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 nutrient-enriched foods.

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 organic farming.”