Organic Production Increases Yields and Builds Soil Quality in Iowa

Yields increase, soil resilience soars; Long-term research proves organic promise
By ANNE LARSON, Special to the Leopold Center

Year-by-year comparisons, ISU Organic Ag web site

Coupling long-term cropping research with rigorous replication yields reliable results. That’s the premise that drove establishment of the Center’s Long-Term Agricultural Research (LTAR) initiative in 1998 at the Neely-Kinyon Research Farm near Greenfield. The study is believed to be the largest randomized, replicated comparison of organic and conventional crops in the nation.
Kathleen Delate presents information at the August 2006 Neely-Kinyon field day, which drew more than 200 people.
An aerial view of the ISU organic field test plots, which are believed to be the longest-running, largest, randomized comparison of organic and conventional crops in the nation.
Nine years later, leader Kathleen Delate, Iowa State University horticulture and agronomy professor, can display results that convincingly show greater yield, increased profitability, and steadily improved soil quality in organic over conventional rotations. The results bode well for producers looking for higher returns while building soils. “The long-term project enables us to achieve repeatable results,” Delate explains. “If you get the same results over time, they become much more credible to farmers, scientists and policymakers,” she adds.The LTAR has been funded by the Leopold Center to examine short- and long-term physical, biological and economic outcomes of certified organic and conventional grain-based cropping systems. The Neely-Kinyon farm research is testing whether organic systems relying on inputs such as composted manure can promote stable yields, soil quality and plant protection. Those results are being compared with a corn-soybean (C-S) rotation supported by greater levels of externally acquired inputs such as fossil-based fuels. The rotations used on the organic plots have been corn-soybean-oat/alfalfa (C-S-O/A) and corn-soybean-oat/alfalfa-alfalfa (C-S-O/A-A).In the LTAR project, organic crop yields were equal to conventional acres in the three years of transition. In the fourth year, organic corn yields in the longest rotation outpaced those of conventional corn. Organic soybean, which can be grown for a price premium, also out-yielded conventional soybean in the fourth year of the rotation. The research also reported remarkable consistency of yields during the first three transitional years.
One of the things that sets the research apart in addition to its length and design, is that the plots are 42 meters by 21 meters (about 138 ft. by 69 ft., or about 0.2 acre), large enough to accommodate conventional farm equipment. Soil scientist and co-investigator Cynthia Cambardella of the USDA National Soil Tilth Laboratory says the large plots were part of what initially drew her to the research. The biggest attraction was the chance to study changes in soil quality during the transition from conventional to organic management within a completely randomized, replicated experiment.Cambardella has monitored a number of soil quality characteristics as part of the project. Those factors include:
soil organic carbon (C);
potentially mineralized nitrogen (N);
particulate organic matter C;
microbial biomass C;
inorganic N;
pH; and
soil structure.
All of these measures have some impact on soil quality. Potentially mineralized N is an estimate of the available part of N that is held in reserve in the soil, cycling and becoming available when temperature and moisture favor microbial activity. Particulate organic matter C comes primarily from the plant root systems and is an easily digestible source of energy for soil microorganisms. Microbial biomass C comes from the bodies of soil organisms and is one of the most easily digestible food sources in the soil. The nutrient needs of organically managed crops are met entirely through the recycling of nutrients from crop residue, roots, green manures and added amendments. High-quality soils cycle nutrients more efficiently and make them available when and where the plants need them.The organic plots are amended in early spring with composted swine manure, made from a mixture of manure and corn stover that was removed from deep-bedded swine “hoop house” structures located nearby. The organic plots are disked, rotary-hoed and cultivated, with an average of two row cultivations per year.On the organic plots, the organic matter from the composted manure quickly helped enhance the resilience of the soil.“Key to this is organic matter and the supply of nutrients,” Cambardella explains. “Biologically active nutrients can be tapped by the plant when temperatures and moisture will drive availability,” she adds. “The exciting news is that, rather quickly, easily decomposable N began to be reserved in the soil in forms that are not subject to leaching with spring rains,” Cambardella says. Soil structural stability also remained good, despite the increased tillage involved with the organic rotations.Cambardella has observed a number of factors that point toward improved soil health on the organic plots, as compared with conventional C-S. After seven years of organic management, she has seen:
more soil organic C,
more biologically-active organic matter,
reduced soil acidity, and
maintained or improved crop yield.
Delate says the ultimate benefit of the long-term project will be to maximize confidence in the data and to monitor any unexpected results that appear over longer periods of time. Researchers will continue to examine the effects of crop sequence and length on long-term pest disruption and attraction of beneficial insects to the organic system.

Moving from conventional to organic: What is the local payoff?
Read executive summary from report

Organic cropping systems help build soils, but can they also help build local communities?That was the question explored by David Swenson and Liesl Eathington of the ISU economics department and Craig Chase, an ISU Extension farm management field specialist. They received a grant from the Leopold Center Marketing and Food Systems Initiative to assess potential region-wide economic impacts of farmers who convert operations from conventional to organic systems. They used as their model a unique Woodbury County plan that provides tax abatements for producers who make the organic transition.The project, “Determining the methods for measuring the economic and fiscal impacts associated with organic crop conversion in Iowa,” affirms existing ISU research which demonstrates that operators who choose organic methods will receive greater economic returns than those who opt for conventional practices. Next, the economic impact of that difference was measured considering all linkages with the regional economy. The study found that the economic impacts of the organic alternative were substantially larger than the conventional configuration, a significant observation for those engaged in rural and regional economic development. Specifically, organic rotation farming produced 52 percent more gross sales revenue, 110 percent more value added, and 182 percent more labor income than from the same 1,000 acres farmed using conventional corn-soybean rotation practices. According to Swenson, “the organic alternative requires greater mechanical inputs, more labor and yields a higher return to the operators. All of these factors combine to yield greater amounts of income-based economic impacts in the study region.” These outcomes will hold up, he adds, even with the recent spike in corn prices as the spread between organic and conventional crop prices has remained relatively constant.The analysis for the effective economic use of property tax abatements as an incentive for farmers to shift from conventional to organic production is not as promising. The study concludes that over a reasonable period of time, the county is not likely to recover the forgone property tax revenue used to fund the original program with sufficient new, economic impact-driven, property tax collections, as well as fund the county and public school services needed by additional workers (along with their household members) in all impacted economic sectors of the organic conversion. However, there may be important non-economic criteria in favor of a property tax inducement to alter farming practices. These would include environmental benefits, diversifying agricultural production, and supporting the development of organic foods production, processing, and consumption in the region.