Assessing the Benefits of Radish As a Cover Crop.

Oilseed radish (Raphanus sativus L) is a popular cover crop for no-till farmers in Wisconsin, especially among those that include winter wheat in rotation since radish can accumulate large amounts of nitrogen (N). However, previously presented research in Wisconsin has not shown a clear N credit for a subsequent corn crop. Additionally, there is a lack of information that quantifies other benefits of radish, including compaction reduction and nematode suppression. The objective of this project was to determine the effects of radish as a cover crop on optimum N rate, soil compaction, and nematode populations. Radish cover crops were planted in mid-August at two field sites located in Southern and Northeast Wisconsin. Each radish treatment was accompanied by a no cover crop treatment, and all treatments were split into increasing amounts of nitrogen fertilizer. Radish biomass and volunteer winter wheat was collected within each whole plot in the fall prior to radish winterkill and analyzed for total nitrogen uptake. Soil nitrate samples were collected pre-plant and pre-sidedress to determine any potential N credit. During the growing season, soil samples were collected for each plot and analyzed for root lesion and soybean cyst nematodes. Soil compaction was measured in each plot using a portable constant-rate cone penetrometer. Results have shown that while radish N uptake can be quite substantial, we have not been able to determine an N credit across six site years. However, in some cases, soil nitrate samples would suggest an N credit. Soil penetrometer data did not indicate any difference in soil compaction between treatments. Soybean cyst nematodes were detected in only a few plots so the data were not analyzed. The root lesion nematode data is currently being analyzed.