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Organic agriculture has expanded to a $13 billion industry in the United States in 2005, continuing the nearly decade-long trend of 20% annual growth. Despite the growth in organic agriculture, our scientific knowledge of organic agriculture farming systems remains limited. Interest in sustainable and organic education at the university level has increased in recent years. To help address this need, the Iowa State University Graduate Program in Sustainable Agriculture (GPSA) was established in 2001 to meet three principal objectives: 1) provide students with the analytical and problem-solving skills required to meet the challenges confronting agriculture in the 21st century; 2) develop an innovative interdisciplinary and interdepartmental approach to graduate education; and 3) position Iowa State University at the forefront of institutions conducting research and extending knowledge about sustainable agricultural systems. As of 2004, more than 70 faculty from various departments and 29 students have participated in the program. Students have the opportunity to investigate organic issues within the context of the five new GPSA courses and to conduct organic agriculture farming systems research in thesis and dissertation studies. Producers and agricultural professionals are involved with GPSA students through the curriculum and on-farm research. Research questions involving optimizing crop or livestock production, plant protection, soil quality, and socioeconomic benefits of farming systems constitute typical theses.
Sales of organic products reached $8 billion in the U.S. in 2000, continuing the nearly decade-long trend of 20% annual growth. In Iowa alone, organic production for all crops was 5265 ha (13,000 acres) in 1995 but 60,750 ha (150,000 acres) in 1999. Despite the growth in organic agriculture, our knowledge of organic farming systems remains limited. We have adopted a systems theory approach in our current research program at Iowa State University (ISU) to help address this gap in understanding. Systems theory holds that biological systems, such as agroecosystems, consist of integrated units of people, plants, animals, soil, insects and microorganisms, and each subsystem provides feedback to the other. In order to obtain input on research questions and experimental design, the Leopold Center for Sustainable Agriculture and ISU held six focus groups across Iowa in 1998 before long-term site establishment. Producers and agricultural professionals at the focus groups supported the need for long-term agroecological research (LTAR) sites in four distinct agroecological zones in Iowa. The goal of each LTAR is to examine the short- and long-term physical, biological, and socioeconomic effects of organic and conventional farming systems. By establishing long-term experiments, we are testing the hypothesis that longer crop rotations, typical of organic farms, provide yield stability, improve plant protection, and enhance soil health and economic benefits compared to conventional systems with shorter rotations and greater off-farm inputs. Examples of research results from two LTAR experiments in Iowa include similar pepper (Capsicum annuum) and soybean (Glycine max) yields in the conventional and organic systems. Organic systems used mechanical weed control and locally produced compost in place of synthetic fertilizers. Feedback from the local farm associations that are responsible for farm stewardship and farm finances is inherent in the LTAR process.
With the continuing 20% growth rate in the organic industry, organic vegetable crop production has increased to 98,525 acres in the United States. The requirement for certified organic vegetable producers to implement a soil-building plan has led to the development of soil fertility systems based on combinations of organic fertilizers and cover crops. To determine optimal soil fertility combinations, conventional and organic bell pepper (Capsicum annuum) production was evaluated from 2001 to 2003 in Iowa, comparing combinations of two synthetic fertilizers and three compost-based organic fertilizers, and a cover crop treatment of hairy vetch (Vicia villosa) and rye (Secale cereale) in a strip-tilled or fully incorporated cover crop system. Organic pepper growth and yields equaled or surpassed conventional production when nitrogen (N) was provided at 56 or 112 kg·ha−1 from compost-based organic fertilizer. Soil analysis revealed higher N in plots where cover crops were tilled compared with strip-tilled plots, leading to recommendations for sidedressing N in strip-tilled organic pepper production. Increased incidence of disease was also detected in strip-tilled plots. Postharvest weight loss after 6 weeks in storage was similar in organic and conventional peppers. The addition of calcium and sulfur products in conventional or organic fertilizer regimes did not increase pepper production or postharvest storage potential. Despite application challenges, cover crops will remain as critical components of the organic farm plan for their soil-building benefits, but supplementation with approved N sources may be required for optimal pepper production. Organic growers should conduct their own tests of organic-compliant soil amendments to determine cost effectiveness and value for their site before large-scale application.
Abstract
Sweet potatoes (Ipomoea batatas L.) were exposed to low O2 and high CO2 for 1 week during curing or subsequent storage to evaluate the use of controlled atmospheres (CA) as insecticidal treatments for sweet potatoes infested with sweet potato weevil (Cylas formicarius elegantulus). Sweet potato roots tolerated 8% O2 during curing, but, when exposed to 2% or 4% O2 or to 60% CO2 plus 21% or 8% O2, they were unsalable within 1 week after curing, mainly due to decay. Exposure of cured sweet potatoes to 2% or 4% O2 plus 40% CO2 or 4% O2 plus 60% CO2 for 1 week at 25C had little effect on postharvest quality. However, exposure to 2% O2 plus 60% CO2 resulted in increased decay, less sweet potato flavor, and more off-flavor. These results indicate that exposure of sweet potatoes to O2 and CO2 levels required for insect control is not feasible during curing, but that cured sweet potatoes are capable of tolerating CA treatments that have potential as quarantine procedures.
As organic agriculture continues to grow, pressure from students and the public to develop novel curricula to address specific needs of this sector of agriculture also will increase. More students from the cities and with limited background in production agriculture are enrolling in agricultural programs with special interest in organic production. This new student population is demanding new curricula based on a better understanding of agroecology principles and more experiential training. Several universities throughout the nation have engaged in a profound curriculum transformation to satisfy the emerging need of students in organic production. This workshop was organized to bring together experts that are working on different organic and sustainable agriculture curricula throughout the country to share their experiences and lessons learned. Most of these curricula include a traditional classroom teaching component, a major experiential component, a student farm for hands-on experience and internships, and in some cases a marketing—typically a community supported agriculture (CSA)—component. Others programs are more extension oriented, providing applied training to growers outside of the university teaching curriculum.