Organic Vs. Conventional: The Long Term Study

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FB-organic-farm-transBy Judith Redmond of Full Belly Farm, courtesy of  Capay Valley Farm Shop

I participate in a national group that for the past few years has worked to develop policy and action recommendations for food and agriculture.   The group includes people from various parts of the food chain, and it has been clear from the start that while there are many interesting discussions taking place, most of the participants view the practices of organic agriculture as a “niche” or “boutique” part of farming, rather than potentially game-changing solutions to the many challenges faced by the world’s increasing population.   When it comes to addressing the converging and increasingly pressing challenges of hunger, poor water quality and climate change, the proponents of chemicals, monoculture and an industrialized-type approach to farming are well represented.

In part because of my participation in these discussions, I was especially interested in a recently published report about an experiment that was started all the way back in 1998, called the “Long Term Agroecological Research Experiment,” one of the longest running comparisons of organic and conventional agriculture in the U.S. In a nutshell, the   study concludes that producers making the switch to organic crops not only fetch premium prices, they also build healthy soil and sequester carbon, making organic agriculture a useful strategy for dealing with climate change.

“Farmers interested in transitioning to organic production will be happy to see that, with good management, yields can be the same, with potentially higher returns and better soil quality,” said Kathleen Delate, agronomy and horticulture professor at Iowa State University, who leads the project.

The experiment is located on 17 acres at the Iowa State University Research and Demonstration Farm near Greenfield. The project compared four crop rotations using identical varieties that are repeated four times in 44 plots. The conventional rotation received synthetic nitrogen, herbicides and insecticides at recommended rates. The organic corn plots received composted manure from a local chicken operation. Weeds were managed by timely tillage, longer crop rotations and cover crops.

The study found that soils in the organic plots (three- and four-year rotations of corn, soybean, oats and alfalfa) had significantly higher quality compared to the plots using a conventional two-year rotation of corn and soybeans. The organic plots had up to 40 percent more biologically-active soil organic matter, which is important for fertility and nutrient availability. Organic soils also had lower acidity and higher amounts of carbon, nitrogen, potassium, phosphorous and calcium.

Healthy soils hold more water and improve water infiltration, increasing a farm’s resiliency to drought, heavy rainfall and extreme weather events. Farming practices that build soil health also increase carbon storage in soil, called carbon sequestration, which buffers climate change and contributes to better water quality.

Project investigators gathered data on yields and economic viability: Corn and soybean yields were statistically equivalent in the organic and conventional systems during both the transitional phase (1998-2001) and established phase (2002-2010) of the experiment. Yields for organic oats and alfalfa exceeded county averages.

Based on plot-level data, the economic analysis showed that the organic crops fetched roughly $200 more per acre over the 13 years of the study because of premium market prices and reduced input costs. In 2010, for example, an acre of land planted with the four-year organic rotation returned $510, while an acre planted with conventional corn-soybean returned $351.

On average, labor requirements doubled for the organic systems. There was no significant difference in the number of crop pests. The results suggest that skilled management practices can overcome the need for synthetic inputs.


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