise in consistently producing
6. Organic soil fertility methods, which use less readily available forms of
nutrients, especially nitrogen, improve plant gene expression patterns in ways
that lead to more efficient assimilation of nitrogen and carbon in tomatoes.
This improvement in the efficiency of nutrient uptake leaves plants with more
energy to produce beneficial plant secondary metabolites, compounds that promote
plant health as well as human health.
“The work we reviewed over the last decade points directly to two major
scientific challenges,” said Dr. Andrews. “First, we need to understand more
fully how soil biological communities process nutrients and communicate to plant
roots in order to promote improved quality in organically grown crops. And
second, we need better tools to help organic farmers fine-tune their production
systems in order to maximize the soil and nutritional quality benefits of