Nadia Mori, PAg, Regional Forage Specialist, Saskatchewan Ministry of Agriculture
During the 2016 growing season, many cereal growers had a brush with fusarium. Rotating perennial legumes into an annual crop rotation can help break disease cycles plus offer a long list of other benefits.
Rotating legumes helps kick out disease. Breaking cycles of fusarium and ergot requires a minimum of two years where no susceptible or carrier crops are grown. Rotating into a perennial legume crop can offer the needed break by removing host plants from the rotation, thus reducing the level of pathogens in the soil. Production benefits of perennial forages in a crop rotation are optimized after two to three years, but forage production may be extended to increase the return on the forage establishment investment.
Rotating legumes increases fertility. One of the largest benefits of including legumes in an annual crop rotation is the injection of plant fixed nitrogen. The Western Beef Development Centre (WBDC) conducted a four-year cropping rotation study across the different soil zones. The net fertilizer equivalent (NFE) for alfalfa ranged from 35 kilograms per hectare (valued at $43 per hectare) in Swift Current to 373 kilograms per hectare (valued at $460 per hectare) in Melfort. Soil zone and growing season conditions do have significant influence on how effective the fertilization from legumes can be. Proper inoculation of legumes is required for maximum nitrogen fixation to occur. Because forage legumes reach much deeper into the soil horizon compared to annual crops, forages can help retrieve deeply leached nutrients.
Including alfalfa or legume and grass mixtures in a crop rotation also increases organic matter in your soil. More soil organic matter means more nutrient exchange surface and thus more nutrient holding capacity.
Rotating legumes provides environmental benefits. Increased soil organic matter also means more carbon sequestered on your land. Beyond the potential for carbon offset, legumes have long been recognized as soil building crops. The deep root system increases soil aeration. After the root system has broken down, the fine channels left behind increase soil water infiltration and holding capacity. The extensive root system can also improve soil structure by breaking soil clumps into smaller aggregates, which in turn creates larger surfaces where nutrient exchange can happen. Hence perennial forages can provide valuable buffers to minimize nutrient runoff or leaching into nearby water bodies.
For tips on successful forage establishment, marketing your forage crop and effective termination strategies when it comes time to take the forage out of your rotation, please contact the Agriculture Knowledge Centre or visit www.saskatchewan.ca and search for “forage crop production.”
