Winter Rye Best Management Practices to Reduce Loads of Sediment and Nutrients to Minnesota Surface Waters

Abstract

Surface runoff from agricultural fields is potentially harmful to our environment because of excessive loads of sediment and nutrients. Industrialized agriculture has provided food for the world, but has also created unintended water quality problems. Excessive nutrient contamination in the Gulf of Mexico has created a zone of hypoxia where dissolved oxygen levels are too low to support aquatic life. The Upper Midwest agriculture is mostly comprised of corn and soybeans and a large amount of the nitrogen (52%) reaching the Gulf of Mexico is a result of this cropping rotation (Alexander, 2008). In addition, up to 50% of applied synthetic fertilizer on Midwestern soils is lost every year due to rainfall and surface runoff (Tonitto, 2006). However, adding cover crops to an agricultural rotation provides soil cover and retention of nutrients. Various studies have shown that a winter rye cover crop can reduce nitrate leaching by 70% (Tonitto, 2006; Ball Coelho, 2005; Staver and Brinsfield, 1998). However, the use of cover crops in the United States Corn Belt is not widely accepted nor implemented. A survey where 3,500 farmers were asked to provide information on cover crop use showed that only 11% of farmers in the Upper Midwest have used cover crops in the last five years (Singer, 2007). This study will develop Best Management Practices (BMPs) for beef and dairy producers that will make cover crops economically viable. Winter rye offers great potential for environmental benefits on land where corn silage or stover is removed to feed livestock. If the winter rye is established early enough, it can be grazed or harvested as forage in the spring before a cash crop is planted. Two locations in southern Minnesota have been selected for monitoring surface runoff and developing viable cover cropping BMPs. Each location consists of a paired watershed design where one watershed is the control (conventional practice) and the other is the treatment (winter rye following corn harvest). The first location will have winter rye aerially seeded into standing corn grain with spring grazing of the winter rye. The second location will have drilling of winter rye following corn silage harvest with winter rye harvested as forage in the spring prior to soybean planting. This study will encompass two full growing seasons from 2009 to 2011. Additional small plot experiments with the use of a rainfall simulator to evaluate surface runoff differences between conventional practices and cover crop BMPs.