Iowa Cornfield of Dreams

grassby Helen Scharber

In the 1989 movie Field of Dreams, Kevin Costner’s character famously builds a baseball field in Iowa that “reminds us of all that once was good and that could be again.”  In another field in Iowa, two decades later, agricultural researchers also found that what once was good—in this case, crop rotation as a natural way to fertilize soil and kill weeds—could be again.  And could be really good, in fact.   Over the past 40 years, a limited two-crop rotation of corn and soy has become the new normal in U.S. agriculture, along with increased use of chemical fertilizers and herbicides. In a paper published in 2012, the Iowa researchers reported that diversifying crop rotation beyond the usual corn and soybean mix was just as productive and profitable as the conventional method.  Conventional wisdom may tell us that sustainably growing enough food to feed the world is a dream, but this study suggests that the possibility is real.


In the study, which ran from 2003 to 2011 and occupied 22 acres of land, researchers set up three types of plots.  In the “control” plots, they replicated the conventional two-year cycle of planting corn one year and soybeans the next, using typical amounts of chemical pesticides and synthetic fertilizers.  The “experimental” plots used either a three-year rotation, adding small grains or red clover in the third year, or a similar rotation that added a fourth year of alfalfa.  In the three- and four-year rotations, clover and alfalfa residues and composted cattle manure from nearby farms were added as fertilizers, and synthetic nitrogen was applied only as needed. During the corn and soybean years, chemical herbicides were applied in 15-inch bands rather than broadcast spraying. The environmental and human health benefits associated with the three- and four-year rotations were stunning.  In the longer rotations, the need for both chemical fertilizer and herbicide use were reduced by more than 80 percent and overall fossil fuel use was reduced by half.  By the fourth year of the study, the freshwater toxicity potential of the more diverse rotations was one two-hundredth that of the conventional system.  The longer rotations also decreased soil erosion and increased soil health.


Diverse crop rotation and manure application have long been known to be effective and safe ways to kill pests and improve the soil. But is it economically feasible? Good news:  The more sustainable approach had no effect on the bottom line.  Corn and soybean yields were slightly higher in the longer rotations. More labor was needed (about 1.5 hours/acre per year in the four-year rotation versus 0.7 in the two-year rotation) and labor costs were correspondingly higher.  But the higher labor costs were made up for by lower energy and chemical costs and these balanced out so that profits were unaffected. At this point in U.S. history, a system that employs more people and uses less fossil fuel is not only ethical, it also makes more efficient use of scarce resources.


It sounds like everyone wins: environmental and health benefits with no reduction in productivity. Yet, reduced demand for synthetic inputs is not a win for chemical companies like Monsanto or Canada’s PotashCorp, the fertilizer company whose 2012 profits topped Apple’s. What’s more, while the study’s authors found that genetically modified (GM) seeds offered higher net returns than non-GM seeds in the corn-soy rotation, they had no advantage in the more diverse rotations.  Thus, Monsanto and its agribusiness cousins are unlikely to be enthused about government-funded research, extension services or subsidies that would encourage a shift away from GM corn and toward more diverse farming, and they already lobby heavily to influence agricultural policy.


Despite the predictable resistance of chemical companies, there are plenty of possible agents of agricultural change. There are better ways than current practice to farm in a resource-constrained world. Researchers can help build the needed knowledge base, and public awareness of the issues involved can help shift priorities.  The biggest source of potential change, though, lies within the farming community. Changing from a two-crop rotation back to three- and four-crop rotations will require some new skills and the revival of some old techniques, but farmers have long experience adapting to ever-changing conditions. Once there are a few visibly successful early-adopters, it will become easier for more farmers to make the change until these methods become the new norm.  That is, if a few more farmers build it, the rest will hopefully come.



Davis, Adam S., Jason D. Hill, Craig A. Chase, Ann M. Johanns, and Matt Liebman. 2012. “Increasing Cropping System Diversity Balances Productivity, Profitability and Environmental Health.” Edited by John P. Hart. PLoS ONE 7 (10) (October 10).

Leopold Center for Sustainable Agriculture, Iowa State University. 2013. “Frequently Asked Questions About Cropping System Diversity and Profitability.” Leopold Center Website.  

Bittman, Mark. 2012. “A Simple Fix for Farming.” New York Times, October 19, Online edition, sec. Opinion.

Laskawy, Tom. 2012. “Corn Maze: There Is No ‘Simple Fix’ for Commodity Farming.” Grist. October 26.