Crop Plant Nutrition and Insect Response in Organic Field Crop Production: Linking Farmer Observation to University Research and Extension

Non-Technical Summary: A largely informally held concept, based on practical experience and observations of organic farmers around the world is that crop plants grown in organically managed crop rotations receiving biological sources of nutrients such as livestock manure, legume nitrogen, and green manure cover crops are more resistant to insect pests than are conventionally produced crop plants. The emphasis that organic farmers place on insect pest prevention rather than pest control merits serious attention by integrated pest management (IPM) science researchers and Cooperative Extension educators. The purpose of this project is to evaluate two different organic fertility management systems in a grain crop/forage legume rotation under both transition and certified organic systems by comparing soil and crop nutrient profiles with insect response. Research and Extension activities of the project team are structured to increase awareness of how organic fertility management influences field crop plant nutrition and insect pest management, and provide innovative IPM strategies to end-users of the research based information (organic and transitional farmers; extension educators; agricultural consultants; and non-profit organizations providing educational resources to organic farmers). <P> Approach: Two organic fertility management systems will be evaluated in this study to test the general hypothesis that insect pest populations are less variable and stabilize at lower densities under organic fertility management systems which afford crop plant tissue a regulated and balanced supply of nutrients. First, under the standard organic fertility treatment, nitrogen and other crop nutrients are supplied by use of livestock manure, alfalfa hay in the rotation, and small grain/legume winter cover crop green manure. Soil pH corrections are achieved with addition of locally supplied crushed dolomitic limestone as determined by soil test need. Second, the soil balance organic fertility treatment also relies on a combination of livestock manure, alfalfa hay and green manure cover crops, but includes application of high-calcium lime or gypsum soil amendments, regardless of soil pH levels. A controlled experiment will be conducted on approximately 30 acres of land under transition to organic certification at the UW Arlington Agricultural Research Station. Based on recommendations provided by organic grain crop grower project advisors, a four year Small Grain/Alfalfa, Alfalfa, Corn, Soybean rotation was chosen. Each phase of the rotation will be grown each year of the study, replicated four times in a factorial experimental design at the long-term study site. In addition, the project team will conduct on-farm research and data collection under Objectives 1 and 2 from working certified organic farms with similar rotation. Six farms will be grouped into the two organic fertility management categories as described above, three following the standard organic fertility management treatment and three the soil balance treatment. Both the controlled transition experiment and research with growers on certified organic farms will examine grower selected crop-insect associations of economic concern including Soybean and soybean aphid; Alfalfa and potato leafhopper; and Corn and European corn borer. Soil fertility, crop tissue nutrient profiles and pest and beneficial insect response variables will be assessed for each crop/pest association. Greenhouse and laboratory studies will be conducted to further define mechanisms of pest insect and beneficial insect response patterns emerging from field studies. The project focus represents efforts and research priorities of a diverse stakeholder group comprised of a University of Wisconsin-Madison Extension specialist (entomology); a UW-Madison outreach program manager and organic farmer with soil and crop nutrient emphasis; Eight Wisconsin organic farmers from a mix of grain and legume forage crop farming enterprises; a WI Department of Agriculture grazing and organic agriculture specialist; Superintendent of the UW Arlington Agricultural Research station; and a Professor of Biological Sciences at UW- Marathon County, a two year A.A. degree institution in north central Wisconsin.