Does Organic Farming Increase The Quality Of Soil?

To a chemist, organic means that a compound contains carbon. To a farmer, it means using non-synthetic fertilizers and pesticides. It turns out that organic farming actually may make the soil more organic in the chemical sense too.

An analysis of 74 studies on the soils in fields under organic or conventional farming practices, found that over time the carbon content in the organic fields had significantly increased. For farmers, that means organic agriculture results in a richer, more productive soil with plenty of humus. 

Although the carbon in the organic fields is good for the farmers' wallet, the research didn't find evidence that organic farming was trapping enough carbon in the soil to combat climate change. Extraneous sources of greenhouse gas emissions related to agriculture weren't analyzed in the study, hence the study's authors could not determine if organic farming was tilting the scales towards trapping more greenhouse gases than it released.

For example, soil-derived nitrous oxide (a greenhouse gas) emissions weren't accounted for in the research. Nor were emissions resulting from the production of organic fertilizers. Energy-related emissions from farm machinery and irrigation, as well as emissions from livestock and manure, were also not measured.

The study's authors noted that offsetting emissions with trapping carbon in soil only buys time and does not negate the need for emission reduction. - Tim Wall, Discovery News 

Side-by-side comparisons of organic and conventional strawberry farms and their fruit found the organic farms produced more flavorful and nutritious berries while leaving the soil healthier and more genetically diverse.

“Our findings have global implications and advance what we know about the sustainability benefits of organic farming systems,” said John Reganold, Washington State University Regents professor of soil science and lead author of a paper published today in the peer-reviewed online journal, PLoS ONE. “We also show you can have high quality, healthy produce without resorting to an arsenal of pesticides.”

The study is among the most comprehensive of its kind, analyzing 31 chemical and biological soil properties, soil DNA, and the taste, nutrition and quality of three strawberry varieties on more than two dozen commercial fields—13 conventional and 13 organic.

“There is no paper in the literature that comprehensively and quantitatively compares so many indices of both food and soil quality at multiple sampling times on so many commercial farms,” said Reganold. Previous Reganold studies of “sustainability indicators” on farms in the Pacific Northwest, California, British Columbia, Australia, and New Zealand have appeared in the journals Science, Nature, and Proceedings of the National Academy of Sciences.

All the farms in the current study were in California, home to 90 percent of the nation’s strawberries and the center of an ongoing debate about the use of soil fumigants. Conventional farms in the study used the ozone-depleting methyl bromide, which is slated to be replaced by the highly toxic methyl iodide over the protests of health advocates and more than 50 Nobel laureates and members of the National Academy of Sciences. In July, California Sen. Dianne Feinstein asked the EPA to reconsider its approval of methyl iodide.

Reganold’s study team included Preston Andrews, a WSU associate professor of horticulture, and seven other experts, mostly from WSU, to form a multidisciplinary team spanning agroecology, soil science, microbial ecology, genetics, pomology, food science, sensory science, and statistics. On almost every major indicator, they found the organic fields and fruit were equal to or better than their conventional counterparts.

Among their findings:

The organic strawberries had significantly higher antioxidant activity and concentrations of ascorbic acid and phenolic compounds.

The organic strawberries had longer shelf life.

The organic strawberries had more dry matter, or, “more strawberry in the strawberry.”

Anonymous testers, working at times under red light so the fruit color would not bias them, found one variety of organic strawberries was sweeter, had better flavor, and once a white light was turned on, appearance. The testers judged the other two varieties to be similar.

The researchers also found the organic soils excelled in a variety of key chemical and biological properties, including carbon sequestration, nitrogen, microbial biomass, enzyme activities, and micronutrients.

DNA analysis found the organically managed soils had dramatically more total and unique genes and greater genetic diversity, important measures of the soil’s resilience to stress and ability to carry out essential processes. - Public Library Of Sciences 

The PLoS One Report On Organic Soil And Strawberry Quality

Six encouraging conclusions on the impacts of organic farming on soil quality and the nutritional content of food were reached by a panel of scientists participating in a February 13, 2009, symposium 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 was held as part of the largest scientific meeting of the year that spans all disciplines. The AAAS meeting was held this year in Chicago, IL.

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.

The "Living Soil, Food Quality, and the Future of Food" symposium was organized and sponsored by Washington State University and The Organic Center, based in Boulder, CO. The presentations made by the three panelists and other symposium information are posted on The Organic Center website.

A growing body of sophisticated research over the last decade 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, we can conclude that:

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. Most secondary plant metabolites are antioxidants, a class of plant compounds that have been linked to improved human health in populations that consume relatively high levels of fruit and vegetables.

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.

Commenting on the well-attended symposium, Dr. Preston Andrews said, "The work we reviewed over the last decade points directly to two major scientific challenges. 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." - The Organic Center