Weather and Technology in the Production of Soybeans in the Central United States1

Abstract Multiple curvilinear regression analysis was used to measure the influence of weather on the yield of soybeans. A linear time trend was introduced to measure the influence of technology. In the five states, Illinois, Indiana, Iowa, Missouri, and Ohio, yields increased at an annual rate of 21.5 kg per ha from 1930 to 1968. Highest yields have been associated with warmer than normal temperatures in June but with cooler than normal temperatures in July and August. Highest yields have been associated with normal precipitation from September through June and with above normal rainfall in July and August.