Effects of Long-Term Weather Variations on Alfalfa Production in the Midwestern United States.

Confronting the increasing of world population, soil erosion and water stress, investigating the relationship of climate trends and alfalfa yields ahead of time can provide growers and researchers more time to deal with unpredictable stress from climate change and environmental degradation. Assessment of monthly weather variation impacts on alfalfa yields could provide the view of the relationship of annual yield variations and climate trends continuously. Four states, Wisconsin (WI), Indiana (IN), Oklahoma (OK) and North Dakota (ND) were selected in the Midwest of U.S. They cover approximately from north to south and middle areas of Midwest. Most of alfalfa fields from these four states are non-irrigated, isolated the effect of irrigation. The objectives of this study were to investigate the impacts of monthly temperature and precipitation on alfalfa yields in WI, IN, OK and ND from 1985 to 2009, and to assess model validity by inputting weather observations in the recent five years in four states separately. R² values of the regression models of OK, WI, IN and ND were at 91.2%, 88.5%, 84.2% and 75.0%, respectively, which explained the variation in yields from 1985 to 2009. The relationship between alfalfa yield and climate variable were different over four states in the Midwest.