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  • Author or Editor: Kathleen Delate x
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Because cropping systems must fit into the environmental, social, cultural and economic reality of the farming community, it is essential that practitioners are included in designing experimental techniques and evaluating application for their farms. Iowa State Univ. conducted a series of Focus Groups with growers and agribusiness professionals to assist in the design of vegetable cropping systems research trials. Trials were established to investigate vegetable agroecosystem status and needs. An agroecosystem analysis seeks to identify indicators of sustainability in a system, including plant health, biological diversity, soil/water quality, and level of biological control of insects and diseases. From this work, a checklist of ecological parameters has been developed for use in cropping systems research. Examples from Iowa, California, and North Carolina will be presented as case studies, exploring multi-disciplinary approaches to cropping systems research.

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Organic farming has increased to a $4.2 billion industry in the U.S. and continues to expand ≈20% annually. In Iowa alone, organic acreage for all crops has increased from 13,000 in 1995 to 120,000 in 1998. Organic farmers have requested an unbiased analysis of natural soil amendments/fertilizers and compost products on the market for certified organic vegetable and herb production. In our first-year trials at the ISU Muscatine Island Research Farm in 1998, a total of 1,120 `Hungarian wax' pepper plants were transplanted into rows at 31 × 61-cm spacing. Four replications of seven fertilization treatments were planted within the field. The goal of the fertilization program was to obtain equivalent nitrogen and calcium rates in the organic and conventional systems. Leaf height was not significantly different in plants fertilized with organic compost (poultry litter-based) at 50 and 100 kg/ha N compared with conventional fertilizers (at 100 kg/ha N). All organic and conventional treatments had greater biomass than the organic and conventional controls (no fertilizer), respectively (ANOVA, P = 0.05). First harvest fresh weights were greater in the organic treatments, with the greatest number of peppers and greatest fresh weight in the compost plus Bio-Cal® (a liming industry by-product) treatment. Total pepper fresh weight over the five harvest periods was not significantly different among treatments, demonstrating to organic farmers that comparable yields can be obtained in systems employing alternatives to synthetic nitrogen fertilizer.

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Based on citizen demand, Iowa State Univ. (ISU) established the first organic specialist faculty position at a U.S. Land Grant Univ. in 1997, as a shared appointment in the departments of horticulture and agronomy, with a 70% Extension and 30% Research split. A series of Organic Agriculture Focus Groups was convened in 1998 to help direct the new organic research and Extension program at ISU. Partnerships with the Leopold Center for Sustainable Agriculture and the College of Agriculture facilitated the ISU sustainable agriculture Extension leader and organic specialist's participation in an extensive focus group dialogue with a diverse group of farmers (organic and conventional), agribusiness professionals, bankers and consumers in six agricultural communities across Iowa. Paramount in the needs assessment was the establishment of organic research sites, both on-farm and at research stations across the state, to demonstrate the economic and environmental benefits associated with organic farming practices over the long term. Specific outcomes-based Extension needs were articulated, which led to the development of an annual schedule of organic workshops, field days and conferences. In 2001, in a survey of 300 farmers, 90% of respondents reported an increase in soil quality and 67% reported a 6 to 30% increase in farm income as a result of organic farming practices. The success of Land Grant Univ. organic programs will be dependent upon administrative support, sufficient resources, and community involvement in the decision-making process.

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Organic farming has increased to a $6 billion industry in the U.S. and continues to expand 20% annually. In Iowa, organic acreage for all crops has increased from 13,000 in 1995 to 130,000 in 1999. Most organic farmers rely on crop rotations, compost, or manure applications, and cover crops to maintain soil fertility. In our trials at the Iowa State Univ. Muscatine Island Research Farm, a cover crop of hairy vetch (Vicia villosa) and rye was seeded in the fall and incorporated 2 weeks prior to transplanting `Lantern' pepper plants. Other organic and conventional soil treatments were applied at transplanting and at 3 weeks post-planting. Four replications of 40 peppers transplanted at 31 × 61-cm spacing under seven fertilization treatments were observed for plant growth and yields. The fertilization goal was to obtain equivalent nitrogen and calcium rates in the organic and conventional systems. Plants fertilized with the compost at 88 kg/ha N plus BioCal® (a liming industry by-product) were not significantly greater in leaf biomass than plants conventionally fertilized with equal amounts of N. All organic and conventional treatments had greater biomass and yield than the organic and conventional controls (no fertilizer), respectively (P = 0.05). Pepper fresh weight was greater in the vetch-strips treatment than in the vetch-incorporated, and the 44 kg/ha N compost treatment, but significantly less than the conventionally fertilized plants. Second year results demonstrated similar results to the 1998 trial where the greatest yields in the organic system occurred in the compost at 88 kg/ha N plus BioCal® treatment, demonstrating to organic farmers that comparable yields can be obtained in systems employing alternatives to synthetic nitrogen fertilizer.

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Iowa was the sixth largest producer of grapes in the United States in the early 1900s, with 24,000 ha under production. The rapid expansion of petrochemicals post-World War II and grape's sensitivity to 2,4-D herbicides reduced vineyard size in Iowa to 28 ha in 2001. Recent state governmental support for organic fruit research and viticulture in general has led to the expansion of the grape and wine industry in Iowa. As of 2001, 5883 ha of organic grapes were produced in the United States. Challenges to organic grape production in the Midwest include diseases and weeds. The cultivation of American grape cultivars is essential in organic viticulture in the Midwest, including cultivars that are relatively cold hardy and disease tolerant. From 2003 to 2004, we experimented on-farm at Kirkland Vineyards, Norwalk, Iowa, with methods of organically approved weed management. Three replications of plots consisting of five vines each of `Marechal Foch' were laid out in 2003 in a completely randomized design in a 1-year-old vineyard. Treatments consisted of wood chips, wood chips plus vinegar herbicide (All-Down™, Summer Set Co., Chaska, Minn.), and mowing when weeds and groundcover reached 15 cm. Wood chips decreased weed load significantly over mowing alone, but wood chips plus vinegar herbicide provided the most control over 2 years of the experiment. There was a trend toward greater plant height in the wood chip treatment, but no significant differences in plant height were observed among treatments.

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Consumption of Echinacea, one of the most popular botanical supplements, continues to expand in the United States. In addition, organic herbal products have captured a large share of the botanical supplement market. We evaluated commercial organic production of the three most-important medicinal species of Echinacea, E. angustifolia DC, E. purpurea (L) Moench., and E. pallida (Nutt.) from two seed sources. Plants were grown in the field for 3 consecutive years. We found that, during the first year, screen cages were associated with enhanced post-transplanting establishment. Growth of E. angustifolia was not affected by either production system or seed source after 3 years, and yields were equivalent for years 2 and 3 for this species. Growth of E. purpurea was affected by production system, but not by seed source, during the first 2 years. In year 3, neither seed source nor production system affected growth of E. purpurea. Yield of E. pallida was greater in the open field the first year; no difference between production systems was found during the second; and, by the third year, plants growing in screened cages produced more than plants growing in the open field. Production system affected yield of E. purpurea only during year 2, and yield was greater in the open field than in screened cages. Echinacea plants in the open field, however, were more affected by aster yellows disease, with an infection rate of 17% for E. purpurea in the open field compared to 3% under screen cages. Based on these results, in areas of aster yellows incidence, excellent Echinacea root yields can be obtained under screen cages using organic seeds.

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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.

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Organic production of one of the most popular botanical supplements, Echinacea, continues to expand in the U.S. Echinacea seeds typically show a high degree of dormancy that can be broken by ethephon or gibberellic acid (GA), but these methods are currently disallowed in organic production. In order to determine the efficacy of nonchemical seed treatments, we evaluated the effect of varying seed source and supplying light, with and without cold-moist stratification, on seed germination of the three most important medicinal species of Echinacea, E. angustifolia DC, E. purpurea (L) Moench, and E. pallida (Nutt.) Nutt. Treatments included cold-moist stratification under 24 hours of light, 24 hours of dark, and 16/8 hours of light/dark to break seed dormancy. We found that germination was greater in the E. purpurea and E. pallida seeds from a commercial organic seed source compared to a public germplasm source. When seeds were not cold-moist stratified, 16 to 24 hours light increased germination in E. angustifolia only. Echinacea angustifolia, E. purpurea, and E. pallida seeds that were cold-moist stratified under 16 to 24 hours of light for 4 weeks had a significantly greater percentage and rate of germination compared to seeds germinated in the dark. Therefore, cold-moist stratification under light conditions is recommended as a method to break seed dormancy and increase germination rates in organic production of Echinacea.

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With the increase in popularity of echinacea as a botanical supplement, organic production of this herb continues to grow. Echinacea seeds typically show a high percentage of dormancy that can be broken by ethephon or gibberellic acid, but these methods are not accepted in organic production. We examined in three experiments the effects of varying seed source and germination conditions on echinacea growth. To determine the efficacy of nonchemical treatments, we evaluated the effect of light with and without cold-moist stratification on seed germination of the three most important medicinal species of echinacea, E. angustifolia, E. purpurea, and E. pallida. We used cold-moist stratification under 24 h light, 24 h dark, and 16/8 h (light/dark) to break seed dormancy. We found that germination was enhanced in seeds from a commercial organic seed source, compared to a public germoplasm source. When seeds were not cold-moist stratified, light increased germination in E. angustifolia only, suggesting differential dormancy among the three species. We found that when seeds were cold-moist stratified under 16–24 h of light for 4 weeks, the percentage and rate of germination increased 10% over the control, suggesting this method as an alternative to chemical seed treatments.

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Echinacea is one of the best-selling medicinal plants in the United States. It was historically harvested from wild populations, but its demand has increased so significantly that commercial production has become a necessity to supply the increasing demand and to protect wild populations. The medicinal properties of echinacea are associated with secondary metabolites that are produced mainly in the roots. Hairy roots, induced by the Ri plasmid of Agrobacterium rhizogenes, have been produced in other crops as alternative sources of secondary metabolites that commonly are produced and synthesized in the roots of mature plants. This method of production offers some advantages over traditional agricultural systems, such as the possibility of producing novel compounds year-round. The overall goal of this project is to explore the utility of hairy root cultures (mediated by A. rhizogenes) as an efficient, alternative, and enriched source of secondary compounds with medicinal properties, such as alkamides, flavonoids, and caffeic acid derivatives. We have been successful in transforming roots from E. angustifolia, E. pallida, and E. purpurea plants, and confirming the presence of rol ABC genes in hairy roots using molecular techniques. Roots from control plants show no active growth under dark conditions, whereas transformed roots from E. pallida and E. purpurea show a low degree of branching with a slow growth rate on solid media under darkness. However, transformed E. angustifolia show a faster growth rate and higher degree of branching under the same conditions. Currently, we are working on the optimization of the growing conditions of the transformed roots and will proceed to the biochemical analysis phase of the project.

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