Paulo Pagliari, Soil Scientist
Carl Rosen, Soil Scientist
Lee Klossner, Research Fellow
University of Minnesota, Southwest Research and Outreach Center
March 31, 2016
The University of Minnesota Southwest Research and Outreach Center (SWROC) near Lamberton, MN, built three organic high tunnels in 2010 that have been used for research and outreach programs. The experiments conducted in these three tunnels focused on variety trials and soil fertility and plant nutrition, with manure compost and green manure being the main source of nutrients. The research conducted was very successful and generated results that have helped local organic growers to improve management of their high tunnels. However, the research results also showed that the nutrient management philosophy of using manure compost to supply a crop’s requirement for nitrogen (N) has the potential to negatively affect the sustainability of the tunnels and lead to soil health problems. The high amount of soluble salts present in manure compost, can lead to salt build up in the soil to levels that are limiting to production of most vegetable crops. The very high concentration of nutrients that can be found in soils from repeated manure and compost application as the main source of nutrients can also cause an imbalance of nutrient uptake by plants leading to physiological disorders and yield reduction. Therefore, being able to maintain soil health is the key to maintain soil productivity and sustainability. Crop rotation can be used as a remedy for soil salinity and high nutrient levels, if the correct plant species and adequate rotations are used. For example, crops such as potato and sweet potato can export a large amount of nutrients from soils; and in combination with other vegetables can provide the tools to improve soil health in tunnels that are starting to become or already are problematic.
The use of high tunnels to extend the growing season is increasing in Southwest MN; however, there is a lack of research that provides information on productivity of a diverse number of crop species that could be used in rotation to help improve and maintain soil health. Therefore, our objectives are: 1) continue the current research and identify a wider number of economically viable vegetable crop species to incorporate in a rotation that improve soil health; 2) provide high tunnel producers with information on how to remediate soil nutrient imbalance to maintain sustainability; 3) determine the nutrient value of cover crops and plant compost compared with beef manure compost; and 4) provide organic growers information on how to improve and maintain sustainability of vegetable production in organic high tunnel in Southwest MN and other regions.