Potential of forages to diversify cropping systems in the northern Great Plains

Cultivated forage crops are grown on almost 12 million ha on the northern Great Plains. This paper reviews the benefits of diversifying annual crop rotations with forage crops and highlights innovations in forage systems. Agronomic benefits of rotating forage crops with annual grain crops include higher grain crop yields following forages (up to 13 yr in one study), shifts in the weed population away from arable crop weeds, and improved soil quality. Perennial legumes in rotation also reduce energy requirements by adding significant amounts of N to the soil. Soil water availability may limit the extent to which forages benefit following crops. Under semiarid conditions, forages can actually reduce yields of the following crops, and as such, tillage practices that conserve soil water have been developed to partially address this problem. Forages in rotation provide environmental benefits, such as C sequestration, critical habitat for wildlife, and reduced NO₃ leaching. A wider range of annual plant species are now used in forage systems in an effort to extend the grazing season and to maximize use of water resources. Intensive pasture management using cultivated forages is on the increase as is the use of alfalfa (Medicago sativa L.) in grazing systems; in some cases, bloat-reduced alfalfa cultivars are used. Pasture-based systems appear to provide benefits for both animal and human health and arguably the health of the environment. Pasture systems are less nutrient exhausting than hay systems. As a result, nutrient management strategies will differ in the following crop. Additional research is required to optimize the role of cultivated pastures in grain-based cropping systems.