Farmers interested in transitioning some or all of their land into organic production need information regarding the best management practices for these systems. Soil fertility and weed management strategies are imperative for optimum plant growth and yields. Current research in organic herb production at Iowa State University has included investigations into certified organic methods of fertilization and use of organic mulches for weed suppression. Organic medicinal herbs research plots were established in 1999 in Ames, Iowa, to investigate the effect of organic fertilizer and compost on Echinacea purpurea, E. angustifolia and lemon balm plant growth and yields. Although increased yields were obtained with vegetables (broccoli and green peppers) fertilized with composted turkey manure (UltraGroÆ, Ellsworth, IA), results with herb crops were not consistent. Soil amendments increased herb leaf growth only in the case of Echinacea angustifolia. With lemon balm (Melissa officinalis), which is harvested for leaf matter, fertilization effects were more pronounced, but not to the level of significantly improving yields. Echinacea root production, the most important factor for commercial sales, was not significantly affected by soil amendments. Because Echinacea is a native plant, and Iowa soils are rated as sufficiently fertile, additional fertilization does not appear necessary to increase yields. The long-term benefits of compost to the soil-plant system in terms of improving soil structure through the addition of organic matter, soil moisture retention, and soil microbial activity may exceed benefits derived from the supply of plant nutrients alone. This information was transferred through on-farm Field Days and workshops at Iowa State University. Additional organic medicinal herbs (catnip and St. Johnís Wort) research plots were established in 2001 in a 2-3 year project to identify, through replicated trials, which organic mulches provide the optimum level of weed suppression, yields, and herbal quality. Weed suppression and yield increase were obtained from natural mulches (flax mat, wool mat and oat straw). Comparisons of biochemical constituents and essential oil yields for both projects are underway at Iowa State University, Rutgers University and Frontier Natural Products Cooperative, Norway, IA. Funding from the Organic Farming Research Foundation helped support a graduate student (Lisa Duppong) for her analysis of the soil amendment component of this project, and establishment of the weed management component. Funding was also used to support the establishment of an herb demonstration site with the Organic Herb Producers Cooperative in Lakeville, Minnesota.
