Average statewide yields for both corn and soybeans have increased in the last half century. Corn has increased at an average rate of 2.1 bushels per acre per year, while soybeans only increased 0.5 bushels per acre per year (See Figure 1 & 2). This dispersion in yield growth rate has led to corn yields that are more than 3 times that of soybean yields, this trend started around the mid-1990s.
As corn yields have grown at an increased rate compared to soybeans; the yield ratio of corn to soybeans has increased at an average rate of 1.4 percent per year (See Figure 3).
The soybean to corn yield ratio did not increase as rapidly in the later part of the 20th century. However, in the current century the average yield in corn has been more than 3 times that of soybeans in every year since 1996. In 2003 corn yields were nearly 5 times greater than soybean yields.
Both corn and soybeans have seen significant growth in yield since 1970, however, the corn yield growth has been more rapid especially since the mid-90s. This ratio has shown an increasingly positive trend since 1996 as a result of hybrid corn varieties as well as variations in soybean yield bringing the trend average down during that time period. Furthermore, this is an average corn and soybean yield being spoken of in this article meaning that there are some that are both higher and lower than what is represented here.
Preston Lyman is a Research Analyst with Decision Innovation Solutions (DIS). DIS is an Iowa-Based economic research firm which provides regular farm economics research and analysis to the Iowa Farm Bureau staff and members.